3D-printed stainless steel circular tubes: Residual stress measurements and proposed models

This paper presents an experimental investigation on the residual stresses in 3D-printed, namely wire arc additively manufactured (WAAM), stainless steel circular hollow sections (CHSs) utilizing the hole-drilling method. The WAAM CHS specimens were manufactured by feedstock wire ER308L with a diameter of 1.2 mm. The details of fabrication procedure for the specimens are first outlined, after which four specimens were designed and printed for residual stress measurements. Strain-gauge rosettes were used for the measurements of strains in three directions. The general patterns of the residual stress distributions across the section and along the length, as well as the influence of deposition strategies and heat treatment, were obtained and analyzed. Generally, it was found that the longitudinal membrane residual stress distributions across the sections exhibited a trapezoidal wave pattern consisting of alternating uniform tensile and compressive stress regions separated by narrow transition zones. The experimental results were compared with the predictions by using the existing residual stress models for conventionally fabricated CHS steel and stainless steel tubes, including those with seamless normal-strength steel, welded normal-strength steel, welded high-strength steel and welded stainless steel. The results of comparison showed that the residual stress distributions in WAAM stainless steel CHSs differed significantly from the predictions of the existing models. Finally, new residual stress distribution models, comprising a unified pattern with two alternative magnitudes for non-heat-treated and heat-treated WAAM stainless steel CHSs, were proposed and evaluated, which showed more accurate and consistent predictions than the existing models.