沉积路径对激光增材制造结构件残余应力的影响

Effect of Deposition Path on Residual Stresses of Laser Additive Manufacturing Structures

以H13工具钢粉末为原材料,使用激光金属沉积技术快速成形薄壁结构件.采用Fluent开发气体/金属粉末流计算流体动力学(CFD)模型,分析强制对流热损失参数.建立沉积过程热流本构方程,采用生死单元技术模拟金属沉积,基于APDL语言进行编译加载,实现激光金属沉积3D热-力顺序耦合有限元模拟.分析沉积路径对薄壁结构热分布和残余应力场分布不同模式的影响.结果表明:直壁结构拐角局部存在超过工件拉伸强度的残余拉应力,从而导致裂纹生成;与单向沉积路径不同,之字形沉积路径在沉积层中诱导不同符号的残余切应力;单向沉积壁温度梯度相对较低,其残余应力略低于之字形沉积壁,但成形结构件的整体质量较低;残余应力计算结果与实验测量值相吻合,可为特定零件几何形状沉积提供参考.

H13 tool steel powder is used as a raw material to rapidly form thin-walled structures using laser metal deposition technology. The gas/metal powder flow computational fluid dynamics(CFD) model was developed using Fluent software to analyze the forced convection heat loss parameters. The heat flow constitutive equations of the deposition process are established, the metal deposition is simulated using the life-and-death element technology, and the 3 D thermo-mechanical sequential coupled finite element simulation of the laser metal deposition is performed based on the APDL language. The effects of deposition paths on the thermal distribution and residual stress field distribution of thin-walled structures were analyzed. The results show that there is a local residual tensile stress exceeding the tensile strength of the workpiece in the corners of the straight wall structure, resulting in cracks. Unlike the one-way deposition path, the zig-zag deposition path induces different symbolic residual shear stresses in the subsequent deposition layer. The temperature gradient of the one-way deposition wall is relatively low, and the residual stress is slightly lower than the zig-zag deposition wall, but the quality of the formed structures is low. The residual stress calculation results are in agreement with the experimental measurements, and can provide operation references for the deposition of specific part geometry.