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  • Articles  (8,781)
  • Springer  (8,131)
  • American Chemical Society  (584)
  • Blackwell Science Ltd  (66)
  • 2010-2014
  • 1995-1999  (8,781)
  • 1998  (8,781)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (8,781)
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  • Articles  (8,781)
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  • 2010-2014
  • 1995-1999  (8,781)
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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
    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 
    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 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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  • 6
    Electronic Resource
    Electronic Resource
    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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  • 7
    Electronic Resource
    Electronic Resource
    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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  • 8
    Electronic Resource
    Electronic Resource
    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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  • 9
    Electronic Resource
    Electronic Resource
    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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  • 10
    Electronic Resource
    Electronic Resource
    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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  • 11
    Electronic Resource
    Electronic Resource
    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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  • 12
    Electronic Resource
    Electronic Resource
    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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  • 13
    Electronic Resource
    Electronic Resource
    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 
    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 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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  • 14
    Electronic Resource
    Electronic Resource
    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 
    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 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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  • 15
    Electronic Resource
    Electronic Resource
    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 
    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 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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  • 16
    Electronic Resource
    Electronic Resource
    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 
    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 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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  • 17
    Electronic Resource
    Electronic Resource
    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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  • 18
    Electronic Resource
    Electronic Resource
    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 
    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 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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  • 19
    Electronic Resource
    Electronic Resource
    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 
    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 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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  • 20
    Electronic Resource
    Electronic Resource
    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 
    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: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00127.x
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  • 21
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00085.x
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  • 22
    Electronic Resource
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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 
    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 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.
    Type of Medium: Electronic Resource
    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 
    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: 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 
    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 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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  • 25
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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 
    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: 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 
    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: 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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  • 27
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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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  • 28
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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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  • 29
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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 
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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: 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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  • 30
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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 
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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: 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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  • 32
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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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    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 
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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: 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 
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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: 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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  • 35
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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 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 
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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 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 
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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: 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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    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 
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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 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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  • 40
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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 
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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 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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    EDITORIAL (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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00002.x
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    NUMERICAL MODELLING OF A 3D RAIL RCF ‘SQUAT’-TYPE CRACK UNDER OPERATING LOAD (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 analysis is based on the 3D FE model of the rail Rolling-Contact-Fatigue (RCF) ‘squat’-type crack, which tends to be common in tracks with high-speed passengers and mixed traffic. The model incorporates the section of rail and a wheel of real geometry, in which the wheel is rolling over the running band of rail containing the ‘squat’-type crack. The state of stress in the vicinity of the crack front is determined, and consequently the values and ranges of the stress intensity factors (SIFs) KI , KII andKIII at the crack front are calculated for the cycle of rolling. To simulate loading conditions occurring in practice, residual, bending and thermal stresses acting in the presence of the tractive force were taken into account. The results indicate a significant role of face friction and tractive force in the loading mechanism at the ‘squat’. The longitudinal and lateral residual stresses may also influence the loading cycles, especially for the cases with reduced friction between the crack faces. Reduction of the face friction coefficient to values close to zero creates conditions for crack propagation driven by the shear mode mechanism. These results were obtained under a project sponsored by the ERRI D173 Committee, Utrecht, The Netherlands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00082.x
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    MODAL APPROACH FOR PROCESSING ONE- AND THREE-POINT BEND TEST DATA FOR DSIF–TIME DIAGRAM DETERMINATION. PART II—CALCULATIONS AND RESULTS (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 Part I of this paper, using the modal superposition method, equations for dynamic SIF calculations are derived for an arbitrary linear model of an impact bend specimen. In this paper (Part II), modal parameters and other data which are necessary for the DSIF determination have been calculated for three types of specimen model: the Euler–Bernoulli beam model, and two- (2D) and three-dimensional (3D) solid models. For the latter two cases, calculations were performed using the finite element program ADINA. Results for the 2D model of the specimen were fitted by polynomials for a wide range of specimen geometry parameters and Poisson’s ratio values. Considerable differences were observed between the beam model parameters and the 2D or 3D ones. The differences in results for the 2D and 3D models are small and mainly connected with non-uniformity of the SIF distribution along the front of a through-crack in the 3D solid. Results of processing one- and three-point bend test data reported in the literature are presented. Numerical DSIF values are compared with the experimental ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00088.x
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    CREEP BEHAVIOUR OF FULL-SIZE WELDED JOINTS: DEFECT ACCEPTANCE CRITERIA (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 order to explore the creep crack growth behaviour in welds of real components, creep tests were performed at 600 °C on large specimens made of 316L(N) stainless steel plates. Manual Metal Arc (MMA) welds were investigated. The overall deformation of the specimens, and in many instances the local deformations of the welds, were recorded. The evolutions of the defects were followed by potential drop techniques. The experimental results were compared with two-dimensional finite element computations, based on the creep behaviour of the base and weld metals, determined with small standard specimens. The time to creep crack growth initiation was correlated with the C* parameter determined from the load–displacement rate. The times to initiation of creep crack growth were compared with evaluations using the RCC-MR code and R5 rules, as well as other methods, in particular those derived by finite elements analysis
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00065.x
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    A STATISTICAL INVESTIGATION OF THE FATIGUE LIVES OF Q235 STEEL-WELDED 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: An investigation into the fitting of six assumed distributions (three-parameter Weibull, two-parameter Weibull, extreme minimum value, extreme maximum value, normal and lognormal distributions) of 23 groups of fatigue life data for Q235 steel-welded joints is performed in terms of linear regression analyses. The results reveal that the fatigue life distribution shapes mostly tend to be positively skewed. Therefore, the extreme minimum value and normal distributions are not the most appropriate distributions to assume for a fatigue life evaluation. The three-parameter Weibull distribution may give misleading results in fatigue reliability analyses because the shape parameter is often lesss than 1. This means that the hazard rate decreases with fatigue cycling. This is contrary to the general understanding of the behaviour of welded joints. Reliability analyses may also be affected by slightly non-conservative evaluations in tail regions of the three-parameter Weibull distribution. The two-parameter Weibull distribution does not give as good a fit as either the extreme maximum value distribution or the lognormal distribution. On the other hand, the extreme maximum value and lognormal distributions can be safely assumed in reliability analyses due to the good total fit effects and the conservative evaluations in tail regions. In addition, the extreme maximum value distribution is in good agreement with the general physical understanding of the structural behaviour of welded joints.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00064.x
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    CRACK CLOSURE AND THE FATIGUE-CRACK PROPAGATION THRESHOLD AS A FUNCTION OF LOAD RATIO (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 phenomenon of crack closure, which involves the premature closing of fatigue cracks during the unloading portion of a fatigue cycle resulting in the development of crack-tip shielding due to crack wedging, has become widely accepted as a critical mechanism influencing many aspects of the behaviour of fatigue cracks in metallic materials; these include effects of load ratio, variable-amplitude loading, crack size, microstructure, environment and the magnitude of the fatigue threshold. Recently, however, the significance of crack closure has been questioned and alternative suggestions made for many of these phenomena, e.g. the effect of the load ratio (i.e. the ratio R of the minimum to maximum loads) on threshold behaviour. In the light of this, the present paper provides evidence to rebut the assertion that crack closure is an insignificant process. Particular attention is given to the effect of crack closure on the threshold level as a function of load ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00069.x
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    THE ENGINEERING FLAW ASSESSMENT METHOD (EFAM) (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: This communication gives an introduction to the Engineering Flaw Assessment Method (EFAM) presently being developed at GKSS. The EFAM consists of various documents describing experimental procedures for determining fracture properties under various conditions, as well as analytical procedures for estimating the crack tip opening displacement in terms of δ5 , the rate of δ5 , (dδ5 /dt), and the J-integral as driving force parameters.
