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  • Articles  (7,062)
  • Wiley-Blackwell  (6,898)
  • Blackwell Science Ltd  (164)
  • American Meteorological Society
  • PANGAEA
  • 1995-1999  (7,062)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (6,695)
  • Electrical Engineering, Measurement and Control Technology  (367)
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  • Articles  (7,062)
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  • 1
    Electronic Resource
    Electronic Resource
    THE COALESCENCE OF VOIDS IN PRESTRAINED NOTCHED ROUND COPPER BARS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Notched round copper bars are prestrained to various extents, recrystallized, and finally strained until fracture. Void nucleation and growth during prestraining cause a decrease in the macroscopic void coalescence strain. Modelling of this experiment requires a proper account of the changes in void sizes and their interdistances during prestraining. Modelling based on the Gurson–Leblond–Perrin model for void growth and the Thomason model for void coalescence is proposed. Comparison with experimental results allows a demonstration of the validity of the Thomason model and the inadequacy of models based on a critical porosity value. Porosity at coalescence is found to depend on the initial void volume fraction, the flow properties and the stress state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00123.x
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  • 2
    Electronic Resource
    Electronic Resource
    SMALL CRACK GROWTH AND FATIGUE LIFE PREDICTIONS FOR HIGH-STRENGTH ALUMINIUM ALLOYS: PART I—EXPERIMENTAL AND FRACTURE MECHANICS ANALYSIS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The small crack effect was investigated in two high-strength aluminium alloys: 7075-T6 bare and LC9cs clad alloy. Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks. In the experimental program, fatigue tests, small crack and large crack tests were conducted under constant amplitude and Mini-TWIST spectrum loading conditions. A pronounced small crack effect was observed in both materials, especially for the negative stress ratios. For all loading conditions, most of the fatigue life of the SENT specimens was shown to be crack propagation from initial material defects or from the cladding layer. In the analysis program, three-dimensional finite element and weight function methods were used to determine stress intensity factors and to develop SIF equations for surface and corner cracks at the notch in the SENT specimens. A plasticity-induced crack-closure model was used to correlate small and large crack data, and to make fatigue life predictions. Predicted crack-growth rates and fatigue lives agreed well with experiments. A total fatigue life prediction method for the aluminium alloys was developed and demonstrated using the crack-closure model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00080.x
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  • 3
    Electronic Resource
    Electronic Resource
    FRACTURE AND FATIGUE OF FERROELECTRICS UNDER ELECTRIC AND MECHANICAL LOADING (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A switch in the domain polarization direction near the tip of a flaw plays an important role in the fracture and fatigue of ferroelectrics under electric and mechanical loading. The present paper adopts a small-scale switching model with the domain switch based on the combined electric and mechanical work increment. The model is capable of explaining electric fracture, fracture toughness anisotropy and electric fatigue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00107.x
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  • 4
    Electronic Resource
    Electronic Resource
    EFFECTS OF STRESS–STRAIN CONDITIONS ON HYDROGEN-INDUCED FRACTURE (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Effects of stress–strain fields and stress–strain history on hydrogen-induced fracture (HIF) have been studied. The investigation covers I/II and I/III mixed mode HIF, redistribution of hydrogen near a mixed-mode crack tip, correlation between HIF initiation sites and critical stress intensity factors, and the influence of overloading on HIF life.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00109.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of tempering treatment on hydrogen-induced cracking in high-strength steel (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The fracture characteristics of high-strength steel ASTM A-490 under a hydrogen environment were investigated, with special emphasis placed on changes in fracture characteristics due to a tempering treatment at temperatures from 200 to 400 °C. A mechanical test was performed on cathodically charged specimens subjected to a constant load. Experimental analyses show that tempering treatment in the range from 200 to 400 °C does not alter the essential nature of delayed fracture due to crack growth. However, the role of intergranular (IG) cracking becomes prominent in the subcritical crack growth period with an increase in the tempering temperature to 400 °C. This development of IG cracks in the subcritical crack growth period is uniquely dependent on the tempering treatment performed in the tempering range from 250 to 400 °C. Furthermore, an increase in the fraction of the IG facet in the subcritical crack growth area is dependent on the increase in the stress intensity at the crack tip in those specimens tempered at 300 and 400 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00171.x
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  • 6
    Electronic Resource
    Electronic Resource
    A crack in a linear-elastic material under mode II loading, revisited (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A sharp crack in a two-dimensional infinite linear-elastic material, under pure shear (mode II) loading is re-examined. Several criteria have been proposed for the prediction of the onset and direction of crack extension along a path emanating from the tip of the initial crack. These criteria date back some three decades and are well documented in the literature. All the predictions from the different criteria are close and indicate that the crack extension takes a direction at an angle of ≈ −70° measured counterclockwise from the positive x-axis, in the case of a remotely applied positive shear stress. However, the possibility seems to have been overlooked that the crack extension may initiate not from the crack tip itself, but instead may initiate on the free surface at an infinitesimal distance behind the crack tip. The effect of crack tip plasticity on the relevant stresses in the region of the crack tip is investigated by the application of an elastic–plastic finite element program.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00178.x
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  • 7
    Electronic Resource
    Electronic Resource
    Fatigue life assessment of nodular cast iron containing casting defects (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The fatigue behaviour of a nodular cast iron containing casting defects has been investigated in the high-cycle fatigue regime. In this paper, we propose a fatigue life assessment model for flawed materials based on a fracture mechanics approach which takes into account the position and size of the defect, short crack behaviour and the notch effect introduced by the defect. The fatigue behaviour of smooth samples, and long and short crack behaviour have been experimentally determined in order to identify the relevant mechanical parameters; these being introduced into the model. An experimental study has been made both in air and in vacuum in order to account for the position of the defect, noting that internal defects are supposed to be under vacuum conditions. Experimental results, which are based on a two-crack front-marking technique specially developed for this study, show that the propagation of natural cracks is controlled by the effective stress intensity factor in air as well as in vacuum. The K calculation for a short crack in the stress field of a notch is analysed using numerical elastic–plastic results. Comparison between experimental results and the computation of fatigue life for fatigue lives less than 106 cycles shows that the fatigue behaviour of nodular cast iron is controlled by a propagation process. The model proposed is thus relevant for fatigue lives less than 106 cycles so that the defect can be considered as a crack and the initiation stage neglected. Closer to the fatigue limit, this study shows that the initiation stage should be considered in the assessment of fatigue life of nodular cast iron, because a single macroscopic propagation assessment is not enough to describe the whole fatigue life. The defect cannot be considered as a pre-existent crack in the high-cycle fatigue range (〉106 cycles), and the initiation stage that contains microcrack propagation around the defect should be evaluated when assessing the high-cycle fatigue life of nodular cast iron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00162.x
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  • 8
    Electronic Resource
    Electronic Resource
    Modelling of crack surface interference under cyclic shear loads (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Crack surface interference under cyclic shear loads is studied by an analytical method. The proposed model simulates the effects arising from both the residual stresses and the asperity interactions. A closed-form and a discrete approach are presented in obtaining the crack surface interference solutions. Backlashes of shear displacements, peeling or group sliding behaviours and induced cyclic mode I stress intensities are predicted under three configurations of residual stress distributions. The effects of a static mode I load, the facet angle and the frictional angle are also analysed. The predicted relationship between the effective shear mode stress intensity range and the R-ratio is discussed together with the experimentally observed ‘contrasting’ R effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00152.x
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of frequency on fatigue crack growth at elevated temperature (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effects of frequency on fatigue crack growth behaviour have been studied in a prealloyed powder material, Udimet 720Li, at 650 °C. Fracture mode and fatigue crack growth behaviour were studied at frequencies ranging from 0.001 to 5 Hz using a balanced triangular waveform. Tests were carried out under constant ΔK control, with load ratio and temperature being held constant. A mechanism map was constructed where predominantly time, mixed and cycle-dependent crack growth behaviour were identified. The results were verified by SEM analyses. Cycle-dependent crack growth data were obtained at room temperature, while fully time-dependent crack growth data were generated under sustained loads at 650 °C.It was found that mixed time/cycle-dependent behaviour is of most significance for this material at the temperature and frequencies studied. Data for other nickel-based superalloys from various sources in the literature were compiled and compared with those of U720Li alloy at a given stress intensity and temperature in the mixed regime. An analysis was developed to rationalize the observed effect of frequency on fatigue crack growth rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00160.x
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  • 10
    Electronic Resource
    Electronic Resource
    Deformation behaviour at the tip of a physically short fatigue crack due to a single overload (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A two-dimensional elastic–plastic finite element analysis was utilized to investigate the transition behaviour of a physically short fatigue crack following the application of a single overload cycle. The deformation accommodated at the tip of a crack artificially advancing with a fully reversed load was considered. The development of the cyclic crack tip opening displacement was computed and then modelled to include the effects of the stress level of the base cycles, overload pattern and crack length at which the transient cycle was applied.The cyclic crack tip opening displacement was initially of a relatively high value. It decreased and then increased to match the behaviour under the base load cycles. The extent and location of both the minimum and matching points were dependent on the overload crack length and the stress compared with the material’s yield stress. In the case of the yield stress being exceeded by the overload, the minimum and the-return-to-normality points are identical.A previously developed crack tip deformation parameter was invoked to predict relevant experimental fatigue growth rates of short cracks reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00141.x
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  • 11
    Electronic Resource
    Electronic Resource
    Interfacial fatigue crack growth in foam core sandwich structures (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper deals with the experimental measurement of face/core interfacial fatigue crack growth rates in foam core sandwich beams. The so-called ‘cracked sandwich beam’ specimen is used, slightly modified, which is a sandwich beam that has a simulated face/core interface crack. The specimen is precracked so that a more realistic crack front is created prior to fatigue growth measurements. The crack is then propagated along the interface, in the core material, during fatigue loading, as is assumed to occur in a real sandwich structure. The crack growth is stable even under constant amplitude testing. Stress intensity factors are obtained from the FEM which, combined with the experimental data, result in standard da/dN versus ΔK curves for which classical Paris’ law constants can be extracted. The experiments to determine stress intensity factor threshold values are performed using a manual load-shedding technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00148.x
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  • 12
    Electronic Resource
    Electronic Resource
