Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session P4: Inelastic Deformation IV |
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Chair: Yogi Gupta, Washington State University Room: Fairmont Orchid Hotel Plaza II |
Thursday, June 28, 2007 10:30AM - 10:45AM |
P4.00001: Dynamic Plastic Response of Aluminum at Temperatures Approaching Melt Stephen Grunschel, Rodney Clifton This study uses the pressure-shear plate impact configuration to investigate the rate-controlling mechanisms of the plastic response of metals at strain rates on the order of 10$^{6}$ s$^{-1}$ and at temperatures that approach melt. In similar experiments by Frutschy and Clifton (\textit{JMPS }\textbf{46, }1998, 1723-1743) on OFHC copper, the flow stress decreases with increasing temperature and increases with increasing strain rate over the full range of temperatures and strain rates examined. No conclusive evidence of a change in rate-controlling mechanism was obtained. In the current study, temperatures that are larger fractions of the melting temperature are accessible because of the lower melting point of aluminum. So far, the shearing resistance has been measured at temperatures up to 630 C, which is 81{\%} of the melting temperature at the concurrent pressure. Several approaches are being explored to obtain even higher fractions of the melting temperature, possibly exceeding it. Results of these approaches will be presented. [Preview Abstract] |
Thursday, June 28, 2007 10:45AM - 11:00AM |
P4.00002: Effects of Shock-Breakout Pressure on Ejection of Micron-Scale Material from Shocked Tin Surfaces Michael Zellner, James Hammerberg, Robert Hixson, Kevin Morley, Andrew Obst, Russell Olson, Jeremy Payton, Paulo Rigg, William Buttler, Michael Grover, Adam Iverson, Gregory Macrum, Gerald Stevens, William Turley, Lynn Veeser, Nathan Routley Los Alamos National Lab (LANL) is actively engaged in the development of a model to predict the formation of micron-scale fragments ejected (ejecta) from shocked metal surfaces. The LANL ejecta model considers that the amount of ejecta is mainly related to the material's phase on shock release at the free-surface. This effort investigates the relation between ejecta production and shock-breakout pressure for Sn shocked with high explosives to pressures near the solid-on-release/partial-liquid-on-release phase transition region. We found that the amount of ejecta produced for shock-breakout pressures that resulted in partial-liquid-on-release increased significantly compared to that which resulted in solid-on-release. Additionally, we found that the amount of ejecta remained relatively constant within the partial-liquid-on-release, regardless of shock-breakout pressure. [Preview Abstract] |
Thursday, June 28, 2007 11:00AM - 11:15AM |
P4.00003: Transition from solid to liquid spall in tin under laser shocks of increasing intensity Thibaut De Resseguier, Loic Signor, Andre Dragon, Pierre Severin, Michel Boustie When a shock-loaded target is melted on compression or on release, the tensile stresses generated upon reflection of the pressure pulse from a free surface are induced in a liquid state. Instead of the well-known spallation process occurring in solid targets, cavitation takes place in the melted material and liquid fragments are ejected from the free surface. Although increasing interest is manifested on the subject, related data are still scarce. In a recent paper, we have reported an exploratory investigation of liquid spall in tin samples submitted to laser shocks of very high intensities [\textit{J. Appl. Phys.} \textbf{101}, 013506, 2007]. Here, we present new experimental results obtained over a lower pressure range ($\sim $14 to 60 GPa), where we focus on the progressive transition from the ductile behaviour of solid tin to the cavitating spall expected above melting. Both time-resolved free surface velocity measurements and post-test examination of the recovered samples clearly show such transition. The drop in tensile strength associated with melting is evaluated from the velocity profiles. Detailed views of the fracture surfaces provide an insight into the cavitation process. Experimental data are compared to preliminary computations. [Preview Abstract] |
Thursday, June 28, 2007 11:15AM - 11:30AM |
P4.00004: Fragment-size prediction during dynamic fragmentation of melted tin. Experimental investigation and modelling issues Gilles Roy, Loic Signor, Thibaut De Resseguier, Andre Dragon, Fabrice Llorca A triangular shock-wave of sufficient intensity propagating in a metal sample may induce melting. When it reaches the free surface, tensile stresses are generated in the liquid state and lead to the creation of an expanding continuum of liquid debris. This phenomenon called micro-spalling consists of a dynamic fragmentation process in the melted material. Relevant data are still few but important for developing robust and physics-based models. Recently, we have reported a qualitative investigation of micro-spall in tin samples submitted to laser shocks [J.~Appl. Phys. 101, 013506, 2007]. The present paper contains new experimental results including fragment recovery using a low density PVC-foam and post-test evaluation of the fragment-size distribution using X-ray microtomography. These results are compared to theoretical predictions from hydrocode simulations coupled with a modified formulation of the well-known energy fragmentation model of D.E. Grady [J. Mech. Phys. Sol., 36(3), pp.353-384, 1988]. [Preview Abstract] |
