复杂铝型材挤压成形有限体积仿真

Finite Volume Simulation of Extrusion of Complex Aluminum Profile

根据型材挤压成形属于特大变形、热-力耦合、坯料头部存在变形死区等特点,采用欧拉描述有限体积法(FVM)模拟了3级复杂型材的挤压成形过程,避免了传统刚塑性有限元法无法模拟变形死区,拉格朗日描述有限变形弹塑性有限元法难以重划特大变形网格等难题.模拟过程中,采用欧拉描述FVM仿真坏料流动,采用拉格朗日描述有限元法仿真模具变形和应力,采用显式动态接触算法仿真坏料与模具之间的相互作用.确定了兼顾仿真精度和速度的有限体积网格的最小尺寸和单元最大数量,提高了计算效率;建立了6063-T5铝合金在不同变形温度下的系列热-本构-摩擦模型,获得了金属流动、力能、温度、密度变化分布.为工艺和模具参数优化提供了依据.

According to the characteristics of aluminum alloy extrusion, which means severe large deformation, thermo-dynamics coupled, and a dead zone at the front of billet, a finite volume method (FVM) based on Eulerian description was adopted to simulate the extrusion deformation of complex profile grade 3. With FVM, the traditional problems and difficulties, such as dead zone faced by rigid-plastic FEM, and grid distortion and remeshing faced by Lagrangian described finite deformation elastic-plastic FEM, can be effectively avoided. During the simulation, Eulerian described FVM is used to simulate the flow of billet, Lagrangian described FEM is used to simulate the deformation and stress of mold, and explicit dynamic contact algorithm is used to simulate the counteraction between the billet and the mold. In order to improve the efficiency of calculation, appropriate minimum size of FV grid and maximum number of FV elements are ascertained based on the good balance between the accuracy and speed of simulation. A series of thermo-constructional-frictional models are set up according to different deforming temperatures. Elaborate deformation results including exactly distributions of metal flow, stress, strain, temperature, and density in both plastic and plastic-elastic zones are obtained, which is a good base for the future optimization of process and mold parameters.