繰返し曲げと静的ねじり負荷が重畳する平板に発生した表面き裂の進展挙動

抄録

Crack propagation behavior under combined stress state of cyclic bending and static torsion is investigated for A7075 aluminum alloy. The propagation direction and the propagation rate of a fatigue crack that occurs from a small hole machined at the specimen surface are affected by a static shearing stress. Especially, the crack propagation rate increases by the existence of a static shearing stress. If the maximum stress intensity factor obtained by using equivalent alternating stress Σ_a and equivalent static stress Σ_m is used for arranging the crack propagation rate, all data fall on the almost same curve. Crack opening displacement at the crack tip perimeter increases by the existence of a static shearing stress. The opening component of a static shearing stress is considered to be responsible for this result. If the crack opening displacement behind 50μm from crack tip is used for arranging the crack propagation rate, the unique relation is obtained regardless of the presence of a static shearing stress.