冷間圧延したアルミニウムの疲労き裂先端近傍の下部組織 (<小特集>X線材料強度小特集)

概要

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Crystallographic deformation near the fatigue crack tip in annealed and cold-rolled aluminium was observed by the X-ray microbeam technique. The crack propagation rate is expressed by a power function of the stress intensity factor. However, the exponent and the coefficient vary with the materials and thus the propagation rate of fatigue crack cannot be uniquely defined by the stress intensity factor. On the other hand, according to the observation of microstructure, the recovery of substructure introduced by cold-rolling is not homogeneous in a grain at the crack tip in the heavily cold-rolled material. In this case, if attention is focused only on the micro-structure just ahead of the crack tip, the same relation holds for all materials between the crack propagation rate and the subgrain size or the excess dislocation density in a grain at the crack tip. Therefore the propagation of fatigue crack can be said to be ruled by the substructure ahead of the crack tip.
1978-03-15