Eulerian Modeling of Plasma-Pressure Driven Laser Impact Weld Processes

Abstract

In this study, details of the rapidly evolving state of a laser impact welding (LIW) process are simulated by incorporating a hydrodynamic plasma pressure model into a high-fidelity thermomechanical Eulerian numerical approach. Detailed evolution of the localized velocities, shear stresses, plastic strains, and temperature state in the vicinity of the weld interface during its formation are revealed. The presented simulation technique applies a load distribution that is temporally and spatially modeled based on the plasma pressure induced during surface ablation by a nanosecond-pulsed infrared laser. Due to the Gaussian plasma-pressure loading profile, significant shear stress patterns are observed to develop in the flyer foil prior to its collision with the target foil, the character of which appears to be significant in achieving a successful impact weld. Moreover, features already known to be critical to successful impact welding of thin foils are captured by the combination of the high-fidelity Eulerian control volume and the plasma pressure model, including the requisite collision velocity and impact angle. During the impact welding, interfacial material ‘jetting’ is observed, in addition to concentrated shear stress fields along the weld front. A wavy interface arising from a regular pattern of material mixing is confirmed to occur, in addition to significant plastic strains and heat generation due to the plastic deformation, all of which indicate the formation of a collision joint due to the more realistic loading condition imposed.