Isothermal extrusion speed curve design for porthole die of hollow aluminium profile based on PID algorithm and finite element simulations

基于PID算法和有限元模拟的空心铝型材分流模等温挤压速度曲线设计

The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency.By taking the optimal solution temperature of the secondary phase as the target temperature,the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained.Results show that in the traditional constant extrusion speed process,the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement.As the extrusion speed increases,the temperature difference at the die exit of the profile along the extrusion direction increases.The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9℃.Furthermore,the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container,porthole die and external environment.

利用增量式PID控制算法和有限元模拟相结合的方法,研究复杂空心铝型材的等温挤压过程。以最大挤压力和生产效率确定挤压速度范围。以二次相的较优固溶温度为目标温度,获得实现等温挤压的挤压速度−行程曲线。研究结果表明:在常规等速挤压过程中,随着挤压行程的增加,型材出模口横截面的平均温度先迅速升高后缓慢上升。随着挤压速度的增加,沿挤压方向的型材出模口温差增大。采用变化的挤压速度曲线,沿出模口挤压方向的前后温差约为6.9℃,挤压过程中塑性变形和摩擦所产生的热量与工件向挤压筒、分流模和外部环境传递的热量达到平衡。