    A microstructural approach to flaw size dependence of strength in engineering ceramics (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this work, microstructural effects on the flaw size dependence of ceramic strength were investigated from aspects of stress analysis in the grain just ahead of the crack tip and also R-curve behaviour. In the analysis, it was assumed that the stress averaged in one grain just ahead of the crack tip, in ceramics, might control the fracture from a flaw. A microstructurally modified fracture criterion using the averaged stress was established by introducing the R-curve due to the grain bridging effect for longer cracks. A new R-curve of an exponential type was proposed for the fracture criterion. The criterion could adequately express the central trend in the dispersal of experimental results in the strength versus flaw size relation. To explain the scatter of results, the size distribution and the crystallographic anisotropy of the grain ahead of the crack tip were examined as dominant factors. The lower bound of strength scatter was estimated from the largest grain size, and the strength dispersion was reduced by decreasing the range of grain size variation. In FEM simulations, each element was regarded as one grain with a different crystallographic orientation, which was randomly selected by using a series of quasi-uniform random numbers. It was revealed that the scatter of strength due to crystallographic variations was smaller than the strength dispersion caused by a distributed grain size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00227.x
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  • 13
    Electronic Resource
    Electronic Resource
    A discrete-integral strength criterion for complicated stress states (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The atomic structure behaviour at a crack tip in closely-packed layers of atoms is studied. The deformation of a three-atomic chain for the complicated stress state is analysed. This study includes the analyses of bifurcation and post-bifurcation behaviour as well as the sensitivity of the limit strength to fixing conditions. The numerically obtained values of theoretical strengths are compared with the available experimental results and the theoretical estimates. The discrete-integral strength criterion for complicated stress states is proposed. Contrary to the classical criteria, the proposed criterion allows a limiting transition of the crack length parameter and describes the strength of cracked and crack-free solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00231.x
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  • 14
    Electronic Resource
    Electronic Resource
    Guest Editorial (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00241.x
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  • 15
    Electronic Resource
    Electronic Resource
    Assessment of stress corrosion cracking susceptibility by a small punch test (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The object of this study is to establish a new test method for evaluating stress corrosion cracking (SCC) susceptibility of high-strength steel using a small punch (SP) test and acoustic emission (AE). A miniaturized specimen (10 × 10 × 0.5 mm) is adopted for SCC evaluation. The experiments are conducted at various loading rates and at various orientations of the specimen. The cumulative average amplitude of the AE signal per unit equivalent fracture strain (εqf ) increases as the SCC susceptibility increases. Through the load–displacement behaviour, the fracture energy (ESP ), the SEM fractographs, and the correlation between the SCC susceptibility and the AE characteristics, it is proved that the small punch test method combined with AE measurements is a useful method to evaluate the SCC susceptibility of high-strength steel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00218.x
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  • 16
    Electronic Resource
    Electronic Resource
    A numerical investigation on the effect of an overload on fatigue crack opening and closure behaviour (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of a superimposed single tensile overload or a compressive overload in a block of constant-amplitude cycles on the crack opening and closing stresses is investigated using an elastic–plastic finite element analysis. The results obtained are in basic agreement with the experimental observations. Following an applied tensile overload cycle, the crack opening and closing stresses increase instantaneously, while the imposition of a compressive overload cycle results in a small decrease of the crack opening and closing stresses. A detailed discussion of the residual stress and strain patterns caused by the plastic deformation during the overload cycle and the corresponding crack profiles is included. The main governing mechanism resulting in the change of crack growth due to an overload is pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00223.x
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  • 17
    Electronic Resource
    Electronic Resource
    Manufacturing and ultimate mechanical performance of carbon fibre-reinforced epoxy composite suspension push-rods for a Formula 1 racing car (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The contemporary Formula 1 racing car makes extensive use of advanced composite materials in its construction. The design, manufacture and ultimate performance under compression of composite suspension push-rods, that typically could be used in a Grand Prix racing car, are described in this present paper. An aerofoil cross-section has been used based on different lay-ups of carbon/epoxy composite. One push-rod was manufactured using a uniform layup of unidirectional and woven cross-ply prepreg, whilst a further three push-rods were manufactured with a tapered layup of unidirectional and woven cross-ply prepreg. Failure mechanisms including fibre microbuckling, fibre kinking and fibre fracture were observed, whilst comparisons have been made between the experimentally observed failure strains and those that were predicted using simple buckling theory. The ultimate compressive strength of the structural component was significantly less than that of the carbon/epoxy composite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00133.x
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  • 18
    Electronic Resource
    Electronic Resource
    Statistical analysis and reliability prediction with short fatigue crack data (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper proposes a probability model to describe the growth of short fatigue cracks. The model defines the length of each crack in a specimen as a random quantity, which is a function of randomly varying local properties of the material microstructure. Once the model has been described, the paper addresses two questions: first, statistical inference, i.e. the fitting of the model parameters to data on crack lengths; and secondly, predicting the future behaviour of observed cracks or cracks in a new specimen. By defining failure of a specimen to be the time at which the largest crack exceeds a certain length, the solution to the prediction problem can be used to calculate a probability that the specimen has failed at any future time.The probability model for crack lengths is called a population model, and the statistical inference uses the ideas of Bayesian statistics. Both these concepts are described. With a population model, the solution to statistical inference and prediction requires quite complicated Monte Carlo simulation techniques, which are also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00140.x
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  • 19
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    Electronic Resource
    A STUDY ON THE CHANGE OF FATIGUE FRACTURE MODE IN TWO TITANIUM ALLOYS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The appearance of the fatigue fracture surface and crack growth curve have been examined for a Ti–2.5Cu alloy with different microstructures (two equiaxed and two lamellar microstructures), and for TIMETAL 1100 with a lamellar microstructure. With increasing ΔK, a slope change in the crack growth curve correlates with a transition in the fracture surface appearance (induced by a fracture mode transition); this being found in each microstructure. The microstructure size that controls the fatigue fracture is found to be the grain size for equiaxed microstructures and the lamella width for lamellar microstructures. The transitional behaviour can be interpreted in terms of a monotonic plastic zone size model in microstructures having a coarse microstructure size and in terms of a cyclic plastic zone size model for microstructures having a fine microstructure size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00095.x
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  • 20
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    FATIGUE CRACK GROWTH BEHAVIOUR OF SM45C STEEL UNDER MIXED-MODE I AND II LOADING (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The practical applications of studies related to constant amplitude mode I loading are somewhat limited in situations where more than one mode exists. So, criteria, rules and laws for these situations have to be validated with experiments. This paper extends previous results by the authors for mixed-mode I and II fatigue loading. An effective stress intensity factor range which considers crack closure and crack surface interference is described for the analysis of a crack under mixed-mode I and II fatigue loadings, and this factor is assessed from experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00103.x
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  • 21
    Electronic Resource
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    MODAL APPROACH FOR PROCESSING ONE- AND THREE-POINT BEND TEST DATA FOR DSIF-TIME DIAGRAM DETERMINATION PART I—THEORY (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A hybrid experimental/numerical method for the determination of the variation in the dynamic stress intensity factor (DSIF) with time during one- or three-point bend impact tests is presented. According to the concept of hybrid methods, a DSIF–time diagram is calculated for a particular mathematical model for the specimen using experimentally registered loading as the model excitation. The simple expression for the impact DSIF–response function is derived for an arbitrary linear model of the specimen, using the modal superposition method. Finally, formulae for DSIF calculations for different types of loading approximation are derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00087.x
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  • 22
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    HIGH-TEMPERATURE LOW-CYCLE FATIGUE AND CREEP BEHAVIOUR OF NICKEL-BASED SUPERALLOYS WITH HEAT-RESISTANT COATINGS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The problems associated with nickel-based superalloys with heat-resisting coatings, as used in aerospace, have been addressed in this paper. The influence of the heat-resisting coating technology on both the fatigue and creep behaviour of the alloys has been shown. Low-cycle fatigue and creep tests have been performed. Lifetime conditions have been determined in relation to low-cycle fatigue, isothermal creep and creep at cyclically variable temperatures, as a function of the chemical composition of the coating, parameters of the thermal treatment and thickness of the coating. Possible processes and mechanisms of fracture are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00090.x
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    FATIGUE CRACK GROWTH IN TWO ADVANCED TITANIUM ALLOYS UNDER CONSTANT AND VARIABLE AMPLITUDE LOADING AT 25 AND 175 °C (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue crack growth of β-21S and Ti-62222 in sheet form was investigated under constant and miniTWIST flight spectra loading conditions at 25 and 175 °C. Variable amplitude results were compared with life calculations performed using NASA/FLAGRO software and constant amplitude fatigue crack growth results. Single tensile overloads under constant ΔK were performed to evaluate load interaction effects. Constant amplitude results showed that fatigue crack growth resistance was slightly better for Ti-62222 than β-21S at 25 and 175 °C. The presence of crack closure under various conditions caused moderate shifts in the fatigue crack growth data. Under miniTWIST flight spectra loading, Ti-62222 exhibited a greater extension in life in comparison to the β-21S at elevated temperature, consistent with the NASA/FLAGRO calculations. This was also consistent with the single tensile overloads where 25 °C tests were comparable for both materials, while at 175 °C, delay cycles were greater by a factor of almost three for Ti-62222. Extensive secondary cracking in Ti-62222 at elevated temperature accounted for the extended fatigue lives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00067.x
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  • 24
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    CONTINUOUS SEM OBSERVATIONS OF CREEP-FATIGUE DAMAGE PROCESSES (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In order to examine the relation between damage evolution and changes in microstructure, e.g. from creep cavities, surface micro-cracks and dislocation structures at high temperature, strain controlled creep-fatigue tests were performed and interrupted at several damage levels on Types 304 and 316 stainless steels. The creep-fatigue tests on Type 304 stainless steel at a low strain level were conducted in a high-temperature fatigue testing machine combined with a scanning electron microscope, and the micro-crack initiation and growth behaviour were continuously observed to clarify the damage extension mechanism. It was found that even though many cavities were initiated and grew on the internal grain boundaries of the specimens during the strain-controlled tests, the failure life was governed by the propagation of surface cracks. On the other hand, micro-cracks of about the order of one grain size were initiated mainly along grain boundaries normal to the loading axis under low stress creep-fatigue, and the crack propagation rate of the micro-cracks was slow and random due to the nature of the microstructures. The micro-cracks gradually opened in the loading direction with increasing number of cycles and coalescence contributed to growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00072.x
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  • 25