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    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00114.x
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    DESCRIPTION OF SHORT FATIGUE CRACK GROWTH IN A SHOT=PEENED MEDIUM CARBON 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: A probabilistic and simplified approach to the description of short crack growth in shot-peened, medium carbon steel specimens is presented. In order to model the dynamics of short crack growth, a difference equation has been formulated with coefficients originating from a two-parameter Weibull distribution of crack advance. The Fokker–Planck partial differential equation is the source of a solution based on the form of a probability density function of crack length. The resolved function allows one to calculate the expected crack length, crack growth rate and standard deviation of crack length. The viability of the probabilistic method has been verified using experimental data gained for shot-peened specimens fatigued under reversed torsion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00081.x
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    LOAD INTERACTION EFFECTS DURING FATIGUE CRACK GROWTH UNDER VARIABLE AMPLITUDE LOADING—A LITERATURE REVIEW. PART I: EMPIRICAL TRENDS (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 summary is given of reported trends in fatigue crack growth observed in variable amplitude fatigue tests on metallic materials, specifically on steels, under both simple and complex load histories. The effects of load variables, specimen geometry, material properties, microstructure and environment are considered. Attention is given to the threshold behaviour and small crack effects. The reviewed data suggest that, depending on a particular combination of load parameters, material, geometry and environment, variable amplitude load sequences of the same type can produce either retardation or acceleration in fatigue crack growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00083.x
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    ANALYSIS OF CAST STEEL FRACTURE MECHANISMS FOR DIFFERENT STATES OF STRESS (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 of fracture in a low-carbon cast steel was studied for different states of stress. As a result of heat treatment, two different microstructures have been obtained: ferritic-pearlitic and bainitic. The triaxial states of stress were realised by tensile tests on specimens with various notch configurations and on smooth specimens subjected to different hydrostatic pressures.During tensile tests carried out under triaxial stress states, the following quantities at fracture were determined: the effective strain, effective stress, stress state components, mean stress and stress triaxiality factor. Fractography of the specimens was carried out to observe the fracture mechanisms and relate them to the state of stress. The fracture mechanism depended on the state of stress and microstructure. With a decreasing stress triaxiality factor, the failure mechanism changed from ductile to shear. The fracture mechanism changed across the diameter of the sample and also depended on the microstructure. The small, smooth samples fractured at a higher stress than the larger samples. Ductile fracture in the ferritic-pearlitic microstructure was controlled by cracking of the matrix–precipitate boundary. Samples with the bainitic microstructure fractured by shear, and fracture depended mainly on the effective stress, although void growth (which is controlled by stress triaxiality) reduced the critical effective stress at positive values of mean stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00089.x
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    ARTIFICIAL RETARDATION OF FATIGUE CRACK GROWTH BY THE INFILTRATION OF CRACKS BY FOREIGN 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: The effects of inducing artificial crack closure into fatigue cracks in AISI 304 stainless steel by infiltrating foreign materials have been investigated. The foreign materials used include pure epoxy resin and resin mixed with 0.3 μm and 4 μm TiO2 , 4 μm Fe, as well as 18 μm AISI 316L stainless steel. In all the cases studied, different degrees of crack growth retardation have been achieved. When the particle size was small enough or when the prop-opening load for infiltration was large enough, crack arrest occurred. Crack retardation and arrest were mainly caused by the infiltrated material rather than the propping load. A rigid-wedge model was found to have limited value in predicting the possible outcome of an infiltration. On the other hand, the degree of crack closure immediately on resumption of a test after infiltration could tell whether the treatment was going to be successful or not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00068.x
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    A MODIFIED STRIP-YIELD MODEL FOR PREDICTION OF PLASTICITY-INDUCED CLOSURE IN SURFACE FLAWS (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 slice synthesis methodology is developed and used to construct a modified strip-yield model for the semielliptical surface flaw, enabling prediction of plasticity-induced closure along the crack front and subsequent fatigue crack growth. A mathematical description of the model is presented. Slice synthesis methodologies have previously been limited to stress intensity factor and elastic crack displacement computation. Predictions of flaw shape evolution under cyclic loading are compared with experimental data for aluminium alloy specimens under uniform constant amplitude loading with R = 0.1, 0.3 and 0.6. Model predictions are shown to correlate well with experimental data. An empirical correlation of relative crack opening stress with applied R ratio from the literature is shown to underestimate the level of closure at the deepest point of penetration when compared with the model predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00073.x
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    FATIGUE CRACK GROWTH DUE TO TWO SUCCESSIVE 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 behaviour of fatigue growth and cyclic tip deformation of long cracks due to two successive single overloads was investigated both experimentally and numerically. The results show the effect of the ratio of the second and first overloads, and the crack increment between the two overloads. The contributions of both crack tip blunting and residual stress fields were separated and accommodated in a previously developed crack tip deformation parameter, which was utilized to predict the resulting fatigue crack growth behaviour.The following trends were experimentally observed. Should the ratio of the second and first overloads not be less than one, fatigue crack growth rates followed the predictions based on the second overload. Otherwise, either of the following two situations resulted: (1) when the two overloads were closely applied, the second overload caused an initial acceleration in growth rates followed by a behaviour controlled by the first overload; (2) when the second overload was applied after the crack growth had reached its minimum rate due to the first overload, more retardation in growth rate was observed.Based on the model developed in the paper, it is possible to enhance the retardation effect of an overload if this overload is preceded by another overload. This enhancement depends on the ratio of the two overloads and the crack increment between them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00117.x
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    IMPROVING THE FATIGUE CRACK RESISTANCE OF WASPALOY BY SHOT PEENING (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: Four-point bending fatigue tests were conducted to study the effect of shot peening on the fatigue life of the nickel-base superalloy, Waspaloy. The influence of shot peening intensity on crack initiation, Stage I crack growth and the Stage I-to-Stage II crack growth transition phases, has been examined to identify the mechanisms by which shot peening improves fatigue resistance. The potential for extending the fatigue life of fatigue-damaged Waspaloy components has been explored by shot peening specimens which had been cyclic damaged to various degrees. The fatigue test was then continued after peening to ascertain the possibility of crack arrest or extending fatigue life. These experiments explore the possibility of ‘healing’ fatigue damage by a surface engineering treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00125.x
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    STRESS INTENSITY FACTORS FOR A FUNCTIONALLY GRADED MATERIAL CYLINDER WITH AN EXTERNAL CIRCUMFERENTIAL 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: This paper presents mode I stress intensity factors for external circumferentially cracked hollow cylinders, which are assumed to be made of functionally graded materials and subjected to remote uniform tension. The conventional finite element method is improved by introducing isoparametric transformation for simulating the gradient variations of material properties in the finite elements. This improved finite element method is verified to be effective and efficient. Various types of functionally graded materials and different gradient compositions for each type are investigated. The results show that the material property distribution has a quite considerable influence on the stress intensity factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00130.x
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    NUMERICAL ANALYSIS OF CRACK PROPAGATION IN PIEZOELECTRIC CERAMICS (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 formulation of an isoparametric displacement – electric potential finite element method that accounts for the electro-mechanical coupling effect of piezoelectric materials is briefly presented in this paper. The crack propagation behaviour and the elasto-electric fields near a crack tip in a PZT-5 piezoelectric ceramic under mechanical, electrical and mechanical – electrical mixed loads are investigated using this electro-mechanical finite element method. From the numerical results, it can be seen that crack propagation along the crack plane direction will be impeded and the crack will tend to propagate at an angle of about 84° to the crack plane under a negative electric field on the basis of the maximum stress criterion. The physical explanation of the phenomena is presented in this paper and it is shown that the mechanical strain energy release rate is not a good criterion for predicting crack propagation in the case where the ratio of the electric field to the mechanical load becomes large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00084.x
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    A MICROMECHANICAL DAMAGE THEORY FOR BRITTLE MATERIALS WITH SMALL 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: For brittle solids containing numerous small cracks, a micromechanical damage theory is presented which accounts for the interactions between different small cracks and the effect of the boundary of a finite solid, and includes growth of the pre-existing small cracks. The analysis is based on a superposition scheme and series expansions of the complex potentials. The small crack evolution process is simulated through the use of fracture mechanics incorporating appropriate failure criteria. The stress–strain relations are obtained from the micromechanics analysis. Typical examples are given to illustrate the potential capability of the proposed theory. These results show that the present method provides a direct and efficient approach to deal with brittle finite solids containing multiple small cracks. The stress–strain relation curves are evaluated for a rectangular plate containing small cracks.
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    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00094.x
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    ENGINEERING ESTIMATION OF THE LOWER BOUND TOUGHNESS IN THE TRANSITION REGIME OF FERRITIC STEELS (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 simple engineering method for estimating a lower bound fracture toughness in the ductile-to-brittle transition region is presented. It is based on empirical evidence that the lower tail of the failure probability versus fracture toughness curve tends to be a straight line rather than a Weibull curve. Fitting the lower tail by a straight line, however, gives an engineering lower bound at a theoretical failure probability of zero. The method enables one to obtain lower bounds using small data sets of three or four specimens.
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    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00048.x
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    CYCLIC FATIGUE CRACK GROWTH AND CLOSURE BEHAVIOUR IN ALUMINA CERAMICS (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: Cyclic fatigue crack growth behaviour in alumina ceramics is investigated and the effect of grain size discussed. Special attention is given to crack closure effects. Cyclic fatigue tests were carried out using four-point bend specimens, and the load–strain and load–differential strain curves were monitored. These curves show hysteretic behaviour probably related to frictional sliding of bridging grains, and also include non-linearities due to crack closure. The crack opening load is determined from the load–differential strain curve by using a method introduced in this study. Growth rates can be successfully described by the relationship da/dN = C[ΔKeff /(1 − Kmax /KIC )]m which is proposed in this study to account for the effects of crack closure and the maximum stress intensity factor. Irrespective of grain size, growth rates can be well represented by the above relationship, implying that the grain size exerts an influence on growth rates not only because of crack closure behaviour but also the material fracture toughness. The growth rate curve based on the proposed relationship shows a sigmoidal form for ceramic materials, which is similar to metals.
    Type of Medium: Electronic Resource
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    EFFECT OF LASER BEAM RADIATION ON FATIGUE CRACK PROPAGATION IN AISI 4150 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: The effect of laser beam radiation on fatigue crack growth in AISI 4150 steel was performed on compact-tension (CT) specimens, in which a composite region (CR) comprised of the hardened zones (HZs) on the top and bottom surfaces and the base metal (BM) in the interior, was aligned either along or normal to the crack growth direction. The microstructure of the HZs consisted of martensite, while lower bainite was present in the 300 °C preheated laser-hardened specimens. When the crack propagated along the laser tracks (LTs), the fatigue crack growth rates (FCGRs) of the laser-hardened specimen were lower than those of the base plate, particularly at low ΔK ranges. On the other hand, for a crack propagating normally to the LTs, decelerated FCGRs in the regions preceding the CR and accelerated FCGRs within the CR itself were found. However, enhanced FCGRs in the CR were not found in preheated specimens with a bainite structure in the HZs as the crack grew normal to the LTs. The enhancement of FCGRs in the CR, which became more accentuated at high ΔK values, was closely related to an embrittled microstructure (martensite) in the HZs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00101.x
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    CYCLIC DEFORMATION OF A DIRECTIONALLY SOLIDIFIED COBALT-BASE SUPERALLOY (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: An investigation has been carried out on the cyclic deformation and changes in microstructure of a directionally solidified cobalt-base superalloy. The tests are conducted at 700 °C and 850 °C in air under different total strain amplitudes. The alloy tested at 700 °C exhibits an initial hardening, a short saturation stage and an evident secondary hardening, while the alloy at 850 °C suffers continuous cyclic hardening until fracture. TEM examinations indicate that the initial hardening of the alloy at 700 °C is caused by the pile-ups of dislocations and stacking faults at the stacking fault intersections, while the stress saturation is due to the weakening of obstacles against the dislocation movement. The secondary hardening has a contribution from the formation of sessile dislocation tangles. The early stage of continuous hardening of the alloy at 850 °C is related to the pile-ups of dislocations and stacking faults at the intersections, and the later stage is controlled by the interaction between precipitates and dislocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00118.x
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    MECHANICAL REASONS FOR PLASTICITY-INDUCED CRACK CLOSURE UNDER PLANE STRAIN CONDITIONS (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 mechanical explanation of plasticity-induced crack closure under plain strain conditions is given first by means of dislocation mechanics and then by the methods of continuum mechanics. In plane strain, the event of crack closure is due to transport of material from the wake to the crack tip. It is an elastic effect caused by the response of the matrix surrounding the plastic wake. The transported material produces a wedge which follows the crack tip, and unlike the plane stress condition it does not leave a remaining layer on the crack flanks. The length of the produced wedge at the crack tip is of the same scale as the plastic zone. It is then shown that in spite of its smallness this wedge is able to cause the experimentally observed shielding effect. The results also suggest that the discrepancies concerning the interpretation of fatigue crack growth and closure experiments are likely to be due to differences in accuracy in the detection of such small but nevertheless effective wedges.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00131.x
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    EFFECT OF GRAIN SIZE ON COLLECTIVE DAMAGE OF SHORT CRACKS AND FATIGUE LIFE ESTIMATION FOR A STAINLESS 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: In the short crack regime of the fatigue process, grain boundaries in steels are barriers against crack growth. In this paper, we use: (1) a method involving crack density; and (2) a method of dimensional analysis, to evaluate the effects of grain size and grain-boundary resistance on short crack behaviour and fatigue life. The results show that the fatigue life increases with a decrease in grain size and an enlargement in the obstacle effect of a grain boundary. An experimental investigation is consequently performed and four groups of stainless steel specimens are used with different grain sizes. The experimental measurements show the dependence of fatigue properties on grain size, which are in good agreement with the theoretical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00093.x
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    TRANSIENT RESPONSE OF A CRACKED INFINITE PIEZOELECTRIC STRIP UNDER ANTI-PLANE IMPACT (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: By using the well-established integral transform methodology, the dynamic response of stress and electric displacement around a finite crack in an infinite piezoelectric strip are investigated under anti-plane impact. The dynamic intensity factors of stress and electric displacement are obtained analytically. The results show that the dynamic electric field will promote or retard the propagation of the crack at different stages of the loading process. On the other hand, the response of the electric field is coherent with the applied electric load and independent of the external mechanical load. The result obtained for the anti-plane impact of a cracked infinite piezoelectric ceramic can be regarded as a special case of the present work when the width of the strip tends to infinity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00108.x
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    NUCLEATION, BLUNTING OR PROPAGATION OF A NANOCRACK IN DISLOCATION-FREE ZONES OF THIN CRYSTALS (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: Nucleation, blunting and propagation of nanocracks in dislocation-free zones (DFZs) ahead of crack tips in ductile and brittle metals have been investigated by tensioning in situ with a TEM, and analysed using microfracture mechanics. The results show that in either ductile or brittle metals, many dislocations could be emitted from a loaded crack tip and a DFZ formed after equilibrium. The stress in the DFZ may be up to the cohesive strength of the material, and then a nanocrack is initiated in the DFZ or directly from the crack tip. In ductile metals, the nanocrack is blunted into a void or notch during constant displacement. In brittle metals, the nanocrack propagated as a cleavage microcrack rather than being blunted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00122.x
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    EFFECT OF DISPLACEMENT RATES ON EAC OF AISI 4340 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 environmentally assisted cracking (EAC) of AISI 4340 steel in synthetic ocean water was investigated using the rising displacement test method. The stress intensity factor for crack initiation, Kinit , in precracked compact tension specimens, was observed to increase with the displacement rates. However, a critical displacement rate existed which was associated with the KIEAC of the steel in the environment. Here, KIEAC is the threshold value of the stress intensity factor below which no EAC is expected. Constant load and constant deflection tests resulted in similar KIEAC values. The method pursued in this investigation for the determination of the initial displacement rate needed to obtain a valid KIEAC was found to be quite effective for the rapid and satisfactory evaluation of KIEAC , requiring a minimum number of tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-2695.1998.00100.x
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  • 67
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    Copolymerization of styrene and methyl methacrylate with nickel acetylacetonate/methylaluminoxane catalyst system (1998)
    Springer
    Polymer bulletin 40 (1998), S. 423-429 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The present work deals with copolymerization of styrene (STY) and methyl methacrylate (MMA) catalysed by nickel acetylacetonate - Ni(acac) 2 , employing methylaluminoxane (MAO) as cocatalyst. This catalyst system presented low catalyst activities for STY homopolymerization and very high activities for MMA. It seems that the catalyst system based on Ni(acac) 2 /MAO is effective for the copolymerization of MMA and STY to give block copolymer but it also produced polystyrene and poly(methyl methacrylate) homopolymers. The polymers were characterized by 13 C NMR, GPC and FTIR. The polystyrene homopolymer was identified by IR and NMR analyses of the cyclohexane soluble fraction. The presence of absorption bands correspondent to carbonyl group and aromatic ring was observed in the IR spectrum of the acetic acid soluble part. This result is a clue that STY-MMA copolymer with low molecular weight was produced. The high molecular weight copolymer (acetic acid insoluble fraction) was also characterized by IR analysis which indicated the presence of characteristic absorption bands of carbonyl group and aromatic ring. These results were confirmed by 13 C NMR analysis.
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    URL: http://dx.doi.org/10.1007/s002890050272
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  • 68
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    Small-angle X-ray scattering from sodium hyaluronate in aqueous sodium chloride (1998)
    Springer
    Polymer bulletin 40 (1998), S. 555-562 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Four narrow-distribution samples of sodium hyaluronate with weight-average molecular weights M w of 3.8 × 103 to 1.1 × 104 in 0.02 and 0.1 M aqueous NaCl at 25°C have been studied by small-angle X-ray scattering. Data for their z-average radii of gyration 〈S2〉z 1/2 and particle scattering functions P(θ), together with previous 〈S2〉z data from light scattering for high molecular weights, are compared with relevant theories for the wormlike chain with or without excluded volume, using the parameters estimated previously from intrinsic viscosity ([η]) data. It is shown that for M w lower than 1.1 × 104, 〈S2〉z, P(θ), and [η] of the polysaccharide in the aqueous salts are all consistently explained by this model without excluded volume.
