Residual strains in HY100 polycrystals: Comparisons of experiments and simulations

Abstract

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.

Microscale prediction of deformation in an austenitic stainless steel under uniaxial loading

“…In their simulations, no comparisons with in-situ ND measurements are presented as their examinations are targeted to virtual materials with different single crystal elastic anisotropy. There are some FE based studies comparing ND measurements with FE predictions for BCC materials (ferritic steels) (see, Dawson et al, 2000;Quinta da Fonseca, 2006). However, these have employed rather simple models of the grain shape (e.g.…”

The effect of prior deformation on subsequent microplasticity and damage evolution in an austenitic stainless steel at elevated temperature

“…Full field polycrystal models have been formulated using fast Fourier transform techniques for materials with periodic microstructure, which have been employed for lattice strain predictions (see, e.g., [25,26]). More commonly, finite element (FE) methods have been used to complement in-situ ND observations, with either simplified grain topology [7,8,12,20,22] or complex/realistic geometries [19,[27][28][29][30] taken into account. As shown in a recent work [29], an accurate prediction of lattice strain evolution can be achieved using a microstructure-based FE model for austenitic stainless steels.…”

Combined near- and far-field high-energy diffraction microscopy dataset for Ti-7Al tensile specimen elastically loaded in situ

“…2), where we conducted ff-HEDM measurements at each load level. The specimen was initially overloaded past each of these desired axial load levels and then unloaded approximately 10 % to minimize any change in material state during the ff-HEDM measurements due to stress relaxation [19]. From Fig.…”

“…This kind of data can be used to instantiate a CPFEM or other micromechanical modeling techniques such as the fast Fourier transform (FFT) methods. While the full aspects of these methods are beyond the scope of this work, many studies have directly incorporated microstructure into a micromechanical modeling framework and then attempted to validate the accuracy of the model on the microstructural level [26][27][28][29][30][31][32][33][34].…”