切口试样破坏过程试验与细观数值分析

EXPERIMENT AND MESOMECHANICAL NUMERICAL ANALYSIS FOR DEFORMATION AND FAILURE PROCESS OF NOTCHED SPECIMENS

对切口圆棒试样与切口板试样进行单向拉伸试验和有限元数值分析 ,以试样最小横截面上各点变化的应力应变场为体胞演化的载荷控制条件 ,采用三维含球形微孔洞体胞模型分别对各点微孔洞长大规律进行数值模拟。结果表明 ,在试样得到的断口韧性区域内 ,微孔洞的生长速度较快 ;试样失稳前微孔洞相对体积百分数最大的区域与试验时试样的起裂位置一致 ,因而证实微孔洞的演化是导致试样材料在拉伸条件下破坏的主要原因 。

The fracture surfaces of notched bar specimens and notched plane specimens under tensile tests were analyzed. Based on the macro finite element numerical calculation, the three dimension cell model with a spherical void was employed to simulate the deformation and fracture progress for these two typical notched specimens under local stress and strain field on the minimal cross section. The loading control on the cell was obtained from triaxial stress parameter, Lode parameter and plastic strain. The results show that the void in the cell model grows faster in the ductile region on the minimal cross section than that on the other areas. The position of the maximal relative volume fraction before the specimen failure is consistent with the position of fracture in the experiment. The results verify that the void growth in the ductile materials is the main reason of failure. And the cell models which are used to analyze the specimens deformation and failure process is valid.