A study on a representative heat source model for simulating laser welding for liquid hydrogen storage containers

Abstract

Laser welding enhances the productivity with high speed, and minimizes thermoelastic distortion with a concentrated heat source for a narrow area over a short period of time. With these strengths various industries such as the automobile, aviation, and shipbuilding adopt that. However welding distortion is still one of principal problems, simulation of distortion and corresponding design are very important for applying that technology. Naturally accurate laser welding heat source model is needed, but there is not representative heat source model which can cover diverse types of models. This study proposes a multi-layered heat source model as a representative model, and develops a welding heat source that complies with welding conditions by comparing it to the bead-on-plate welding experiment on 304L stainless steel, a material used for cryogenic purposes with liquid hydrogen condition. To derive a welding heat source, a parametric study was used as it was able to identify an appropriate solution by changing the parameter values constituting the heat source for finite element analysis, where the physical properties for each temperature were applied. For this process optimization method was applied, and the objective function and constraints were defined based on the value of temperature through simulation, also a global optimization algorithm was adopted. In this study, we suggest a representative model that can be used under most welding conditions; this is a method that can be of great help in future welding distortion analyses and can be used in a design that can tolerate distortion.