Dynamic Behavior of Materials IX: Strength and Spall II / X-ray, Spectroscopy and Imaging 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
Tuesday 8:30 AM
March 1, 2022
Location: Anaheim Convention Center
Session Chair: George Gray, Los Alamos National Laboratory; Michael Demkowicz, Texas A&M University
Dynamic Materials Experiments at High Pressures and High Strain Rates on the National Ignition Facility Laser*: Bruce Remington1; 1Lawrence Livermore Nat Lab
Experiments at the National Ignition Facility laser are probing matter at high pressures using ramped compression in various Discovery Science campaigns. The equation of state of iron has been measured to 1.4 TPa (14 Mbar) peak pressure and diamond up to 5 TPa using time resolved velocity interferometry. The phase of carbon has been measured to pressures of 2 TPa with x-ray diffraction, showing no phase transitions over the ~10 ns duration of the experiment. Magnesium has also been studied with diffraction to 1.3 TPa, showing multiple phase transitions. And 2D plastic flow studies of iron driven by the Rayleigh-Taylor instability to peak pressures and strain rates of ~400 GPa and ~1.e7 1/s suggest significant increases of strength at these extreme conditions. Examples from these experiments will be presented. *This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Richtmyer-Meshkov Instability Plate Impact Experiments on Three Body-centred Cubic Metals: Ben Adams1; Glenn Whiteman1; Ben Thorington-Jones1; James Turner1; 1Awe Plc
Richtmyer-Meshkov instability experiments are a sensitive means with which to infer the dynamic strength of materials in a high strain-rate, low pressure regime. Here we present an initial series of experiments examining the instability growth and spall behavior of three body-centred cubic metals; molybdenum, niobium and vanadium. Plate impact experiments on the three materials with machined free surface sine wave shaped perturbations of wavelength ~250 µm and amplitudes in the range 24–86 µm have been undertaken at impact stresses in the range ~9-20 GPa. Limiting values for impact stress and ripple amplitude at which an initial spike in the free surface velocity measurement is unclear have been determined. Some of the experimental challenges associated with this type of experiment will be highlighted. A series of hydrocode simulations, undertaken to develop material strength models by comparison to the experimental data, are discussed. UK Ministry of Defence ©Crown Owned Copyright 2021/AWE.
On Phase Transformation in the Weak Shock Regime: Neil Bourne1; George Gray2; Saryu Fensin2; 1University of Manchester; 2Los Alamos National Laboratory
The limits of elastic behaviour change with the nature of the impulse applied to a target and the size of volume interrogated by a measurement, since it is the pre-existing defects sampled within its rise that determine the response observed. Above the ultimate shear strength of a material during shock (the Weak Shock Limit - WSL) dislocations are homogeneously nucleated and the shock front becomes supersonic. In the inhomogeneous flow up to this stress, local shear triggers martensitic phase transformation and the presence of contained interstitials triggers bulk transitions in the solid. We shall discuss loading of the metals BCC Iron and HCP Titanium through the weak shock regime and into the strong and discuss the onset of transformation in these materials under shear at lower stresses.
Measurement and Simulation of Dynamic Friction via Kolsky Bar Technique: Benjamin Morrow1; Virginia Euser1; Clarissa Yablinsky1; Nicholas Denissen1; 1Los Alamos National Laboratory
Interfacial friction (resistance to movement between two different surfaces/materials) is important for many engineering applications (ex. machining, forming, ballistic processes). Though dynamic (high rate) friction is an important factor in overall material behavior of larger integrated experiments and engineering assemblies, it is not commonly measured experimentally. This is partially due to the complexity of the measurements/subsequent analysis of signals, and the relative difficulty of linking these observations to materials behavior during such sliding events. Here we attempt to measure dynamic friction using a modified Kolsky bar (split-Hopkinson pressure bar) technique. This data is directly compared to simulations using the LANL-developed FLAG hydrocode to attempt to validate current friction models, build greater predictive capability for dynamic friction, and streamline analysis of experimental tests and reduce experimental uncertainties. An overview of the present technique will be given, with recent results to demonstrate both successes and challenges of the measurements and simulations.
9:50 AM Break
Exploring the Effect of Microstructure on the Dynamic Behavior of 1045 Steel: Virginia Euser1; George Gray1; David Jones1; Daniel Martinez1; Saryu Fensin1; 1Los Alamos National Laboratory
The goal of this study is to understand damage nucleation and growth as a function of microstructure in 1045 steel, which is a medium carbon steel. Systematic heat treatments were used to modify the overall microstructure of this material to tempered martensite, ferrite-pearlite, and spheroidized. The strength of these microstructures was investigated at quasi-static and high strain rates and used to fit the mechanical threshold stress (MTS) strength model as a function of microstructure. The various microstructural conditions were then subjected to incipient spall experiments and recovered to explore any differences in not only the spall strength, but also in the mechanisms for void nucleation and growth.
Prospects and Challenges in Understanding the Strength of Materials in Extremes: Marc Meyers1; Gaia Righi1; Hye Sook Park2; Bruce Remington2; Chris Wehrenberg2; Carlos Ruestes3; Eduardo Bringa3; 1University of California-San Diego; 2LLNL; 3U. Nacional de Cuyo
Coordinated laser compression and release experiments in combination with molecular dynamics simulations are paving the way for an enhanced understanding of the strength of materials under compression and tension in a regime of strain rates above 106 s-1. Experiments have been conducted at four major facilities: the LLNL National Ignition Facility, the LLNL Janus laser, the Omega facility within the Laboratory for Laser Energetics, and the Dynamic Compression Sector at the Advanced Photon Source of Argonne National Laboratory. Characterization of recovered specimens in combination with VISAR have been instrumental in determining the tensile strength and mechanisms of failure of iron in spalling. For covalent materials, the effect of the powerful shear stresses in combination with pressure have resulted in the production of nanoscale amorphous layers which act as efficient paths for plastic deformation. The results and their significance are discussed. Research support: CMEC (DOE NNSA DE-NA0003842); LLNL ACT-UP(subcontract B639114).
Dynamic-tensile-extrusion for Investigating Large Strain and High Strain Rate Behavior: Eric Brown1; George Gray1; Nicola Bonora2; Carl Trujillo1; 1Los Alamos National Laboratory; 2University of Cassino
Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) is a novel test method for the investigation of material response under extreme tensile conditions, comprising the combined conditions of large tensile strains and high strain rates. The technique, in general, generates stable extruded jets that are observed via high-speed photography. These jets may accumulate subcritical damage during deformation, revealing damage processes that may only activate in a principally tensile deformation. Dyn-Ten-Ext produces spatially and temporally heterogeneous deformation fields, making it an integrated test, analogous to Taylor Impact. The range of strains and strain rates that evolve throughout the test, combined with the simple well defined boundary conditions, produce outstanding datasets for the validation of material models under conditions not accessible by classic testing techniques. This work presents an overview of Dyn-Ten-Ext as a technique for investigating extreme tensile deformation and damage in metals (including copper, depleted uranium, and tantalum) and polymers (including polyethylene,polyurethane, polytetrafluoroethylene, and polycarbonate).