激光金属沉积成形过程热应力的数值模拟

Numerical simulation of thermal stress on laser metal deposition shaping

根据有限元分析中的“单元生死”技术，利用APDL编程实现了对多道多层激光金属沉积成形过程热应力的三维数值模拟。模拟采用了Gauss热源模型，并引入了沿长边的平行往复扫描方式。计算结果表明，熔池区域以及试样与基板相邻区域是高热应力区，试样内部的热应力较小；试样沿厚度增加方向的热应力在沉积过程中幅值很大并且以拉伸应力为主，是导致试样产生裂缝的主要原因；沉积过程中沉积开始的位置对热应力的分布和强度影响很大，同一沉积层首道各节点热应力值几乎是末道各节点热应力值的一倍。在与模拟过程相同的条件下，实际成形试样裂缝的产生和发展规律与模拟结果相符。

Based on the ＂element life anti death＂ technique of＂ Finite Element Analysis （FEA）, a 3D muhi-track anti multilayer numerical simulation analysis for laser metal deposition shaping （LDMS） was conducted with the ANSYS parametric design language （AFDL）. In the simulation, long edge reciprtwating scanning paths were introduced anti Gauss thermal source model was adopted. The computing results showed that the molten pool region and the part of the sample which was close to the substrate were high thermal stress regions, and the thermal stress in the sample was quite low; the thermal stress along the direction of thickness increasing was tensile stress and its amplitude was large, which was the main reason for cracks of the sample ; the beginning point of each deposition layer had great effect on the distribution and intensity of thermal stress, and the thermal stress of the nodes belonging to the first track was almost one time higher than that of the nodes belonging to the last track of the same layer in the sample. Using the same processing parameters, the generation and development of cracks of the samples fabricated by LMDS showed good agreement with the simulation predictions.