Mechanical Response of Materials Investigated through Novel In-situ Experiments and Modeling: Session III
Sponsored by: TMS Structural Materials Division, TMS: Thin Films and Interfaces Committee
Program Organizers: Saurabh Puri, VulcanForms Inc; Amit Pandey, Lockheed Martin Space; Dhriti Bhattacharyya, Australian Nuclear Science and Technology Organization; Dongchan Jang, KAIST; Jagannathan Rajagopalan, Arizona State University; Josh Kacher, Georgia Institute of Technology; Minh-Son Pham, Imperial College London; Robert Wheeler, Microtesting Solutions LLC; Shailendra Joshi, University of Houston
Wednesday 8:30 AM
February 26, 2020
Room: 32B
Location: San Diego Convention Ctr
Session Chair: Dongchan Jang, Korea Advanced Institute of Science and Technology; Jedsada Lertthanasarn, Imperial College London
8:30 AM Keynote
Microstructure-driven Mechanical Properties of Explosives Quantified with In-situ Tomography: John Yeager1; Brian Patterson1; Lindsey Kuettner1; Amanda Duque1; Virginia Manner1; Caitlin Woznick1; Darla Thompson1; David Walters1; 1Los Alamos National Laboratory
Plastic-bonded explosives (PBX) are polymer matrix composites, highly loaded (typically >80%) with micron-sized organic explosive crystals within the polymer binder. Microstructural characterization in these materials can be difficult due to safety concerns, material fragility, non-conductive properties, and similar CHNO composition between crystals and binder. Yet microstructural deformation mechanisms such as crystal-crystal cracking, binder delamination, and void nucleation are believed to dominate mechanical response of PBX materials under thermomechanical stimuli. Here, we show the exceptional promise of using laboratory scale micro-computed X-ray tomography with in situ mechanical loading to characterize such microstructure-driven damage mechanisms in PBX and mock materials. Properties such as binder stiffness and crystal-binder adhesion determine intergranular or transgranular fracture. The fully 3D microstructure measured with tomography is suitable for segmentation and generating meshes for simulations, enabling mesoscale modeling. Multiscale experimental results and corresponding mesoscale simulations will be presented.
9:10 AM Keynote
A Novel X-ray Diffraction Simulation Framework for Rapid Thermo-mechanical Processes: Darren Pagan1; Thien Phan2; Joel Bernier3; 1Cornell High Energy Synchrotron Source; 2National Institute of Standards and Technology; 3Lawrence Livermore National Laboratory
The past few years have seen significant advances in the ability to perform X-ray diffraction experiments at extremely short times scales (microseconds) to study rapid thermo-mechanical processes and develop new constitutive models. However, the wide energy bandwidth optics utilized and thermo-mechanical gradients present across the probe volume often make quantitative analysis of the measurements difficult. To help aid these analyses, we present a new polychromatic diffraction-based simulation framework for analysis of area detector diffraction data gathered during thermo-mechanical processing of crystalline materials. Results generated using the framework will focus on deconvolution of spatial thermal gradients during rapid heating and cooling (i.e., during the additive manufacturing process).
9:50 AM
Understanding Pseudomorphic bcc Mg Under Extreme Conditions of Pressure, Temperature and High Strain Rates: Manish Jain1; Rajaprakash Ramachandramoorthy2; Marko Knezevic3; Nenad Velisavljevic4; Nathan Mara5; Irene Beyerlein6; Johann Michler2; Siddhartha Pathak1; 1University of Nevada Reno; 2EMPA; 3University of New Hampshire; 4Argonne National Laboratory; 5University of Minnesota, Minneapolis; 6University of California, Santa Barbara
We study the response of body centered cubic (bcc) Mg under extreme conditions of pressure, temperature and strain rate. Bcc Mg was stabilized at ambient pressures in an Mg/Nb multilayer nanocomposite where the adjacent Mg/Nb interfaces are spaced within a few nanometers. We investigate the structure of the unknown bcc Mg phase within the nanocomposite under high pressures in a diamond anvil cell experiment using synchrotron radiation x-ray diffraction (XRD). Additionally, we perform high temperature micro-pillar compression tests and strain rate jump tests on Mg (bcc)/Nb 5nm/5nm and Mg (hcp)/Nb 50nm/50nm nanolaminates to compare the responses of hcp vs. bcc Mg. Results from these tests are analyzed in terms of the measured activation energies and activation volumes from sub-micrometer sized Mg/Nb multilayer nanocomposites.
