レーザピーニングによるＡＣ４ＣＨアルミニウム合金の疲労き裂進展抑制

概要

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The effect of laser peening to retard fatigue crack propagation has been demonstrated through rotating bending fatigue tests conducted on pre-cracked AC4CH casting aluminum alloy. The apparent maximum stress intensity factor at the surface of laser peened specimens was nearly equal to four times of the threshold stress intensity factor of long surface fatigue cracks just starting the propagation on AC4CH. The increase of the threshold stress intensity factor was due to the effect of compressive residual stress introduced by laser peening. The three dimensional (3D) image of fatigue cracks was reconstructed by micro computed tomography (<I>μ</I>CT) using synchrotron radiation of SPring-8. The reconstructed images were used to visualize the crack propagation behavior inside the specimens, which could not be attained by usual replication technique. The 3D image of a laser peened specimen showed a legible plastic deformation on the surface of the specimen.