Infrared imaging surface roughness criticality assessment of Wire Arc Additive Manufactured specimens

Abstract

Wire Arc Additive Manufacturing is an additive manufacturing process with a high rate of material deposition capable of producing near-net shape parts. This process involves the reduction of production costs (material and lead times) and considers innovative designs. However, the deposition technique induces heterogeneities in the material, in particular the presence of porosity and a degraded surface finish. The process-induced surface asperities have a first-order influence on the fatigue life of as-built parts as they act as stress raisers. Various finishing treatments can be considered to reduce the criticality of the surface finish influence over crack initiation and propagation: conventional ones such as hammer, laser or shot peening and some specially developed for Additive Manufacturing (AM) processes such as in-situ cooling or hot rolling. The multitude of AM parameters and the different finishing surface post-treatments entail many configurations that will modify fatigue properties. For this reason, rapid fatigue evaluation methods are an asset for process evaluation.

Thermo-elastic Stress Analysis (TSA) is a non-contact technique for measuring the distribution of stress at the surface of a component subject to cyclic loading using an infrared camera. The analysis of the thermo-elastic coupling amplitude maps allows the detection of initiation and monitoring of crack propagation. A four-point bending fatigue test protocol is conducted on CuAl9 WAAM specimens take in different direction for the deposition direction. Then failure mode and life duration are compared for the 2 directions.