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    URL: http://dx.doi.org/10.1007/s002890050290
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    Functional polythiiranes 8. Influence of the terminal group on the thermotropic behaviour of side chain liquid crystalline polythiiranes and identification of a crystalline phase (1998)
    Springer
    Polymer bulletin 40 (1998), S. 569-574 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Three new side chain liquid crystalline polythiiranes were prepared with new substituants on the mesogenic groups. Their thermotropic liquid crystalline behaviour was studied by the usual techniques (DSC, X-ray diffraction and polarized optical microscopy). Unlike the polyoxiranes described in the literature, the size of the terminal group has no influence on the nature of the mesophases of polythiiranes ; only slight changes of the transition temperatures were observed. In this series of polymers, a phase, denoted X, appeared at temperatures below the smectic E phase, and could not be identified by usual characterization techniques. An isothermal kinetic study for the smectic E / X phase transition resulted in an Avrami exponent close to 1, suggesting a one-dimensional ordering occurred during the transformation from the smectic phase. This result, combined with other observations, helped us to assign the X phase to the crystalline phase.
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    URL: http://dx.doi.org/10.1007/s002890050292
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    Properties of PVC-titania hybrid materials prepared by the sol-gel process (1998)
    Springer
    Polymer bulletin 40 (1998), S. 583-590 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Hybrid materials from Polyvinyl chloride (PVC) and titania were prepared using sol-gel technique. In-situ generation of titania network in the PVC matrix was carried out by introducing required amounts of tetrapropylorthotitanate (TPOT) followed by hydrolysis/condensation of TPOT in the matrix. Homogeneous and semi-transparent films were obtained by casting and solvent evaporation. Mechanical properties of these films up to 15 wt. % titania contents were studied. The results showed an increase in the Young's modulus, length at rupture and toughness of the unplasticised PVC. However, the tensile strength and stress at break point decreased with the addition of titania contents. Thermal stability of the material was studied using dehydrochlorination (DHCl) technique and thermogravimetric analysis. The PVC samples with small amount of titania were found to be more stable as compared with the pure PVC.
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    URL: http://dx.doi.org/10.1007/s002890050294
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    An improvement of the Mc Bain's microbalance to study transport of solvent vapours into polymeric films (1998)
    Springer
    Polymer bulletin 40 (1998), S. 591-598 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: SUMMARY The sorption characteristics of benzene and cyclohexane vapours in the poly(urethane-urea) (PUU) with well defined structure were measured using an improved version of the Mc Bain's microbalance. The diffusion coefficients were calculated for the different vapour activities from the kinetics of solvent uptake, i.e. the sorption isotherms over time. Sorption and diffusion coefficients measured, showed a strong dependence of the applied vapour activity. The obtained transport parameters were discussed with regard to the polymer structure. Based on the sorption and diffusion data, the pervaporation performance of the PUU-based membrane in separation of the benzene/cyclohexane mixtures was predicted and compared with the experimental pervaporation characteristic.
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    Isospecific polymerization of styrene with supported nickel acetylacetonate/methylaluminoxane catalysts (1998)
    Springer
    Polymer bulletin 40 (1998), S. 689-694 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The polymerization of styrene with catalysts based on Ni(acac)2 supported on SiO2 and Al2O3 was investigated. Using catalysts based on MAO supported on silica, a highly isotactic polystyrene was obtained. Nevertheless, the Al2O3-supported catalyst can promote isospecific polymerization activated by common. alkyl aluminum compounds even by any prior support treatment with MAO.
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    Synthesis of polymer having β,β-triketone unit in the main chain and its copper (II) complex (1998)
    Springer
    Polymer bulletin 40 (1998), S. 701-706 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A novel polymer having β,β-triketone unit in the main chain was prepared by polycondensation of triethylene glycol bis(p-butoxycarbonylphenyl) ether (1) with triethylene glycol bis(p-acetylacetophenyl) ether (4). The obtained polymer was soluble in CHCl3, DMF, and DMSO. The structure of the polymer was confirmed by 1H-NMR. Insoluble brownish yellow copper (II) chelate was obtained by adding a methanol solution of copper (II) acetate to a chloroform solution of the polymer. The IR analysis and the measurement of copper content by iodometric titration showed the quantitative formation of binuclear copper (II) complex.
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    URL: http://dx.doi.org/10.1007/s002890050311
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    Synthesis and polymerization of 1-trimethylsiloxy- or 1-triphenylsiloxysilacyclobutanes (1998)
    Springer
    Polymer bulletin 40 (1998), S. 715-720 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Synthesis and polymerization behavior of 1-trimethylsiloxy- or 1-triphenylsiloxy-silacyclobutane derivatives were studied. These monomers gave polymers with reasonably high molecular weight by platinum catalyst like platinum 1,3-divinyl-1,1,3,3-tetramethyldisfloxane complex. Side-chain smectic, liquid crystalline polymer was obtained from 1-methyl-1-[3-{(4-cyanobiphenyl-4'-yl)oxy}propyl]dimethylsiloxysilacyclobutane. In the polymerization by butyllithium or phenyllithium, monomers corresponding to the amounts of the initiator were consumed, but no polymers were formed. Apparently, elimination of the trimethylsiloxy or triphenylsiloxy group occurred in the nucleophilic attack of the initiator or propagating species on the silicon atom of the monomer.
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    Preliminary investigations on polymerization catalysts composed of lanthanocene and methylaluminoxane (1998)
    Springer
    Polymer bulletin 40 (1998), S. 729-734 
    Details
    ISSN: 1436-2449
    Keywords: (Keywords: lanthanocene; methylaluminoxane; polymerization; butadiene; isoprene; styrene.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The polymerization of butadiene(Bd), isoprene(Ip) and styrene(St) has been examined using the six catalyst systems composed of lanthanocene, (C5H9Cp)2NdCl(I), (C5H9Cp)2SmCl(II), (MeCp)2Sm OAr'(III), (Ind)2NdCl(IV), Me2Si(Ind)2NdCl(V) and (Flu)2NdCl(VI), and methylaluminoxane(MAO) respectively. All of them can be used to form the polyisoprene with molecular weights of 1 to 10 thousand and cis-1,4-unit contents of 41 to 47%. (I), (II) and (III) of them can be also used to form the polybutadiene with molecular weights of 10 to 20 thousand and cis-1,4-unit contents of 62 to 78%. In addition, the catalysts from (II) to (V) are still active for St polymerization and (II) of them gives a syndio -rich random polystyrene. It is noteworthy that (II) and (III) are active for homopolymerization of Bd, Ip and St in the same polymerization condition.
