非均质材料微成形过程的晶体塑性模拟

Crystal plasticity simulation study on the micro-forming of heterogeneous materials

微塑性成形中,由于参与变形的晶粒数量有限,材料非均质现象显著,基于均匀化假设的宏观弹塑性模型不再适用,为了研究有限数量晶粒组成的材料塑性变形过程,需结合其微结构与微观塑性变形机制.参照金属材料的微结构,构建了非均质多晶模型,采用晶体塑性本构关系和Cauchy应力更新算法,设计了材料子程序(VUMAT),对含不同晶粒数目的圆形板料拉深过程进行模拟分析.研究表明,非均质多晶板料成形的筒形件具有明显制耳,但制耳轮廓无规律.晶粒数目增加会弱化材料非均质现象,使制耳高度降低,但又引起晶粒间约束增强,使拉深力小幅增长.

In the micro-forming process,as the grains involved in deformation are limited,the material becomes obvious heterogeneous.The phenomenological elasto-plastic model,which is based on the homogeneous hypothesis,is not suitable to this case.In order to study plastic deformation of the material consisted of limited grains,the material microstructure and crystalline deformation mechanism should be considered.The deep drawing process of the material consisted of different amounts of grains was simulated by building a heterogeneous polycrystalline model.A material subroutine（VUMAT）,adopting the crystalline plasticity constitutive relation and Cauchy stress updating algorithm,was developed to describe the plastic behavior of grains.The simulations show that remarkable earing occurs during the deep drawing of the heterogeneous material,and the ears are lack of regular pattern.Increasing the number of grains will weaken the heterogeneity and make the height of ears lower.On the contrary,the restrictions between grains are strengthened,and the deep drawing force increases slightly.