Residual stresses in additively manufactured parts: predictive simulation and experimental verification

Abstract

PurposeThe purpose of this paper is to investigate a simulation solution for estimating the residual stresses developed in metal fused filament fabrication (MF3) printed parts. Additionally, to verify these estimates, a coupled experimental–computational approach using the crack-compliance method was investigated in this study.Design/methodology/approachIn this study, a previously validated thermomechanical process simulation was used to estimate the residual stresses developed in the MF3 printing process. Metal-filled polymer filament with a solids loading of 59 Vol.% Ti-6Al-4V was studied. For experimental validation of simulation predictions, the MF3 printed green parts were slitted incrementally and the corresponding strains were measured locally using strain gauges. The developed strain was modeled in finite-element-based structural simulations to estimate a compliance matrix that was combined with strain gauge measurements to calculate the residual stresses. Finally, the simulation results were compared with the experimental findings.FindingsThe simulation predictions were corroborated by the experimental results. Both results showed the same distribution pattern, that is, tensile stresses at the outer zone and compressive stresses in the interior. In the experiments, the residual stresses varied between 1.02 MPa (tension) and −2.28 MPa (compression), whereas the simulations were predicted between 1.37 MPa (tension) and −1.39 MPa (compression). Overall, there was a good quantitative agreement between the process simulation predictions and the experimental measurements, although there were some discrepancies. It was concluded that the thermomechanical process simulation was able to predict the residual stresses developed in MF3 printed parts. This validation enables the printing process simulation to be used for optimizing the part design and printing parameters to minimize the residual stresses.Originality/valueThe applicability of thermomechanical process simulation to predict residual stresses in MF3 printing is demonstrated. Additionally, a coupled experimental–computational approach using the crack-compliance method was used to experimentally determine residual stresses in the three-dimensional printed part to validate the simulation predictions. Moreover, this paper presents a methodology that can be used to predict and measure residual stresses in other additive manufacturing processes, in general, though MF3 was used as demonstrator in this work.