基于热弹塑性本构模型的LPBF全尺寸热-力耦合数值模拟研究

Numerical simulation of full-scale thermal-force coupling for LPBFbased on thermoelastic-plastic intrinsic model

  • 摘要: 激光粉末床熔融(Laser Powder Bed Fusion, LPBF)是金属增材制造技术中的重要分支,具有个性化、自动化等优势。然而,在逐层制造过程中残余应力不断积累,进而易引发变形、断裂、疲劳等问题,限制了其进一步应用。为预测金属增材制造制件的位移和残余应力,本文借助开源有限元求解代码JAX-FEM,开展基于热弹塑性本构模型的LPBF全尺寸热-力耦合数值模拟研究。其中,根据能量守恒原理确定等效激光功率、等效激光半径以及扫描速度,简化计算模型、减少计算时间;通过修改制件底面的应力状态实现模拟制件从基板上切割分离的过程,预测了应力释放的影响。分析扫描策略与扫描速度对LPBF热-力耦合行为的影响,对比发现采用水平Z型扫描策略相较于垂直扫描策略所产生的最大位移降低了24.0%,最大残余应力降低了13.6%;扫描速度从0.8m/s增大到2m/s时,产生的最大位移降低了8.9%,最大残余应力降低了13.1%。本文有助于为调控LPBF残余应力和变形提供科学指导。

     

    Abstract: Laser powder bed fusion (LPBF) is an important branch of metal additive manufacturing technology, offering advantages such as customization and automation. However, during the layer-by-layer fabrication process, residual stresses continuously accumulate, which can readily induce issues like deformation, fracture, and fatigue, thereby limiting its wider application. To predict the displacement and residual stress in metal additively manufactured components, this study employs the open-source finite element solver JAX-FEM to conduct full-scale thermo-mechanical coupled numerical simulations of LPBF based on a thermo-elastoplastic constitutive model. Equivalent laser power, equivalent laser radius, and scanning speed were determined according to the principle of energy conservation to simplify the computational model and reduce calculation time. The process of separating the component from the substrate was simulated, and the effects of stress release were predicted by adjusting the stress state at the component's bottom surface. The influences of scanning strategy and scanning speed on the thermo-mechanical coupled behavior during LPBF were analyzed. Comparative results reveal that employing a horizontal zigzag scanning strategy, compared to a vertical scanning strategy, resulted in a 24.0% reduction in maximum displacement and a 13.6% reduction in maximum residual stress. Increasing the scanning speed from 0.8 m/s to 2.0 m/s led to an 8.9% reduction in maximum displacement and a 13.1% reduction in maximum residual stress. This study offers scientific insights for regulating residual stress and deformation in LPBF.

     

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