Q345试件细观损伤的声发射量化评价实验研究

EXPERIMENTAL STUDY ON ACOUSTIC EMISSION QUANTITATIVE ASSESSMENT OF Q345 SPECIMEN'S MESOMECHANICAL DAMAGE

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。

Based on the mesomechanical damage theory and micro-void damage mechanism, a void growth ratio VG was selected as the damage variable so as to establish an acoustic emission(AE) quantitative evaluation model. Carrying out tensile experiment on Q345 notched bar specimen obtained the AE information from a yield to fracture process. The meso-damage parameters distribution of a tensile specimen was simulated with the Gurson-Tvergaard- Needleman model, and their numerical solutions were achieved. Based on AE testing and Finite Element Simulation, the quantitative evaluation formula for Q345 between the void growth ratio VG and AE cumulative hits N was advanced. The result shows that, in the tensile process of Q345 steel from yield to fracture damage, the function relationship of N and VG can be divided into two stages, namely a linear damage stage and a nonlinear damage stage, and that when the N reaches 128, the material is at the transition state from a linear damage stage to a nonlinear damage stage.