Modelling and monitoring of scaling effects in multi-scan laser forming

Abstract

The laser forming process has garnered considerable interest in industrial applications due to its flexibility and ability to create freeform shapes without the need for component-specific tooling. However, scaling this process for industrial use requires investigating various influencing factors, particularly scaling effects. In multi-scan laser forming, phenomena like strain hardening and heat accumulation impact the bending angle after each pass. Additionally, changes in specimen geometry affect the thermal mass and section modulus, complicating deformation predictions. This study focuses on experimentally and numerically analyzing bending behavior in multi-scan laser forming for different specimen widths. Realtime monitoring system which includes pyrometers for temperature gradient measurement and a laser displacement sensor for deformation capture was used for monitoring the bending behavior and its variation with number of passes. A finite element model is developed to assess stress evolution across multiple scans and its correlation with deformation. For 20 and 40 mm wide specimens, heat accumulation shifted the bending mechanism from the temperature gradient mechanism (TGM) to the buckling mechanism (BM). In contrast, the 60 mm specimen retained the TGM due to increased thermal mass and more efficient cooling. In the 20 mm sample, the bending angle per pass initially decreased due to strain hardening, later showing an increasing-decreasing trend due to changes in flow stress and thermal softening. The observed deformation behavior with number of passes and its correlation with stress behavior is further validated by the numerical model, providing insights that are otherwise difficult to measure experimentally.