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    FATIGUE LIMIT OF BLUNT-NOTCHED COMPONENTS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The position and effective resistance of microstructural barriers and their relation to the fatigue strength of blunt-notched specimens are analysed and modelled for three low-carbon steel microstructures. A relationship for the notch size effect on the basis of the experimental evidence that the fatigue limit (both plain and notched) represents the threshold stress for the propagation of the nucleated microstructurally short cracks, was derived. The derived relationship characterizes the fatigue notch sensitivity by means of the parameter ktd defined as the stress concentration introduced by the notch at a distance d from the notch root surface equal to the distance between microstructural barriers, and was experimentally verified for two notch geometries in three microstructures: ferrite, ferrite–bainite and bainite–martensite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00115.x
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  • 26
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    TORSIONAL FATIGUE OF A MEDIUM CARBON STEEL CONTAINING AN INITIAL SMALL SURFACE CRACK INTRODUCED BY TENSION–COMPRESSION FATIGUE: CRACK BRANCHING, NON-PROPAGATION AND FATIGUE LIMIT (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In order to examine the threshold condition for the fatigue limit of materials containing a small crack under cyclic torsion, reversed torsional fatigue tests were carried out on 0.47% C steel specimens containing an initial small crack. Initial small semi-elliptical cracks ranging from 200 to 1000 μm in length were introduced by the preliminary tension–compression fatigue tests using specimens containing holes of 40 μm diameter. The threshold condition for the fatigue limit of the specimens containing artificial small defects under rotating bending and cyclic torsion are also reviewed. Crack growth behaviour from an initial crack was investigated. The torsional fatigue limit for a semi-elliptical small crack is determined by the threshold condition for non-propagation of Mode I branched cracks. The torsional fatigue limit of specimens containing an initial small crack can be successfully predicted by the extended application of the √area parameter model in combination with the σθmax criterion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00128.x
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  • 27
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    PLASTIC DAMAGE ANALYSIS FOR THE PROCESS ZONE OF A FATIGUE CRACK (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The process zone of a mode I fatigue crack is described asymptotically with damage coupled plastic constitutive relations. A parametric study is conducted to obtain the orders and angular distribution modes of stress, strain and damage fields, as well as the profiles of the related process zones. The fatigue crack growth rate is also formulated theoretically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00121.x
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  • 28
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    MICROMECHANICAL MODELLING OF DAMAGE AND FRACTURE OF DUCTILE MATERIALS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A micromechanical model of ductile damage by void nucleation, growth and coalescence is widely and successfully applied to describe phenomena of ductile tearing. The model’s fundamental principles, and especially the constitutive equations of Gurson, Tvegaard and Needleman (GTN-model), are briefly described. Some of the material parameters of the GTN-model are calibrated by performing cell model calculations, which is a method of determining the structural behaviour of a single void in a plastic material. The approach is used to study the dependence of material strength and toughness on microstructural features of nodular cast iron. The numerical simulations were realized within the FE-program ABAQUS by a user-supplied material model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00078.x
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  • 29
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    THE ETM METHOD FOR ASSESSING THE SIGNIFICANCE OF CRACK-LIKE DEFECTS IN ENGINEERING STRUCTURES (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Engineering Flaw Assessment Method, EFAM, is presently being developed at GKSS. It consists of several individual documents for determining material properties and the crack driving force. The present paper briefly describes the document EFAM ETM 97 which provides guidance for estimating the crack tip opening displacement (CTOD) and the J-integral as driving force parameters for homogeneous structures. The CTOD and J can be expressed as functions of applied force or applied strain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00112.x
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    Measurement of fatigue crack growth in large compact tension specimens using an AC magnetic field method (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue crack growth rate data are required in order to carry out a numerical analysis of the fatigue performance of complex structural components. These data are obtained by measuring crack growth in standard fracture mechanics specimens. A new method for measuring fatigue crack growth in compact tension specimens has been developed. The technique is based on the measurement of the surface magnetic fields produced when passing a high-frequency alternating current through the specimen. Fatigue crack growth data recorded using this method indicated an accuracy of ±0.02 mm when compared with optical measurements. The technique is suitable for computer-controlled operation and could easily be applied to other standard specimen geometries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00136.x
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  • 31
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    THE FAILURE OF LIGAMENTS DUE TO MULTIPLE-SITE DAMAGE USING INTERACTIONS OF DUGDALE-TYPE CRACKS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A self-similar, narrow-strip Dugdale model is invoked to determine interactive crack tip plastic zones. Symmetric collinear multiple-site damage (MSD) cracks are considered for the coalescence of plastic zones between adjacent cracks. The Swift’s ligament failure criterion is employed to predict the residual strength with or without considering the interaction between Dugdale-type plastic zones. Better agreement is achieved between the calculated results and experimental data if the interaction between the plastic zones is implemented in a computing scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00070.x
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  • 32
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    A THEORETICAL MODEL FOR PREDICTING FATIGUE CRACK GROWTH RATES IN FIBRE-REINFORCED METAL LAMINATES (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper is concerned with the development and application of an analytical model for predicting fatigue crack growth in fibre-reinforced metal laminates (FRMLs). An analytical model for the distribution of bridging traction is first introduced. Based upon observations of the delamination shapes in FRMLs under fatigue loading and a model for characterizing delamination growth in FRMLs, a model for predicting crack growth rates in CCT specimens of FRMLs is developed. The model is applied to two GLARE laminates (2/1, 3/2 lay-ups) under various cyclic stress levels and stress ratios. The predicted crack growth rates are compared with experimental data. The predicted crack growth rates agree well with the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00076.x
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    A CRACK GROWTH APPROACH TO LIFE PREDICTION OF SPOT-WELDED LAP JOINTS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue behaviour of spot-welded lap joints is modelled as a single-degree-of-freedom crack growth problem. Although such a model involves simplification of a complicated problem, predictions are in good agreement with experimental results. The model developed here allows a design engineer to analyse the fatigue behaviour of spot-welded steel sheets, which are commonly used in structures, without knowledge of metallurgical and fine geometric details of spot-welds. Only fatigue properties of the sheet metal are needed, so no laboratory facilities are required to generate fatigue data specific to spot-welds or weld metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00099.x
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    An apparatus for quantitative fretting testing (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The design and construction of an apparatus for performing quantitative fretting fatigue experiments is described. The device allows accurate measurement and control of normal contact force, tangential contact force, relative displacement between contacting surfaces and bulk fretting loads, as well as measurement of average friction coefficients. Its design is simple, and includes interchangeable fretting contact pads, allowing the use of various pad geometries without major adjustment. The device incorporates many points of adjustment for alignment and compliance, making it a robust frame for a wide variety of fretting fatigue conditions involving different materials. The capabilities of this device are also verified by results of fretting fatigue experiments conducted on a 7075-T6 aluminium alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00145.x
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    Smoothing and differentiating load–displacement data using a low-pass filter for improved crack opening load estimates (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The presence of even small amounts of noise in experimental data significantly influences numerically determined derivatives. Dynamic programming is used to construct a low-pass filter enabling the smoothing and differentiation of noisy data. The filter is used to smooth and differentiate load–displacement data for a propagating fatigue crack to obtain smoothed compliance as a function of applied load. The smoothed compliance is shown to allow for improved subsequent estimates of the crack opening load.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00164.x
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    THE FATIGUE BEHAVIOUR OF METAL–MATRIX COMPOSITES UNDER SINGLE OVERLOADS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The fatigue crack growth response of Ti-based metal–matrix composites (MMCs) under single overloads was investigated. Extensive debonding and failure of bridging fibres were confirmed to be the major controlling mechanisms accelerating crack growth after peak overloads. Numerical predictions show that the fatigue damage severity is increased when the overload is applied at shorter crack lengths. Finally, extensive debonding and failure of bridging fibres was corroborated with a fatigue damage map to provide design guidelines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00124.x
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  • 37
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    CORROSION FATIGUE FRACTURE BEHAVIOUR OF A SiC WHISKER–ALUMINIUM MATRIX COMPOSITE UNDER COMBINED TENSION–TORSION LOADING (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: We describe an investigation into the fatigue fracture behaviour under combined tension–torsion loading of a SiC whisker-reinforced A6061 aluminium alloy fabricated by a squeeze casting process. Special attention was paid to the environmental effects on fatigue fracture behaviour. Tests were conducted on both the composite and its unreinforced matrix material, A6061-T6, under load-controlled conditions with a constant value of the combined stress ratio, α = τmax /σmax in laboratory air or in a 3.5% NaCl solution at the free corrosion potential. The corrosion fatigue strength of both the matrix and composite was less in the solution than in air. The dominating mechanical factor that determined the fatigue strength in air was either the maximum principal stress or the von Mises-type equivalent stress, depending on the combined stress ratio. However, in the 3.5% NaCl solution, the corrosion fatigue strength of both materials was determined by the maximum principal stress, irrespective of the combined stress ratio. In the case of the matrix material, crack initiation occurred by a brittle facet normal to the principal stress due to hydrogen embrittlement. However, in the composite material, the crack was initiated not at the brittle facet, but at a corrosion pit formed on the specimen surface. At the bottom of the pit, a crack normal to the principal stress was nucleated and propagated, resulting in final failure. Pitting corrosion was nucleated at an early stage of fatigue life, i.e. about 1% of total fatigue life. However, crack initiation at the bottom of a pit was close to the terminal stage, i.e. about 70% or more of total fatigue life. The dominating factor which determined crack initiation at a pit was the Mode I stress intensity factor obtained by assuming the pit to be a sharp crack. Initiation and propagation due to pitting corrosion and crack growth were closely examined, and the fatigue fracture mechanisms and influence of the 3.5% NaCl solution on fatigue strength of the composite and matrix under combined tension–torsion loading were examined in detail.
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    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00127.x
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    MODELLING THE INFLUENCE OF STRAIN HARDENING AND PLASTIC CONSTRAINT ON CRACK CLOSURE OF ARBITRARILY THICK CCT-SPECIMENS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The triaxial stress constraint and the effective yield stress distribution in the plastic zone for strain hardening materials are studied, and then a modified strip-yield model is proposed to investigate the thickness effect of CCT specimens. Consequently, a plastic constraint factor α is defined and analysed in detail. The results show that the factor α can comprehensively account for the influence of thickness, crack length, loading level and hardening exponent. A simple expression for the plastic zone length and a fitting expression involving α are obtained. Application of the modified strip model to Newman’s crack closure model, and comparison with FEM results, show that the model can account for the influence of thickness on crack closure.
