磁脉冲成形板坯动态结构失稳力学分析

Mechanical analysis of the dynamic structural instability of sheets during electromagnetic forming process

为揭示磁脉冲成形过程中板坯的塑性失稳机制,基于板坯磁脉冲拉伸成形工艺试验,结合板坯在脉冲电磁力作用下的变形特点,对板坯在动态加载条件下的结构失稳行为进行了力学解析。结果表明,脉冲电磁力作用的板坯动态变形过程中惯性力的影响显著。惯性力作用下,板坯变形依次经历脉冲力加载和惯性运动两个典型阶段,其动态塑性变形符合初期塑性变形伴随着动能的吸收、后期塑性变形产生于动能的耗散模式。惯性力的存在使得板坯对自身的结构失稳具有自我抑制作用,有助于分散变形,提高板坯的塑性。

In order to reveal the plastic instability mechanism of sheets during electromagnetic forming （EMF）, the dynamic structural response of blank undergoing pulsed magnetic forces was analyzed on the bases of the dynamic plastic deformation char acteristies of EMF upon establishing the typical dynamic magnetic tensile experiments. Mechanical analysis results show that iner- tia force plays an important role in dynamic forming, which results in two typical deformation stages, the pulsed magnetic force affecting stage and the inertial motion stage, successively. The involved dynamic deformation modes accord with the law that the initial plastic deformation associated with the absorption of kinetic energy and the latter plastic deformation produced from the dis- sipation of the kinetic energy. And the presence of inertia force makes the blank exhibit the characteristic of self-inhibition of its own structural instability, which is helpful to spreading deformation instability and to improving the formability of sheets.