Constitutive models of plasticity for anisotropic sheet metals for cold/warm forming and their forming simulation applications

本工作涉及塑性本构模型及其在板料成形模拟中的应用。（1）提出了一种能较好地描述板料的Bauschinger效应、循环硬化特性和各向异性的大应变循环塑性本构模型--Yoshida-Uemori模型。通过循环塑性和双向拉伸试验，将模拟结果与相应的试验结果进行了比较，验证了该模型的正确性。(2)提出了一个描述退火钢屈服点现象的模型。(3)研究了温度和应变速率对A5083铝合金和AZ 31镁合金板材粘塑性行为的影响。根据试验结果，提出了粘塑性本构模型。[2]板料成形数值模拟与工艺设计（1）将上述Yoshida-Uemori模型应用到商业有限元程序PAM-STAMP中，对帽形拉弯成形和S形轨成形进行了有限元模拟。结果表明，该模型对板料拉深和回弹的预测比传统的各向同性硬化塑性模型更准确。(2)提出了一种考虑模具弹性变形的回弹分析新算法。(3)提出了一种通过优化拉延筋设置来控制回弹的方法。(4)本文提出了一个板料拉弯断裂极限的判据。(5)通过实验和数值模拟研究了胶接板料的成形性能。(6)提出了一种局部加热板料渐进成形新工艺。

This work deals with the constitutive modeling of plasticity and its application to sheet metal forming simulations. The summary of the research results is as follows :[1] Constitutive modeling(1) A constitutive model of large-strain cyclic plasticity, which properly describes the Bauschinger effect and cyclic hardening characteristics, as well as the anisotropy of sheet metals, Yoshida-Uemori model, has been proposed. This model has been verified by comparing the simulated results with the corresponding experimental results for deformation behavior in cyclic plasticity and bi-axial stretching tests.(2) A model to describe the yield-point phenomena of annealed steels has been proposed.(3) The effects of temperature and strain rates on the visco-plastic behavior of an aluminum alloy (A5083) and a magnesium alloy (AZ31) sheets were experimentally investigated. Based on the experimental observations, constitutive models of visco-plasticity have been presented.[2] Numerical simulations and process design for sheet metal forming(1) The above Yoshida-Uemori model has been implemented to a commercial FE code of PAM-STAMP, and using this, FE simulations of a hat-type draw-bending and S-rail forming were performed. From the results, it was found that the predictions of sheet draw-in and springback by this his model are more accurate than those calculated by a conventional model of the isotropic hardening plasticity.(2) A new algorithm for springback analysis taking account of the elastic deformations of dies has been proposed.(3) A method of springback control by optimum drawbead setting has been presented.(4) A criterion for fracture limits of sheet metals under stretch bending has been proposed.(5) Formability of adhesively-bonded sheet metals has been investigated by performing experiments and numerical simulations.(6) A new technology of incremental sheet-metal forming with local heating has been proposed.