Abstract
The lattice strain and intensity evolution obtained from in-situ neutron diffraction experiments of 316L cruciform samples subjected to 45° and 90° load path changes are presented and predicted using the multi-scale modeling approach proposed in Upadhyay et al., IJP 108 (2018) 144-168. At the macroscale, the multi-scale approach uses the implementation of the viscoplastic self-consistent polycrystalline model as a user-material into ABAQUS finite element framework to predict the non-linearly coupled gauge stresses of the cruciform geometry. The predicted gauge stresses are then used to drive the elasto-viscoplastic fast Fourier transform polycrystalline model to predict the lattice strain and intensity evolutions. Both models use the same dislocation density based hardening law suitable for load path changes. The predicted lattice strain and intensity evolutions match well with the experimental measurements for all reflections studied. The simulation results are analyzed in detail to understand the role of elastic anisotropy, plastic slip, grain neighborhood interactions and cruciform geometry on the microstructural evolution during biaxial load path changes.
Highlights
Sheet metals and alloys are often subjected to biaxial loadings and load path changes (LPCs) during their forming processes
The main aim of this work is to use the multi-scale modeling approach presented in (Upadhyay et al, 2018), i.e. VPSC-FE and elasto-viscoplastic fast Fourier transform (EVP-FFT) models implemented with crystallographic-RGBV hardening law, to predict and explain the lattice strain and intensity evolution obtained from in-situ neutron diffraction measurements during biaxial LPC tests of 316L cruciform samples
4) What is the role of elastic anisotropy, plastic slip and grain neighborhood on the lattice strain evolution? 5) What is the role of elastic anisotropy and grain neighborhood on the intensity evolutions? 6) What is the role of the cruciform geometry induced non-linear gauge stress response on the lattice strain evolution during the 90°
Summary
Sheet metals and alloys are often subjected to biaxial loadings and load path changes (LPCs) during their forming processes. As noted in several works (Bonnand et al, 2011; Hoferlin et al, 1998; MacEwen et al, 1992; Upadhyay et al, 2017b), for most cruciform geometries it is difficult to define the gauge cross-sectional area. This prevents the analytical computation of the gauge stresses. Foecke and co-workers (Foecke et al, 2007; Iadicola et al, 2014, 2008) proposed to use the sin x-ray diffraction approach to obtain the gauge stresses during biaxial testing Their approach requires making several assumptions on the gauge stress state and obtaining a reliable stress-strain response during LPCs is very time consuming. The most information that can be extracted from a cruciform test setup is the applied forces/displacements in the arms, and the gauge surface strain evolution using techniques such as digital image correlation (DIC)
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