大尺寸纯铝棒材等径角挤压计算机模拟

Computer simulation of equal channel angular pressing for large-sized pure aluminum bar

为研究等径角挤压(Equal Channel Angular Pressing,ECAP)条件下大尺寸试样的变形机理,实现由小体积试样到大尺寸试样的ECAP技术转变,通过DEFORM-3D有限元软件对大尺寸纯铝棒材的等径角挤压变形过程进行了计算机模拟,获得了变形过程的载荷-行程曲线和等效应力、等效应变、等效应变速率及金属流动速度分布情况。研究结果表明:变形过程中,挤压力是不断变化的,其数值可由0 kN达到115 kN,由于受到摩擦阻力的影响,使得挤压力在整个变形过程中产生了波动;经单道次挤压后,试样的应力应变分布不均匀,使得试样内部的晶粒也呈现不均匀的分布,对材料的性能产生了重要的影响;随着挤压行程的增大,应变量逐渐增加并最终趋于稳定。

In order to investigate the deformation mechanism of large-sized sample for equal channel angular pressing （ECAP） and realize the technology transformation from small volume sample to large-sized sample, the process of ECAP for large-sized pure aluminum bar was simulated by DE- FORM-3D software. The load-stroke curve, the distribution of effective stress, effective strain, effec- tive strain rate and metal flow velocity were obtained through computer simulation. The load changed by extrusion bar reflected the deformation process of equal channel angular pressing. The homogene- ous degree of effective-stress and strain reflected the influence on deformation uniformity of sample for ECAP. The results showed that the pressure was constantly changing in the process of deforma- tion and its value varies from 0 kN to 115 kN. Due to the influence of frictional resistance, the pres- sure produced fluctuations in the whole deformation process. The stress and strain distribution of sample was not uniform after one extrusion. It also made the grain of sample exhibit a nonuniform distribution and produced important influence on the properties of material. With the increase in ex-trusion distance, the strain increased gradually and tended to be stabilized eventually.