Advanced Characterization Techniques for Quantifying and Modeling Deformation: Session II
Sponsored by: TMS Extraction and Processing Division, TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Materials Characterization Committee
Program Organizers: Arul Kumar Mariyappan, Los Alamos National Laboratory; Irene Beyerlein, University of California, Santa Barbara; Wolfgang Pantleon, Technical University of Denmark; C. Tasan, Massachusetts Institute of Technology; Olivia Jackson, Sandia National Laboratories
Monday 2:00 PM
March 20, 2023
Room: Aqua 311A
Location: Hilton
Session Chair: Jaafar El-Awady, Johns Hopkins University; Ricardo Lebensohn, Los Alamos National Laboratory
2:00 PM Invited
Full Integration of FFT-based Methods for Optimization and Modelling of Micromechanical Data Obtained by Advanced Characterization Techniques: Ricardo Lebensohn1; 1Los Alamos National Laboratory
We report recent advances in the integration of FFT-based formulations with advanced characterization techniques, both for micromechanical modelling, as well as for improved data reduction. In connection with these two integration approaches, we show: a) applications of the large-strain elasto-viscoplastic FFT-based (LS-EVPFFT) model to interpret data from 3D x-ray diffraction (3DXRD), nano-pillar experiments, and micro-indentation, and b) a novel FFT-based methodology to impose micromechanical constraints to arbitrary voxelized stress fields obtained by 3DXRD. The proposed stress filtering method consists in finding the equilibrated stress field closest to a non-equilibrated field, posed as an optimization problem. The method is demonstrated by filtering synthetic piecewise constant stress fields and comparing with the corresponding ground-truth, and applied to filter stress fields in beta-Ti alloy obtained by imposing diffraction constraints only.
2:30 PM
Surface Roughness in Polycrystalline Copper under Cyclic Thermal Loading: FFT-based Thermomechanical Modelling with Experimental Verification for Accelerator Applications: Zhangxi Feng1; Miroslav Zecevic2; Rodney McCabe2; Daniel Hooks2; Marko Knezevic1; Ricardo Lebensohn2; 1University of New Hampshire; 2Los Alamos National Laboratory
During normal operations, accelerator cavities—made of a polycrystalline metal with extremely flat surfaces— experience pulsed heating due to radio-frequency loss, which induces surface temperature rises of about 50 K per heating cycle at a frequency of 60 Hz. This ultra-high-cycle thermal loading results in the development of surface roughness that affects the surface currents and eventually limits the operando lifetime of these cavities. A large-strain thermo-elasto-viscoplastic Fast Fourier Transform (LS-TEVPFFT) formulation [1] has been coupled with the solution for heat conduction, adding thermo-mechanical effects that enable microstructure-sensitive predictions of surface roughness in polycrystalline copper under high-cycle thermal loading. The new capabilities of the model are demonstrated via the comparison between predictions and cyclic heating experiments followed by roughness measurements by Atomic Force Microscopy (AFM).[1] M. Zecevic, R.A. Lebensohn and L. Capolungo "New large-strain Fast Fourier Transform-based formulation..."(2022).
2:50 PM
Investigating the Influence of Precipitates on Strengthening Mechanisms in Mg Alloys Using Phase-field Simulations: Darshan Bamney1; Laurent Capolungo1; 1Los Alamos National Laboratory
Precipitation hardening is a key strategy for improving the overall strength and ductility of Mg alloys. In Mg-Al alloys, basal precipitates are known to impede the growth of deformation twins resulting in a substantial increase in the critical resolved shear stress (CRSS) necessary for continued growth. Although several models have been proposed to quantify the influence of precipitate shape, size, and volume fraction on the CRSS, there is considerable scatter in the predictions. Moreover, the role of the local stress state at the precipitate-matrix and precipitate-twin interface on hardening remains to be understood. In this study, we systematically investigate the interactions between {10-12} twins in Mg, and Mg-Al precipitates to scrutinize the predictive capabilities of proposed hardening models, using atomistically-informed 3D phase field simulations. Ultimately, the hardening data is used to propose a model for the CRSS required for continued twinning deformation in the presence of precipitates.
3:10 PM Cancelled
Spatial Quantification of Deformation by Combining Data Collected from Digital Image Correlation and EBSD: Alex Forsey1; Ehsan Afshin1; Suzanne Cheney1; Salih Gungor1; Richard Moat1; 1The Open University
Quantifying local variations in deformation is desirable for applications ranging from developing mechanistic understanding of deformation processes to improving the reliability of lifeing models. Diffraction, high resolution digital image corelation (DIC) in an SEM and crystal plasticity modelling are all relatively mature techniques for this kind of study, however all are very expensive, time consuming and/or require specialist equipment. In this study, DIC using consumer digital cameras and high magnification lenses combined with EBSD has been used to map local variations in plastic mechanical properties in a variety of alloys. Neutron diffraction has been used to corroborate results and shows reasonable comparison between the micromechanical conclusions possible from the data generated in this way.
3:30 PM Break
3:50 PM
Three-dimensional Surface Morphology Reconstruction for In-situ Scanning Electron Microscope Experiments: An Alternative to Digital Image Correlation (DIC): Khalid El-Awady1; Steven Lavenstein1; Jaafar El-Awady1; 1Johns Hopkins University
We develop a new frameworkd for reconstructing 3D models of the surface of a material undergoing in situ scanning electron microscope deformation. Specifically we reconstruct the evolving 3D surface morphology (out-of-plane intrusions and extrusions) and lateral (in-plane) motion from multiple views of the sample at the end of the experiment, combined with a reverse optical flow propagation backwards in time that utilizes interim single view images. These measurements can be subsequently mapped to the strain tensor of all surface points, which can lead to better understanding of slip localization. This approach offers an alternative to the commonly used digital image correlation (DIC) technique which relies on tracking a speckle pattern applied to the material surface. DIC based on single camera input only produces in-plane two-dimensional (2D) measurements whereas our approach enables reconstruction of the 3D surface morphology and is completely non-invasive (requires no pattern being applied to the material surface).
4:10 PM
Crystallographic Slip System Activity Fields Identified Automatically from DIC Data for Intersecting, Diffuse and Cross Slip: Tijmen Vermeij1; Ron Peerlings1; Marc Geers1; Johan Hoefnagels1; 1Eindhoven University Of Technology
Plastic deformation in metals predominantly occurs through crystallographic slip, which requires identification to advance the understanding of metals. Current identification methods include (i) the use of the Schmid Factor (SF), (ii) matching of observed experimental slip traces to theoretical slip traces as determined by, e.g., EBSD and, (iii) calculation and matching of the ‘Relative Displacement Ratio’ (RDR) along a pre-determined slip trace, derived from SEM-DIC data. However, these methods require the presence of clear and straight slip traces in the strain field. To identify plasticity which involves, e.g., cross-slip, curved slip, and/or diffuse slip, a method is required that performs a one-step identification, locally, on the SEM-DIC displacement/strain field, i.e., without requiring an initial identification of slip trace lines in the strain map. We developed a method that yields quantitative slip system activity fields directly from DIC (and EBSD) data, which is validated on challenging FCC and BCC case-studies.
4:30 PM
Using the Digital Image Correlation Techniques in Unique Ways: Carl Cady1; Cheng Liu1; 1Los Alamos National Laboratory
It is obvious that the digital image correlation technique is a useful tool for measuring strains in tension or compression, but what happens if you want to measure very large deformations? How about when for correlation field breaks down, non-traditional sample geometeries, or non-uniform deformation? Obviously, the strength of DIC is that it can be used to measure strain fields across an entire sample that can be observed during loading. It is good for any geometry and at any loading rate where images can be captured and can be used on 3-D samples. In this talk examples will be presented that show how the technique can be used to measure strains to 90%, how to use the technique to measure crack boundaries for crack velocity and fracture toughness, and for geometries where there is non-uniform deformation (like shear). It is also ideal for small scale – high speed applications.