Residual strains in HY100 polycrystals: Comparisons of experiments and simulations

Residual stresses commonly arise in metallic components following plastic deformation and can have a significant effect on the mechanical properties. At the scale of the crystals, stresses are directly related to changes in lattice spacing. Neutron diffraction provides an effective method of measuring the spacing of atomic planes in crystal lattices with sufficient precision to determine the elastic (lattice) strains. In this work, tensile specimens were loaded and unloaded in situ to progressively larger amounts of plastic strain. Neutron diffraction measurements were taken at various points in the loading history, and the data were reduced to give the average elastic strains in subsets of the crystals characterized by common crystallographic directions. Using the finite element method, lattice strains were computed at the crystal level by modeling a polycrystal grain by grain. Elastic strains were extracted for sets of crystals corresponding to those sets examined by diffraction at comparable points in the loading history. Detailed comparisons for a steel (HY100) indicate that the model shows good agreement in predicting the lattice strains, both in the loaded and unloaded states. Further, the simulations elucidate aspects of the distributions of lattice strains that arise from the grain-to-grain interactions.