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    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00085.x
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    FATIGUE CRACKING POSSIBILITY ALONG GRAIN BOUNDARIES AND PERSISTENT SLIP BANDS IN COPPER BICRYSTALS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper, the fatigue cracking possibility in different kinds of copper bicrystals with large-angle grain boundaries (GBs) and copper multicrystals containing some low-angle GBs are compared. The results showed that the fatigue cracks, in the copper bicrystals, always nucleated firstly along GBs no matter whether the GBs are perpendicular or parallel to the stress axis. Whereas, for the copper multicrystals containing low-angle GBs, the persistent slip bands (PSBs) are always the preferential sites to initiate fatigue cracks no matter whether low-angle GBs are perpendicular or parallel to the stress axis.Additionally, the fatigue lives of the GBs, and the [1¯23] and [3¯35] grains in the [1¯23] ⊥ [3¯35] and [5¯913] ⊥ [5¯79] bicrystals were measured at different cyclic stresses and strain amplitudes. The results show that intergranular fracture always occurred prior to transgranular fracture in those bicrystals. The fatigue lives increased in the order of the GB, the [1¯23] and the [3¯35] grains in the [1¯23] ⊥ [3¯35] bicrystal under cyclic tension–tension loading. On the other hand, the fatigue life of the GB in the [5¯913] ⊥ [5¯79] bicrystal is about two to three times higher than that in the [1¯23] ⊥ [3¯35] bicrystal. Based on these experimental results from the copper bicrystals and multicrystals, it is indicated that the possibility of fatigue cracking increased in the order of low-angle GBs, PSBs and large-angle GBs. It is suggested that both the PSB–GB mechanism and the step mechanism required for GB fatigue cracking were questionable, and the interaction modes of PSBs with GBs may be more important for intergranular fatigue cracking.
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    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00092.x
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    THE DEVELOPMENT OF AN INHOMOGENEOUS DAMAGE FIELD IN AN ELASTIC-PLASTIC MODEL (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: By making use of the evolution equation of the damage field as derived from the statistical mesoscopic damage theory, we have preliminarily examined the inhomogeneous damage field in an elastic–plastic model under constant-velocity tension. Three types of deformation and damage field evolution are presented. The influence of the plastic matrix is examined. It seems that matrix plasticity may defer the failure due to damage evolution. A criterion for damage localization is consistent with the numerical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00119.x
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    THREE-DIMENSIONAL FINITE ELEMENT SIMULATION OF CRACK EXTENSION IN ALUMINIUM ALLOY 2024FC (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A simulation of 3D crack extension using a cohesive zone model (CZM) has been carried out for a side-grooved compact tension specimen and a surface-crack tension specimen of aluminium 2024FC. Detailed finite element calculations were conducted by assuming crack extension only along the crack plane (mode I). For comparison, a 2D plane strain simulation is also presented. Load, displacement and crack extension histories are predicted and compared with the experiment. It is shown that the 2D approximation appears to agree reasonably well with experimental results, and that the 3D calculation gives very good agreement with test data. The determination of the CZM parameters is also discussed. Numerical results show that the CZM is a workable computational model which involves only a few microstructurally motivated phenomenological parameters for crack extension simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00096.x
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    A COMMENTARY ON THE ROLE OF NITROGEN IN ENHANCING SLOW CRACK GROWTH IN C–Mn STEEL (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: More than two decades ago, cracks growing slowly at temperatures below the creep range were first discovered in tubing of C–Mn steel in thermal power plants. So far, no completely satisfactory explanation for such behaviour has been found. Available information on the influence of nitrogen on deformation and cracking of C–Mn steel under prevailing conditions, however, seems to indicate that this element may play a critical role in the failure in question. It appears that a mechanism involving both metallurgical and mechanical processes has to be considered more comprehensively and in a more integrated manner than is usually the case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00075.x
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    ESTIMATION OF TORSIONAL FATIGUE STRENGTH OF MEDIUM CARBON STEEL BARS WITH A CIRCUMFERENTIAL CRACK BY THE CYCLIC RESISTANCE-CURVE METHOD (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Near-threshold fatigue crack propagation tests were performed on circumferentially precracked round bars of a medium carbon steel under torsional loading. The crack propagation rate decreased with crack extension, because of the shear contact of crack faces. The crack propagation rate without the influence of crack-surface contact was determined by extrapolating to zero crack extension the relationship between the crack propagation rate and crack extension. The applied stress intensity factor range was divided into two parts: one was the effective value responsible for crack growth and the other was the value corresponding to crack-tip shielding. The resistance-curve method was used to predict the fatigue limit for crack initiation and fracture. The R-curve was constructed using the experimentally determined threshold value of the stress intensity range, which was the sum of the threshold effective stress intensity range and the threshold shielding stress intensity range. The threshold effective stress intensity range was constant. The R-curve was independent of the precrack length and specimen dimensions. The predicted values agreed well with the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00105.x
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    BIMODAL CONCEPT OF HIGH-CYCLE FATIGUE LIFE PREDICTION FOR CONSTANT AND VARIABLE AMPLITUDE FATIGUE (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A bimodal concept for the prediction of the high-cycle fatigue life of structural details subjected to constant- or variable-amplitude loading is considered in this paper. The total fatigue life was separated into two phases: crack initiation and crack propagation. The portion of life spent in crack initiation was estimated by using S–N data obtained on smooth specimens. A fracture mechanics concept was used to calculate the portion of life spent in crack propagation, and the S–N curve, including the fatigue limit of a structural detail, was determined by using material properties and the geometry of the detail. The bimodal concept was applied to a welded stiffener and the results are compared with experimental data reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00102.x
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    STATISTICAL MODELLING OF INTERGRANULAR BRITTLE FRACTURE IN A LOW ALLOY STEEL (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The intergranular brittle fracture (IBF) behaviour of a low alloy steel 16MND5 (A508 Cl. 3) was investigated. A temper embrittlement heat treatment was applied to the material to simulate the effect of local brittle zones (ghost lines) which can be found in the as-received material condition. An increase in the Charpy V toughness transition temperature and a significant decrease in the fracture toughness measured on CT-type specimens were observed in the embrittled material, as compared to the reference material which was submitted to the same austenitizing and tempering heat treatment, but which was not subjected to the temper embrittlement treatment. Tensile tests on notched specimens were carried out to measure the Weibull stress and scatter in the results. A statistical model, the Beremin model, originally proposed for brittle cleavage fracture was applied to IBF. It is shown that this model is not able to fully account for the results, in particular for the existence of two slopes in a Weibull plot. Systematic fractographic observations showed that the low slope regime in this representation was associated with the existence of MnS inclusions initiating brittle fracture, while the larger slope was related to microstructural defects. Initiation of IBF from MnS inclusions can occur when the material is still elastically deformed while the second population of microstructural defects is active in the plastic regime. A modified statistical model based on the Beremin model and taking into account these specific aspects is proposed in the framework of the weakest link theory. The parameters of this model are identified from test results on notched specimens. It is shown that this model is able to predict the temperature dependence of fracture toughness and the scatter in the experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00126.x
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    INFLUENCE OF PARTICLE SIZE AND VOLUME FRACTION ON DAMAGE AND FRACTURE IN Al–Al3 Ti COMPOSITES AND MICROMECHANICAL MODELLING USING THE GTN MODEL (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Six different Al–Al3 Ti composites were prepared via the powder metallurgy route. The size and volume fraction of Al3 Ti particles was varied for a systematic investigation of fracture behaviour. The dominant failure mechanism in the composites is particle fracture and void growth starting from the broken particles. In comparison with the pure Al–matrix, an incorporation of Al3 Ti particles reduces the crack initiation toughness and reduces the slope of the crack growth resistance curve. The inter-particle distance was found to be the main microstructural parameter controlling the slope of the crack growth resistance curve. The modified Gurson–Tvergaard–Needleman model (GTN model) was applied to one of the composites. The behaviour of tensile specimens could be successfully modelled, whereas the experimentally observed crack propagation in precracked single edge bend specimens [SE(B)] could not be simulated with the GTN model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00113.x
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    Probabilities of occurrence and detection of damage in airframe materials (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The reliability of airworthiness assessment and the effective management of ageing fleets of aircraft depend critically on the quality of tools for predicting damage nucleation and accumulation and its detection, i.e. on the interrelationship between the probabilities of occurrence and detection. To illustrate these interrelationships, a mechanistically based probability approach involving localized pitting corrosion and subsequent fatigue cracking is presented. A probability of detection based on a typical state-of-the-art technique for non-destructive evaluation is used for comparison and probabilistic assessment. The results suggest that the probability of detection is inadequate, and information on damage size should be included as part of an effective airworthiness assurance methodology. An appropriate target for detecting and sizing damage of ≈ 0.10 mm with a probability of detection and a confidence level of at least 90% is suggested, versus the current capability of 1.27 mm at only 50%
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00168.x
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    The characterization of fatigue crack growth behaviour by constant ΔK control testing (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Essential to the assessment of the fatigue integrity of critical components is the prediction of their crack propagation lives. This requires the effective and efficient characterization of the fatigue crack growth behaviour of the material when using a small number of specimens. A test facility, able to control the range of applied load (ΔP ) and range of stress intensity factor (ΔK ), has been used to determine the fatigue crack growth rates in corner notched specimens of Udimet 720 for stress ratios of 0.5, 0.1 and −1.0. Initially, the results were analysed in terms of the three-point secant data reduction method. Subsequently, the benefits to be gained by the use of alternative methods involving regression analysis have been examined. The effectiveness of the procedures has been assessed in terms of the extent to which they reduce the width of the scatter band representing the fatigue crack growth behaviour and the accuracy with which the experimental observed fatigue lives are predicted. On this basis, the results from the ΔK controlled tests were superior to those obtained under ΔP control, when analysed by similar data reduction methods. In addition, the results from ΔK tests were improved when the secant method was replaced by a linear regression method, which allowed the sample interval to be reduced and more levels of constant ΔK to be examined in a single specimen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00174.x
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  • 49
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    High-cycle fatigue of Ti–6Al–4V (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The definition of the critical levels of microstructural damage that can lead to the propagation of fatigue cracks under high-cycle fatigue loading conditions is a major concern with respect to the structural integrity of turbine-engine components in military aircraft. The extremely high cyclic frequencies characteristic of in-flight loading spectra, coupled with the presence of small cracks resulting from fretting or foreign object damage (FOD), necessitate that a defect-tolerant design approach be based on a crack-propagation threshold. The present study is focused on characterizing such near-threshold fatigue-crack propagation behaviour in a Ti–6Al–4V blade alloy (with ~60% primary α in a matrix of lamellar α + β), at high frequencies (20–1500 Hz) and load ratios (0.1–0.95) in both ambient temperature air and vacuum environments. Results indicate that ‘worst-case’ thresholds, measured on large cracks, may be used as a practical lower bound to describe the onset of naturally initiated small-crack growth and the initiation and early growth of small cracks emanating from sites of simulated FOD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00194.x
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    Application of ultrasound for fatigue testing of lightweight alloys (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The use of aluminium and magnesium alloys offers a great potential for weight reduction in automotive applications. Load-bearing car components are subjected to 108 cycles and more during service, and the high-cycle fatigue properties of construction materials are therefore of great interest.The time-saving ultrasound fatigue testing method has been used to study the fatigue properties of a high-pressure, die-cast magnesium alloy AZ91 hp and a post-forged, cast-aluminium alloy AlSi7Mg0.3 in ambient air and saltwater (5wt% sodium chloride) spray. In ambient air, fatigue cracks in AZ91 hp emanate from voids, and it is possible to correlate void areas with the numbers of cycles-to-failure. Post-forging of AlSi7Mg0.3 reduces the numbers and size of voids. The remaining small voids (void areas smaller than 9000 μm2 ) do not significantly reduce lifetimes. Saltwater deteriorates the fatigue properties of both the lightweight alloys. With increasing numbers of cycles, the influence of the corrosive liquid on fatigue strength becomes more pronounced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00205.x
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    Competing roles of microstructure and flaw size (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Historically, engineers have relied on macroscopic properties, e.g. hardness and tensile strength to predict fatigue limits as analytical tools to model the process did not exist. Consequently, many empirical modifications to the fatigue limit have been made to account for variables, e.g. surface roughness, state of stress, inclusion content, environmental effects, etc. A mechanistic model is proposed to quantify the effects of these parameters on the fatigue limit of metals, specifically steels. Fatigue resistance, i.e. the threshold condition of a non-propagating crack, is determined by two parameters: non-propagating defect or crack size; and the strength of the barrier to crack propagation. The concept of three defect types associated with three different flaw-dominated fatigue regimes is introduced. Furthermore, application of the model to fatigue mechanisms in high-strength steels, synergistic effects of surface finish and intergranular cracks, competition between surface and subsurface fatigue nucleation, tempering, and scatter in fatigue behaviour is demonstrated. The model can be implemented in material screening, selection and processing, as well as a guide for future material research and design. Overall, the model is proven as a simple and robust tool for qualifying and statistically quantifying material behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00190.x
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    REPRESENTATION OF CYCLIC PROPERTIES OF AUSTENITIC STEELS WITH PLASTICITY-INDUCED MARTENSITIC TRANSFORMATION (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study is part of a wider research project on the cyclic properties, energy cumulation and fatigue life of metastable austenitic steels undergoing a martensitic transformation induced by plastic straining.This paper considers the representation of the σ–ε hysteresis loop over a wide range of strain. A novel, power-function model of cyclic elastic–plastic material behaviour was used. The model allows the occurrence of a cyclic yield point and the characteristic inflection point of the CSS curve, which separates the single-phase (austenite) region from the two-phase (austenite + martensite) one. The plastic strain corresponding to the inflection point is assumed to be a material constant and is termed the martensitic transformation cyclic limit ε1 . The generalization of the model made possible the representation of cyclic softening of the two-phase material.In addition, the study chose a measurement technique that assisted the estimation of the cyclic plastic strain (ε1 ) inducing the martensitic transformation. The crossed magnetomechanical (Villari) effect was shown to be applicable in detecting the nucleation and estimating the increase of the α′-martensite content.The identification was performed making use of experimental results obtained from an AISI 304 high nickel content steel. The tests were performed under both increasing and constant plastic strain amplitude. The measured quantities were: total strain εt elastic strain εe , plastic strain εp , stress σ and hysteresis loop area ΔW. The results justify the assumed model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00086.x
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    ERRATUM (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00001.x
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  • 54
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    INFLUENCE OF INTERMEDIATE LOADING RATES AND TEMPERATURE ON THE FRACTURE TOUGHNESS OF ORDINARY CARBON–MANGANESE STRUCTURAL STEELS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Three-point bend and compact tension specimens, taken from beam sections of modern and older ordinary C–Mn structural steels, were tested at intermediate loading rates at room temperature and −30 °C. The experimental work, except the loading rates used, was performed according to ASTM E-813. In order to investigate transferability of data, full-scale beam sections were also tested at intermediate loading rates. The fracture toughness of C–Mn structural steels depends strongly on the loading rate, and decreases rapidly with increasing loading rate at and just above the maximum prescribed in ASTM E-813. Fracture toughness data for structures exposed to intermediate loading rates indicate the requirement for testing at appropriate loading rates. The behaviour of full-scale structural elements subjected to intermediate loading rates can, provided certain conditions are fulfilled, be predicted from data obtained from small laboratory specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00066.x
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  • 55
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    A BOUNDARY ELEMENT MODEL OF PLASTICITY-INDUCED FATIGUE CRACK CLOSURE (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper describes a plane stress boundary element model of plasticity-induced fatigue crack closure. A simple Dugdale-type strip yield zone is used and quadratic programming techniques are employed to establish crack shape, stress and plastic deformation. The technique is extremely effective and the model can be readily implemented on a personal computer. Predictions of crack closure behaviour are produced for cracks growing under constant amplitude loading, and also following an overload or overload/underload cycle. These results are compared with an empirical R-ratio correction due to Walker and with experimental measurements taken from the literature. The model is found to give good predictions of crack behaviour under constant amplitude loading. Predictions for crack closure levels following an overload cycle give qualitative agreement with experimental results; the differences observed may well be due to the different definition of crack closure in the experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00071.x
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    INFLUENCE OF SURFACE DEFORMATION AND ELECTROCHEMICAL VARIABLES ON CORROSION AND CORROSION FATIGUE CRACK DEVELOPMENT (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents experimental data for a 0.2%C steel/artificial seawater system showing the influence of shear loading on corrosion response, via measurements of electrochemical variables, e.g. anodic/cathodic Tafel slopes and polarization resistance. Based on the results of these tests, several corrosion fatigue tests were conducted at different stress levels under potentiostatic control. Analysis of the results shows there to be a dependence of corrosion rate on the ratio of applied/yield strain and test frequency. In addition, the corrosion current associated with corrosion fatigue (CF) damage appears to be dependent upon the crack size, which in turn shows a relationship with fatigue crack growth rate. This paper sets out to determine the influence of stress on electrochemical parameters, i.e. free corrosion potential, Ecorr , polarization resistance, Rp , anodic, τa and cathodic, τc Tafel constants. Based upon these results, it is found that a simple linear relationship between stress and corrosion damage does not exist. Furthermore, analysis of the corrosion current fluctuations during corrosion fatigue crack growth shows a minimum current coincident with the point at which a crack is growing at its slowest rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00074.x
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  • 57
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    Fatigue crack growth in a structural steel under single and multiple periodic overload cycles (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Preliminary results of a research program on fatigue crack growth in a low-carbon steel under a variable amplitude loading are presented. First, test results are reported on crack growth under simple loading sequences containing single and multiple tensile overloads applied periodically between smaller, constant amplitude cycles. Next, the observed crack growth behaviour is compared to predictions from a theoretical model developed by the authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00219.x
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    Intersonic mode II crack acceleration (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An analytic solution is given for intersonic mode II crack acceleration. The solution is obtained by first considering a self-similar problem, motion of a semi-infinite crack at constant velocity, under the action of a constant crack face load, appearing behind the crack edge. This solution is then repeatedly used in a superposition scheme, which finally yields the solution for an accelerating crack.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00129.x
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  • 59
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    SURFACE FLAWS IN CYLINDRICAL SHAFTS UNDER ROTARY BENDING (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The propagation of a surface flaw in a cylindrical shaft subjected to rotary bending is analysed using a two-parameter theoretical model. The stress-intensity factor distribution along the crack front is numerically determined for any position of the flaw with respect to the bending moment axis. The crack front is assumed to present an elliptical-arc shape with aspect ratio α = a/b (a, b = ellipse semi-axes), whereas the relative depth ξ of the deepest point on the front is equal to the ratio between the maximum crack depth, a, and the bar diameter, D. The results for rotary bending are compared to those for reversed cyclic bending.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00120.x
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    A normalization of corrosion fatigue behaviour: an example using an offshore structural steel in chloride environments (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A normalized presentation of the metal fatigue process is proposed and applied to the corrosion fatigue behaviour of an offshore structural steel under different loading conditions. Corrosion fatigue development in this steel under different stress levels and frequencies is presented in both ‘normal’ and ‘normalized’ terms. Experimental results on pitting and corrosion fatigue-crack growth are used to introduce the new normalized presentation approach, which may be employed to illustrate the corrosion fatigue behaviour of any given metal/environment system. This allows a description of the initiation and growth of defects to be made, involving both time-dependent and cycle-dependent stages. It is suggested that a set of dependencies between fatigue-characterizing parameters may be presented in graphic form and used as a ‘fatigue certificate’ for any given metal/environment system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00169.x
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    A two-dimensional elastic–plastic finite element analysis of friction effects on sliding crack surfaces in full or partial contact (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Sliding crack surfaces are analysed, that are completely or partially in contact, using a two-dimensional plane-stress elastic–plastic finite element technique. Our in-house program was modified to account for the friction which acts between two rough mating surfaces. The analysis is applied to a cantilever beam cracked along its span through its centroidal plane. Twelve cracks with length-to-span ratios ranging from zero to 0.5 were analysed. The effect of friction was investigated by considering 0, 0.4, 0.8, 1.2 and 1.6 as values for the coefficient of friction with each crack length. The results show the influence of friction on the beam stiffness, strain energy release rate, modes of crack tip and surface displacements, and the development of plastic deformation. The present finite element outputs assist in the explanation of experimental events associated with mode II crack tip displacement data found in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00143.x
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    Fatigue striation formation in an Fe–3%Si alloy—effects of crystallographic orientation and neighbouring grains (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In order to know the criterion of fatigue striation formation, fatigue fracture surfaces and crack paths were investigated in Fe–3%Si single and bicrystals having various crystallographic orientations. On single crystals, striations were formed when the loading direction was close to a 〈110〉 direction. In this direction, the crack grew perpendicular to the loading direction. When the loading direction was near a 〈111〉 direction and the crack grew along an inclined plane, no striations were observed. Even in this orientation, when the crack grew perpendicular by necessity using bicrystals, striations were observed. This suggests that striations are not formed on a special crystallographic plane, but are formed when the fatigue crack plane is perpendicular to the loading direction regardless of crystallographic orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00150.x
