基于Normalized C&L准则的ECAP裂纹萌生趋势的数值模拟

Numerical simulation of crack initiation trends during ECAP based on Normalized Cockcroft & Latham ductile fracture criterion

根据Normalized Cockcroft&Latham韧性断裂准则,利用Deform-2D对6061Al等径角挤压过程进行了裂纹萌生趋势的模拟,在一道次模拟中,得出了模具拐角φ、外转角半径r与背压对试样裂纹损伤分布的影响:模具拐角越大,裂纹损伤值越小;外转角半径r=6 mm为最佳,大于6 mm时裂纹损伤值增大;施加背压有利于减少裂纹的产生,背压越大,裂纹损伤值越小,但是,考虑到ECAP的效率,背压值不能选择太大的数值。对多道次ECAP进行数值模拟,并与实验结果进行对比验证。结果表明,三道次、A路线挤压后裂纹损伤值在上表层最大。

Based on the Normalized Cockcroft &Latham ductile fracture criterion,the crack initiation trends during equal channel angular pressing of 6061 Al alloy was simulated by Deform-2D.At the simulation of one pass ECAP,the effect of the die angle,the outer corner radius and the back pressure on the crack damage distribution were conducted.The greater the die angle is,the smaller the crack damage;the optimum outside corner radius is 6 mm:the crack damage value will increase when it is greater than 6 mm;the back pressure imposed is helpful to reduce the cracks;the greater the back pressure is,the smaller the crack damage.However,considering the efficiency of ECAP,the back-pressure shall not be too large.The simulation of multiple pass ECAP was carried out and testified with the three-pass ECAP experiments.The experimental results show that the crack damage after three-pass A route ECAP is maximum at the upper-layer of the specimen.