ISSN:
1460-2695
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Maschinenbau
Notizen:
Abstract— Fatigue crack propagation behaviour under variable amplitude loading is significantly influenced by load history induced sequence effects. Because the understanding of the causes of such sequence effects is still rather limited, crack propagation predictions become difficult. In the present investigation an exploratory test program with simple variable amplitude load sequences was performed, which was designed to improve the general understanding of sequence effects and to offer a basis both for an evaluation of existing crack propagation prediction models and for the development of improved methods.The investigations were performed on center cracked 8 mm thick Al 7475-T7351 specimens. In the first part of the study constant amplitude tests were performed over a wide range of R-ratios. The test results and the transition of the fracture mode during tests could be represented on the basis of the effective ΔK-value.In the second part of the paper tests with simple systematically varied sequences of high loads, low loads and underloads were performed and the crack propagation behaviour was measured. In order to obtain detailed information on the crack propagation increments per cycle, fractographic analyses were also performed. It was found that also under variable amplitude loading the crack propagation approximately followed the effective ΔK-values, except in one case.A linear (non-interaction) prediction model could not describe the observed crack propagation behaviour. The results of the application of a model assuming a constant crack opening level are also given. Finally, some general viewpoints regarding further developments of models are outlined.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1460-2695.1987.tb00210.x
Permalink