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    Phase transition of 2,3-O-methylcellulose (1998)
    Springer
    Polymer bulletin 40 (1998), S. 741-747 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this work, a series of 2,3-O-methylcellulose (MC) with different DS value were prepared. Its phase transition behavior in aqueous solution was studied in terms of DS value, concentration and molecular weight. The the following conclusions were obtained. (1) All the 2,3-O-MC samples show no sol-gel transition in aqueous solution despite the molecular weight. (2) No phase separation was observed for the 2,3-O-MCs with a DS value lower than 1.0, even when the temperature was raised to 95°C. (3) The precipitation temperature is surprisingly different between 2,3-O-MCs. and other MCs possessing comparable total DS value. (4) The precipitation temperature of 2,3-O-MCs depends on the molecular weight rather than on the concentration.
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    Polyacrylamide obtained by plasma-induced polymerization for a possible application in enhanced oil recovery (1998)
    Springer
    Polymer bulletin 40 (1998), S. 757-764 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Ultrahigh molecular weight polyacrylamides (PAAM) were obtained by plasma-induced polymerization in water solutions. The influenceof monomer concentration, sealing pressure, initiation time and post polymerization period on polymer yield and molecular weight were investigated. The viscosity and “screen factor” measurements, as well as the thermally stimulated depolarization currents spectroscopic data of the synthesized polymers, indicate good properties as efficient viscosity modifiers in displacement of fluids for enhance oil recovery (EOR).
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    The relaxation behavior of amorphous PET in global chain orientation but nearly random segmental orientation (GOLR) state (1998)
    Springer
    Polymer bulletin 40 (1998), S. 773-778 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In this report, the relaxation behavior of amorphous poly(ethylene terephthalate) (PET) in global chain orientation but nearly random segmental orientation (GOLR) state is studied by infrared dichroism, optical birefringence and hot shrinkage measurements at temperatures below or up PET's glass transition temperature, Tg. The results indicate that the difference in the relaxing rate between global chains and segments is at least in ∼ 102 times order above PET's Tg (∼ 84°C), with a rough approximation; while the sudden decrease of small Δn of the sample (∼ 10−4) upon being treated at about 85 ∼ 90°C, implies us that the small Δn is closely related with the orientation of global chains.
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    In memoriam: Reimund Stadler, Editor of Polymer Bulletin (1998)
    Springer
    Polymer bulletin 41 (1998), S. 129-130 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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    URL: http://dx.doi.org/10.1007/s002890050342
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    High molecular weight polyurethanes and a polyurethane urea based on 1,4-butanediisocyanate (1998)
    Springer
    Polymer bulletin 41 (1998), S. 131-138 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary New biomedical polyurethanes and a polyurethane urea based on Ε-caprolactone and 1,4-butanediisocyanate have been developed. On degradation, only non-toxic products are produced. The polyurethane urea with poly(Ε-caprolactone) soft segments and butanediisocyanate/butanediamine hard segments shows a high tensile strength, a high modulus and a high resistance to tearing but as a result of the strong interactions between the solvent and the polymer processing is difficult. When butanediamine is replaced by butanediol in the chain extension step, a processible polyurethane is obtained but the polymer lacks the desired mechanical properties for biomedical applications. By chain extending with a longer urethane diol block, a processible polymer was obtained with mechanical properties comparable to the polyurethane urea. This polyurethane has been made porous and can be used as a meniscal prosthesis.
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    Inversion of stereoselectivity in 1,3-butadiene polymerization with a niobium catalyst induced by a change in the solvent system (1998)
    Springer
    Polymer bulletin 41 (1998), S. 175-182 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Catalytic 1,3-butadiene polymerization systems can be obtained with the new complex [NbO(C16H11O6 −)(C2O4 2−)] as a catalyst. When the catalysis occurs in a homogeneous medium (toluene as a solvent) in conjunction with AlEt2Cl, cis-1,4-polybutadiene is obtained. A remarkable inversion of stereoselectivity has been observed when the catalysis is carried out in a two phase system with the molten salt AlCl3.1-methyl-3-n-butyl-imidazolium chloride (MBIC) as a solvent and AlEt2Cl as a cocatalyst, giving the trans 1,4-polybutadiene.
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    Use of branched aliphatic linkers for the preparation of selective chiral media for the HPLC separation of enantiomers (1998)
    Springer
    Polymer bulletin 41 (1998), S. 183-189 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Highly branched aliphatic molecules have been used for the first time as tethers in the preparation of polymeric chiral stationary phases. Attachment of a specifically designed chiral selector to organic porous polymer beads through a branched linker substantially increases the enantioselectivity compared to that of the equivalent separation medium with a traditional linear tether.
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    An EPR study of polysaccharide copper(II) complexes in composite dextran/epichlorohydrin gels (1998)
    Springer
    Polymer bulletin 41 (1998), S. 199-206 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The EPR spectra of composite dextran and carboxymethyldextran gels were studied in order to identify the functional groups involved in copper(II) complexation depending on pH. The porous structure resulting from crosslinking of polymer chains of dextran, via epichlorohydrin, forces the immobilization of Cu2+ ions surrounded by different oxygen groups of the polymer gel matrix. The different polynuclear structures are postulated to be formed depending on the type of polysaccharide derivatives. The results indicate that carboxyl and deprotonated hydroxyl groups participate in the complex formation.
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    Electronic absorption spectroscopy of liquid systems containing polystyrene and polyacrylonitrile 1. Individual polymer solutions (1998)
    Springer
    Polymer bulletin 41 (1998), S. 207-213 
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    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Individual polystyrene (PS) and polyacrylonitrile (PAN) solutions in N,N-dimethylformamide (DMF) were studied by electronic absorption spectroscopy. Upon increasing the polymer concentration in the PS-DMF binary system a bathochromic shift of the band at about 260 nm was found. This spectral effect could be explained by an association of PS phenyl groups and/or by a complex formation between DMF and PS. The UV spectrum of PAN in DMF solution was interpreted in terms of the variety of possible donor-acceptor complex formations. The specific intermolecular interactions in the investigated binary liquid systems were discussed on the basis of the spectral data.
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    Swelling behavior of emulsion polymer particles: comparison between fully cross-linked and partially cross-linked poly(acrylate) latexes (1998)
    Springer
    Polymer bulletin 41 (1998), S. 231-237 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Measurement of swelling is used to estimate the extent of cross-linking of latex particles prepared by emulsion polymerization. In this paper we report swelling data as a function of solvent activity for two latexes: (1) a poly(butylacrylate) (PBA) latex, and (2) a poly(isodecylacrylate) latex. In the latter case comparison is made between the swelling behavior of fully cross-linked, i.e., networks without free polymer chains, and partially cross-linked latexes. It is demonstrated that the equilibrium swelling properties are only slightly affected by the presence of uncross-linked chains. Swelling gives reliable results for the cross-link density only if the latex does not contain free chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050356
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  • 86
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    The strength of the tailored polymer/inclusion interface in polymer composites evaluated in situ by acoustic emission (1998)
    Springer
    Polymer bulletin 41 (1998), S. 247-252 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary A correlation between interface strength and data of acoustic emission measurements in particle filled polymer composites was found. The method allows the evaluation of the interface strength in situ in polymer composite specimens at uniaxial loading. The measurements have shown that the tailored interface with the monomolecular tethered polymer layers of various grafting density change the mechanism of microdefect formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050358
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  • 87
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    The synthesis and thermal phase transition behavior of poly(N-isopropylacrylamide)-b-poly(ethylene oxide) (1998)
    Springer
    Polymer bulletin 40 (1998), S. 455-460 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary By using the redox reaction between Ce(IV) and terminal -CH2OH groups of polyethylene oxide(PEO), block copolymers composed of poly(N-isopropylacrylamide)(PNiPAAm) and poly(ethylene oxide) was prepared. The aqueous solution of the block copolymers exhibited thermal phase transition and the phase transition temperature of these block copolymers became higher than the PNiPAAm homopolymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050276
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  • 88
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    Side-chain liquid crystalline polyurethanes on the basis of biphenyl mesogenic units (1998)
    Springer
    Polymer bulletin 40 (1998), S. 469-476 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Liquid crystalline diols containing a biphenyl mesogenic core, methoxy or cyano terminal groups and spacers of various lengths were synthesized and used for the preparation of side-chain thermotropic polyurethanes. The structure of the synthesized diols and polymers was confirmed by elemental analysis, FTIR and NMR spectroscopy. Phase transition temperatures were studied by DSC, while optical textures were characterized by polarizing microscopy. A smectic type arrangement was found for the mesophases of all products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050278
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  • 89
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    Polyurethane toughened polylactide (1998)
    Springer
    Polymer bulletin 40 (1998), S. 485-490 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Brittle polylactide (PLA) was toughened by introducing 5 wt % of a poly(ɛ-caprolactone)(PCL) diol- and triol-based polyurethane (PU) network. The extent of cross-linking of the PU was varied by changing the ratio between diol and triol. The effects of the PU content and its crosslink density on the mechanical properties and the toughness of PU/PLA blends were investigated. Maximum toughness of PU/PLA blends, an order of magnitute higher than that of pure PLA, could be achieved by the use of a proper amount of PU and a proper extent of cross-linking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050280
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  • 90
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    Effects of cyclization and electrostatic interactions on the termination rate of macroradicals in free-radical crosslinking copolymerization (1998)
    Springer
    Polymer bulletin 40 (1998), S. 491-498 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Effects of cyclization and ionic group contents on the termination rate of macroradicals formed at zero monomer conversion were investigated. For this purpose, the pregel regime of free-radical methyl methacrylate / ethylene glycol dimethacrylate (MMA/EGDM) and acrylamide / N,N'-methylenebisacrylamide (AAm/BAAm) copolymerization systems was studied by means of the dilatometric technique. To eliminate the chain-length dependent variation of the termination rates, different sets of experiments were carried out each at a fixed monomer and initiator concentration. At low crosslinker contents, the termination rate of zero-conversion macroradicals was enhanced in crosslinking copolymerizations compared to linear polymerization. This is due to the cyclization reactions which reduce the size of the macroradical coils and thus, enhance the termination rates due to the lowering of the thermodynamic excluded volume effect. As the amount of the crosslinker increases, an enhancement in the initial rate of polymerization is observed in all series of experiments, indicating that steric effects on segmental diffusion dominate at high crosslinker contents. The results also indicate a slower rate of termination of ionic macroradicals compared to the non-ionic radicals of the same molecular weight and points the significance of the thermodynamic excluded volume effect on rising the ionic group content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050281
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  • 91
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    Thermal stabilities of end groups in hydroxyalkyl terminated polydimethylsiloxane oligomers (1998)
    Springer
    Polymer bulletin 40 (1998), S. 525-532 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thermal stabilities of α,ω-hydroxypropyl, α,ω-hydroxybutyl, α,ω-2-hydroxypentyl and α,ω-hydroxyhexyl terminated polydimethylsiloxane (PDMS) oligomers were studied. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating, through the loss of functional end groups as determined by FT-IR spectroscopy and gel permeation chromatography. α,ω-Hydroxyhexyl and α,ω-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. Instability of the end groups is due to the back biting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5 and 6 membered, stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the oligomers produced, as determined by gel permeation chromatography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050286
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  • 92
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    Use of mass spectrometry for the analysis of molecular weight distribution and macrocycles in fuctionalized oligo-ɛ-caprolactones synthesized by heterogeneous AROP in protic conditions (1998)
    Springer
    Polymer bulletin 40 (1998), S. 541-548 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary. Functionalized oligo-ɛ-caprolactones synthesized by heterogeneous coordinated anionic ring opening polymerization (AROP) in protic conditions have been analyzed by mass spectrometry in order to investigate the molecular weight distribution as well as the possible occurrence of macrocycles. Mass spectra obtained from LSIMS revealed the presence of fragmentation products and some of them have been identified. Macrocycles were also detected. Nevertheless, ESI and MALDI-TOF spectrometries do not confirm the presence of macrocycles in the samples. The same results have been obtained by analysis of commercially available polycaprolactones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050288
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  • 93
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    Apparent contrast reversal in tapping mode atomic force microscope images on films of polystyrene-b-polyisoprene-b-polystyrene (1998)
    Springer
