基于逐层建模的电弧增材制造过程有限元仿真方法

Finite Element Simulation Method of Wire Arc Additive Manufacturing Process Based on Layer-by-Layer Modeling

传统的有限元仿真模式都是通过预先建立整体的几何模型,再结合单元生死技术来实现增材过程的仿真计算.由于这一模式需要预先设置好增材构件的整体尺寸及每层高度,因此不适用于需要在增材过程中优化调整工艺的复杂零件的仿真;更重要的是,增材过程逐层累积的变形量会使得计算域偏离预设位置进而出现计算不收敛的问题.为了解决增材制造的数值模拟过程中存在的上述难题,本研究提出了一种新的逐层建模的有限元计算方法.该方法采用逐层建模逐层计算的方式进行仿真计算,仿真过程与实际的增材过程一致,彻底解决了变形累积导致的计算不收敛问题的发生.首先,基于ABAQUS有限元软件,分别采用整体建模和逐层建模两种方法建立了20层的电弧增材制造(WAAM)仿真模型,并分别进行了热力耦合仿真计算.计算结果表明:逐层建模法获得的温度场和应力应变场的结果与传统整体建模法的基本一致,初步证明了所提出的逐层建模法对模拟增材过程的可行性.其次,为了分析逐层建模法对增材过程的变形累积敏感性问题,设计了一个单边约束的WAAM试验,并采用上述两种建模方法分别进行了仿真计算.计算结果表明:传统的整体建模模型计算至第2层就因为变形过大而被系统终止计算,而逐层建模模型则成功地完成了计算,而且计算结果与试验测试结果基本吻合,证明了该方法对变形累积不敏感的独特优点.

The traditional finite element simulation mode is used to establish the holistic geometric model in advance and combined with the“element birth technique”to realize the simulation of additive manufacturing(AM)process.Because this mode requires the overall size of the AM component and the height of each layer to be set in advance,it is unsuitable for the simulations of complex parts that require the optimization and adjustment of the process.More importantly,the layer-by-layer accumulative deformation during the AM process will cause the deviation of calculation domains from the preset positions and consequently result in a nonconvergence error.To solve the abovemen-tioned problems in the numerical simulation of AM,this study proposes a new layer-by-layer modeling finite element method by synchronously employing the layer-by-layer modeling and calculation.The proposed method is consistent with the actual AM and completely solves the problem of the nonconvergence error caused by the accumulative deformation.First,based on the ABAQUS finite element software,two methods of traditional modeling and layer-by-layer modeling were used to establish the 20-layer wire arc additive manufacturing(WAAM)simulation models and conduct coupled thermal-mechanical simulations,respectively.The calculation results show that the temperature and stress-strain field results obtained by the layer-by-layer modeling method areconsistent with those of the traditional modeling method,which preliminarily proves the feasibility of the proposed layer-by-layer modeling method.Second,to analyze the sensitivity of the layer-by-layer modeling method to the accumulative deformation of the AM process,a unilateral constrained WAAM test was designed and the two modeling methods were used to perform simulations.Calculation results show that the traditional holistic geometric model is terminated by the system when it is calculated to the second layer because of excessive deformation,while the layer-by-layer modeling model success-fully completes the calculation.Calculation results of the new model are consistent with the experimental results,proving the proposed method’s unique advantage of insensitivity toward the accumulative deformation.