ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00711.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract—This paper is concerned with the use of a Markovian stochastic crack growth model to predict crack growth behavior in zones affected by a single overload application. The model introduces an effective stress intensity factor in the definition of the transition intensity of the stochastic process. This in turn, generates a unified probability growth law that was used to predict scatter in single overload history. An experimental program was carried out on compact tension specimens of Ti‐6Al‐4V material to generate sample crack growth curves, each of which contains three single overload zones. The sample curves were then manipulated into experimental constant probability growth curves. These curves were compared with those theoretically generated using the proposed model. A good agreement was established between these two data

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00712.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract—Fatigue crack propagation rates and the fatigue threshold of HT80 steel were measured by maintaining the maximum load during the whole period of random loading in order to prevent fatigue crack closure. The random loading pattern involved 62 level block loadings in which the waveform was approximated to the Rayleigh distribution of peaks. The fatigue crack propagation rates under random loading were well predicted from those obtained from constant amplitude loading and assuming a linear cumulative damage law. That is, da/dn =C{ΔKmeq−ΔKmth} where the equivalent stress intensity factor, ΔKeq={=niΔKmi/dni}1/m, whereni= 0 for ΔKi≤ΔKth, orni=nif

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00713.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract—The feasibility of conducting anR–curve test on centre crack test pieces with a length/width ratio of between 1.3 and 0.25 has been investigated. To allow for the undefined mixed mode loading present with short, wide test pieces, two experimental methods of determining the geometric correction for the stress intensity factor have been proposed and compared. Also an experimental determination of the compliance calibration used to calculate the effective crack length has been made for these geometries. These methods have been evaluated by conductingR‐curve tests on clad 2024‐T3 aluminium alloy centre crack sheet test pieces. 2 m and 760 mm wide panels with length/width ratios of>1.3, 0.5 and 0.25 were tested. The derivedR‐curves agreed well for both widths and for length/width ratios as l

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00714.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract—In order to clarify the statistical behaviour of microcracks, rotating bending fatigue tests of plain specimens were carried out using two kinds of carbon steel with different microstructures, normalized 0.21% C steel and heat‐treated 0.45% C steel. The emphasis is to investigate separately the statistical properties of the initiation and propagation of microcracks through successive observations of the specimen surface. Results show that the microcrack initiation life distributions of normalized and heat‐treated steels are expressed by a two‐parameter Weibull distribution and a Weibull distribution of the mixed type, respectively. On the other hand, the microcrack propagation life distributions of these steels are represented by three‐and two‐parameter Weibull distributions, respectively. The three‐parameter Weibull distribution is well fitted to the crack length distribution for bo

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00715.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract—Recent observations of fatigue cracks bridged by continuous fibers in titanium alloy and titanium aluminide composites are compared to analogous observations in fiber‐reinforced ceramics under monotonic loading. Three failure modes have been identified under axial loading in each case: longitudinal failure (failure parallel to the fibers) and noncatastrophic and catastrophic mode I failure (failure normal to the fibers). The criteria for transition from one failure mode to another are reviewed. Models developed previously to describe the failure of fiber‐reinforced ceramics are extended to describe the mechanics of mode I fatigue crack growth. The extension is straightforward as long as the fibers do not fail in the crack wake, i.e. the failure mode is noncatastrophic mode I fa

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00716.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract—Static and cyclic fatigue in vacuum and air have been investigated for pressureless sintered silicon nitride. Cyclic crack propagation occurred even in vacuum where environmental effects are negligible. Hence such damage is attributed to pure mechanical fatigue unaffected by environment. Crack growth occurs in air even belowKISCCand the growth rate is higher than in vacuum. Therefore, it is believed that cyclic crack growth in air is accelerated by stress corrosion cracking for a wide range ofKmaxvalue

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00717.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00710.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY