Boundary Effects in the Eigenstrain Method

Abstract

We present a comprehensive study of the effects of internal boundaries on the accuracy of residual stress values obtained from the eigenstrain method. In the experimental part of this effort, a composite specimen, consisting of an aluminum cylinder sandwiched between steel cylinders of the same diameter, was uniformly heated under axial displacement constraint.During the experiment, the sample temperature and the reaction stresses in the load frame in response to changes in sample temperature were monitored. In addition, the local (elastic) lattice strain distribution within the specimen was measured using neutron diffraction. The eigenstrain method, utilizing finite element modeling, was then used to predict the stress field existing within the sample in response to the constraint imposed by the load frame against axial thermal expansion. Our comparison of the computed and measured stress distributions showed that, while the eigenstrain method predicted acceptable stress values away from the cylinder interfaces, its predictions did not match experimentally measured values near them. These observations indicate that the eigenstrain method is not valid for sample geometries with this type of internal boundaries.

An iterative technique for the reconstruction of residual stress fields in a butt-welded plate from experimental measurement, and comparison with welding process simulation

“…Reißner was the first to use such inelastic strains to discuss misfit strains (Reißner, 1931). Recently, Lee et al (Lee et al, 2018) used a simpler definition based on elastic energy, since residual stresses are formed due to the external and/or internal constraints in the eigenstrain region. One example of the application of the eigenstrain technique is the inverse eigenstrain method used by Jun and Korsunsky (Jun and Korsunsky, 2010) in which eigenstrains were estimated by analysing limited measurements.…”