摘要:

AbstractFatigue cracks were grown in the 5 layer aluminum alloy‐Aramid fiber laminate composite ARALL‐4 over the range of cyclic stress intensity factors (ΔK) from 3.5 to 91 MPa✓m. Near the threshold, crack growth rate was about the same as for unreinforced aluminum alloys, but at high ΔK, crack growth rates were significantly lower. Crack closure was measured over this range of growth rates and found to be different than for unreinforced aluminum alloys. The magnitude of closure was also dependent on crack length. Cracks opened progressively towards the tip with increasing load in much the same way as for unreinforced aluminum alloys. Removal of the aluminum outer layer and some of the epoxy revealed that fibers were intact close to the crack tip, but heavily damaged further away. By adjusting the fatigue crack growth curve of an unreinforced aluminum alloy for the closure exhibited by the composite, it was possible to approximate the crack growth rate for the composite over the lower to mid range of ΔK, but at higher values of ΔK, this model seriously overestimated measured crack growth rates. Therefore, fiber bridging affects both closure and maximum stress intensity factor at the crack tip. Standard fracture mechanics cannot be applied to describe thes

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper presents a simple method for determining the stress intensity factors for small notch‐emanating cracks. The proposed method is based on similarities between elastic notch‐tip stress fields described by two parameters; the stress concentration factorK1, and the notch‐tip radius ρ. The method developed here is rather general, and can be used for a variety of central and edge notches with through‐thickness of semi‐elliptical cracks. The predicted values are in good agreement with the available nume

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractResults are presented of elastic, elastic‐plastic and elastic‐plastic‐creep analyses of an actively cooled cowl lip. A cowl lip is part of the leading edge of an engine inlet of proposed hypersonic aircraft and is subject to severe thermal loadings and gradients during flight. Values of stresses calculated by elastic analysis are well above the yield strength of the cowl lip material. Such values are highly unrealistic, and thus elastic stress analyses are inappropriate. The inelastic (elastic‐plastic and elastic‐plastic‐creep) analyses produce more reasonable and acceptable stress and strain distributions in the component. Finally, using the results from these analyses, predictions are made for the cyclic crack initiation life of a cowl lip. A comparison of predicted cyclic lives shows the cyclic life prediction from the elastic‐plastic‐creep analysis to be the lowest and, hence,

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractAspects of combined rate‐dependent deformation and crack growth in α‐titanium at room temperature are examined. Results are presented for tests carried out on pre‐cracked three point loaded single edge notch bend and compact tension specimens subjected to constant crack opening displacement rates and constant load. Curves of the ratio of the reference stress to the yield stress as a function of the ratio of the plastic displacement to specimen width are found to be different for different rates. The stress difference between continuously loaded curves and curves obtained from load relaxation tests (“relaxed” curves) is found to be similar to uniaxial results. Earlier uniaxial tests show that the “relaxed” curve represents a boundary below which no further creep takes place. The pre‐cracked specimen constant load curves cross the “relaxed” curve, even though the contribution from crack growth to the overall deformation is found to be small. Sustained load crack growth is observed to take place under contained yielding conditions and the sustained load resistance curves are found to be different for differen

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn contrast with overloads, small numbers of underloads lead to acceleration in crack growth rate after application of the underloads. Larger numbers of underloads, however, give rise to retardation effects comparable with the effects of overloads. The retardation effects are attributed to the development of shear lips. Irregular shear lips show a greater effect than regular (smooth) shear lips. Increasing numbers of underloads give rise to greater retardation. For high numbers of underloads at high ΔKeffthere is even an increase in the total life of the fatigue specimen with respect to the situation without underloads. High numbers of underload at high ΔKeffcause crack arrest at one side of the centre‐cracked tension specimen. The non‐growing side is often in single shear, the growing side always in double

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper describes the rationale and details of a conservative pop‐in assessment procedure that has been included in some new ASTM and BSI fracture toughness test methods. The procedure may be used for either graphical or numerical assessments of pop

ISSN:8756-758X    

DOI:10.1111/j.1460-2695.1991.tb00009.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.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY