摘要:

Abstract—During constant amplitude loading, two different types of crack systems have been reported In the high cycle fatigue (HCF) region, cracks nucleate on a small number of maxium shear strain amplitude planes One of these cracks becomes a dominant crack and leads to failure of the specimen In the low cycle fatigue (LCF) region, equally developed microcracks are observed over the entire gage section and grow during the majority of the life. The failure is due to a linking in which the microcracks join up during the last few cycles of the fatigue life.To investigate the interaction of these two types of crack systems in biaxial fatigue, experiments were performed on thin‐wall tubular specimens in tension, torsion and combined tension‐torsion loading The test program included step loading and block loading in which two equivalent strain amplitudes were employed. One of the equivalent strain amplitudes is in the HCF region and the other was in the LCF regionFatigue lives were predicted from constant amplitude damage curves when a single crack system dominated the fatigue process Two competitive crack systems were sometimes developed on the maximum shear strain amplitude planes in a single specimen under block loading This resulted in a conservative prediction of the fatigue

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01197.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—Long life corrosion fatigue behaviour is discussed. The importance of (i) quantification of corrosion pit depth (or surface roughness caused by corrosion) as a function of service period and (ii) corrosion pit modelling is emphasized. Extreme value statistics is useful for corrosion pit depth quantification. It is demonstrated that a corrosion pit can be treated as an elliptical crack with the same depth and surface length as a pit. From these considerations, a method for determination of a reasonable allowable stress in corrosion fatigue is proposed. Finally, an example of an allowable stress is given, i.e. the allowable stresses of a real machine component under rotating bending stress are determined from estimation curves of pit depth together with corrosion fatigue crack growth dat

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01198.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—Fretting fatigue strengths of high strength spring steel (JIS SUP9) and low strength medium carbon steel (JIS S45C) were examined by clamping the contact pads of the same individual materials. The pad contact pressures were kept constant at 60 MPa for SUP9 steel and at 45 MPa for S45C steel. The fretting reduced the fatigue strengths by a factor of about two in both the steels. Cyclic J‐integral concepts were successfully employed to predict crack propagation lives using measured data on frictional forces between the fretting pads and the specim

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01199.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—A fracture mechanics model of fretting fatigue has been developed. This enables the calculation of the critical size of defect which can grow under fretting conditions. The model has been applied to the fretting of aluminium alloy 2014A fatigue specimens in contact with 3.5NiCrMoV steel fretting contact pads. The input parameters to the model include externally applied stresses, contact pressure between pad and specimen and frictional forces between the two contacting surfaces. The latter have been measured using a strain gauge technique. Small fretting defects in the fatigue specimens have been investigated metallographically and fractographically. There is good agreement between their size and critical defect sizes calculated using the fretting mode

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01200.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—Recent experimental work on the growth of small fatigue cracks is surveyed and critically analyzed. It is shown that microcracks grow at anomalous rapid rates relative to large ones only when certain criteria, involving crack size, plastic zone size, and micro‐structural element size, are met. Retardation and arrest of microcracks is found to correlate with microstructural element size, hence with crystallographic influe

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01201.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—The paper addresses some aspects of the differences in fatigue crack growth rate behaviour and threshold values obtained for long through‐cracks, short through‐cracks and surface cracks. Attention is focused on plasticity induced closure in the wake behind the growing crack tip. For long cracks at highKmax, closure is found to depend in a linear manner onKmax, i.e.Kop, increases with the size of the monotonic plastic zone. Closure increases at low δKand this is primarily a consequence of the load shedding procedure. If short through‐cracks are prepared by machining specimens containing long cracks, a substantial part of the plastic wake is removed and this can produce marked effects on the closure contribution during subsequent growth. The length of crack “closed” in a long crack threshold test was found to be of the order of 1 mm. Cracks less than this length exhibited “short crack” behaviour: greater than this length, they behaved as “long cracks”, with plastic wake effects apparently fully operative. Small surface cracks exhibit “long crack” behaviour at lengths as short as 0.2 mm and reason

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01202.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract—The behaviour of a low carbon steel has been studied, in particular the initiation, growth and coalescence of fatigue microcracks on the surfaces of smooth specimens via surface replicas and photomicrographs. From the study, quantitative information on the initiation period, growth and coalescence of cracks, statistical distributions of crack length and crack depth, density of cracks, distribution pattern and characteristics of the major crack, were obtained. Knowledge of these parameters is critical for non‐destructive inspection during service life and the application of fracture mechanics to life assessm

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01203.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1985.tb01196.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY