镦粗过程中摩擦对空洞演变行为的影响

采用有限元模拟方法,模拟计算了摩擦因子为0. 3,0. 5和0. 7时,锻件不同位置空洞的闭合情况。分析了不同摩擦因子下,锻件不同位置的空洞高度的变化规律,结果发现:锻件内部空洞比边缘的空洞更容易闭合,并且随着摩擦因子的增大,内部空洞闭合速度加快,边缘空洞闭合速度减慢。分析摩擦因子、静水应力、等效应变、空洞闭合速度的关系发现:在锻件的内部位置,随摩擦因子增大,静水应力绝对值增大、等效应变增大、空洞闭合速度增大;在锻件的边缘位置,随着摩擦因子增大,等效应变减小、空洞闭合速度减小。摩擦因子对锻件边缘位置空洞闭合情况和等效应变的影响大于对锻件内部位置空洞的影响。

Influence of friction on void evolution behavior during upsetting

The void closure in different positions of forgings was simulated by the finite element method when the friction factors were 0. 3,0. 5 and 0. 7,and the change laws of void height in different positions of forgings under different friction factors were analyzed. The result show that the inner voids are easier to close than the edge voids,the closing speed of the inner voids increases with the increasing of friction factor,and the closing speed of the edge voids slows down. By analyzing the relationship among friction factor,hydrostatic stress,equivalent strain and closing speed of voids,it is found that in the internal position of forgings,with the increasing of friction factor,the absolute value of hydrostatic stress increases,the effective strain increases,and the closing speed of voids increases. At the edge of forgings,with the increasing of friction factor,the effective strain decreases,and the closing speed of voids decreases. Thus,the influence of the increased friction factor on the void closure and the equivalent strain at the edge position of forgings is greater than that in the center of forgings.