材料常用流动应力模型研究

Research on material flow stress models in common use

材料流动应力模型是金属成形数值模拟的重要参数之一。对于中厚板体积成形而言,经常规板料拉伸试验所得的流动应力范围达不到数值模拟的需要,对应大应变的流动应力一般借助外推模型进行估测。选用不同的外推模型使得中厚板体积成形数值计算所得的成形力存在较大的偏差,这种偏差会影响压力机的选择和模具强度的校核。基于中厚板材料的拉伸试验曲线结果,采用物理分析和数学推导相结合的方法研究了8种外推模型的拟合准确度、物理意义、硬化程度等因素。研究结果对中厚板体积成形数值模拟中材料流动应力模型的选择具有一定的理论指导。

Material flow stress model is an important parameter in finite element simulation of metal plasticity forming. The range of flow stress tested in ordinary sheet tensile test can not satisfy the demand to simulate the bulk forming of medium-thick sheet. And the flow stress at large strain is usually estimated by extrapolating model. In the numerical simulation of medium-thick sheet metal forming, different extrapolating models may lead to large deviations in the forming forces, which could influence the selection of press machine and the strength checking of die. Based on the tensile curve of the medium-thick sheet, some factors of eight extrapolating models, such as the accuracy of curve fitting, physical meaning and hardening degree were studied by the complex method of physical analysis and mathematical derivation. The results could provide some theoretical reference for the selection of material flow stress models in medium-thick sheet metal bulk forming simulation.