Abstract
An investigation was carried out on the propagation of cracks in coarse-grained bainitic 0·5 Cr-Mo-V material under both load- and displacement-controlled cyclic loading conditions. All tests were performed at 838 K using cyclic frequencies in the range 10−3–10−5 Hz. Crack initiation and propagation were found to occur as a result of the formation, growth, and linkage of grain-boundary creep cavities and wedge cracks, irrespective of cyclic frequency. Notch-tip creep displacements at crack initiation were comparable to those observed in statically loaded specimens, and time-dependent crack propagation rates also agreed well with data obtained in static tests. Time-dependent crack propagation rates were a function of the specimen displacement rates, suggesting that cavity growth occurred by either a plastic or a constrained-diffusion mechanism.
MST/56
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