Recently, a technique has been developed to render harmless surface cracks which reduce the fatigue limit of metals by 20~60% by the effects of compres-sive residual stress induced by shot peening. This technique is called as sur-face crack non-damaging technology. For the purpose of contributing to reliability improvement of high strength steel equipment by surface crack non-damaging technology, the following research was carried out:
(a) The effects of aspect ratio of surface crack on maximum harmless crack depth (
ahlm) of a high strength was calculated for three residual stress distributions.
(b) Assuming the value of safety factor, the relationship between the maximum allowable crack depth (
acrN) and
ahlm was investigated.
(c) The relationship between maximum detectable crack depth by non-destructive inspection (
aNDI) and
ahlm was compared, assuming that nondestructive inspection could detect the crack with sufficient probability.
(d) The relationship between
ahlm,
aNDI and
ahlm were compared.
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