Fatigue-life predictions including the effects of hold time and multiaxial loads on crack-coalescence behaviour

Brown, M.W., Gao, N. and Miller, K. J. (2000) Fatigue-life predictions including the effects of hold time and multiaxial loads on crack-coalescence behaviour. Strength of Materials, 32 (6), 502-516. (doi:10.1023/A:1005200314976).

Abstract

Two aspects of crack-coalescence behavior are reported. The first concerns a regime frequently referred to in the literature as creep-fatigue interactions but which in this paper is essentially a time-dependent, fatigue-failure process. The second relates to crack coalescence under a wide range of different multiaxial stress-strain states. In the framework of the first approach, a fatigue-crack growth model is derived based on experimental observations during high-temperature, high-strain, reversed-bend, hold-time tests on AISI 316 stainless steel. Essential features of these tests are the compressive and the tensile 60-min hold periods on different surfaces, which induce, respectively, transgranular-short and intergranular-long cracks. The latter, more damaging cracks involve the coalescence of numerous short cracks to form a dominant Stage II crack that leads to failure. Then, in the framework of the second approach, the crack-coalescence model is advanced to predict the fatigue lifetimes for multiaxial, variable amplitude, proportional loading of a medium carbon steel commonly used to manufacture engineering components. It is shown that under high strain fatigue conditions the models used for the calculations of lifetime must necessarily involve crack-coalescence behavior if unsafe lifetime predictions are to be avoided

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Contributors

Author: N. Gao

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