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  • Articles  (61)
  • Blackwell Publishing Ltd  (61)
  • 1995-1999
  • 1980-1984  (61)
  • 1925-1929
  • 1984  (29)
  • 1980  (32)
  • 1927
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (61)
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  • Articles  (61)
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  • 1995-1999
  • 1980-1984  (61)
  • 1925-1929
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract— Impact fatigue tests were carried out using a rotating-disk type impact fatigue testing machine. The influence of prior austenite grain size, ductile-brittle transition temperature and test temperature on impact fatigue crack growth rate was investigated by means of fracture mechanics and fractography in quenched and tempered Cr-Mo alloy steel in which the prior austenite grain size was varied from 8–3 to 25-4 μm. The results in impact fatigue tests were compared to those under non-impact conditions. The crack growth rates associated with striation formation were insensitive to the change in prior austenite grain size, ductile-brittle transition temperature and test temperature regardless of impact and non-impact fatigue. When the material was in the brittle condition, impact fatigue gave rise to a transition from striation formation to intergranular and cleavage cracking. Such a transition will result in the acceleration of crack growth rate. The Paris Law exponent values in impact fatigue were reasonably expressed by the ratio of test temperature to ductile-brittle transition temperature.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract—The detection and measurement of surface microcracks in unnotched specimens are becoming more important, both from the point of view of description of crack growth by linear elastic fracture mechanics and from the classical endurance limit approach. Theoretical analyses of the current distribution in a cylindrical test specimen show promise that the a.c. potential drop method will become more sensitive for surface microcracks when higher current frequencies are applied. This effect was experimentally affirmed during fatigue tests on unnotched cylindrical specimens. With a 40 kHz current frequency semicircular surface microcracks with an area of 0.0066 mm2 (0.05% of the specimen cross-section) were detected. For accurate and reproducible crack growth measurements, a 5 kHz current frequency is preferable.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract—A fully age hardened Al-4%Cu-1%Mg alloy has been subjected to plain-fatigue and fretting-fatigue and the resulting fracture surfaces compared. Crack initiation in the plain-fatigue sample occurred at cracked inter-metallic inclusions and subsequent crack growth was at 90° to the surface. Crack initiation in the fretting-fatigue sample occurred at the edge of wear scar and subsequent crack growth was at 45° to the surface. Measurement of fatigue striation spacing on the fracture surfaces showed that, for the same applied stress, the initial crack propagation rate was an order of magnitude higher in the fretting-fatigue sample. This accelerated crack propagation rate was maintained until the crack reached a depth of 0.5–1.0 mm; thereafter the growth rate was the same as that in the plain-fatigue sample.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract—Ultrasonic bulk measurement technique was used to measure crack closure and a clip-on gage surface measurement technique was used to measure residual displacement at the crack tip of a propagating fatigue crack in 2219 and 7075 aluminum alloys. Experiments were carried out in vacuum, humid air, dry O2 gas, N2 gas, and deuteriated water vapor environments to evaluate effects of environments on residual strain and crack closure loads. It was observed that the closure load detected by ultrasonics decreased with introduction of humidity while the residual strain parameter dincreased with the humidity. The results are modeled as a build-up of oxide layer in addition to strengthening of asperities on the fracture surface. In the light of these observations, the effectiveness of surface and bulk measurements is evaluated. The results demonstrate that surface measurements are not always representative of the bulk behavior and use of such measurements in predictive analysis for fatigue can be misleading.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract— Optical and scanning electron microscopy have revealed the existence of grain boundary cavities in a series of specimens which had been cyclically deformed in the strain range ±0.25% with hold times ranging from 0 to 1000 min. The way in which these defects increase in size and number has been measured and found to correlate with the creep strain accumulated during the hold periods.A further observation is that a critical amount of deformation is required before either fatigue or creep type damage is nucleated. These observations lead to an alternative method to the currently accepted linear damage summation rule for estimating a lower bound of the creep-fatigue endurance.
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  • 6
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    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 puts forward a new method for analysing the behaviour of very short fatigue cracks. A probability function is introduced into the definition of the growth threshold, which rationalises the scatter in experimental data produced using an aluminium bronze alloy. This probability function can be visualised in terms of the microstructure of the material.It is shown that, in this material as in mild steels, fatigue crack initiation is not the critical stage. Initiation occurs relatively easily, but the cracks so formed may grow to only a few grain diameters in length before being arrested; thus it is the behaviour of cracks of this length which is critical in determining the fatigue strength of the material.These observations, when combined with the probability functions, allow estimation of the probability of failure of a component or structure in service with greater confidence than the methods used at present.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 high temperature low cycle fatigue properties of modified 9Cr-1Mo ferritic steel in a hot forged and a hot rolled condition have been evaluated. The hot forged material exhibited inferior fatigue properties as compared to the finer grained hot rolled material. Analysis of the data indicates that a larger grain size adversely affects the initiation stage but has little effect on the propagation stage. A steeper slope on the Coffin-Manson plot results when the number of cycles to initiation is reduced.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 overload induced fatigue crack propagation behavior of several aluminum and steel alloys was examined as a function of the baseline stress intensity factor range (δKb). In order to gain a clearer understanding of the parameters which influence the cyclic delay phenomenon, under both plane strain and plane stress conditions, tests were conducted at δKb values ranging from the near threshold regime to high δK levels approaching fast fracture. Large amounts of overload induced cyclic delay (˜100,000 cycles) were observed at both high and low δK levels (provided the plastic zone size/thickness ratio and plastic zone size/grain size ratio approached unity, respectively) with significantly less delay occurring at intermediate δK values. All alloys examined exhibited this type of delay behavior which can be described by a “U-shaped” plot. The delay phenomenon at high δKb levels under plane stress conditions was attributed to increased crack closure associated with large tensile displacements in the wake of the advancing crack. At low δKb levels increasing cyclic delay was attributed to an increased effective overload ratio as δK approached δKth.
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  • 9
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: Changes in the crack growth behavior of 7075-T651 aluminum specimens which had been exposed to temperatures between 121 and 179°C were evaluated. Specimens were fatigue tested at room temperature under flight-by-flight loading conditions. Results from these tests were then compared with data from the as-received material. Exposure to 141°C or more produced a definite increase in specimen life, apparently due to a decrease in crack growth rate. In contrast, preliminary experiments using constant amplitude loading did not show noticeable effects of these thermal treatments on fatigue lifetime. The thermal treatments were found to cause overaging of the metastable precipitate microstructure, which was thought to be responsible for the changes in fatigue response.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 initiation stage and short crack behaviour in torsional fatigue of a 0.4% C steel was investigated by a replication technique.The fatigue cracks initiated and propagated in the ferrite phase which is located at the prior austenite grain boundaries in the form of long allotriomorphs. At this stage of crack development it is proposed that crack growth rate depends on the extent and intensity of plasticity at the tip of the crack. Crack growth per cycle is correspondingly proportional to the strength of the slip band. The ferrite-pearlite boundaries are strong barriers to crack propagation, which is manifested by a deceleration of growth and possible arrest. On raising the stress level the previously non-propagating cracks may continue to grow by branching or joining with other cracks in the ferrite phase. This process is repeated until the stress fields of one or more dominant cracks attain a critical value to sustain continued growth that leads to failure.
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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: CT type specimens containing two layers of 309L and 308L cladding stainless steels welded to A508 carbon steel and 316 stainless steel were specially devised to test the influence of R ratio and environment on the crack propagation rate behaviour of cladding materials at 300°C. Large effects are shown. The crack growth rate under vacuum can be smaller by more than one order of magnitude as compared to air. Large differences are also shown on the fracture surfaces, where it is observed than vacuum promotes the formation of large crystallographic {111} facets. The effect of environment is briefly discussed on the basis of existing gas adsorption models.
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  • 12
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 monitoring of fatigue crack initiation mechanisms and short fatigue crack growth usually involves interrupting otherwise continuous load cycling for examination of the test-piece. This permits attainment of high resolution over a large area of surface where the fatigue cracks could initiate. However, breaks in the fatigue cycling can affect the fatigue endurance of the test-piece and in the present study of Ti-6A1-4V this has been shown to depend on the duration of the rests, the number of cycles between rests, the type of examination employed and the hydrogen content of the material. The results of the work are discussed in terms of the possible influence of the monitoring technique on the fatigue process.
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  • 13
    Electronic Resource
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: Abstract— Fatigue crack tip opening displacements and strains in the material very close to the crack tip have been determined from measured displacements for cracks grown in both vacuum and humid air environments. The environment alters both the relations between crack tip opening displacement and crack tip strain, and the effect of cyclic stress intensity on these factors. Results of dynamic observation of intermittent crack growth are correlated with fractographic evidence. The relationships between crack tip parameters are used in a previously developed mathematical model. The effect of wet air on fatigue crack growth is found to be a reduction in crack tip plasticity.
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  • 14
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: Abstract— Unexpected arrest of long fatigue cracks was observed in mild steel single edge notch three-point bend specimens tested under constant amplitude loading. Arrest was associated with a low, but still positive, slope of the crack length against stress intensity factor curve, and can be explained using the R -curve concept for fatigue-crack growth. At a stress ratio of 0.1, the fatigue threshold was 6.6, 7.3 or 8.0 MN/m3/2 depending on the definition of threshold used. This has obvious implications for both the development of a standard test method for the fatigue threshold and the application of data to practical problems.
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  • 15
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract—The application of dimensional analysis and similarity methods to the study of the speed of fatigue crack growth is considered. It is shown that the Paris range of the crack propagation diagram is an intermediate-asymptotic stage of the crack growth process. Over this stage the influence of the initial conditions on the process of fatigue crack growth has disappeared but the influence of the instability has not yet intruded. So-called incomplete self-similarity prevails at this stage with respect to a basic similarity parameter, equal to the ratio of the stress intensity factor amplitude to the fracture toughness. It is shown that for a certain material under fixed external loading conditions the exponent in the Paris power law is a universal function of the ratio of specimen thickness to the ultimate size of the cyclic plastic zone. Processing of available experimental data confirmed the results obtained by this approach.
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  • 16
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract— Fracture surfaces of both service and laboratory fatigue fractures frequently show dark tongue-shaped marks. In fatigue tests on 7075–T6 specimens such tongues were produced by high peak loads. Measurements indicated that a tongue is not formed during a single burst of crack extension but is the result of a number of successive pop-ins requiring an increasing load. Therefore tongue formation is a quasi-stable phenomenon. The tunnelling fracture in the centre of plate thickness is accompanied by unfailed ligaments at the plate surfaces which reduce the stress intensity at the crack tip. The effect of different material conditions and loading direction on tongue forming was studied. A new model was developed to describe the growth of a tongue. The model was in good agreement with the various test results. The analysis of the problem has some relevance to validity requirements for K1c. A formula pertaining to tongues proposed by Forsyth was slightly modified and found to be approximately correct for the present results.
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  • 17
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract— A theoretical development based on a simple physical model is proposed to help the designer predict high strain multi-axial fatigue behaviour. This approach hypothesises that the maximum shear strain γ*, on planes driving the crack through the thickness, controls the fatigue crack propagation rate and hence the life. The direct strain δ*n acting normal to the plane of γ* can exert a secondary modifying influence. Experimental results from several research laboratories have been analysed in this manner with some success.
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  • 18
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract— Strain controlled continuous cycling fatigue tests are reported on three casts of Type 316 steel; the results obtained are shown to be consistent with published data.Strain controlled creep/fatigue tests are reported involving a hold period per cycle of between 0·2 and 168 h on one batch of Type 316 steel. An empirical extrapolation of the data and one involving a linear damage summation suggest that the existing Code Case N47 creep/fatigue design curve and rules are over-conservative. A stress relaxation/fatigue endurance correlation shows some promise for predictive purposes. Although many of the mechanical test and metallurgical features observed are consistent with a fundamental crack growth extrapolation approach, further consideration of detailed aspects are necessary before it can be used with confidence. It is concluded that there are no entirely reliable methods of extrapolation currently available for Type 316 steel and longer term tests are therefore essential to reduce the extrapolation uncertainties.
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  • 19
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract— Fatigue crack propagation tests were carried out in different environments on 7075–T6 and 2024–T3 centre-cracked sheet specimens. Observations were made on the macroscopic transition from tensile mode to shear mode. The transition is suppressed by an aggressive environment, whereas it is promoted by an inert environment. As a consequence there is no unique correlation between the state of stress and the mode of cracking. Both the state of stress and the environment have a significant effect on the mode of cracking. A simple model for the effect of environment on fatigue crack growth is presented. The implications for crack growth under corrosion fatigue conditions are discussed.
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  • 20
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 have been determined on standard specimens containing long cracks (∼5–10mm) and on specimens containing two-dimensional short cracks (∼0.10–0.50mm). Large differences have been observed indicating that at a given stress intensity factor short cracks propagate much faster than long cracks. Mouth opening displacement measurements for both specimen geometries have shown that the crack closure effect is largely responsible for the observed effect. These results are used to rationalize the behaviour of short cracks initiated from natural sites which were either graphite nodules or microshrinkage pores. The three-dimensional aspect of these natural small cracks is analysed and discussed in detail.
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  • 21
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: For ultra-high strength steels and aluminium alloys, a fatigue crack could initiate from a notch tip under cyclic compressive load. The threshold value for fatigue crack initiation under compressive load can be as great as four times that under tensile load. The crack grew at a decreasing rate until eventually it stopped growing altogether under cyclic compressive load with a maximum length of 0.2-0.5 mm. If the minimum compressive load was near zero, i.e. compression to zero load cycling, the threshold value was near that under tensile loading and the compressive fatigue crack could continue to grow; however, the crack growth rate under compression to zero load fatigue was 10–100 times less than that under the tensile fatigue loading.
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  • 22
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 investigation has been carried out on austenitic stainless steel 0Kh16N15M3B under normal conditions and also to neutron irradiation of 6.8 × 1016nm-2s-1 (E 〉 0.1 MeV) intensity. Thin-walled torsion cylindrical specimens were tested in strain-controlled fully reversed loading mode at 923 K. Various ranges of strain, pre-loading fluences and half-cycle hold times (1, 5 and 30min) were applied. Neutron irradiation was found to result in hardening of the steel, stimulating cyclic stress relaxation and a reduction in cyclic life. When acting together, neutron irradiation and static loads cause a more significant reduction in the number of cycles to failure than if summed up as independent factors. Application of a kinetic failure criterion based on a damage parameter enables an estimation to be made of the limiting state of the steel under high-temperature cyclic loading with hold periods.
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  • 23
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    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 propagation tests have been made on 150 mm wide panels of 1.6 mm thick 7475-T761 clad aluminium alloy sheet with and without adhesively bonded patches of pre-formed carbon fibre reinforced plastic (CFRP). The test frequency was 10 Hz, the minimum stress: maximum stress ratio, R, was 0.1 and the peak applied fatigue stress was 60 MPa.The tests were undertaken to assess the possibility of preventing the growth of fatigue cracks, or reducing their rate of growth, by the application of CFRP patches to one face only of pre-cracked aluminium alloy sheet. The variables examined included the type of patch and adhesive; the size, shape and thickness of the patch; and the effect of chamfering the edges of the patch and the removal of the cladding prior to patching.Results indicated that correctly designed and bonded CFRP patches substantially decreased the subsequent crack growth rate. The size and thickness of the patch had significant effects upon the reduction of fatigue crack growth rate whereas the shape of the patch, chamfering and the removal of the cladding prior to patching had little influence.
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  • 24
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 experimental investigation is reported of the possible effects of adiabatic shear bands, caused by projectile impact, on the fatigue strength of a titanium alloy (Ti-6%A1-4%V). No significant reduction in fatigue strength due to the presence of adiabatic shear bands was found, nor did the fatigue cracks initiate from the bands. The results are relevant to the problem of foreign object impact damage to compressor blades in gas turbine aeroengines.
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  • 25
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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 study creep-fatigue interactions under multiaxial stress states, both push-pull and reversed torsion low-cycle fatigue tests were carried out using an austenitic stainless steel, SUS 304, at 923 K in air. From the tests, it is concluded that the hold-times introduced at the peak strain reduce low-cycle fatigue lives in the push-pull mode, but in the torsional mode they were not so harmful. This difference in the hold-time effect is discussed from considerations of crack formation and propagation and the stress amplitude applied to the specimen.Both maximum principal strain range, Δε1, and the von Mises' equivalent strain range, Δεeq, provide a nearly adequate comparison base for the assessment of biaxial low-cycle fatigue lives in tests without strain hold-time but are inadequate for hold-time tests. An equivalent stress range, Δσ*, which includes the effect of the stress parallel to the fatigue crack and which was previously proposed by the authors for no hold-time tests, is applied to the hold-time tests in the biaxial stress state. It is found that Δσ* is a good parameter for the correlation of biaxial low-cycle fatigue data in both no hold-time and hold-time tests.
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  • 26
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: Small fatigue crack growth behaviour in a low alloy steel was investigated under two stress step multiple loading in which the secondary stress was below the fatigue limit. Crack growth rates were presented in terms of a stress intensity factor and compared with data obtained under constant amplitude loading. In the higher ΔK region, crack growth rates increased monotonously with increasing ΔK even though the stress level was below the fatigue limit, and tended to be lower than those for constant amplitude loading. In the lower ΔK region, cracks showed a complicated behaviour, that is, an initial high growth rate was observed followed by an arrest or a drop to a minimum value and then a gradual increase. The average crack growth rates per cycle at both primary and secondary stresses in each block were approximately consistent with the da/dn-ΔK relation for constant amplitude loading. A suggestion for the prediction of crack growth life is given.
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  • 27
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 28
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: Abstract— Tests for fatigue crack initiation were carried out on two different aluminium alloys. Results and analysis of initiation under constant amplitude loading are presented; elastic and elastoplastic analyses are applied. Initiation under programmed block loading is investigated and damage accumulation is discussed. Tests were performed on two notch root radii:5 and 0.5mm. The electric potential method was used to detect fatigue crack initiation. Three point bending tests on smooth specimens were carried out to follow the evolution of damage during the crack initiation phase.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: Abstract— High strain fatigue properties of AISI 316, AISI 316N and Sandvik 253MA have been investigated at 600°C. The two latter alloys, which contain significant amounts of N, exhibit a higher resistance to fatigue than 316. This effect is accompanied by a planar dislocation slip mode in 316N and 253MA as opposed to a wavy slip mode in 316. The results provide strong evidence that N improves fatigue strength in austenitic stainless steels, by inhibiting cross-slip of screw dislocations.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
    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: Abstract— A phenomenological model of cumulative creep damage combining simulated grain boundary cavitation with internal redistribution of stress is developed and matched to constant load tensile creep data for an AISI 316 stainless steel tested at 550°C. The model is shown to predict the creep life of the material when it is subjected to single step changes in load provided the strain rates subsequent to the change are imposed in the model. It is inferred that this supports current suggestions that cavitation failure may be strain controlled.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract—Measurement of the energy expended during growth of a fatigue crack in the near threshold region and how it is affected by a water vapor environment is coupled with direct observation of the crack tip to produce a modification of the damage accumulation model for fatigue crack growth which incorporates threshold and environmental effects.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— On the basis of fatigue data derived from a large number of experiments, the load progression methods of Locati and Prot as well as a method operating on a thermometric basis have been comparatively evaluated in an experimental and analytical (statistical) study. The last-named thermo-method can provide useful estimates for a fatigue limit corresponding with ca. 0 to 5% probability of fracture with only 1 to 3 experiments.The Prot-method, set up and evaluated in a certain way, provides a useful estimate of the fatigue limit and, additionally, an approximate indication of the width of the transition range of the corresponding Wöhler-type tests after experiments on not less than about ten specimens.The load progression, contrary to the original Prot-concept, must not necessarily be applied in a continuous mode, but can occur stepwise with increments Δσ smaller than ca. 15 Nm-2.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Linear-elastic fracture mechanics techniques were used to characterize the effect of temperature on the fatigue-crack propagation behaviour of precipitation heat-treated. Inconel X-750 in an air environment over the temperature range 24 to 649°C. In general, crack growth rates were found to increase with increasing temperature, particularly at the highest test temperature (649°C). The effect of stress ratio on the fatigue-crack growth behaviour of Inconel X-750 was examined at 538°C, and results indicated that the elevated temperature fatigue response of this nickel-base superalloy was relatively insensitive to stress ratio level at the growth rate levels studied. Metallographic and electron fractographic examination of Inconel X-750 fatigue fracture surfaces revealed operative crack growth mechanisms to be a function of temperature and prevailing stress intensity factor. Under room temperature and intermediate temperature conditions (up to 538°C), all fatigue fracture surfaces exhibited a faceted crystallographic morphology at low crack growth rates followed by striations in the higher growth rate regime. At the highest test temperature (649°C), the fatigue crack was found to propagate by an intergranular mechanism.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— In this paper the strain distribution and the plastic zone size at a fatigue crack tip are discussed. From this analysis and considering the critical condition for plastic-blunting, a simple analytical formula for calculating the threshold stress intensity range for fatigue crack propagation at R= 0 is proposed. It is found that calculated values are in good agreement with existing experimental results.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— The plastic work to propagate a fatigue crack by a unit area, U, measured by the foil strain gage technique requires an extrapolation to estimate the contribution closer than 100 μm to the crack tip. This is due to the size of the strain-gages used, 200 × 210 μm. Conversely, the electron channeling technique for determining U is useful mainly close to the crack tip where subgrains form. In the present work U was measured by both techniques in the same low carbon steel at ΔK= 8 MN/m3/2. The contribution to U from closer than 100 μm of the crack tip was determined to be 1·7 × 106 J/m2 using electron channeling and 2·0 × 106 J/m2 by extrapolation. The measured contribution to U from further than 100 μm from the crack tip was 3·6 × 106 J/m2 giving 5·3 × 106 J/m2 for U. Thus, a large amount of energy is absorbed outside the region where sub-grains form. The non-hysteretic plastic work was found to be about four orders of magnitude smaller than the hysteretic plastic work, and may be neglected. A map of the plastic zone results from the strain-gage measurement. Rice's theory predicts the measured plastic zone sizeif the proper material's strength is employed in the formula.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    ISSN: 1460-2695
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— This paper deals with the effect of accumulated (oriented) plastic deformation (cyclic creep) on the life of metals under conditions of cyclic loading typically in the range of low-cycle fatigue. Specific features of cyclic creep of aluminium, titanium alloys and structural steels were investigated for the lives ranging from 05 to 2 × 105 cycles to rupture as well as specific features of transition from quasistatic to fatigue fracture associated with the variation in the mode of deformation of metals. It is shown that under conditions of repeated stress-controlled loading in a wide range of low temperatures, the cyclic creep processes are the predominant ones determining life of metals over a wide range of cycles, and when calculating life under these conditions it is necessary to take into account the rate of these processes irrespective of the type of fracture: quasistatic or fatigue. An equation was obtained for calculating life under low-cycle loading conditions which takes into account the interrelationship between the life, the accumulated plastic strain, steady-state cyclic creep rate and the resistance of the material to cyclic creep.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Stress gradients at the root of a notch are significant for the notch effect and the size effect of fatigue properties. Usually the gradient of the stress distribution in the minimum section is considered. In the present paper the variation of the tensile stress along the edge of the notch is considered. Calculations are made for a variety of notches. The results indicate a remarkable conformity of stress distributions at the notch root if the same peak stress and notch root radius (ρ) apply. Consequently K1and ρare highly characteristic for the stress distribution around the notch. Along the edge of the notch the stress decreases at a much slower rate than in the minimum section going away from the material surface. For the stress along the edge of the notch a stress gradient coefficient is defined. The variation of this coefficient is fairly small for several notches and K1, values. A 5% lower stress as compared to the peak stress at the notch root is obtained at about 0.02 ρbelow the material surface and at a distance of about 0.18 ρalong the material surface.
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  • 40
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— –The rate of propagation of macrofatigue cracks down to near threshold was measured in air in three tempered martensitic steels; HY80, HY130 and 4140 (650°C temper). The value of ΔKth was determined by the load-shedding technique in center notched panel specimens. Of the three steels, 4140 tempered at 650°C had the lowest ΔKth, 3–5 MN/m3/2, while HY80 had the highest, 4.2 MN/m3/2. The 4140 (650°C temper) is intermediate in strength between HY80 and HY130. The results are discussed in terms of a recent theory of one of the authors.The fatigue crack propagation rates in the mid-ΔKrange in HY80 and HY130 in argon were also studied by measuring, with foil strain gages, the cyclic plastic work to propagate a fatigue crack by a unit area, U.HY80 has a lower crack propagation rate and correspondingly higher U.This was attributed in part to the higher yield strength of HY130 but the dislocation structure and carbide composition and morphology also play roles. Microstructural changes due to cyclic plastic deformation inside the plastic zone in HY80 and HY130 were observed by TEM of thin foils. SEM studies of the fracture surfaces at ΔK= 20 MN/m3/2 indicate a more ductile fracture mode for HY80 than for HY130. The fatigue crack propagation rate of HY130 is substantially higher in laboratory air (47% relative humidity) than in dry argon. This is not the case for HY80.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A fatigue crack growth damage accumulation model is used to derive laws for the fatigue crack growth rates of brittle and ductile materials. The damage accumulated during cyclic loading is assumed to be proportional to the cyclic change in the plastic displacement in the crack tip yielded zone. The static mode contribution to the fatigue damage is assumed to be proportional to some power of the crack tip displacement. The laws are applicable in either the small or large scale yielding regimes provided that the stress ratio remains positive. Static modes are assumed to be controlled by the fracture toughness value in brittle materials, and by the gradient of the crack growth resistance curve in ductile materials. In the analysis of ductile materials it is assumed that the crack growth resistance of the material is not significantly altered by fatigue crack growth.The growth rate equations are expressed in terms of the near field value of the J-integral, i.e. the value which would be calculated from assuming the material deformed in a non-linear elastic manner during the increasing load part of the fatigue cycle. Examples are given of the predictions of the growth law for ductile materials. It is predicted that after the initiation of stable tearing the crack growth rate, when expressed in terms of the cyclic change in the stress intensity factor, depends on both the structural geometry and the degree of crack tip plastic deformation. In both brittle and ductile materials the fatigue crack growth rate is predicted to accelerate as the failure criteria relevant to static crack instability are approached.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of cycle ratio R on the crack propagation rate for two aluminium alloys is analysed. Fatigue crack growth under programmed block loading is presented, linear damage accumulation is established for some flight simulation tests. Aspects covered include microscopic and fractographic observations. The incidence of crack closure is examined and the concept of equivalent constant amplitude is applied. The agreement between predictions and test results is very promising.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The progressive nature of fatigue damage under multiaxial stress states has been investigated. Experiments were performed on thin-wall tubular specimens of 1045 steel in tension, torsion and combined tension-torsion loading. Two equivalent strain amplitudes, one in the high cycle fatigue (HCF) region and one in low cycle fatigue (LCF) region were employed in this study. Four recently proposed damage theories were evaluated. Crack depth was used as a damage parameter in comparing damage curves under different loading modes.Different types of crack systems were observed in the HCF and LCF regions. The damage curve obtained in tension loading can be used to evaluate the damage behavior under combined tension—torsion loading. The results of torsion loading show that torsional damage behavior is different from the above two loading modes.