基于单元生死技术的微熔滴沉积成形温度场模拟与试验研究

Numerical Simulation for Temperature Field of Micro-Droplet Deposition Manufacture Based on Element Birth and Death Technology and Experimental Study

采用有限单元法和单元生死技术,建立了气动按需熔滴沉积成形温度场计算模型,模拟了7075铝合金薄壁件微熔滴沉积过程温度场的演变规律。结果表明:薄壁件成形温度场随熔滴沉积位置的移动而呈现周向动态变化,不同位置熔滴单元节点的热循环曲线存在不同个数的温度峰值和谷值;随着沉积层高度的增加,1～10层相邻搭接层间熔滴的冷却速率降低,熔滴所在沉积层中的高温区域逐渐扩大,使零件在成形方向上呈现变化的温度梯度,并导致1～10层相邻层间熔滴结合处的晶粒尺寸发生变化。模拟结果与7075铝合金薄壁件微熔滴沉积试验结果基本吻合,较好反映了实际成形过程中零件的温度场变化规律。

The numerical model of temperature filed for micro-droplet deposition manufacture was established by adopting finite element method and element birth and death technology. The transient evolution of temperature filed was simulated during fabricating 7075 aluminium alloy thin-wall part by micro-droplets. The results show that the forming temperature filed of thin-wall part presents circumferentially dynamic change along with the moving of droplet depositing position; the thermal cyclic curves of different droplet element nodes include different number of temperature peak and valley values. With increasing the height of deposited layer, the cooling rate of adjacent overlapping droplets from the first to the tenth layers was decreased gradually, the high temperature region in deposited layer was enlarged gradually and the variable temperature gradient was shown in part building orientation, which causes the grain size of adjacent overlapping droplets to change. Experiments were carried out to validate the proposed numerical model in this paper. The simulated result and the experimental results are in good accordance.