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    Effects of a single tensile overload on fatigue crack growth in a 316L steel (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The aim of this study was to investigate the effects of a single tensile overload on subsequent fatigue crack growth in a 316L stainless steel. Fatigue tests were conducted under the plane stress condition, and further supplemented with compliance measurements and field emission scanning electron microscopy (FESEM) observations. Effects of a tensile overload, e.g. initial acceleration and subsequent retardation of fatigue crack growth, were explained and quantified by FESEM and compliance measurements. The FESEM observations suggest that the initial crack growth acceleration stems from void and quasi-cleavage fracture within the fatigue damage zone in the vicinity of the crack tip. Systematic compliance measurements taken during fatigue crack growth suggest that the overall crack growth retardation is related to strain hardening and residual compressive stress produced by the plastic deformation associated with the tensile overload.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00225.x
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    An ultimate crack resistance concept (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A two-parameter fracture criterion is discussed in terms of an ultimate crack resistance concept. The difference is found between the failure assessment diagram and the ultimate crack resistance. The concept of an ultimate crack resistance provides one with the ability to estimate crack resistance behaviour in cases of brittle, ductile and intermediate fracture states with the customary use of stress intensity factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00229.x
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    An upper bound limit load for overmatched scarf-joint specimens (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A simple kinematically admissible velocity field involving single jump lines is proposed to find an upper bound limit load for overmatched scarf-joint specimens. It is shown that the solution based on the chosen velocity field depends on two dimensionless parameters, while the number of essential dimensional parameters is four. This is a great advantage for engineering applications. The results, for a particular case, are compared with a similar solution for centre-cracked tensile specimens and one which is obtainable from the new solution as a particular case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00233.x
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    Fatigue strength of crack-healed Si3N4/SiC composite ceramics (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Si3 N4 /SiC composite ceramics were sintered and subjected to three-point bending on specimens made according to the appropriate JIS standard. A semi-circular surface crack of 110 μm in diameter was made on each specimen. By using three kinds of specimen (smooth, cracked and crack healed), crack-healing behaviour, cyclic and static fatigue strengths were determined systematically at room temperature and 1000 °C. The main conclusions are as follows: (i) Si3 N4 /SiC composite ceramics have the ability to heal after cracking; (ii) crack-healed specimens showed similar cyclic and static fatigue strengths as smooth specimens, this being caused by crack healing; (iii) crack-healed zones had a sufficient fatigue strength and most fractures occurred outside the pre-cracked zone in those crack-healed specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00210.x
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    Effects of notch geometry on the local cleavage fracture stress σf (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An elastic–plastic finite element method (FEM) is used to analyse the stress and strain distributions ahead of notches with various depths and flank angles in four-point bending (4PB) specimens of a C–Mn steel. By accurately measuring the distances of the cleavage initiation sites from the notch roots, the local cleavage fracture stress σf is measured. By increasing the notch depth and notch flank angle from 2.25 to 8.25 mm and 10 to 90°, respectively, the distributions of high stress and strain at the moment of fracture show considerable variations. However, the value of σf stays relatively constant. The critical fracture event is thus shown to be identical, i.e. the propagation of a ferrite grain-sized crack into the neighbouring matrix. It is concluded that σf is mainly determined by the length of the critical microcrack, while the notch geometry and its associated stress volume have little effect on the value of σf . The cleavage site ahead of a notch is determined by the stress distributions and the positions of the weakest grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00222.x
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  • 68
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    Fatigue behaviour of a box-welded joint under biaxial cyclic loads (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Multiaxial fatigue behaviour of box-welded (wrap-around) joints in a JIS SM400B steel (12-mm-thick plate) was examined using a biaxial fatigue test facility. For the specimen, two stiffeners were attached to a main plate by a CO2 semi-automatic welding procedure. Residual stress measurements and finite element (FE) analyses were also performed. Fatigue tests were performed under both uniaxial and biaxial (mainly out-of-phase) cyclic loads, and both results were compared and examined.It was found that fatigue cracks in the biaxial fatigue test specimens were initiated at the boxing-weld toes and propagated almost in the direction of the lateral loads. This is considered to be due to the dominant direction of tensile residual stresses from welding and the stress concentration in the vicinity of the boxing-weld toe.From the relation between the strain range near a weld toe, Δε5 , and the fatigue lives, it was found that crack initiation life, Nc , was almost equivalent in the biaxial and uniaxial fatigue tests, while the failure life, Nf , was slightly longer in the biaxial tests. However, when the fatigue lives are put in order using the stress range near a weld toe, Δσ5 , the crack initiation life, Nc , in the out-of-phase biaxial tests (phase difference of π) is ~30% lower than in the in-phase biaxial and uniaxial tests, while the failure life, Nf , was almost equivalent in the biaxial and uniaxial tests. From these results, it is concluded that an increase in Δσ5 (lowering of the minimum value of σ5 ), induced by the out-of-phase lateral loads, leads to an increase in fatigue damage where the high tensile welding residual stresses exist in the vicinity of the boxing-weld toe.Finally, a simple life estimation for the biaxial fatigue tests was made using FE analyses and the results of the uniaxial fatigue tests, proving that the effects of the lateral loads should be taken into consideration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00224.x
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    The crack-modelling technique: optimization of parameters (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The crack-modelling technique is a method for prediction of fatigue in components using finite element (FE) analysis. The technique, which is based on the estimation of equivalent K factors for stress-concentrators, has had some initial success in analysing components of complex shape, but this has raised a number of questions about the potential accuracy of the method and its sensitivity to the choice of operating parameters. The present paper reports on a systematic study using four different specimen types and one component geometry. Accurate estimates of equivalent K values are shown to be possible for both sharp notches and blunt notches, loaded in uniaxial tension or bending, using a very simple approach in which the stress distribution from the notch is compared to that from a standard cracked body. The method shows some sensitivity to the optimization routines used, and to some extent to the choice of the standard cracked body. It is relatively insensitive to mesh refinement and can be used with simple, elastic FE models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00135.x
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    Stress singularities in composite wedge-shaped materials (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Calculations of the stress singularity in the vicinity of the tip of two bonded wedges are described. Plasticity in the near-tip region is accounted for within the framework of the Ramberg–Osgood relation. It is shown that the singularity can be larger for two bonded wedges than for a single wedge, and figures are presented to indicate how the stress singularity depends on the relevant parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00138.x
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    Retrogression, reaging and residual stresses in 7010 forgings (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Open die forgings of the aluminium alloy 7010 (DTD5636) have been retrogressed at temperatures between 200 and 240 °C and then reaged (RRA). Tensile, fracture toughness and stress corrosion cracking values are reported. Retrogression at 200 °C offers the most promising combination of properties, and the long retrogression time of approx. 2500 s will enable thick sections to be treated. Residual stresses induced during quenching are also predicted, and initial experimental results suggest that some stress relief occurs during the retrogression heat treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00137.x
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    A finite element model for crack arrestor design in gas pipelines (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Steel rings are frequently used as crack arrestor devices in steel gas transmission pipelines to prevent the possibility of long running axial cracks. These arrestors have the effect of reducing the pipe opening as the crack propagates. This decreases the available crack driving force and, as a result, crack arrest can take place. This essentially is a second line of defence against catastrophic failure in the event that crack initiation cannot always be prevented. This paper describes a novel analysis methodology that has been developed to investigate the suitability of these crack arrestors. This is based on a fluid/structure/fracture interaction package, PFRAC. Here, a curved beam element has been implemented into PFRAC to simulate the behaviour of the arrestor. The contact conditions between the pipe wall and the arrestor, along with the various computational procedures, are described here. Several numerical results for a cracked pipe with arrestors are presented along with comparisons with pipes that do not have arrestors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00139.x
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    A NOTCH INTENSITY FACTOR APPROACH TO THE STRESS ANALYSIS OF WELDS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In the context of linear elastic stress gradients that are present in welded joints, a stress field approach based on notch stress intensity factors is presented with the aim of describing stress distributions in the neighbourhood of weld toes, since fatigue strength is dependent on such distributions. This paper summarizes the analytical fundamentals and gives an appropriate definition of the parameters for stress components under opening and sliding modes. Then, by comparing the expected results with those obtained by numerical analysis, the contributions of the symmetric and skew-symmetric loading modes are quantified for different geometries, and summarized into concise expressions which also take into account the influence of the main geometrical parameters of the welded joint. The range of validity and the application limits of this field approach in the presence of weld toe radii are discussed. Finally, a synthesis of experimental fatigue strength data based on the new field parameters is reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00097.x
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    R-CURVE TESTING AND ITS RELEVANCE TO STRUCTURAL ASSESSMENT (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Crack growth resistance can be substantially affected by the constraint conditions of a structural member which in turn are mainly a function of geometrical variables and the degree of plasticity. Standardized test methods are restricted to high constraint conditions as represented by deeply cracked bend-type specimens and may hence lead to conservative structural assessments. It is demonstrated that adjusted testing can be used to reduce the degree of conservatism. Due to rapidly increasing computer capabilities, a combination of conventional R-curve testing with micromechanical models emerges as an accurate tool which may permit routine evaluations of practical situations in the near future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00110.x
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    Influence of microstructure of (α+β) Ti-6.2.4.6 alloy on high-cycle fatigue and tensile test behaviour (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Tensile and gigacyclic fatigue behaviour of Ti–6Al–2Sn–4Zr–6Mo alloy were investigated as a function of lamellar primary α- and β-transformed microstructures. Three thermomechanical processes (TP1, TP2, TP3) were selected to produce different combinations of microstructural features on two slightly different compositions of the alloy (A and B). Ultrasonic fatigue tests were performed in air and liquid nitrogen at a frequency of 20 kHz (R = −1, T = 300 and 77 K), giving fatigue tests up to 109 cycles. Microstructural features and the fracture initiation dependence on the primary α lamellar phase were observed by SEM and/or characterized by quantitative image analysis. It has been found that the microstructure of alloy B produced by TP1 represents a better compromise between resistance to initiation and resistance to microcrack growth. Quicker initiation occurs in coarser α-platelets (TP2, alloy B), and the continuous partially transformed β matrix appears to effectively decrease the tensile and HCF resistance. The bimodal structure (TP3, alloy B) has the best resistance at room temperature, but the presence of a coarse globular phase decreases this fatigue resistance at low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.t01-1-00197.x