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The fatigue strength of 7075-T6 aluminium alloy under combined axial loading and torsion was examined. The S-N relations were correlated with the von Mises criterion for the high cycle region (Nf≥ 104 cycles) and with the Tresca criterion for the low cycle region (Nf 〈 104 cycles), where Nf is the cycles to failure. This transition at Nr= 104 cycles was related to the occurrence of macroscopic plastic straining and a change in fracture modes. The results are discussed in comparison with those for a high strength steel (SNCM8) in a previous study. Particular attention is given to differences in cyclic deformation behaviour, fracture modes and fatigue crack growth rates between the two materials.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: S-N curves have been determined for continuous cycling and for interrupted cycling using commercial purity titanium, and also a Ti-6Al-4V alloy in four different states of heat treatment. The incorporation of rest periods during the fatigue tests resulted in increased lives to fracture to an extent which appeared to be independent of specimen composition or microstructure, and hence primarily a function of the titanium itself. Failures from internal crack origins were found at longer lives from some specimens for both continuous and interrupted tests. It is suggested that the observed effects are due to localised hardening and strain ageing as a consequence of oxygen and/or nitrogen pick-up from the testing environment, and also as a result of oxygen and/or nitrogen present in the starting material.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The fatigue behavior of a hot-rolled, control-cooled, plain carbon eutectoid rail steel has been characterized. The data include monotonic and cyclic stress-strain curves, low cycle fatigue data and near-threshold fatigue crack growth rate behavior in air and in vacuo. The effects of environment and mean stress on the near-threshold fatigue crack growth rates of rail steel are significant. At a low stress ratio (R), ΔKo is lower in vacuum (7 MPa √m) than in moist air (10 MPa √m). At high R, ΔKo is higher in vacuum (6 MPa √m) than in air (4 MPa √m). The beneficial effect of moist air on FCGR at low ΔK and low R is attributed to an increase in closure due to fracture surface roughness and oxide film.
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    Fatigue & fracture of engineering materials & structures 7 (1984), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The cyclic deformation of polycrystalline A1-4%Cu alloy containing θ precipitates was investigated by strain controlled tests, and compared to monocrystalline cyclic behavior. The cyclic deformation of the polycrystals was found to depend on the grain size, and in coarse-grained material (grain diameter = 1 mm) a definite plateau was observed in the cyclic stress-strain (CSS) curve. In order to explore the relationship of cyclic behavior between single crystals and polycrystals, three available orientation factors were examined. This relationship can be interpreted by selection from the different types of orientation factors (Taylor factor, Sachs factor and Maximum Schmid factor), which operate to different degrees depending on the magnitude of the strain amplitude and the grain size.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— An analysis is presented of factors causing fatigue crack resistance in metals exposed to liquid corrosive environments. A new approach involving invariant diagrams is proposed that takes simultaneous account of the stress-strain state and the electrochemical conditions at the tip of a crack. Variations in electrochemical conditions at the tip of a stationary crack and the relationship between the electrochemical conditions at the crack tip and the fatigue crack growth rate in aqueous corrosive environments are discussed with the aid of these diagrams.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A model is proposed for calculating the fatigue crack opening load based on the concept of residual strain in the overload plastic zone. An equation relating the fatigue crack opening load to loading parameters is given. The model is used to evaluate the retardation effect due to overload under various loading conditions. It is found that the calculated results agree with test data.
