孔洞在晶界上长大行为的模拟

通过编制率相关有限元用户子程序,运用晶体有限元,通过建立一个包含球形孔洞的双晶粒模型,对FCC晶体中孔洞在晶界的长大行为进行了分析。计算中,晶粒1的取向固定为(0°,45°,90°),晶粒2的取向分别为(35°,45°,90°),(60°,45°,90°),(0°,0°,0°),分别对应于单胞A,单胞B,单胞C,晶界与X轴方向的夹角θ分别取0°,45°,60°。计算结果表明:单胞的断裂模式与两晶粒的取向因子的差异有关,对于两晶粒的取向因子差异最大的单胞B,单胞沿晶界处的等效塑性应变比单胞其它地方的应变大,且最大等效塑性应变在三个单胞中为最大,单胞易于发生沿晶断裂。而对于两晶粒的取向因子差异最小的单胞C,沿晶界的等效应变较小,单胞易于发生穿晶断裂。晶界与X轴方向的夹角θ为45°时,单胞沿晶界处的等效应变较大,单胞易发生沿晶断裂。

SIMULATION OF THE GROWTH BEHAVIOR OF VOIDS LOCATED AT THE GRAIN BOUNDARY

The growth behavior of voids located at the grain boundary is numerically simulated using the three dimensional finite element method considering crystal plasticity theory. To do that, a user material subroutine is created to describe the rate dependent crystal plasticity behavior. A two-grain model including a spherical void is developed, where the orientation of grain1 is (0°, 45°, 90°), and the orientations of grain 2 are (35°, 45°, 90°), (60°, 45°, 90°) and (0°, 0°, 0°) respectively, corresponding to cell A, B and C; the angle between grain boundary and X axis, θ, is 0°, 45° and 60° respectively. Results show that the fracture mode depends on the orientation difference between the two grains. For cell B, with the largest orientation difference, the equivalent plastic strain along the grain boundary is also the largest, as well as the maximum equivalent plastic strain, meaning the unit cell is prone to fail in intergranular fracture. For cell C, with the smallest orientation difference, the equivalent plastic strain along grain boundary is low, and the unit cell is prone to fail in transgranular fracture. The maximum equivalent plastic strain along the grain boundary corresponds to the case of θ = 45°, where the unit cell is prone to fail in intergranular fracture.