アルミニウムの疲労き裂伝ぱに及ぼす結晶粒径の影響

概要

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The effect of grain size on the fatigue crack propagation was studied on pure aluminium in fully reversed plane bending. The crystallographic deformation in the vicinity of fatigue crack was observed by means of the X-ray microbeam technique and optical microscopy. The propagation rate of fatigue crack was found to increase with increasing grain size. The crack propagation was observed to be occasionally retarded by the grain boundary. Since the crack meets the grain boundaries more frequently in the specimen of smaller grain sizes, the crack propagation rate is smaller than that in the specimen of larger grain sizes. This interprets the grain size dependence of crack propagation. On the other hand, the propagation rate of fatigue crack could be expressed by a power function of the excess dislocation density in subboundary (Db)_<max> or the subgrain size t in the grain at the crack tip with a positive or negative exponent. By analysing the development of substructure and the propagation of crack, the crack propagation in one grain seems to be essentially ruled by the substructure .
1977-12-15