Equivalent heat source approach in a 3D transient heat transfer simulation of full-penetration high power laser beam welding of thick metal plates
Equivalent heat source approach in a 3D transient heat transfer simulation of full-penetration high power laser beam welding of thick metal plates
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DOI：
10.1016/j.ijheatmasstransfer.2018.02.058
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发表时间：
2018-07
影响因子：
5.2
通讯作者：
A. Artinov;M. Bachmann;M. Rethmeier
中科院分区：
文献类型：
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作者：
A. Artinov;M. Bachmann;M. Rethmeier
建立了一个三维多物理场数值模型，用于计算合适的等效体积热源，预测熔焊过程中及熔焊后的瞬态热循环。因此，建模过程分为两项研究。首先，以焊接速度为2 m min-1、激光功率为18 kW，对15 mm低合金钢厚板进行平板位置的全熔透小孔激光焊接的稳态过程模拟。采用正圆锥形固定小孔考虑工件吸收的能量，对模型进行标定。在熔池几何形状和局部温度场的计算中，考虑了相变、热毛细对流、自然对流和材料物性随温度变化直至蒸发温度的影响。然后，在随后的研究中使用所获得的局部温度场作为等效热源，用于计算激光焊接过程中的瞬态温度场和零件的冷却阶段。用有限元软件COMSOL Multiphysics 5.0对稳态传热和流体动力学方程组进行了强耦合求解。瞬态传热模拟中的能量输入通过节点温度的规定来实现。指定的节点再现了定义等效体积热源的计算的局部温度场。他们的平移运动通过部分建模的移动网格的方法。为了避免高度扭曲的单元，使用了额外的网格重划分条件和辅助线。用拉普拉斯光顺法计算多边形网格单元的位置。数值计算和实验观察到的焊缝形状和瞬态温度分布之间的良好的相关性。
A three-dimensional multi-physics numerical model was developed for the calculation of an appropriate equivalent volumetric heat source and the prediction of the transient thermal cycle during and after fusion welding. Thus the modelling process was separated into two studies. First, the stationary process simulation of full-penetration keyhole laser beam welding of a 15 mm low-alloyed steel thick plate in flat position at a welding speed of 2 m min-1 and a laser power of 18 kW was performed. A fixed keyhole with a right circular cone shape was used to consider the energy absorbed by the workpiece and to calibrate the model. In the calculation of the weld pool geometry and the local temperature field, the effects of phase transition, thermo-capillary convection, natural convection and temperature-dependent material properties up to evaporation temperature were taken into account. The obtained local temperature field was then used in a subsequent study as an equivalent heat source for the computation of the transient thermal field during the laser welding process and the cooling stage of the part. The system of partial differential equations, describing the stationary heat transfer and the fluid dynamics, were strongly coupled and solved with the commercial finite element software COMSOL Multiphysics 5.0. The energy input in the transient heat transfer simulation was realised by prescription of the nodes temperature. The prescribed nodes reproduced the calculated local temperature field defining the equivalent volumetric heat source. Their translational motion through the part was modelled by a moving mesh approach. An additional remeshing condition and helper lines were used to avoid highly distorted elements. The positions of the elements of the polygonal mesh were calculated with the Laplace’s smoothing approach. Good correlation between the numerically calculated and the experimentally observed weld bead shapes and transient temperature distributions was found.