The Influence of Surface Irregularities on the Mechanical Properties of Thin-Walled Wire and Arc Additively Manufactured Parts

Abstract

Wire and Arc Additive Manufacturing (WAAM) is a metal additive manufacturing process commonly used to deposition medium to large, near net-shaped parts. It can efficiently use materials and deposit objects with fewer assembly parts. The main disadvantage of WAAM is the surface quality. This work investigates the geometry shift defect that could be formed due to the wear of the welding contact tip. As a result of the wear, the filler wire deviates from the nominal position, and errors occur in the positioning of individual layers of printed parts. The main objective of this work is to investigate the influence of surface irregularities on the mechanical properties of as-deposited thin-walled WAAM parts. Finite element modeling of static and cyclic tensile and compressive tests showed that the surface waviness formed during layer-by-layer deposition increases the stress level under static loading applied transversely to the deposited layers. Surface waviness also significantly reduces the life of parts under cyclic loading. Replacement of a worn contact tip causes the layers to shift, and the resulting load eccentricity increases the stress level. Uneven stress distribution throughout the cross section means reduced material usage efficiency. During compressive loading, the load eccentricity destabilizes, causing the specimen to deform after exceeding the yield strength in stress concentration zones. The relationship between unmachined and machined walls with equivalent stresses was obtained, allowing the influence of surface waviness on the strength and durability of structures to be considered at the design stage.