一种结合晶体塑性及扩展有限元的短裂纹扩展模拟方法

The short crack growth process of polycrystalline metal materials is affected by the microstructure such as grain sizes, crystallographic orientations and grain boundary blocks, which results in the crack growth rate showing obvious fluctuation characteristics. With the same stress intensity factor, the growth rate of short crack is higher than that of long crack, which makes the prediction of short crack growth process based on long crack growth model often get dangerous results. Therefore, combined with crystal plasticity and extended finite element method, a short crack growth simulation method reflecting the effect of microstructure was proposed in this paper, and the in situ test of fatigue short crack growth of powder superalloy FGH96 was verified. Using EBSD test results as a input, a mesoscopic finite element model of short crack growth was built to characterize the effects of grain sizes and crystallographic orientations. The crystal plasticity was introduced into extended finite element method to characterize the effect of grain boundary block based on slip system constitutive and plastic shear strain rate. The results show that the proposed method can effectively describe the fluctuation characteristics of short crack growth rate, and the prediction accuracy of fatigue short crack growth life is significantly improved.