    Polymer bulletin 40 (1998), S. 549-554 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thin films of phase separated polystyrene-b-polyisoprene-b-polystyrene block copolymers were studied by tapping mode atomic force microscopy. The relative contrast in height and phase mode images of the phase separated regions was found to be very sensitive to changes in the operating conditions of the microscope. Contrast variations and reversals were observed for height and phase mode images as a function of the set-point amplitude ratio and drive frequency. No unique height or phase contrast was observed for the the tri-block copolymer system examined in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050289
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  • 94
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    Dielectric studies on allyl methacrylate-methyl methacrylate copolymers in a slightly polar medium (1998)
    Springer
    Polymer bulletin 40 (1998), S. 563-568 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Dielectric constants of allyl methacrylate-methyl methacrylate copolymers are measured in toluene solution at a constant frequency of 2 MHz, within a wide temperature range (20–70°C). Soluble copolymers have been prepared by group transfer copolymerization. Dipole moments are calculated from Guggenheim-Smith equation. The effects of allyl group on the dipole moments of copolymers in a slightly polar medium are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050291
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  • 95
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    Influence of some aromatic amino acids on the swelling behavior of acrylamide/maleic acid hydrogel (1998)
    Springer
    Polymer bulletin 40 (1998), S. 575-581 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Influence of some aromatic amino acids (histidine, phenylalanine and tryptophan) on the swelling behavior of acrylamide/maleic acid hydrogel (AAm/MA) prepared by γ-radiation was investigated. Swelling tests of AAm/MA hydrogel were made in buffer solutions and amino acid solutions at various pH at 37°C. The pH values are ionization of α-carboxyl groups (pK'1), α-amino groups (pK'2) and, isoelectric points (pI) of amino acids. The swelling of AAm/MA hydrogel increased when pH values of solutions were increased. The value of equilibrium swelling of AAm/MA hydrogel was 1035% at pH 10 buffer, while it was 880% at pH 2 buffer. The values of equilibrium swelling of AAm/MA hydrogel in phenylalanine, tryptophan and histidine solutions varied among 1130–1245% at pH 10, while they were among 790–975% at pH 2. The rate constant of swelling, diffusional exponent, network parameter and, diffusion and intrinsic diffusion coefficient were calculated by swelling kinetics. Diffusion of the penetrants into the hydrogel was found to be non-Fickian character. The diffusion coefficients of the hydrogel varied between 3.33×10−6– 7.71×10−6 cm 2s−1, while the intrinsic diffusion coefficients waried between 4.03×10−6– 8.48×10−6 cm 2s−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050293
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  • 96
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    Study of rubber-modified epoxy resin using thermally stimulated current (1998)
    Springer
    Polymer bulletin 40 (1998), S. 599-605 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In order to characterize the low temperature relaxation of epoxy resin modified with amine-terminated butadiene acrylonitrile copolymers (ATBN), thermally stimulated current (TSC) and relaxation map analysis (RMA) were investigated. Four relaxation peaks at around −140, −100, −60 and 0°C were observed as the indication of γ-, β-relaxation of epoxy resin, Tg, new unknown peak of ATBN, respectively. The unknown peak at around 0°C was observed due to dipole orientation. The RMA data was showed that compensation temperature (Tc) and degree-of-disorder (DOD) were increased with increasing the content of acrylonitrile and ATBN, whereas the compensation time (τc) was decreased. It can be concluded that the cooperative molecular motion in cured epoxy resin was more active as the concentration of acrylonitrile and ATBN content increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050296
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  • 97
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    Conducting copolymers of polypyrrole/polytetrahydrofuran (1998)
    Springer
    Polymer bulletin 40 (1998), S. 639-645 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Bifunctional living polytetrahydrofuran (PTHF) was terminated with potassium salt of pyrrole to yield polymers with electrochemically active end groups. These polymers were employed in the second stage to obtain conducting polypyrrole/polytetrahydrofuran block copolymers with short and long polytetrahydrofuran segments by potentiostatic anodic polymerization of pyrrole in different electrolytic media. Syntheses of block copolymers were achieved in media where tetrabutylammonium fluoroborate, sodium perchlorate and sodium p-toluenesulfonate were used as the supporting electrolytes. Characterizations were based on DSC, TGA, SEM, FTIR, and CV analyses. No significant effect of the chain length of polytetrahydrofuran segments on the properties of the copolymers was observed; however, thermal, electrochemical behaviors, and surface morphologies of the films were greatly affected by the supporting electrolytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050302
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  • 98
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    Effect of the molecular structure of graft copolymer on the interfacial behavior between two immiscible homopolymers: A Monte Carlo simulation (1998)
    Springer
    Polymer bulletin 40 (1998), S. 607-612 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The effects of molecular structure of graft copolymer on the interfacial properties are investigated using a Monte Carlo simulation. The interfacial activity is analyzed by calculating the surface coverage and the concentration profile of graft copolymer at the interface. At low interaction energy between two segments, the graft copolymer having fewer grafting sites and longer grafting chains locates better at the interface than the graft copolymer having more grafting sites and shorter grafting chain. At high interaction energy, this situation is reversed: the graft copolymer with more grafting sites locates better than the copolymer with fewer grafting sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050297
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  • 99
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    Vinyltrimethylsilane-co-N-vinyl-2-pyrrolidone and vinyltrimethoxysilane-co-N-vinyl-2-pyrrolidone copolymers Synthesis and reactivity ratios (1998)
    Springer
    Polymer bulletin 40 (1998), S. 707-713 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Copolymers containing vinyltrimethylsilane and vinyltrimethoxysilane with N-vinyl-2-pyrrolidone at different compositions were synthesized and characterized. The reactivity ratios was estimated by using the classical Fineman-Ross and Kelen Tüdos linear fitting procedures. These parameters were also estimated through a computer program based on nonlinear minimization algorithm, starting from the r1 and r2 values obtained by the former procedures. The analysis of the results allow us to interpret the reactivity behaviour of these polymers in terms of the relative reactivity of the substiuents. The effect of the chemical structure of the polymer side group is discussed in terms of the different contributions to the stabilization of the radical intermediates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050312
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  • 100
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    Highly Pb(II)-selective resin based on crosslinked poly(acrylamido glycolic acid) copolymer (1998)
    Springer
    Polymer bulletin 40 (1998), S. 721-728 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: SUMMARY The crosslinked poly(acrylamido glycolic acid) (180-250 µm) was used in the adsorption/desorption studies. Adsorption rate, capacity of the resin for the selected metal ions, i.e. Cd(III), Zn(II), Hg(II), Pb(II), and Cr(III) were investigated in aqueous media. At different pH values (1.0–5.0) very high adsorption was observed for Pb(II) at pH 3 and 5. The adsorption equilibrium was rapidly achieved in about 5–10 min. However, when the Pb(II) ions competed with Cd(II) (in the case of the adsorption from their binary mixture) the amount of adsorption for Pb(II) decreased. Desorption of Pb(II) was studied by using 1-4M HNO3 and 1-4M HClO4. High desorption ratios (more than 90%) were achieved in all cases. Adsorption/desorption cycles showed the possibility of repeated use of this resin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050314
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