Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session H6: Inelastic Deformations, Fracture and Spall IV: Copper |
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Chair: Ernest Baker, Army Research Laboratory, Benjamin Morrow, Los Alamos National Laboratory Room: 8/9/10 |
Tuesday, June 16, 2015 9:15AM - 9:30AM |
H6.00001: Deformation and Failure of OFHC Copper Under High Strain Rate Shear Compression Andrew Ruggiero, Gabriel Testa, Nicola Bonora, Gianluca Iannitti, Italo Persechino, Magnus H\"ornqvist, Nooshin Mortazavi Hat-shaped specimen geometries were developed to generate high strain, high-strain-rates deformation under controlled, prescribed conditions. These specimen geometries offer also the possibility to investigate the occurrence of ductile rupture under low (close to zero) or negative stress triaxiality where most of failure models fails. In this work, three top-hat specimen geometries were designed, by means of extensive numerical simulation, to obtain desired stress triaxiality values at the center of the adiabatic shear band that develops across the ligament. Material failure was simulated using CDM model formulation with unilateral condition for damage accumulation and validated comparing with quasi-static and high strain rate compression tests results on OFHC copper. Preliminary results seem to indicate that ductile tearing in the shear band initiates at the specimen corner location where positive stress triaxiality occurs because of local rotation and eventually propagates along the ligament. [Preview Abstract] |
Tuesday, June 16, 2015 9:30AM - 9:45AM |
H6.00002: Mechanical behavior and strength distribution in a spalled material Shraddha Vachhani, Carl Trujillo, Ellen Cerreta, George Gray III Damage evolution during dynamic testing is known to be via the nucleation and coalescence of voids. Once damaged, relatively little is known about the strength of the material, although the properties are expected to depend on amount of damage. For example, the strength of the materials close to the spall plane of a plate impact specimen is expected to have very different response as compared to material far from the spall plane. In this work, we examined the bulk compressive and tensile response of the different regions of a dynamically damaged sample. High purity copper is used as a model material. The copper sample was dynamically damaged using a plate impact experiment in a 100mm gas gun to impart moderate damage. Post-mortem analysis of the recovered sample using optical microscopy and electron back-scatter diffraction (EBSD) was be used to correlate the observed, post-damage, mechanical behavior with the local structure. [Preview Abstract] |
Tuesday, June 16, 2015 9:45AM - 10:00AM |
H6.00003: Spall Response of Annealed Copper to Direct Explosive Loading Simon Finnegan, Malcolm Burns, Glenn Whiteman Taylor wave spall experiments were conducted on annealed copper targets using direct explosive loading. The targets were mounted on the back of an explosive which was initiated using a gas gun plate impact. The explosive and target were separated by a layer of foam in order to reduce the peak amplitude and strain rate of the Taylor wave pulse. This technique creates a high stress state, with a lower strain rate than an equivalent plate impact experiment, within the target. An advantage of using a gas gun is that the explosive run to detonation following impact can be studied separately. Four shots were performed on two differently annealed batches of copper to investigate the effect of annealing on the spall response. One pair of targets was annealed at 1123 K for 4 hours and the other pair was annealed at 723 K for 1 hour. The free surface velocity profiles were recorded using a heterodyne velocimetry (HetV) probe, focussed on the centre of the target. To quantify the effect of the annealing the pullback shapes in the free surface velocity profiles and the calculated spall strengths were compared for the four targets. [Preview Abstract] |
Tuesday, June 16, 2015 10:00AM - 10:15AM |
H6.00004: Modelling and Simulation of Dynamic Recrystallization (DRX) In OFHC Copper at Very High Strain Rates Gabriel Testa, Nicola Bonora, Andrew Ruggiero, Gianluca Iannitti, Magnus H\"ornqvist, Nooshin Mortazavi At high strain rates, the deformation process is essentially adiabatic and if the plastic work is large enough, dynamic recrystallization can occur. In this work, an examination on microstructure evolution in Dynamic Tensile Extrusion (DTE) test of OFHC copper, performed at 400 m/s, was carried out. EBSD investigations, along the center line of the fragment remaining in the extrusion die, showed a progressive elongation of the grains, and an accompanying development of a strong \textless 001\textgreater $+$\textless 111\textgreater dual fiber texture. Meta-dynamic discontinuous dynamic recrystallization (DRX) occurred at larger strains, and it was showed that nucleation occurred during straining. A criterion, based on the evolution of Zener-Hollomon parameter during the dynamic deformation process, was proposed. Finally, DTE test was simulated using the modified Rusinek-Klepaczko constitutive model incorporating restoring effects induced by recrystallization processes. [Preview Abstract] |
Tuesday, June 16, 2015 10:15AM - 10:30AM |
H6.00005: The Study on spall and damage in convergent geometry Pei Xiaoyang, Peng Xui, He Hongliang, Li Ping Spallation damage in ductile materials is the process of void nucleation, growth and coalescence due to states of high tensile stress. Typical experiments are conducted in a planar, uniaxial stress configuration. Here, the effect of convergent geometry on the properties of dynamic damage evolution of OFHC are investigated. The spall fracture experiments are conducted using explosive generators. The damage evolution process are studied using the time-resolved free-surface velocity interferometry, post-experiment metallurgical analysis of the soft recovered samples. It indicated that, the convergent effect is a very important factors for the spallation damage, and the distinct differences are observed in the damage pattern between planar and convergent experiment. [Preview Abstract] |
Tuesday, June 16, 2015 10:30AM - 10:45AM |
H6.00006: Spin-Separated Spherical Low-Range Hypervelocity Impact Response of Carbon-Fiber/Metallic-Glass Fiber Metal Laminate Composite Rene Diaz, Nikhil Shukla, Christopher Lo, Lee Hamill, Scott Roberts, Marc Davidson, Steven Nutt, Greg Kennedy, Douglas Hofmann, Naresh Thadhani In this work, ballistic impact tests were conducted to compare the performance of Whipple shields consisting of metallic glass fiber-metal laminates (FML) with a baseline comparison of the shields currently utilized by the International Space Station. The threat of micro-meteoroid and orbital debris (MMOD) collisions with spacecraft and satellites has been escalating with the increasing worldwide use of low earth orbit spacecraft. Fiber metal laminates (FML) consist of alternating layers of metal and fiber reinforced polymer composite. Our study investigates the use of bulk metallic glass (BMG) sheets with carbon-fiber reinforced epoxy. The hybrid FML design gains structural rigidity from the carbon fiber composite and impact resistance from the metallic glass. Utilizing a single-stage, light gas gun, 3 mm spherical projectiles mounted a serrated, segmented sabot made of glass-filled polycarbonate is accelerated and spin-separated through a rifled barrel and sabot stripper impact velocities of 0.7-1.5 km$\cdot$s$^{-1}$. The design of the impact set-up and the characteristics of the metallic-glass based shield, along with results obtained to date will be presented. [Preview Abstract] |
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