Dynamic Behavior of Materials IX: Strength and Spall 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
Monday 2:00 PM
February 28, 2022
Room: 304D
Location: Anaheim Convention Center
Session Chair: Bruce Remington, Lawrence Livermore National Laboratory; Alexandra Burch, Los Alamos National Laboratory
2:00 PM
In-Situ X-ray Diffraction Shock Experiments on Titanium Diboride: Cyril Williams1; 1US Army Research Laboratory
Titanium diboride (TiB2) exhibits numerous excellent properties such as high melting point and high elastic modulus. The shock wave velocity profile of TiB2 reveals an anomalous double cusps with the first appearing between 4.2 GPa and 5.8 GPa, the second between 9.0 GPa and 17.0 GPa. Numerous shock wave research studies have being conducted to elucidate the cause for both cusps and one such study clearly shows that failure waves are only active between both cusps. To further explore the two cusps phenomenon, in-situ XRD shock experiments were conducted between the two cusps at 7.2 GPa shock stress, just above the second cusp at 15.6 GPa shock stress, and at 38.2 GPa shock stress. The acquired results not only confirmed that failure waves are active between both cusps but also suggest dilatancy. The experimental evidence show that both processes do not operate above the second cusp.
2:20 PM
Shock Response of Single-crystal Boron Carbide along Orientations with Extreme Elastic Moduli: MD Simulations and Experimental Comparison: Ghatu Subhash1; Amith Cheenady1; 1University of Florida
The influence of planar shock loading on boron carbide single crystal along orientations with the highest and lowest elastic moduli have been simulated using molecular dynamics simulations. Shock loading along the stiffest orientation generates an elastic precursor and a plastic wave while along the most compliant orientation, an elastic precursor is followed by two plastic waves. At particle velocities above 2.5 km/s a reduction in shear strength is observed along both orientations compared to those below 2.5 km/s. For Up > 2.5 km/s, overlapping Hugoniot states and release isentropes were observed due to shock induced temperature exceeding the melting point. Thus an invariance in the Hugoniot state of boron carbide with crystal orientation at high shock intensities is noted. The simulation-derived Hugoniot and hydrostatic curves align well with experimental data up to 140 GPa, while the Us-Up relationships agree with experimental measurements.
2:40 PM
Dynamic Compressive Response of Highly-oriented MAX Phases under Planar Confinement: Xingyuan Zhao1; Tarek Elmelegy2; Maxim Sokol3; Michel Barsoum2; Leslie Lamberson1; 1Colorado School of Mines; 2Drexel University; 3Tel Aviv University
MAX phases are layered ternary carbides and nitrides comprising of early transition metals (M), A group elements (A), and carbon and nitrogen (X). They are typically comprised of plate-like grains and combine advantageous properties of both metals and ceramics such as damage tolerance and a useful combination of toughness and strength. In the MAX phases only basal slip is active under ambient temperatures that in turn leads to ripplocation formation, buckling and kink-band formation. In this work, we use highly-oriented MAX phases to investigate the influence of grain orientation, material composition, and confinement on the dynamic compressive behavior of these layered materials. Their associated failure mechanisms will also be discussed. Experimental observations on our samples suggest that high loading-rates and confinement both increase the overall compressive failure stress. Modeling on MAX phases and other layered materials suggests that confinement plays a critical role and increases kink mode and nucleation stress.
3:00 PM
Structure / Property (Constitutive and Dynamic Strength / Damage) Characterization of Single-phase FeAl: George Gray1; Saryu Fensin1; David Jones1; H Wang2; Kenneth Vecchio2; 1Los Alamos National Laboratory; 2Univ. of CA, San Diego
In this presentation, the results of a study quantifying the constitutive behavior of two different B2-structured FeAl intermetallics, as well as an FeAl-based metallic-intermetallic laminate (MIL) composite is presented. One textured and layered polycrystalline FeAl was fabricated using an innovative “multiple-thin-foil” configuration and “two-stage reaction” strategy. Layers of metallic Al and Fe foils were alternating stacked and then processed utilizing a combination of a multiple pressure & temperature processing procedure to produce fully-dense single-phase FeAl samples. This same approach was used to fabricate the MIL composite. An equiaxed, random polycrystalline single-phase FeAl sample was fabricated from powders to be used as a reference material. In this paper, the influence of the constitutive behavior as a function of loading orientation, temperature, and strain rate, from quasi-static to dynamic rates, is presented. The dynamic damage evolution and failure response of the three materials was probed using flyer-plate impact driven spallation experiments.
3:20 PM Break
3:40 PM
Dynamic Compression Behavior of Composite Media with Varying “Microstructural” Conditions: Mukul Kumar1; 1Lawrence Livermore National Laboratory
A significant body of work has developed for the case of dynamic compression response of polycrystalline and multi-phase alloy microstructures. The experimental studies have been augmented by constitutive laws that describe the flow behavior under these high strain rate, high pressure loading conditions. Composite media with constituents that do not chemically interact with each other have been less frequently studied, though they have importance where multi-functionality can only be introduced through artificial means. We will compare the volumetric response of composite microstructures using free-surface velocimetry measurements. As an analog with multiphase alloys, the effects of a length scale encoded in particle volume fraction and size will be elucidated. This will be discussed in the context of processes such as internal wave reverberation, multiphase drag, and particle-particle force transfer that determine the rate of compression in a shock deformed particulate composite.
4:00 PM
MOVED TO WEDNESDAY PM - Investigating Spall Failure in Shock Compressed Iron: Gaia Righi1; Carlos Ruestes2; Camelia Stan3; Suzanne Ali3; Robert Rudd3; Hye-Sook Park3; Marc Meyers1; 1University Of California San Diego; 2Universidad Nacional de Cuyo; 3Lawrence Livermore National Lab
Spall response of pure iron was studied using high power pulsed laser experiments at the LLNL Jupiter facility. Thin iron foils of varying initial microstructures were subjected to peak pressures of 60 GPa and strain rates ranging from 106 s-1 – 107 s-1. Simultaneous time-resolved free surface velocity measurements and recovery techniques were used to investigate spall strength and failure mechanisms. These uniaxial strain experiments yielded strengths between 5 and 10 GPa for nanocrystalline and single crystal iron, respectively. Post-shock characterization and Molecular Dynamics simulations verify that this difference is due to void initiation sites. Grain boundaries in nano and polycrystalline iron are favorable sites for voids nucleation and will consequently cause failure to occur along grain boundaries perpendicular to the shock direction. In contrast, the formation and interaction of twin boundaries in single crystal iron are the cause for void initiation, growth, and coalescence that ultimately cause ductile failure.
4:20 PM
Path Dependence in Spall Fracture: David Jones1; Daniel Martinez1; Ramon Martinez1; Saryu Fensin1; Neil Bourne2; George Gray1; 1Lanl; 2University of Manchester
Materials subjected to shock or impulsive loading can undergo spall fracture, where the rapid unloading after the shock event drives a state of high strain-rate tension. In ductile metals, damage accrues through void nucleation, growth, coalescence, and then possibly full fracture of a spall scab. It is well known that spall is a weak-link dominated process, with microstructural features such as grain boundaries, twins, impurities etc. acting as nucleation sites for damage. Here, we present a method to study the effect of loading path - the entire stress-strain history of the material up to failure - on the spall process. Gas-gun flyer-plate impact experiments are used to investigate how the peak stress and pulse duration of the shock event affect the dynamic response of copper and titanium. Soft recovery is used to identify how the loading path changes the microstructure, and examine the effect on damage nucleation.