摘要:

AbstractA model for predicting the crack growth rate of an initially angled crack under biaxial loads of arbitrary direction is suggested. The model is based on a combination of both the Manson–Coffin equation for low cycle fatigue and the Paris equation for fatigue crack propagation. The model takes into consideration the change in material plastic properties in the region around the crack tip due to the stress state, together with the initial orientation of the crack and also its trajectory of growth. Predictions of crack growth rate for any mixed mode fracture is based on the results of uniaxial tension experiment

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00060.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper presents a method for the statistical processing of results of initiation and propagation of short fatigue cracks. The distribution of the lengths of these cracks followed a Weibull distribution function. The value of the size parameter of this distribution grows with the number of cycles, but the value of the shape parameter declines as the number of cycles increases. A study of the modal value of fatigue crack lengths as a function of the number of cycles yielded a statistical criterion defining the conversion of the short fatigue crack initiation and propagation stage into the long fatigue crack propagation stage. One condition for this conversion is a zero magnitude of the first derivative of the modal value of fatigue crack lengths by the number of cycles. When the dependence of the Weibull distribution shape parameter and size parameter upon the number of cycles was inserted in this condition, solution of the resultant expression revealed the critical number of cycles that is necessary for the formation of a long fatigue crack.

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00061.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractStress‐controlled, low‐cycle, push‐pull fatigue tests were performed on three variants of the bearing steel SAE 52100 with slightly different compositions and heat treatments. The experiments demonstrated differences in the cyclic plastic behaviour of differently hardened steels (bainitically‐hardened and martensitically‐hardened, respectively), whereas the two martensitic variants, which differ in composition, behaved very similarly. Bainitically‐hardened SAE 52100 steel exhibited initial hardening followed by cyclic softening above a stress amplitude level of 1200 MPa. In contrast, the martensitically‐hardened variants showed a pronounced cyclic hardening. The deformation behaviour of the martensitically‐hardened bearing steel in a monotonic tensile test and during the first cycles can be well understood on the basis of the transformation of retained austenite. This process leads to an onset of plastic deformation at lower stresses compared to the bainitically‐hardened bearing steel. As a result of the subsequent cyclic hardening of the martensitic variants, the CSS curves are almost identical for the differently hardened conditions under investigation. Additional tests under pulsating compression documented that a high negative mean stress enhances the

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00062.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper examines the effect of beam size, fibre volume fraction and various fibres on the flexural behaviour of concretes, and their fracture resistance. The ratio of flexural strength to tensile strength is used as a measure of brittleness; a low value indicating a more brittle material.Two flexural toughness indices are used which provide a basis for analysing load–deflection curves. The relation between these structural indices and the material fracture resistance is assessed by adopting parameters which involve flexural and tensile strengths alone and fibre length to reflect fracture resistanc

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00063.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA fracture mechanics‐based model is developed for the fatigue limit of hardened steels. In such steels, non‐metallic inclusions are known to initiate fatigue cracks. In this work, these inclusions are modelled as spherical voids and, as the fatigue process continues, fatigue cracks are thought to develop from these sites.The growth or arrest of these cracks is analysed in terms of the effective stress intensity range and the corresponding effective threshold for crack propagation. Elasto‐plastic crack closure is evaluated by finite element calculations. The fatigue limit of a sample is defined in terms of crack arrest at all inclusions. Simple equations of the model are presented and compared to experimental data from the literature as well as to an earlier model by Mur

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00064.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA model based on surface strain redistribution and the reduced closure stress of short cracks is shown to successfully predict the fatigue limit and short crack growth behaviour for aluminium alloy 2024‐T351. Using this approach, the length of non‐propagating cracks can be anticipated. The local stress intensity range may be resolved into two components (first the linear elastic fracture mechanics component and the second is due to surface strain concentration). Consequently, the local stress intensity range of aluminium alloy 2024‐T351 is a maximum at a depth of approximately half a grain diameter and a minimum at a depth slightly in excess of three grain diameters. The reduced closure stress for short cracks coupled with the increased applied stress intensity caused by surface strain redistribution accounts for the variation of the effective stress intensity parameter as a function of crack depth. This parameter is a maximum for the smallest possible crack (3 μm) and decreases as crack length inc

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00065.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractThe “cohesive‐crack model” is adopted, together with the hypotheses of small deformations and linear elasticity outside the process zone or “craze”, for the simulation of fracture processes in structures of concrete‐like materials. A “direct”, collocation, multidomain boundary element method is employed and shown to be computationally effective in the considered situations, which are characterized by non‐linearity on interfaces only. Iterative algorithms for the direction search and interface adjustment in propagation analysis and for the determination of the response to a craze‐tip advancement are developed and numerically tested. Softening as an instabilizing factor embodied in the cohesive‐crack model may give rise to path bifurcations (“equilibrium branching”), instability under load control and intrinsic (“snapback”) instability. These phenomena are analysed by the proposed boundary el

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00066.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1992.tb00059.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY