Unveiling Mechanisms and Onset Threshold of Humping in High-Speed Laser Welding
Research Poster Engineering 2025 Graduate ExhibitionPresentation by Zen-Hao Lai
Exhibition Number 75
Abstract
The fabrication of fuel cells relies on a rapid laser welding process. However, challenges arise with the occurrence of humping when the welding speed surpasses a critical threshold, which poses difficulties in achieving a smooth surface finish and a consistent weld strength. This study aims to elucidate the humping mechanisms by analyzing the morphology of molten pool and the characteristics of melt flow at varying welding speeds via in situ synchrotron high-speed X-ray imaging and computational fluid dynamics simulations. Our findings indicate that the short keyhole rear wall, the high backward melt velocity, and the prolonged tail of molten pool are the primary factors contributing to the onset of humping. Furthermore, a dimensionless humping index was introduced, which successfully captured the onset threshold of humping across different literatures. This index not only provides a quantitative description of the humping formation tendency but also serves as a valuable tool for optimizing the laser welding process.
Importance
High-speed laser welding is essential for fabricating fuel cells, but humping can form on the weld seam, compromising weld quality and strength. This study sheds light on the causes of humping by analyzing keyhole and molten pool dynamics using in situ synchrotron X-ray imaging and simulations. By identifying the key factors that trigger humping and introducing a new index to predict its occurrence, this research provides valuable insights for optimizing welding conditions. These findings can enhance fuel cell manufacturing efficiency while ensuring strong, reliable welds in industrial applications.