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.

在本后续项目中，将扩展描述高板厚低合金钢高功率激光束焊接中所谓凸区形成的多物理场耦合数值模型，以提高激光能量输入的射线追踪算法的准确性。为此，考虑了两种更准确地描述吸收能量及其在蒸汽毛细管中的分布的方法。第一种方法是基于物理自适应网格细化，第二种方法是基于虚拟网格细化。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，在考虑蒸汽毛细管的瞬态局部计算的情况下，将为在较高工艺速度下焊缝胀形的尚未解释的形成机制提供贡献。在此基础上，利用数值模型研究了膨胀区对中心裂纹缺陷形成的影响。通过研究加工速度、激光功率、焦点位置等不同实验参数对胀形效应的影响，探讨胀形效应发生的关键因素。所得结果将用于热裂敏感性的量化。在这里，检测参数的敏感性将评估胀形区域的发展和中心线裂纹缺陷的趋势，特别是部分熔透和完全熔透焊接之间的区别将得到解决。该项目的目的是通过数值和实验相结合的研究方法来确定凸起区域的形成机制，并阐明焊缝凸起的位置和强度与中心线裂纹缺陷形成之间的关系。最后，在工艺优化方面能够适应一个数值模型，以避免所研究的凸起区域的形成，从而以及中心线开裂将是可用的。