Thursday, June 28, 2007 11:30AM - 11:45AM |
P4.00005: The dynamic behavior of mortar under impact-loading Nobuaki Kawai, Kenji Inoue, Satoshi Misawa, Kyoji Tanaka, Shizuo Hayashi, Ken-ichi Kondo, Werner Riedel Concrete and mortar are the most fundamental structural material. Therefore, considerable interest in characterizing the dynamic behavior of them under impact-loading exists. In this study, plate impact experiments have been performed to determine the dynamic behavior of mortar. Longitudinal and lateral stresses have been directly measured by means of embedded polyvinylidene fluoride (PVDF) gauges up to 1 GPa. A 200 mm-cal. powder gun enable us to measure longitudinal and lateral stresses at several point from the impact surface, simultaneously. The shear strength under impact-loading has been obtained from measured longitudinal and lateral stresses. The longitudinal stress profile shows a two-wave structure. It is indicated that this structure is associated with the onset of pore compaction and failure of mortar by comparing with hydrocode simulations using an elastic-plastic damage model for concrete. [Preview Abstract] |
Thursday, June 28, 2007 11:45AM - 12:00PM |
P4.00006: Phase Transition Behavior and Abnormal Spall in FeMnNi alloy with Low $\alpha -\varepsilon $ Transition Stress Haibo Hu, Yongtao Chen, Qingzhong Li Phase transition behavior of a FeMnNi alloy with low $\alpha -\varepsilon $ phase transition stress in range of 6$\sim $7GPa and corresponding spall phenomena are studied. Two experiment set up of symmetric impact design with flyer and target of same thickness and reverse impact technique of metal flyer on sapphire window are used. Loading and release wave profile are recorded with help of VISAR with two constants of strip numbers. Experiments are conducted on 100-mm-diameter and two stage light gas gun in velocity range from 300m/s up to 2000m/s. Discussion is focused on the formation of rarefaction shock wave and role of RSW in spallation. It is shown that spallation may happen in symmetric impacts when stress is higher than phase transition point. In velocity range up to 2000m/s, when impacting stress is more than 40GPa and shock front is overdriven, a spallation like oscillation profile is noticed in domain of first plateau in velocity curve. As release wave from impact side should come some time later, it may be raised by reflection of release wave from free surface with reverse phase transition. Specimen is thoroughly broken, although pulse X-ray records at the moment of 14 $\mu$s after impact show no sign of multi-spallation. Further experiments are planned using VISAR with two constants of strip numbers to verify this phenomenon and parameters such as spall strength, spall thickness. [Preview Abstract] |
Thursday, June 28, 2007 12:00PM - 12:15PM |
P4.00007: Shock-induced turbulence and dissipative structures in copper Yuri Meshcheryakov, Natali Zhigacheva, Alexandre Divakov, Inan Makarevich, Boris Barakhtin A shock-wave loading under uniaxial strain conditions of polycrystalline M3 copper reveals a threshold nucleation of dissipative structures of 15$\div$25 \textit{$\mu$m} in diameter. Where observed the turbulent-like formations lie in the grains favorable oriented respectively shock wave propagation direction. Each structure consists of networks of parallel or mutual perpendicular shear bands of 100$\div$300 \textit{nm} spacing, so the size of elementary cell restricted by shear bands in their scale belong to nanostructure. Macroscopically, momentum and energy expended on formation of the structures is quantitatively characterized by ``deficit of particle velocity'' - difference between impact velocity under symmetrical collision and free surface velocity of shock loaded plane target. There is a threshold strain rate higher which the deficit of particle velocity begins to grow very fast and simultaneously the hardness and spall-strength of material grow in the same manner. [Preview Abstract] |
Thursday, June 28, 2007 12:15PM - 12:30PM |
P4.00008: Influence of nano-size inclusions on spall fracture of copper single crystals Sergey Razorenov, Gennady Kanel, Galina Ivanchikhina Spall experiments have been carried out for copper in different structural states. The samples were copper single crystals, crystals of Cu + 0.1{\%} Si, copper crystals with silica particles of 180 nm average size, and polycrystalline copper. Shock pulses of 10$^{-8}$ s to 10$^{-7}$ s duration were generated by aluminum flyer plates 0.1 mm to 0.8 mm in thickness at 0.6 km/s to 1.2 km/s impact velocity. In experiments, the free surface velocity histories were recorded with the VISAR. Solid solution Cu + 0.1{\%} Si demonstrates more prolonged spall process than pure copper crystals. At longer pulse durations its spall strength is slightly less than that of pure crystals but approaches the latter with decreasing pulse duration. Fracture of copper with silica inclusions is completed much faster. The spall strength of this material is close to that of Cu + 0.1{\%} Si crystals and approaches the strength of polycrystalline copper with decreasing the load duration. Mechanisms and kinetics of the spall fracture process are discussed in the light of these new data. The work was supported by Russian Foundation for Basic Research, grant number 06-02-17057-a. [Preview Abstract] |
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