摘要:

Abstract—The framework of a new probabilistic model of short fatigue crack growth was laid down in the preceding paper. In this paper, the model is used to analyze growth rate statistics for surface fatigue cracks in Ti 6Al‐2Sn‐4Zr‐6Mo. Specific models are proposed for the evolution of the stochastic growth control variable, which appears subsequently as an independent variable in a parametric law for the growth rate. Comparison with data shows that for cracks of length 10–250 μm in Ti 6–2‐4–6, fluctuations in the instantaneous rate of propagation of each surface crack tip depend only on the visible surface microstructure in the tip's immediate neighborhood. They are not influenced by the microstructural environment of the subsurface crack front. Furthermore, they probably depend only on the sizes of at most the three grains nearest the crack tip, i.e. those within a

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1987.tb00494.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—The authors previously proposed a simulation model for fatigue crack propagation for varying load ranges by considering retardation behaviour due to high level loads and showed that the model could estimate crack propagation lives under quasi‐random loading. However as the model was somewhat simplified, it was predicted that some problems would occur when estimating lives under actual random loads.In this study the model was modified by considering the interaction effect of retardation and acceleration processes of crack propagation based on the test results of two and three level load programs. The model was verified by executing random load crack propagation te

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1987.tb00495.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—Fatigue crack propagation was investigated in polycarbonate and glass fibre reinforced polycarbonate and the effect of stress ratio and glass fibre content determined. The addition of glass fibre increases the tensile strength, but does not always contribute to an increase in fatigue crack propagation resistance. For polycarbonate the effect of stress ratio can be partly explained by using crack closure concepts as other researchers have suggested, but for glass fibre reinforced polycarbonate this was not possible. Fractography revealed a void growth process, which occurred by decohesion at the interface of the glass fibres and the base material, which was dependent on the maximum stress intensity factor. The process of linking the voids and the main crack growth behavior depended on the stress intensity factor range, ΔK.A proposed crack propagation model can explain the effect of stress ratio on crack propagation in fibre reinforced polycarbona

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1987.tb00496.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—Plastic zone sizes in circumferentially cracked round bars in torsion are estimated using an adaptation of the strip yield model. Results are compared with those from elastic‐plastic finite element solutions for elastic‐perfectly plastic and strain hardening material conditions, as well as with previously published data. The strip yield model gives results which are in close agreement with the finite element solutions over a wide range of to

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1987.tb00497.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—Methods are presented for the determination ofJfrom 3 point bend specimens having 0.1 ≤a/W≤ 0.5 using the load versus crack mouth opening displacement trace. It is intended that the procedure be used to determineJc,Jat unstable fracture in the brittle to ductile transition, from specimens and test procedures which conform to the CTOD test standard BS5762. Elastic‐plastic finite element computations are used to demonstrate the adequacy of the proposed estimation procedures forJand to show that it is still possible to apply them to specimens containing welded joints. The problems of defining a centre of rotation for plastic deformation in shallow notched bend specimens are di

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1987.tb00498.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract—TheJ‐integral is an elastic‐plastic fracture mechanics parameter which can be regarded as a measure of the intensity of the crack tip stress and strain fields, irrespective of the plastic zone size. The value ofJat the onset of stable crack extension,JIC, has been suggested as a fracture criterion for both large‐and small‐scale yielding conditions. In this work the value ofJICfor an extruded, medium‐strength aluminium alloy, 2024‐T351 bar, was determined using; (i) the Hutchinson‐Rice‐Rosengren crack tip model and experimentally‐determined crack tip strain profiles; and (ii) the ASTM standard multiple‐specimen technique. Knowing the critical load for initial crack extension from the crack tip strain profile method also enabledJICto be computed using a finite element‐hybrid contour method and a modified linear elastic fracture mechanics approach. Agreement between theJICvalues obtained by the v

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1987.tb00499.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1987.tb00493.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY