Dynamic Behavior of Materials IX: Plasticity / Modeling and Simulation I
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Eric Brown, Los Alamos National Laboratory; Saryu Fensin, Los Alamos National Laboratory; George Gray, Los Alamos National Laboratory; Marc Meyers, University of California, San Diego; Neil Bourne, University of Manchester; Avinash Dongare, University of Connecticut; Benjamin Morrow, Los Alamos National Laboratory; Cyril Williams, US Army Research Laboratory
Wednesday 8:30 AM
March 2, 2022
Room: 304D
Location: Anaheim Convention Center
Session Chair: Marc Meyers, University of California San Diego; Jeremy Millett, Awe Plc
8:30 AM
Contrasting the Shock Response of Typical Face Centred Cubic and Body Centred Cubic Single Crystals: Jeremy Millett1; Saryu Fensin2; Yu-Lung Chiu3; Glenn Whiteman1; George Gray2; 1Awe Plc; 2Los Alamos National Laboratory; 3University of Birmingham
The behaviour of metals under mechanical loading (including the extremely high strain-rates experienced during shock loading) are influenced at the most fundamental level by the crystalline structure. In this presentation, we examine how representative examples of face centred cubic (aluminium) and body centred cubic (tantalum) single crystals respond to quasi-static and shock loading conditions, both in terms of their mechanical properties and microstructural development. Results show that the response of aluminium is as would be expected from consideration of the relevant Schmid factors whilst tantalum shows a significant non-Schmid response. Deformation in the aluminium was via by dislocation generation, but strongly controlled by orientation to the loading axis, with dislocation density increasing from [100] to [110] to [111] as ease of dislocation motion decreased. In the case of tantalum, twin formation became increasing dominant above a shock pressure of 15 GPa.
8:50 AM Cancelled
Anomalous Strain Rate History Effects in TRIP and TWIP Steels: Christopher Meredith1; Daniel Field1; Daniel Magagnosc1; Timothy Walter1; Jeffrey Lloyd1; Krista Limmer1; 1Army Research Laboratory
A fundamental tenet of metals plasticity is the strain, strain rate, and temperature history that a material has been subjected to influences its subsequent mechanical behavior. Thus, the flow stress is not a unique function of these variables and history effects can be significant. There are two strain rate effects that can be present–an instantaneous response due to the microstructure’s current state (no history dependence), and a change in the strain hardening that describes the historic change in the microstructure up to the current state (history dependent). FCC metals consistently show a large history effect, while the results for BCC and HCP metals is more ambiguous and contradictory, however, rarely is there no strain rate history effect present. This talk presents results on an FCC austenitic TWIP and triplex TRIP steels with anomalous history effects, whose alloying constituents and processing tailored the SFE to activate the aforementioned mechanisms.
9:10 AM
Multi-mechanism Models for Impact on Ceramics: Nilanjan Mitra1; Weixin Li1; K T Ramesh1; 1Johns Hopkins University
Ceramics are typically brittle, and fracture and fragmentation can lead to disintegration into a granular material under conditions such as impact. However, these materials demonstrate numerous mechanisms depending on the stress state and the timescales. The initial material usually contains defects such as stacking faults, inclusions and voids, and descriptions of the global behavior require a micromechanics based approach coupled with an equation of state model. Associated mechanisms include amorphization, dislocation-based plasticity, fracture, damage, fragmentation, and granular flow. We have developed a multi-mechanism model within a finite deformation framework that can be used across a wide range of loading conditions. We describe the model, and discuss spherical and cylindrical projectile impact on thin plates and thick cylinders of boron carbide and silicon carbide to demonstrate the capabilities of the model. This work was developed as part of the MEDE program, funded by the US Army Research Laboratory.
9:30 AM
Modeling Dislocation Evolution in High Velocity Microparticle Impacts: Kevin Larkin1; Abigail Hunter1; Miles Buechler1; 1Los Alamos National Laboratory
Microparticle impacts such as micrometeorite collisions or cold spray adaptive manufacturing create an extreme loading environment in the projectile and target bodies. Plastic deformation in metals is controlled by the complex motion and evolution of dislocations within the crystal lattice. Propagating shock waves cause a wide range of stain rates from quasi-static to rates in excess of 108 s-1. To accurately capture the material response, a flow stress model that precisely captures both the thermal barriers to dislocation motion, during low-rate loading, and phonon drag effects, during high-rate loading, is needed. Additionally, a complex network of evolving mobile and immobile dislocations must be represented. In this work, the recently developed mean first passage time model (MFPT) along with an analytical model for the generation, storage, and annihilation of dislocations, developed by Hunter and Preston, is used to simulate metallic polycrystalline microparticle impacts.
9:50 AM Break
10:05 AM
A Twinning Model Based on Dislocation Kinetics for Polycrystalline Beryllium under Dynamic Loading Conditions: Nitin Daphalapurkar1; Darby Luscher1; Daniele Versino1; 1Los Alamos National Laboratory
In polycrystalline HCP metals, twinning has an increasing contribution to plastic deformation at high rates of loading. We advanced a viscoplastic damage model, incorporating evolution of microcrack and dislocation densities, to include deformation due to twinning. Using the Mechanical Threshold Stress (MTS) model of isotropic plasticity as a baseline, the dislocation-based model for deformation twinning adapted in this work implements a physically-based kinetics of twin boundary motion and interaction with dislocation network. A probabilistic expression for twin density evolution was calibrated for polycrystalline hot-pressed beryllium to demonstrate the applicability of the model to simulate the measured uniaxial stress-strain data from split Hopkinson bar experiments. Further, we demonstrate the versatile applicability of the model to textured specimens. We present results for rolled beryllium specimens in through-thickness and in-plane directions, with reasonable comparisons of simulated twin densities with those observed from dynamic experiments.
10:25 AM
Spall of Tin and Its Sensitivity to Microscale Behaviors – A Computational Study: Kazem Alidoost1; Nathan Barton1; Garry Maskaly1; Fady Najjar1; 1Lawrence Livermore National Laboratory
A robust porosity-mechanics-based constitutive model, suited to large-deformation three-dimensional simulations, has been previously developed [http://dx.doi.org/10.1063/1.4971654]. Simulations of plate impact experiments are performed, with a multilayer flyer configuration that produces two shocks. Experimentally observable results such as the temperature and velocity histories are compared to those obtained by G. Maskaly and coworkers and presented at TMS2020 [LA-UR-20-21774]. The dependence of the simulated results on the microstructural modelling is studied. Simulations are performed for two distinct families of pores, those that are filled with material assumed to lack strength (bubbles) and those that are empty (voids). The mechanisms for porosity nucleation are studied, with particular emphasis on the distribution of nucleation sites. Demonstration three-dimensional large-deformation computations are presented, using this constitutive model in an arbitrary Lagrangian-Eulerian (ALE) simulation framework. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 (LLNL-ABS-823940).
10:45 AM
Mechanical Properties of a Model Co-continuous Two-phase Metal Composite: Lauren Poole1; Avery Samuel2; Frank Zok2; 1University of California-Santa Barbara
; 2University of California-Santa Barbara
Dynamic mechanical properties of multiphase metal composites comprising dissimilar immiscible phases can be controlled through selection of constituents, processing routes and phase topologies. This talk will focus on the quasi-static and dynamic mechanical behavior of a commercial model material made of 58 vol% W and 42 vol% Cu. This composite is of interest because both constituents exist in significant fractions and exhibit highly dissimilar properties (CTE, density, yield stress, elastic modulus, crystal structure). The co-continuous nature of the phases adds further complexity to composite response. Here, finite element simulations and experiments will be used to inform our understanding of the mechanical behavior of co-continuous structures.
11:05 AM
Simulations of Laser-driven Metal Microjet Formation and Their Interactions: Kyle Mackay1; Fady Najjar1; Alison Saunders1; Hye-Sook Park1; Suzanne Ali1; Jon Eggert1; Jeremy Horwitz1; Brandon Morgan1; Yuan Ping1; Camelia Stan1; 1Lawrence Livermore National Lab
Understanding dynamic fragmentation in shock-loaded metals and studying the resulting high-velocity microjets is of considerable importance for applied science and engineering applications. The current work presents hydrodynamic simulations of laser-driven microjetting from micron-scale grooves on a tin surface. The simulations supported designing experiments on the OMEGA and OMEGA-EP lasers. Microjet formation is investigated for 3-120 GPa shock pressures, spanning drives that leave the target solid on release to fully melted. We examine the effect of variations in target geometry for solid, liquid, and partially melted tin microjets. Finally, we present results for two interacting tin microjets and examine the effects of areal density, jet velocity, and material phase on the nature of jet-jet interactions.LLNL-ABS-823916. Work performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC.
11:25 AM
Effect of Surfaces on Dislocation Mobility in the Transonic Regime: Ta Duong1; Michael J. Demkowicz1; 1Texas A&M University
We use molecular dynamics to investigate the effect of free surfaces on the mobility of dislocations in single crystal copper (Cu). Dislocation velocities up to 4000 m/s are modeled. In the subsonic regime, dislocation velocity matches the applied strain rate. However, above the lowest transverse sound speed (c2~1600m/s), the dislocation velocity alternates periodically between c2 and a higher value (~2700m/s). The time spent at each velocity is such that the average velocity again matches the applied strain rate. We rationalize this behavior based on dislocation interactions with the nearby free surfaces in the model. These findings shed new light on the mechanisms of plastic deformation under high strain rate loading.
11:45 AM
High Strain-rate Nanoindentation Testing of Soft and Hard Model Materials: Benjamin Hackett1; Christopher Walker1; Wesley Higgins1; Sudharshan Phani Pardhasaradhi2; Warren Oliver3; George Pharr1; 1Texas A&M University; 2International Advanced Research Centre for Powder Metallurgy & New Materials (ARCI); 3KLA Corporation
A new nanoindentation system designed specifically for testing at high strain rates up to 104 s-1 has been used to explore the strain rate dependence of the hardness of two model materials – soft aluminum and hard fused silica glass. The testing system is based on a very high stiffness specimen translation stage and gantry and a laser interferometer that provides sub-nanometer indenter tip displacement measurement resolution at data acquisition rates up to 10 MHz. The high data acquisition rate is crucial for determining dynamic effects on the load applied to the specimen. In general, the hardness of the materials is observed to increase in a measurable way at the higher strain rates. Three-dimensional imaging of the contact impressions in comparison to those obtained under quasi-static conditions reveals differences in contact geometry that may help to explain the origin of the enhanced hardness.