Experimental and numerical investigation of the formation mechanisms of the bulging effect and its influence on the development of centerline cracking defects in high power laser beam welding of low-alloyed steels of high thickness

大厚度低合金钢高功率激光束焊接中胀形效应形成机制及其对中心线裂纹缺陷发展影响的实验和数值研究

• 批准号: 411393804
• 金额: --
• 依托单位: Abteilung 9: Komponentensicherheit
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/411393804?language=en
• 关键词: Experimental; numerical; investigation; formation; mechanisms

In this follow-up project, a multiphysical coupled numerical model describing the formation of the so-called bulging-region in high-power laser beam welding of low-alloy steels with a high sheet thickness will be extended to improve the accuracy of the ray tracing algorithm for the input of the laser energy. For this purpose, two methods are considered to describe more accurately the absorbed energy and its distribution in the vapor capillary. The first method is based on a physical adaptive mesh refinement and the second on a virtual mesh refinement. Both methods increase the accuracy of the calculation of the reflection points of the sub rays, while the adaptive mesh refinement method as well improves the accuracy of the melt pool flow and the temperature distribution. Thus, a contribution to the yet unexplained formation mechanisms of the bulging of the weld at higher process speeds will be provided under consideration of a transient local calculation of the vapor capillary. Furthermore, with the aid of the numerical model, an investigation of the influence of the bulging-region on the formation of the centerline cracking defect will be carried out. By studying the influence of different experimental parameters such as process speed, laser power and focal position, the critical factors for the occurrence of the bulging effect will be examined. The obtained results will be used for the quantification of the hot cracking susceptibility. Here, the sensitivity of the examined parameters will be evaluated on the development of the bulging region and the tendency to centerline cracking defects, whereby in particular also the difference between partial penetration and full penetration welding will be worked out. The aim of the project is to identify the formation mechanisms of the bulging-region by means of a combination of numerical and experimental studies and to clarify the relationship between location and intensity of the bulge of the weld and the formation of centerline cracking defects. Finally, a numerical model being able to be adapted in terms of process optimization to avoid the formation of the studied bulging-region and thus as well the centerline cracking will be available.

在这个后续项目中，将扩展描述高功率激光束高板厚低合金钢焊接中所谓凸出区域形成的多物理耦合数值模型，以提高射线精度激光能量输入的跟踪算法。为此，考虑两种方法来更准确地描述吸收的能量及其在蒸气毛细管中的分布。第一种方法基于物理自适应网格细化，第二种方法基于虚拟网格细化。两种方法都提高了子射线反射点计算的精度，而自适应网格细化方法也提高了熔池流动和温度分布的精度。因此，在考虑蒸气毛细管的瞬态局部计算的情况下，将提供对较高处理速度下焊缝凸出的尚未解释的形成机制的贡献。此外，借助数值模型，研究胀形区域对中心线裂纹缺陷形成的影响。通过研究不同实验参数（例如加工速度、激光功率和焦点位置）的影响，将检验鼓胀效应发生的关键因素。获得的结果将用于热裂敏感性的量化。这里，将评估所检查参数对胀形区域的发展和中心线裂纹缺陷的趋势的敏感性，从而特别是还可以找出部分熔透焊接和全熔透焊接之间的差异。该项目的目的是通过数值和实验研究相结合的方式确定凸出区域的形成机制，并阐明焊缝凸出的位置和强度与中心线裂纹缺陷形成之间的关系。最后，能够根据工艺优化进行调整的数值模型，以避免形成所研究的膨胀区域，从而避免中心线裂纹。