Simulation based process analysis of the powder bed additive manufacturing process Selective Laser Melting (SLM)

基于激光的增材制造技术，例如基于粉末床的选择性激光熔化，在金属功能部件的生产中允许几乎无限的几何自由度。由于现有的工艺缺陷，如残余应力和零件变形，这种生产高复杂性功能零件的巨大潜力只能以有限的方式加以利用。这是由于目前对相互作用或工艺区域中的局部物理过程（例如粉末层中的光束传播，蒸发）和部件中的全局物理过程（热机械学）的理解不足。无论是部分还是特定于材料，目前都没有关于应力或变形最小化过程管理的具体建议。该项目的科学效益是通过SLM过程的多尺度模拟的开发，通过使用多尺度方法和并行算法减少了热机械模拟的计算时间。通过对变形和残余应力的计算预测，对工艺过程的理解将有助于确定应力和变形最小化生产的工艺策略。该项目的目的是通过多尺度方法减少零件模拟所需的自由度（因子1，000 - 10，000），从而实现对焊接顺序、支撑结构和工艺参数进行考虑的过程的宏观模拟。进一步开发现有的工艺区（中尺度）模型，以便在可接受的计算时间（<1小时）内足够准确地计算温度场，这对于构建多尺度模拟是必要的。计算出的温度-时间周期是零件热机械过程多尺度模拟的输入。基于对工艺的理解，将确定相关工艺变量，并使用相关部件开发和验证应力和变形最小化生产的实验工艺策略。

Laser based Additive Manufacturing technologies such as powder bed based selective laser melting allow an almost unlimited geometrical freedom in the production of metallic functional parts. Due to existing process deficits like residual stresses and part distortion this immense potential for the production of functional parts of high complexity can be exploited in a limited way only. This is caused by the currently insufficient understanding of the involved physical processes both locally in the interaction or process zone (e.g. beam propagation in the powder layer, evaporation) and globally in the part (thermomechanics). Neither part nor specific to material there are currently concrete recommendation regarding a stress or distortion minimizing process management. The scientific benefits of the project is given by the development of a multiscale simulation of the SLM process, which reduces the computation time for a thermomechanical simulation by using multiscale methods and parallelized algorithms. By the computational prediction of distortion and residual stresses a gained understanding of the process will help to identify process strategies for stress and distortion-minimizing production. The aim of this project is to reduce the number of degrees of freedom (factor 1,000-10,000) required for simulations of parts by means of multiscale approaches, thus realizing a macro-simulation of the process in which the welding sequence, the supporting structures and process parameters are taken into account. Further development of an existing model for the process zone (meso-scale) which allows a sufficiently accurate calculation of the temperature fields in acceptable computation times (<1h) is necessary for the construction of the multiscale simulation. The calculated temperature-time cycles are the input for a multiscale simulation for the thermomechanical processes of parts. Based on the gained understanding of the process the relevant process variables will be identified and experimental process strategies for stress and distortion-minimizing production will be developed and validated using relevant parts.