金属板材成形中拉深损伤模拟的两种求解方法

Two methodologies for the simulation of ductile damage in sheet metal forming processes

讨论用数值模拟预测板材成形中发生拉深损伤破坏的两种不同的求解方法。第一种是采用完全耦合的弹塑性破坯模型的动力显式数值方法。基于状态参量的不可逆热力学过程 ,完全耦合的本构方程考虑各向同性强化和拉深。这些已引入有限元软件ABAQUS/E用于对金属成形的模拟。在数值技术方面 ,隐式积分方法被用来对本构方程的局部时间积分 ,动力显式技术用于求解总体平衡方程。第二种方案是采用简化的损伤模型的方法 ,被称为逆法 (InveseApprch)。I.A被限定在考虑各向同性强化和损伤的塑性全量理论基础上的简单的本构关系。做比例加载和临界损伤达到以后的损伤饱和假定 ,可以得到损伤演化方程的封闭解。这两种损伤模型在编程中的实施采用两种方式 :计算中考虑或不考虑损伤作用 ,也就是耦合的或非耦合的计算。

This paper deals with two different resolution strategies aiming to predicting the ductile damage occurrence during the numerical simulation of sheet metal forming processes.The first one is a dynamic explicit incremental approach with a fully coupled elastoplastic\|damage model.Based on the thermodynamics of irreversible processes with state variables the fully coupled constitutive equations account for both the isotropic hardening and the ductile damage.They have been implemented into the FE code ABAQUS/Explicit dedicated to the metal forming simulation.For the numerical aspects,an implicit integration scheme is used for local time integration of the constitutive equations and a dynamic explicit scheme is used to solve global equilibrium equations.The second strategy is a more simple method called the 'Inverse Approach'(I.A.)with a simplified damage model.The I.A.is limited to a simple constitutive law based on the total deformation theory of plasticity accounting for the isotropic hardening and damage The assumptions of proportional loading and damage saturation after the damage threshold lead to a closed form solution for the damage evolution equation.The numerical implementation of these two damage models is made in such manner that the calculations can be executed with or without damage effect,i.e.coupled or uncoupled calculations.Some examples will show the advantages of each damage model.