Digital Image Correlation to Assess Residual Strains in WAAM-CMT Manufactured Specimens

Abstract

The wire arc additive manufacturing with cold metal transfer (WAAM-CMT) technique is one of the 3D printing methods that enables the manufacturing and repairing of complex 3D metal structures. However, the physical processes occurring during WAAM-CMT are challenging to model as they depend on multiple technological parameters such as the material used, welding current, voltage, wire feed rate, travel speed, and cooling. One of the important drawbacks of this technique is the introduction of residual strains into the produced structures. The experimental methodology for determining residual strains in samples manufactured on substrates with different thicknesses is examined to optimise the process and minimise residual strains. The method employs 3D digital image correlation to measure strains released during the stepwise unloading of samples produced on pre-clamped substrates. Example experiments were conducted for 316L stainless steel samples with two different substrate thicknesses. The evaluated data were correlated with technological parameters, potentially identifying optimal WAAM-CMT parameters. Moreover, the results were compared to the finite element method model of the manufacturing process to gain a deeper understanding of the physical processes and to improve finite element method modelling. This hybrid approach helps to identify key technological parameters and plan cooling strategies to minimise residual stresses in WAAM structures.