热力耦合数值模拟往复挤压AZ31成形过程

采用刚-粘塑性有限元法对AZ31镁合金往复挤压变形过程进行热力耦合(温度与位移相互作用)数值模拟,分析2道次往复挤压过程中等效应变速率场、等效应变场、等效应力场以及温度场的分布及变化情况。模拟结果表明:凹模细颈区与紧缩区的交接区域应变速率最大,呈弧线状分布;等体积往复挤压过程中,大变形区主要集中在细颈区靠近凹模内壁处以及镦粗一侧紧缩区靠近凹模内壁区域;挤压一侧紧缩区与细颈区的交接处应力较大,随变形的增加,应力最大值有所上升;温度场分布以细颈区中心为圆心,由高到低向外分布,在工件内形成温度梯度,高温区主要分布在细颈区中心区域。

Numerical simulation on reciprocating extrusion of AZ31 alloy by thermal-mechanical coupling method

The rigid visco-plastic finite element method was used for the coupled thermal-mechanical numerical simulation of reciprocating extrusion process of AZ31 Mg alloy. The distribution and variety of equivalent plastic strain rate field, equivalent plastic strain field, equivalent stress field and temperature field were simulated in two-pass reciprocating extrusion. The following conclusions indicated that the peak value of strain rate focuses on the conjoint area of narrow-neck area and shrinking area of the die, which presents a cambered distribution; during the equivalent volume reciprocating extrusion processes, the strong deformation area mainly focuses on the narrow-neck area which closes to the die wall and the shrinking area which closes to the conic shrinking wall of shrinking area that belongs to the stocky side ; the larger stress focuses on the conjoint area of shrinking area and narrow-neck area, and the more deformation causes the larger peak value of stress; the temperature field distributes around the center of narrow-neck area, diffuses from low to high in form of roundness and forms temperature gradient in the workpiece. The high temperature mainly distributes in the center of narrow-neck area.