10:10 AM Break
10:30 AM
High Throughput Creep Data Acquisition by Cantilever Bending Coupled to Digital Image Correlation: Syed Jalali1; Praveen Kumar1; Vikram Jayaram1; 1Indian Institute of Science
Power law creep during cantilever bending is associated with a re-distribution of stress whose complexity has traditionally only allowed the determination of steady state parameters from multiple tests. The present talk will show how, using model systems of aluminium and lead, the determination of location-specific strain history, along and across a beam, by image correlation methods, can be coupled to estimates of the local stress in one sample. Using such methods it is possible to self-consistently determine (a) the stress exponent in steady state from a single test, (b) the primary as well as steady state creep curve under a known uniaxial stress, and (c) the effect of strain gradients in small samples that can otherwise cause artefacts when extrapolated to the behaviour of large components. In addition to increasing the speed of data acquisition, sample-to-sample variability is also minimised.
10:50 AM
Mixed-mode Fracture Behavior of Magnesium Alloys: Vaishakh K V1; Rajvardhan Vilasrao Sarnobat1; Narasimhan Ramarathinam1; Satyam Suwas1; 1Indian Institute of Science
Magnesium alloys have HCP crystal structure, possess tension-compression asymmetry and are highly anisotropic in nature. Mixed-mode (I-II) fracture experiments on rolled AZ31 Mg alloy are conducted using four-point bend (4-PB) specimens along with in-situ imaging. Digital Image Correlation (DIC) technique is used to analyze the images and map out the deformation and strain fields. With increase in the mode II component of loading, notch region undergoes excessive shear deformation and the notched fracture toughness, Jc, decreases monotonically. Detailed microstructural characterization revealed that this reduction in Jc is due to the change in fracture mechanism from void-coalescence to shear cracking. Further, under mixed-mode loading with higher mode II component, density of tensile twins near the notch tips and size of micro-voids decrease. Finite element analysis using a phenomenological, anisotropic plasticity model and polycrystal plasticity model are used to understand the experimental observations.
11:10 AM
Quantifying Deformation Mechanics of High Temperature Alloys using In-situ and Digital Imaging Correlation (DIC) Testing Techniques: James Parkin1; Soran Birosca1; Ross Buckingham2; 1ISM; 2Rolls-Royce
Strain accumulation from either monotonic or cyclic loadings can be heterogeneous in aerospace materials where deformation can become localised depending on microstructural features and processing parameters. The damage mechanisms are further reliant on deformation rates and temperatures. Thus, the characterisation and dynamic observation of strain localisation during deformation at both macro and micro scales is vital for understanding the fracture mechanics of the alloy. In the current study, two major microanalytical tools were utilised to investigate deformation mechanisms in Waspaloy; (1) in-situ mechanical testing in SEM to obtain EBSD crystallographic orientation information at the micro scale, in addition to reveal the changes in grain morphology, texture and misorientation during high temperature deformation. (2) Digital imaging correlation (DIC) during variant mechanical testing to provide a holistic visualisation of the deformation on a macro-scale with the aim of revealing areas of localised plastic strain heterogeneities as the test pieces approaches failure.
11:30 AM
Dislocation-grain Boundary Interaction Investigations Using In-situ DIC and EBSD: Josh Tsai1; 1Brigham Young University
As the development of new materials continues to flourish, knowledge of microstructural interactions is key to producing stronger and safer mechanical components. In this paper, in-situ high resolution DIC performed conjointly with EBSD is employed on pure nickel samples of various grain sizes to investigate interactions between geometrically necessary dislocations and grain boundaries, particularly in their relation to the shear bands which develop. Critical attributes, such as misorientation angle and slip system data, are fed into machine learning algorithms to confirm their correlations and demonstrate the influence of short- and long-range internal stresses on predicting macroscopic properties. The result is a model that improves the current understanding of material behaviors and can accurately predict their macroscopic properties using only microstructural information.