応力勾配のある場における疲労き裂発生過程

概要

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Rotating bending fatigue tests were carried out using electropolished specimens with a small transverse hole in a low-carbon steel and an aluminum alloy. The change in surface state near the hole edge was successively observed by a metallurgical microscope using the replica method, and the difference in crack initiation process between a low-carbon steel and an aluminum alloy was investigated. The main results obtained are as follows. 1) The difference in crack initiation process between them is essentially recognized in the case in which a stress gradient exists, similarly as in the case of plain specimens. That is, in the case of a low-carbon steel, fatigue damage is accumulated at a finite region the size of a grain and the region becoms finally a fatigue crack almost at the same time. On the other hand, in the case of an aluminum alloy, the fatigue crack initiates in a fairly small region and gradually grows with the number of cycles. 2) Notch sensitivity of an aluminum alloy as for crack initiation is higher than that of a low-carbon steel. This is due to the difference in the sizes of the region concerned with crack initiation.
一般社団法人日本機械学会の論文
1990-06-25