Tomographic eigenstrain reconstruction for full-field residual stress analysis in large scale additive manufacturing parts

Abstract

Current experimental and numerical quantification methods are limited in their ability to full-field mapping of the unpredictable distribution of all residual stress and permanent plastic strain components in additive manufacturing parts with discontinuous processing properties. To address this limitation, a tomographic eigenstrain (inherent strain) reconstruction method, that merges eigenstrain reconstruction with diffraction strain tomography for mapping volumetric distribution of all components of eigenstrains and corresponding elastic deformations like residual stresses non-destructively using minimum amount of tomographic scans is presented through numerical experiments, and then applied to the analysis of a CM 247 LC superalloy additive manufacturing part using diffraction strain tomography data. The method reconstructs all eigenstrain and corresponding residual stress components, parallel to the build direction, aligned with the experimental data component accurately, demonstrating its potential in optimizing the performance and reliability of parts designed for high-tech industries such as aerospace. Subsequent validations using the X-ray diffraction sin2ψ and neutron diffraction strain scanning techniques confirm the method's reliability in reconstructing residual stress components parallel to the plane of powder bed that are different from the experimental data component. Furthermore, the novel findings of this study reveal a characteristic residual stress distribution pattern within additive manufacturing parts particularly those featuring rectangular shapes. Microstructural analysis also validates eigenstrain distribution in accordance with the findings on the characteristic distribution of residual stresses, highlighting the significance of this method in advancing materials research and development.