2段繰返し変動荷重下の弾塑性疲労き裂進展挙動

概要

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Load-controlled fatigue crack growth tests were carried out on two kinds of steel, SM 50 A and S 35 C, under constant amplitude loading and repeated two-step loading over a wide range from the linear elastic region to the post-yield one; and crack closure was investigated by using the mini computer-aided unloading elastic compliance method. In the case of SM 50 A at the stress ratio R=0, ratcheting deformation took place remarkably under the post-yield region and affected crack growth behavior. However, it was found that this effect could be explained by considering the maximum J integral, J_<max>, and further, that the crack growth rate under variable amplitude loading could be well predicted by the linear summation rule of crack growth by using √(EΔJ/(1-J_<max>/C)) instead of ΔK_<eff> as the fracture mechanics parameter. In the case of S 35 C at R=-1 where only cyclic plastic deformation was observed, the J integral range, ΔJ, was found to be a good parameter in expressing the fatigue crack growth rate under constant amplitude loading. However, under repeated two-step loadings retardation of crack growth at a high load level was observed, even concerning the ΔJ.
一般社団法人日本機械学会の論文
1986-05-25