(1. 燕山大学 机械工程学院，秦皇岛 066004；
2. 河北省轻质结构装备设计与制备工艺技术创新中心，秦皇岛 066004；
3. 先进锻压成形技术与科学教育部重点实验室(燕山大学)，秦皇岛 066004)
摘 要: 通过理论、实验和模拟相结合的方法，探究超声振动在AZ31B镁合金塑性成形中的“体积效应”影响规律及作用机理。首先基于非局部理论建立了超声振动AZ31B镁合金的应力叠加模型并通过模拟进行了验证，然后基于热激活理论和位错演化理论，建立AZ31B镁合金在超声振动条件下的声塑性模型，并结合实验验证了模型的准确性。结果表明：应力叠加效应导致的应力下降值与超声振动振幅参数正相关。引入超声振动产生的应力下降值可以通过应力叠加效应模型和声塑性效应模型刻画。应力叠加效应导致材料的平均流动应力发生振荡而下降；声软化效应指位错吸收超声能量克服钉扎效应，从而利于材料塑性变形；声残余硬化效应主要体现在高超声能量导致材料位错密度大量增殖，位错在晶界处塞积、堆垛形成位错墙，阻碍塑性流动，导致材料出现残余硬化。
关键字: 超声振动；应力叠加效应；声塑性效应；本构模型
（1. College of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China;
2. Hebei Innovation Center for Equipment Lightweight Design and Manufacturing, Qinhuangdao 066004, China;
3. Key Laboratory of Advanced Forging Technology and Science of Education Ministry (Yanshan University), Qinhuangdao 066004, China）
Abstract:The studies of theory, experiment and simulation were carried out for exploring the “Volume Effect” rule and mechanism of ultrasonic vibration(UV) in plastic forming of magnesium alloy AZ31B. Firstly, the stress superposition model of UV for magnesium alloy AZ31B was established based on non-local theory. And the model was verified by simulation. Then, the UV acoustic plastic model of magnesium alloy AZ31B was established based on thermal activation theory and dislocation evolution theory. The accuracy of the model was verified by the experimental data. The results show that the stress drop is linearly and positively correlated with the UV amplitude. The stress superposition effect model and the harmonic plastic effect model can describe the stress dropping in the ultrasonic assisted forming. The superposition effect causes the average flow stress of the material to oscillate and decrease. Acoustic softening effect refers to the dislocation absorbs ultrasonic energy to overcome the nailing effect, which is beneficial to the plastic deformation of the material. Acoustic residual hardening effect mainly reflects in the high ultrasonic energy leading to a large number of dislocation density proliferation. The dislocation plugs up at the grain boundary to form a dislocation wall, causing the material flow to be blocked. Eventually, the material shows residual hardening.
Key words: ultrasonic vibration; effect of stress superposition; effect of acoustic plasticity; constitutive model