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    Fracture mechanisms and fracture mechanics at ultrasonic frequencies (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Performing fatigue tests at ultrasonic frequencies, e.g. 20 000 Hz, allows one to perform experiments beyond 109 and 1010 cycles within half a day or a week, respectively. The testing technique has led to the construction of fatigue machines of high technical standard. Use of the ultrasound technique to study the mechanisms of crack initiation in pure metal single crystals, in cast alloys with voids being crack initiation sites, and in complicated fibre-reinforced laminates is reported. Likewise, use of ultrasonic loading to study the mechanisms of crack propagation is discussed, as well as LEFM principles; especially when these principles cannot be applied. It is shown how crack growth retardation with increasing crack length is attained in fibre-reinforced laminates by the effect of fibre bridging. Additional experimental possibilities, e.g. random loading, variation of mean load, superposition of shear loads, variation of temperature and environment, and not only axial but also torsional loading at ultrasonic frequency, and recent research results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00180.x
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    The fatigue limit and its elimination (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The classical fatigue limit of ferrous metals is a consequence of testing materials at a constant range of cyclic stress and determining the cyclic stress range below which fatigue failures do not occur. This classical fatigue limit of a material is equated to the condition for which fatigue cracks can not propagate beyond microstructural barriers.This paper discusses the causes leading to the elimination of this fatigue limit, including the introduction of transitory cyclic-dependent mechanisms and time-dependent processes that will permit a previously non-propagating crack to grow across the different threshold states expressed in terms of linear-elastic fracture mechanics (LEFM), elastic–plastic fracture mechanics (EPFM) and microstructural fracture mechanics (MFM).These transitory mechanisms and processes include different loading and environmental conditions, which in a long-life engineering plant (e.g. 30 years lifetime) can lead to apparently premature failures. Of greater concern is the creation of a new crack-initiation zone, i.e. a transfer from a surface-generated crack to an internal-generated crack that eventually dominates the fatigue failure event.The impact of these conditions on the elimination of the classical fatigue limit necessitates changes in Design Codes of Practice, and such changes are discussed in relation to the extremely long-lifetime regime (107 〈 Nf 〈 1012 cycles-to-failure) which is increasingly applicable to the modern day engineering plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00204.x
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    Three-dimensional calculations of high cycle fatigue life under out-of-phase multiaxial loading (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this study, we investigate the prediction of fatigue life at a high number of cycles (〉5 × 104 cycles) for three-dimensional structures. An approach has been developed that includes the results of fatigue tests in a program using the finite element method. Numerical fatigue life calculations using three fatigue criteria were conducted to predict S–N curves. To complete the study and validate this approach, tests were carried out on FGS 700/2 cast iron with different geometrical structures and different fatigue loadings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00172.x
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    Interaction and evolution of short fatigue cracks (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Distinguishing the different contributions to fatigue damage of short cracks having different sizes and locations on the specimen surface, three new concepts, referred to as effective short fatigue cracks (ESFCs), dominant effective short fatigue cracks (DESFC), and density of ESFCs, respectively, are introduced to facilitate an understanding of the mechanism of interaction and evolution of short cracks. These concepts are interrelated and in conjunction produce an ‘effective short fatigue crack criterion’. Replica observations of 19 smooth axial specimens of 1Cr19Ni9Ti stainless steel weld metal during low-cycle fatigue tests reveal that the short cracks contribute to the fatigue damage of specimens due to the formation of a critical density of ESFCs. The density reflects the local microstructural growth conditions ahead of the DESFC tips. The DESFC behaviour is a result of interactive short cracks, and this behaviour is deemed suitable to describe the collective behaviour of short cracks. In the microstructural short-crack stage, the DESFC are located in the weakest zone. Due to an irregular microstructural barrier effect, the crack density is higher in this zone and increases with fatigue cycling to reach a maximum value at the transition point into the physical short-crack stage. Then, due to the effects of accelerating coalescence and the DESFC size shielding the formation of new cracks, the density decreases rapidly and tends gradually to a saturation value. This is why the short-crack growth rate is high initially and tends gradually to that of long-crack behaviour. The difference and change in local microstructural growth conditions ahead of DESFC tips are the intrinsic cause of the statistical behaviour of short cracks and the scatter of fatigue lives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00195.x
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    A note on the limit load of welded joints of a rectangular cross-section (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A flat layer of a rigid perfectly plastic material subjected to tension between two rigid blocks is considered. The layer is assumed to have a rectangular cross-section. The influence of the ratio of the in-plane layer dimensions on the limit load and the maximum tensile stress is studied. Comparison with numerical calculations of the limit load based on the assumption of the plane strain conditions is made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00167.x
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    Stepwise S-N curve and fish-eye failure in gigacycle fatigue (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue failure is normally initiated at the surface of a material. For some materials, failure can be initiated both at the surface and the interior. This twofold materials behaviour in fatigue is represented by a stepwise shape in the S–N curve. An internal failure mode is especially important for fatigue life in the gigacycle range, as this mode is predominant at low stress ranges.Materials with a hardened surface fail from the surface only at high stresses, and at low stresses from the inside, forming a fish-eye facet on the fracture surface. Exactly the same behaviour can be observed for materials without a hard surface, even at elevated temperatures. This paper displays some of the results obtained at NRIM and discusses possible interpretations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00206.x
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    Modelling of initial fatigue crack growth and crack branching under fretting conditions (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Crack propagation during Stage I, in terms of crack initiation sites and growth directions and crack branching mechanisms under fretting conditions, is investigated using both experimental and theoretical approaches. Fretting tests were conducted on an aeronautical aluminium alloy. Two crack types are observed during Stage I corresponding, respectively, to specific mode I and II conditions. Transition from Stage I to Stage II is characterized for both crack types by a crack branching towards a new propagation direction of ≈65° to the specimen surface. Specific parameters linked to mode I and II propagation driving forces are proposed. Crack location and initial growth directions during Stage I are predicted in accordance with these parameters, and are in very good agreement with experimental observations. The conditions governing the transition from Stage I to Stage II are then identified. It is shown that under fretting conditions, cracks branch along a new direction, thereby maximizing the crack-opening amplitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00173.x
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    A Weibull stress model to predict cleavage fracture in plates containing surface cracks (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This study applies recent advances in probabilistic modelling of cleavage fracture to predict the measured fracture behaviour of surface crack plates fabricated from an A515-70 pressure vessel steel. Modifications of the conventional, two-parameter Weibull stress model introduce a non-zero, threshold parameter (σw-min ). The introduction of σw-min brings numerical predictions of scatter in toughness data into better agreement with experimental measurements, and calibration of this new parameter requires no additional experimental data. The Weibull modulus (m) and scaling parameter (σu ) are calibrated using a new strategy based on the toughness transferability model, which eliminates the non-uniqueness that arises in calibrations using only small-scale yielding toughness data. Here, the Weibull stress model is calibrated using toughness data from deep-notch C(T) and shallow-notch SE(B) specimens, and is then applied to predict the measured response of surface crack plates loaded in different combinations of tension and bending. The model predictions accurately capture the measured distributions of fracture toughness values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00202.x
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    The role of reinforcement particles during fatigue cracking of a micral-20™-reinforced 6061 alloy (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00200.x
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    Fatigue damage mechanisms associated with ‘tear-drop’ cracking in UDIMET 720® (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00207.x
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  • 86
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    Upper bound limit load solutions for a round welded bar with an internal axisymmetric crack (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00208.x
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  • 87
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    Technical note High-cycle fatigue crack initiation and propagation behaviour of high-strength sprin steel wires (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An attempt has been made to characterize high-cycle fatigue behaviour of high-strength spring steel wire by means of an ultrasonic fatigue test and analytical techniques. Two kinds of induction-tempered ultra-high-strength spring steel wire of 6.5 mm in diameter with a tensile strength of 1800 MPa were used in this investigation.The fatigue strength of the steel wires between 106 and 109 cycles was determined at a load ratio R = −1. The experimental results show that fatigue rupture can occur beyond 107 cycles. For Cr–V spring wire, the stress–life (S–N ) curve becomes horizontal at a maximum stress of 800 MPa after 106 cycles, but the S–N curve of the Cr–Si steel continues to drop at a high number of cycles (〉106 cycles) and does not exhibit a fatigue limit, which is more correctly described by a fatigue strength at a given number of cycles. By using scanning electron microscopy (SEM), the crack initiation and propagation behaviour have been examined. Experimental and analytical techniques were developed to better understand and predict high-cycle fatigue life in terms of crack initiation and propagation. The results show that the portion of fatigue life attributed to crack initiation is more than 90% in the high-cycle regime for the steels studied in this investigation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.t01-1-00184.x
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  • 88
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    Determination of S–N curves with the application of artificial neural networks (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The present paper describes the application of artificial neural networks for estimating the finite-life fatigue strength and fatigue limit. A comprehensive database with results of single-stage tests on specimens which simulate structural components is evaluated and prepared for processing with the use of neural networks. The available data are subdivided into different classes. A total of six different data classes are specified. The results of the prediction by means of neural networks are superior to those obtained with conventional methods for calculating the fatigue strength. The experimental results are estimated with high accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.t01-1-00198.x
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  • 89
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    There is no infinite fatigue life in metallic materials (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Generally, the shape of the S–N curve beyond 107 cycles is unknown except in some statistical approaches, and this is also true for the fatigue limit. In the case of a statistical approach, the standard deviation applied to the average fatigue limit is certainly not the best way to reduce the risk of rupture in fatigue. Only the exploration of the life range between 106 and 1010 cycles will create a safer basis for modelling.Today, some piezoelectric fatigue machines are very reliable, capable of producing 1010 cycles in less than 1 week. We based our research on accelerated fatigue tests which were performed at 20 kHz in the gigacyclic fatigue regime in order to study several typical alloys from the aeronautical and space industries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00183.x
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  • 90
