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根据金属塑性材料细观损伤理论及微孔洞损伤机理,建立以孔洞扩张比VG为损伤变量的声发射量化评价模型。以Q345钢圆棒缺口试件拉伸断裂过程为例,获取材料从屈服到断裂过程声发射信息;采用Gurson-Tvergaard-Needleman(GTN)模型,模拟得到Q345试件拉伸过程细观损伤参量数值解。结合声发射测试和数值模拟结果,建立Q345试件拉伸过程孔洞扩张比的声发射累积撞击计数N量化评价公式。结果表明:Q345钢从屈服到断裂过程N与VG函数关系分为线性损伤及非线性损伤两个阶段,并确定当N达到128个时,材料处于损伤临界转变点。
According to the theory of meso-damage of metal plastic material and the mechanism of micro-hole damage, a quantitative evaluation model of acoustic emission with hole-expansion ratio VG as the damage variable was established. Take Q345 steel bar notched specimens for tensile fracture as an example, the acoustic emission information of the material from yielding to fracture was obtained. Using the Gurson-Tvergaard-Needleman (GTN) model, the numerical values of mesoscopic damage parameters solution. Based on the results of acoustic emission and numerical simulation, a quantitative evaluation formula of acoustic emission cumulative impact count Q of Q345 specimen during the stretching process was established. The results show that the relationship between N and VG functions of Q345 steel during yielding and fracture is divided into two stages: linear damage and non-linear damage, and it is determined that when N reaches 128, the material is at the critical critical point of damage.