非比例負荷を受けるA7075アルミニウム合金の表面き裂進展寿命予測

抄録

The growth direction and growth rate of fatigue cracks initiated from the surface of A7075 aluminum alloy plate were investigated under 6 sets of nonproportional loadings produced by the combined axial-torsion loading. The digital image correlation method was simultaneously applied to measure the crack opening displacements around the crack tip during the fatigue tests. Fatigue crack tended to propagate orthogonally to the direction in which the resultant normal stress in the nonproportional loading cycle was maximized, suggesting that the maximum resultant normal stress dominate crack growth under nonproportional loadings. The growth lifetime until the surface crack penetrates the plate could be estimated with an accuracy of about 20% based on the modified Paris-type equation through numerical integration.