Numerical Analysis of the Partial Penetration High Power Laser Beam Welding of Thick Sheets at High Process Speeds

Abstract

The present work is devoted to the numerical analysis of the high-power laser beam welding of thick sheets at different welding speeds. A three-dimensional transient multi-physics numerical model is developed, allowing for the prediction of the keyhole geometry and the final penetration depth. Two ray tracing algorithms are implemented and compared, namely a standard ray tracing approach and an approach using a virtual mesh refinement for a more accurate calculation of the reflection point. Both algorithms are found to provide sufficient accuracy for the prediction of the keyhole depth during laser beam welding with process speeds of up to 1.5mmin−1. However, with the standard algorithm, the penetration depth is underestimated by the model for a process speed of 2.5mmin−1 due to a trapping effect of the laser energy in the top region. In contrast, the virtually refined ray tracing approach results in high accuracy results for process speeds of both 1.5mmin−1 and 2.5mmin−1. A detailed study on the trapping effect is provided, accompanied by a benchmark including a predefined keyhole geometry with typical characteristics for the high-power laser beam welding of thick plates at high process speed, such as deep keyhole, inclined front keyhole wall, and a hump.

Elucidation of the Bulging Effect by an Improved Ray‐Tracing Algorithm in Deep Penetration Wire Feed Laser Beam Welding and Its Influence on the Mixing Behavior

“…A sequence of such blocking effects by the separation of the different zones of the weld pool is shown in Figure 9b–e, leading to the bad mixing behavior here that was also found experimentally. In addition to previous studies with an improved ray‐tracing formulation, [ 23 ] an improvement here can clearly be seen for low welding speeds.…”

“…Of course, the situation given in Figure 5 only shows a single point in time during a calculation, but it indicates the advantages of the more sophisticated ray‐tracing approach providing a better physical description of laser energy deposition on the keyhole wall. This is already shown to be critical for the accuracy of the simulated penetration depth, especially for welding speeds above ≈2 m min −1 , see the study by Artinov et al [ 23 ]…”

“…Thereto, it is shown in the study by Artinov et al [ 23 ] that for numerical models using the ray‐tracing approach, a sufficient resolution of the keyhole region is essential for precisely localized energy absorption as this has a significant impact on the calculated penetration depth, especially for thick plate welding at higher processing speeds. Unfortunately, the computational capacity is often a limiting factor, and thus intermediate mesh sizes, for example, 0.2 mm in the study Cho et al, [ 24 ] which are in the order of the laser spot radius, are used.…”

“…Motivated by this obvious issue, an improved ray‐tracing algorithm using a virtual mesh refinement was implemented to calculate the reflection points of the single subrays of the laser radiation more accurately. In the study by Artinov et al, [ 23 ] this method was proposed for the precise calculation of the penetration depth and drilling speed. In the present study, it is shown that this method even shows major improvements in the accuracy of the melt flow behavior in the weld pool during investigations of the bulging effect also for lower welding speeds compared with a conventional ray‐tracing approach.…”

Analysis of supply chain finance risk assessment based on numerical analysis algorithm

“…Simply put, numerical analysis is the science of studying algorithms for continuous problems. The most important concepts in it are algorithms and continuous problems [15]. First, continuous problems are complex model problems abstracted from physics or other disciplines, generally infinite-dimensional problems and almost impossible to find analytical solutions.…”