Validating predictions of keyholing phenomenon in laser weld models

Computer models are being developed to fully understand the laser welding process for critical applications. Validation of these models is an essential part of their development. Sandia National Laboratories’ GOMA code uses an arbitrary Lagrangian / Eulerian finite element method to predict evolution of the fusion zone (including keyhole formation and collapse) in laser spot welds. Recoil pressure caused by evaporation from the high temperature molten surface is a key boundary condition determining deformation of the molten pool surface. Previously, high-speed, video microscopy was used for model validation by measuring solidification velocities in conduction mode laser spot welds. That work is currently being extended to keyhole mode laser spot welds. Additionally, high sensitivity load cell techniques are being developed to simultaneously measure recoil forces associated with keyhole formation. Images of solidifying laser welds and force measurement techniques will be presented and discussed.