数值模拟外转角半径及背压对纯钛ECAP变形的影响

Simulations of influence of outer angular radius and back pressure on ECAP of pure titanium

使用DEFORM-3D软件模拟等通道转角挤压过程中外转角半径及背压对纯钛应力和应变分布的影响,探讨不同R值对材料流动的影响规律。结果显示:当R=6mm时,工件上下表面应力状况较为平衡,从而得到均匀的等效应变分布;当R<6mm时,在外转角形成的死区使材料之间相互搓动,导致工件底部区域出现剧烈畸变,工件不同区域之间的等效应变量差别较大;当R>6mm时,工件上表面与模具内转角之间的相互作用力增加,使工件顶部变形加剧并导致工件等效应变量不均匀;施加背压(pb)后,能有效提高等效应变量;适当的R值与pb匹配可使工件得到均匀的应变分布。

The strain and stress distributions of pure Ti during equal channel angular pressing （ECAP） were simulated by using software of DEFORM-3D with different angular radii and black pressures. The simulated results indicate that the friction forces in the upper and bottom regions can be balanced and the homogeneous equivalent strain distribution can be obtained when R=6 ram. When R〈6 mm, the equivalent strain is non-uniform at the bottom of the workpiece, because the death zone makes the materials interact each other, thus induces the bottom of workpiece acutely distorted and makes the value of equivalent strain vary obviously in different regions of workpiece. At R〉6 mm, the friction force interacts between the upper face of workpiece and inner comer angular of die, which makes the upper of the workpiece deform remarkably and induces non-uniform equivalent strain distribution. The back pressure can increase the value of equivalent strain. Besides, uniform strain distribution can also be obtained by adopting reasonable back pressure and outer angular radius.