Estimation of Residual Stress in Additive-Manufactured NiTi Alloy through Beam Mechanics and Finite Element Analysis

Residual stresses play a vital role in the properties of additive manufactured parts. These stresses must be controlled to obtain the desired properties and structural integrity. This study explores a novel method of predicting residual stresses using beam mechanics equations. The aim of this work was to estimate residual stress in additive-manufactured nitinol beams using the proposed method and compare the predictions with the results from other established techniques. Nitinol beams were built via powder bed fusion using laser beam (PBF-LB) technology on a stainless steel base plate with several sets of thin support structures. When the support structures were removed, the beams were seen to warp due to the relaxation of residual stress present in them. This deflection in the beams was used to estimate the extent of residual stress relief due to beam warpage using conventional mechanics of material beam mechanics. The stress levels obtained theoretically were compared with the results from finite element analysis (FEA) using Ansys software. The experiments were designed based on a Box-Behnken model in which the process parameters were laser power, scanning speed, and hatch spacing. The samples were considered to be cantilever beams and beam mechanics equations were used to predict the stress levels in the samples. The results obtained from beam mechanics and finite element analysis followed a similar trend.