FGH97粉末高温合金缺口试样小裂纹闭合特性数值模拟

Plasticity-induced crack closure (PICC) effect of small crack of notched FGH97 powder metallurgy superalloy specimen was investigated by finite element method (FEM). The influences of five principle factors, namely mesh element size, notch profile, load level, stress ratio and the constitutive model, on crack closure were analyzed. Crack propagation rate was predicted via Walker formula and compared with the test results to confirm the accuracy of FEM. The results show that crack closure level tends to converge if the size of forward plastic zone is ten times bigger than the element size around the crack tip; notch profiles affect crack closure in the closure transient zone, the load determines the crack closure stabilization level; crack closure level decreases with the increase of stress ratio till disappearance; compared with perfectly elastic-plastic constitutive model, the multi-linear elastic-plastic constitutive model shows much less dependency on mesh element size. The predicted crack propagation rate in consideration of crack closure fits well with test results.