摘要
基于林位错强化的晶体塑性有限元模型物理意义清晰简洁,具有广泛的应用。然而,只考虑林位错强化的模型忽略了共面位错之间的相互作用,导致模拟结果常常出现异常的扭曲失稳现象。针对以上问题,通过分析位错之间的相互作用,在林位错强化模型中引入自硬化作用对模型进行改进。对改进前后两个模型模拟单晶体沿单个和多个方向拉伸的变形模式以及冷轧铝板剪切带的形成特征进行了比较。结果显示,对于单晶单滑移,两个模型的稳定性表现一致;但是对于单晶多滑移,改进前的模型出现了扭曲失稳,而引入自硬化的改进模型对于多滑移系的模拟符合真实情况,并改善了模型的稳定性问题。对于冷轧铝板发生剪切变形时剪切带的形成特征,林位错强化模型的不稳定性放大了材料的失稳变形,模型的低稳定性和材料的变形失稳叠加,导致预测的结果失稳程度过高;而引入自硬化作用的改进模型改善了稳定性问题,可以真实地反映材料本身的失稳。
Crystal plasticity finite element model based on forest dislocation strengthening is widely used because of its distinct physical basis. However,due to the neglect of coplanar dislocation interactions,the model only considering forest dislocation strengthening usually leads to distorted simulations. For the above problem,through analyzing the interactions of dislocations,the forest dislocation strengthening model was modified by introducing self-hardening effect. Then the deformation modes of single crystal stretched along single direction and multiple directions as well as the formation characteristics of shear band for rolled aluminum sheet simulated by the models before and after modification were compared. The results show that the stability of the two models are consistent for single slip of single crystal; but for multiple slip of single crystal,the distortion is produced for the unmodified model and the simulation result is accordance with the actual situation for the modified model which improves the stability problem. For the formation characteristics of shear band during shearing of rolled aluminum sheet,the buckling deformation is enlarged by the instability of unmodified model which results in high degree of instability,conversely,the stability problem is improved by the modified model which can truly reflect the instability of the material.
出处
《塑性工程学报》
CAS
CSCD
北大核心
2017年第2期141-148,共8页
Journal of Plasticity Engineering
基金
国家自然科学基金资助项目(22451471107E0108)
关键词
晶体塑性模型
林位错强化
自硬化作用
稳定性
crystal plasticity model
forest dislocation strengthening
self-hardening effect
stability