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    Load interaction effects during fatigue crack growth under variable amplitude loading—a literature review. Part II: qualitative interpretation (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The current understanding of the underlying reasons behind the load interaction effects in fatigue crack growth under variable amplitude loading is presented. Mechanistic arguments proposed to control the load interaction phenomena are reviewed and evaluated based on their capability to qualitatively explain empirical trends in variable amplitude fatigue crack growth summarized in Part I [Fatigue Fract. Engng Mater. Struct. 1998, 21(8), 987–1006] of the present paper. Mechanisms linked to plastic straining at the crack tip enable an interpretation of the majority of the experimental results. Some observations, however, which cannot be understood in terms of plasticity-induced crack closure, or which are even in contradiction with the crack closure approach, indicate a possible role of other factors. A general conclusion is that conditions under which various phenomena can affect variable amplitude fatigue crack growth and interactions between them are insufficiently recognized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00158.x
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  • 91
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    An interpretation of the Ct parameter for increasing load conditions (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The prior assessment equations for Ct , which is a well-known fracture parameter for characterizing creep and creep–fatigue crack growth rates, have applicability to constant loading conditions only. However, crack growth due to creep can also occur under varying load conditions during a fatigue cycle when the loading (or unloading) rate is slow enough such that creep deformation can occur near the crack tip. Hence, the applicability of the Ct parameter should be extended to varying load conditions.In this study, a method of extending the use of the Ct parameter to increasing load conditions is proposed. Based on the concept of Irwin’s effective crack size, new equations for estimating Ct under increasing load conditions are derived and denoted as (Ct )r . Finite element analyses were also performed under various increasing load conditions. From the analysis, the variation of (Ct )r values during the load rise period is obtained and the difference between the (Ct )r value at the end of the load rise period and the Ct value at the beginning of the succeeding load hold period is discussed. A generalized creep–fatigue crack growth model which employs (Ct )r as a parameter characterizing crack growth rate during the rise time is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00221.x
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  • 92
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    Fatigue of cemented hip replacements under torsional loads (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue resistance of hip replacement prostheses is becoming ever more important as the operation is carried out on younger and more active patients. Torsional loading of the implant, which occurs especially during activities, such as rising from a chair or climbing stairs, is implicated in the failure process. To examine fatigue failure of the implant–bone fixation, which is made using polymethylmethacrylate cement, an experimental model was designed and 16 specimens tested at torsional moments of 50 Nm and 80 Nm to both 1 and 2 million cycles. The numbers and lengths of cracks initiated under cyclic loading were quantified using dye penetrant to highlight the cracks and a profile projector to magnify them. The majority of cracks initiated from the PMMA/metal and PMMA/bone interfaces, more often than from pores in the PMMA. A bimaterial fracture mechanics analysis confirmed that the interfaces are too weak to sustain in vivo levels of cyclic loading. It is proposed that, under torsional loading, fatigue failure of PMMA fixated implants originates from pores located on the interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00134.x
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  • 93
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    Fracture modelling of WC-Co hardmetals using crystal plasticity theory and the Gurson model (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The behaviour of edge cracks under Mode I loading in the WC–Co material system is studied using the finite element method (FEM). This work focuses on ductile failure mechanisms in the Co binder. A micromechanical approach is taken whereby Co layers are modelled explicitly. An embedding technique is employed. Crystal plasticity theory and J2 flow theory are used to represent plastic deformation in Co ligaments. Areas of high hydrostatic stress, triaxiality and accumulated slip or effective plastic strain are identified within the binder material. The Gurson model is used to model crack growth in the Co ligaments. Fracture resistance curves are obtained giving a relationship between macroscopic material behaviour and microscopic failure mechanisms. Factors effecting the crack growth in single and multiple ligaments are identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00153.x
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  • 94
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    A VIEW ON DUCTILE-FRACTURE MODELLING (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
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    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Theoretical models of ductile fracture are reviewed in terms of experimental results from metallurgical studies of ductile fracture in metals and alloys. It is shown that the plastic limit-load model, which is based on a criterion of void coalescence by internal microscopic necking of the intervoid matrix, is fully consistent with scanning electron microscope (SEM) observations of both the ductile-fracture surface and the microstructure immediately adjacent to the fracture surface. On the other hand, the dilational-plastic models of ductile fracture, which are based on the dilational-growth of spherical voids to some arbitrary critical void-volume fraction, are inconsistent with the microstructural observations of ductile fracture. This inconsistency between the dilational-plastic models and experimental results is shown to be the combined effect of neglecting the controlling influence of extensional void-growth and the failure to incorporate a physically realistic criterion of void coalescence.The problems of modelling the ductile crack-growth process by both analytical and numerical (finite element) studies, where problems of uniqueness of the plastic velocity field may occur, are also considered. The limitations of the finite-element method in modelling void-coalescence problems, where the equations of plasticity are of second-order hyperbolic form, are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00077.x
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    STATISTICAL ANALYSIS OF DEFECTS FOR FATIGUE STRENGTH PREDICTION AND QUALITY CONTROL OF MATERIALS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A wide range of studies and experimental evidence have shown that the lower bound of fatigue properties can be correctly predicted by considering the maximum occurring defect size. The estimate of this dimension can be done by analysing the defect sizes using the statistics of extremes.The scope of this paper is to discuss and investigate the two key points in a successful application of this technique: the first is the choice of statistical method for the analysis of data; the second is the knowledge of the minimum number of defects needed to obtain a good estimate of extreme defects.The results obtained in this study allow one to formulate a procedure for estimating the extreme defects with a precision suitable for fatigue strength prediction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00104.x
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    FATIGUE CRACK PROPAGATION IN AUSTENITIC STAINLESS STEEL UNDER LOW FREQUENCY LOADING AND SALT WATER CONDITIONS (1998)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 21 (1998), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue crack growth rates (FCGR) for a steel similar to AISI 316LN have been evaluated in air and salt water. At free corrosion potential, a short crack effect appeared for crack lengths shorter than 4 mm. For longer cracks, a segment (called region I) of the corrosion FCGR curve can be described by an equation with the same coefficients as for steels of ordinary resistance to corrosion. Thus, the process controlling crack propagation is presumably the same for both steels. Corrosion FCGR in region II (range of longer crack lengths and higher ΔK values, where the curve cannot be described by the previously mentioned equation) are slower than for ordinary steels. The plateau in FCGR observed at a cathodic potential corresponds to the higher plateau at the free corrosion potential. An interpretation is presented for the shape of the corrosion FCGR curves at both potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00060.x
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  • 97
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    Crack-tip plastic blunting under gross section yielding and implications for modelling physically short cracks (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.00209.x
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  • 98
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    A unification of small- and large-crack growth laws (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A generalized model enhancement is proposed to link small- and large-crack growth laws. The enhancement is based on crack growth rate laws with crack tip plastic zone size formulations. Transition functions are used to transform small-crack plastic zone sizes and crack growth law exponents to those predicted by linear-elastic fracture mechanics. In doing so, influences on crack growth, e.g. constraint, crack aspect ratio and specimen geometry are accounted for. The applicability of the enhancement is directed toward instances where small cracks start from geometric features and grow through stress gradients to eventually become large cracks under nominal LEFM conditions. The enhancement is applied to the Wang model, and crack growth rate and fatigue lifetime predictions are made. The enhancement is shown to provide a good correlation to experimental results for Ti–6Al–4V under various maximum stresses at a stress ratio of R = 0.4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.t01-1-00149.x
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  • 99
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    Closure-free biaxial fatigue crack growth rate and life prediction under various biaxiality ratios in SAE 1045 steel (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Biaxial fatigue tests were performed on thin-walled tubular 1045 steel specimens in a test fixture that applied internal and external pressure and axial load. There were two test series, one in which constant amplitude fully reversed strains (CAS) were applied and another in which large periodic compressive overstrain (PCO) cycles causing strains normal to the crack plane were inserted in a constant amplitude history of smaller strain cycles. Ratios of hoop strain to axial strain of λ = −1, −0.625, −ν and +1 were used in each test series. Fatigue crack growth behaviours under CAS and PCO histories were compared, and revealed that the morphology of the fracture surface near the crack tip and the crack growth rate changed dramatically with the application of the compressive overstrains. When the magnitude of the compressive overstrains was increased, the height of the fracture surface irregularities was reduced as the increasing overstrain progressively flattened the fracture surface asperities near the crack tip. The reduced asperity height was accompanied by drastic increases in crack growth rate and decreases in fatigue life.Using a pressurizing device attached to the confocal scanning laser microscope (CSLM), crack opening measurements were obtained. Crack opening measurements showed that the biaxial cracks were fully open at zero internal pressure for block strain histories containing in-phase PCO cycles of yield stress magnitude. Therefore, for the shear-strained samples, there was no crack face interference and the strain intensity range was fully effective. For PCO tests (with biaxial strain ratios of −0.625 and +1), effective strain intensity data were obtained from tests with positive stress ratios for which cracks did not close. A number of strain intensity parameters derived from well-known fatigue life parameters were used to correlate fatigue crack growth rates for the various strain ratios investigated. Predicted fatigue lifetimes based on a fatigue crack growth rate prediction program using critical shear plane parameters showed good agreement with the experimental fatigue life data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.t01-1-00189.x
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    Propagation of microcracks at stress amplitudes below the conventional fatigue limit in Ti–6Al–4V (1999)
    Oxford, UK : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 22 (1999), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Fatigue crack growth below the conventional fatigue limit was examined in Ti–6Al–4V in two different microstructural conditions, bi-modal and fully lamellar. Tests conducted at R = −1, at room temperature and in air showed that there is a stress dependency in the da/dN–ΔK behaviour in both microstructures. The increasing crack front roughness associated with increasing crack size results in a decrease in the crack growth rate relative to the crack growth rate in a single grain. The da/dN vs. ΔK lines were drawn for each crack size and a ‘threshold’ΔK was determined using the intercept of the lines with da/dN = 10−10 m cycle−1. These values were used to construct modified Takahashi–Kitagawa diagrams to predict microcrack growth below the fatigue limit for each microstructure. A comparison of the two microstructures indicated differences in behaviour in microcrack and macrocrack growth that were explained by differences in crack front roughness at a given crack size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1999.t01-1-00217.x
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