截面形状对材料微孔洞损伤破坏的影响

ON THE EFFECT OF TENSILE SPECIMEN SECTION SHAPE ON VOID DAMAGE OF DUCTILE MATERIALS

为探讨截面形状对金属材料微孔洞损伤破坏的影响,针对圆形、矩形横截面缺口试样进行了拉伸破坏、预拉伸低温冲断试验,断口扫描电镜观察及有限元计算;用细观力学模型计算了缺口试样断裂时微孔洞长大体积率沿断口的分布和断口的起裂位置,并模拟了断口上起裂处微孔洞长大。结果表明:截面形状对材料微孔洞损伤演化有较大的影响,圆形、矩形横截面缺口试样断裂时起裂处微孔洞长大体积率相差较大,微孔洞长大的临界值不是材料常数;用R-T模型、GTN模型模拟非轴对称三轴应力状态下材料微孔洞损伤演化有较大的误差。

In order to discuss the effect of tensile specimen section shape on void damage of metal materials, notch tensile tests and pre-tensile impact crack tests under low temperature are conducted on specimens with round, rectangular section. Fracture surface of SEM is observed. Finite element method is used to simulate the elasto-plastic deformation of the specimens. The distribution of void damage rates along fracture surface , the situation of fracture origin and void growth around the situation of fracture origin are simulated by using mecromechanical model. Results show that section shape of notch specimens have significant influence on void evolution. There exists noticeable difference in void damage rates along fracture surface between round and rectangular section, which means that critical void damage rates is not material constant. There is more error in simulating void growth under unaxisymmetry triaxial stress conditions using R-T model and GTN model.