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    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Plastic zone size and shape and the distribution of strain within the plastic zone are determined for the high-strength aluminium alloys 2024-T4, 6061 T6, and 7075-T6 using the technique of selected area electron channeling. Plastic zone size is found to correlate with the work done in creating a unit of new crack surface and the yield stress, rather than with the stress intensity factor and yield stress. Plastic strain distribution is found to be a logarithmic function of distance from the crack tip, in agreement with the mathematical analysis for a moving crack in plane strain.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— –The da/dNvsΔKrelation for Torbar Steel is obtained by testing specimens cut from 32 mm bar. This relation is compared with available data for Unisteel 410 and with medium strength steels. Also, the pattern of fatigue cracking in Torbar is studied by inspecting bars retrieved from reinforced concrete beams which were subjected to repeated loading. It has been observed that fatigue crack locations in the bars coincided with the locations of concrete cracks traversing the bars. Tension tests on the fatigue cracked bars show that the cracks considerably reduce the ductility of the bars.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract—Conventionally, fatigue growth rate data are correlated in terms of the range ΔKof the applied stress intensity factor. It is argued that a correlation involving both ΔKand the constant stress Tclose to the tip of the equivalent elastic crack should be adequate for moderate stress, biaxial fatigue data. Practical application of these ideas would involve the preparation of “T -term” compendia similar to those already available for K -calibrations. “T -term” data are presented for the case of an edge-cracked strip in tension.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— This work is concerned with the determination of the fatigue threshold ΔKth for an aluminium alloy. No dependency of ΔKth with grain size was observed. Crack closure concepts were applied in order to explain the effect of mean stress and environment. The opening load Pop was determined by the compliance method. Results show no significant variation of Pop with environment (air or vacuum) but partially explain the influence of mean stress on crack growth rates. Fractographic analysis (SEM) of fracture surfaces and evolution of compliance diagrams suggest that a change of mechanism in crack propagation occurs when stage I changes to stage II growth.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— High strain fatigue tests of Type 316 stainless steel have been carried out at room temperature and 600°C. Cold work reduces the life relative to the annealed condition when considered in terms of plastic strain per cycle but not when the total strain range is used. It also renders the material far more resistant to cyclically induced changes in strength than the annealed state in which the strength is more than doubled at 600°C. Strain ageing causes further instability and enhances the hardening and loss of ductility in the annealed material. Because of the large number of variables involved, comparison with other work is unable to identify the parameters most influential in determining endurance. It is argued that where a fatigue–creep interaction occurs, then cyclic hardening will promote a higher creep resistance in a sequential interaction and favour a fatigue dominated failure in a simultaneous interaction.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— A test facility has been developed in which a thin walled tube can be subjected to fully reversed fatigue cycles for all biaxial stress or strain ratios. Twin loop servo-control allied to high resolution gauge length extensometry, load and pressure transducers permits stress or strain controlled testing. The rig is unique in that cyclic stress-strain hysteresis loops can be obtained for both axial and circumferential directions during a test.Results from a strain controlled series of low cycle fatigue tests on a ferritic 1Cr-Mo-V steel obeyed the Manson-Coffin relationship with the exponent being sensibly constant for all strain ratios. For a given maximum principal biaxial strain, the damaging effect increased as the strain ratio φ increased from –1 to +1. By comparing results from solid and hollow cylindrical specimens, geometry effects on fatigue life were revealed. Data on shakedown and cyclic softening under biaxial strain conditions were also obtained.
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract— Cyclic deformation behaviour of medium carbon steel, armco iron and copper has been investigated. A model based on the energy absorbed for the fracture process at the crack tip, given in the form (Δw*p)y where Δw*p is the hysteresis energy at the crack front and the exponent y decides the energy spent for the fracture process, is proposed for the crack growth in low cycle fatigue. The value of the exponent y has been found to be around 0·26 to 0·28 for medium carbon steel and armco iron and around 0·52 for copper. These values of y give good prediction of the relations between the total fracture energy and the stress amplitude and the total fracture energy versus the fatigue life. The energy based approach has been extended to predict the cumulative damage in a single step stress variation. Good correlation has been obtained between the experimental data and the theoretical prediction.
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  • 58
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract—An investigation into the applicability of linear elastic fracture mechanics to very small fatigue cracks growing in a powder metallurgy nickel base superalloy is described. An unusual specimen was designed to facilitate the study of these small cracks. The stress intensity factor for the specimen was estimated and then calculated from the plastic zone size as determined by interferometry. The crack tip deformation field was also observed in the SEM and by stereoscopic viewing. These observations showed that the macroscopic deformation field was the same for both the long and short cracks, and was controlled by the stress intensity. The fatigue crack tip was found to interact strongly with the material microstructure and the localgrowth rate cannot be correlated with fracture mechanics quantities.
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  • 59
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract—An analytical model to represent and predict the influence of frequency on the elevated temperature fatigue crack growth behavior of structural alloys is described. This model was formulated by considering the time dependence of stress and strain rate in the crack tip region due to creep deformation.Fatigue crack growth rate data were generated on ASTM grade A470 class 8 (CrMoV) steel at 538°C (1000°F) for several frequencies to evaluate the model. Based on these results and data taken from the literature on 304 stainless steel, it was concluded that the proposed model is capable of accurately representing and predicting the effect of frequency over several orders of magnitude on the fatigue crack growth rates at elevated temperature.
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  • 60
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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
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  • 61
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Fatigue & fracture of engineering materials & structures 3 (1980), S. 0 
    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: Abstract— The residual stress fields at the tip of a fatigue crack have been evaluated using the Westergaard stress function. Using these values the loads at which the crack tip begins to open have been calculated to give U, Elber's effective stress range factor, as a function of stress ratio R, the ratio of applied stress range to yield stress, Δσ/σy, and the cyclic strain hardening exponent n. The computed values of U are shown to be in good agreement with measured values, and the predicted effect of prior high load cycles on the crack propagation rate at a lower cyclic load, on taking crack closure effects into account, is in excellent agreement with experimental results.
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