Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session T4: Inelastic Deformation VII: Nonplanar Waves |
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Chair: Arunachalam Rajendran, US Army Research Office Room: Hyatt Regency Constellation E |
Thursday, August 4, 2005 1:00PM - 1:15PM |
T4.00001: Study of Compressive Failure of Alumina in Impact Experiments with Divergent Flow Vitaly Paris, Eugene Zaretsky Axisymmetric divergent flow characterized by increasing (with propagation distance) difference between longitudinal and radial stress was produced in the plane-parallel alumina samples by impact of spherical (R=200-600 mm) copper impactors having velocities 210 to 260 m/s. The velocity of the interface between the impacted 5-mm alumina samples and 6-mm sapphire windows was continuously monitored by VISAR. Preliminary AUTODYN simulations show that such impact is capable of producing in the sample the stress states which cannot be produced by planar impact loading and which may result in the brittle failure of alumina. Actually, the waveforms recorded in these experiments contain distinct signatures of the alumina failure. AUTODYN numerical simulations of the experiments allow finding the alumina failure threshold, the path of the increasingly damaged alumina, the kinetics of this damaging and the locus of the states of comminuted material in the principal stress space. Possible applications of the developed experimental/numerical technique and its limitations are discussed. [Preview Abstract] |
Thursday, August 4, 2005 1:15PM - 1:30PM |
T4.00002: Elastic Properties of Shock Loaded Sic-N in Conditions of Spherical Explosion Vitali F. Nesterenko, Paul R. Gefken , Donald R. Curran, Jing Cai High accuracy measurements of elastic properties and Q factors of SiC-N before (C11=482.2 GPa and C44=194.1 GPa, Q=10 000) ) and after shock loading using DRS method will be reported. Silicon carbide (SiC-N) was tested in conditions of spherical explosion with measurements of particle velocity history on different distances from the cavity. Two type of explosives (10 mm radius charge with 6 g of Detasheet, test I, and 10 mm radius charge with 3.6 g of PETN at a density of 1.00 g/cc, Test II). Particle velocities were in the interval 450-60 m/s and 350-20 m/s for these two tests correspondingly. Elastic data indicate that catastrophic failure was not preceded by stage of bulk damage accumulation effecting elastic properties of the material between macrocracks. Containerless hot isostatic pressing of the damaged SiC-N allowed partial recovery of elastic properties of material with macrocracks. [Preview Abstract] |
Thursday, August 4, 2005 1:30PM - 1:45PM |
T4.00003: Confined and Unconfined Alumina Bar-on-Bar Impact Experiments for Improved Material Models N.S. Brar, A.M. Rajendran Unconfined and confined (in steel sleeves) alumina bar-on-bar (1-d stress) experiments are performed to extend uniaxial strain deformation states imposed in flyer plate impact experiments. A number of investigators engaged in modeling the bar-on-bar experiments have varying degrees of success in correctly simulating the measured in-situ axial stress or free surface velocity histories. Axial velocity of the far end of the unconfined and confined AD998 bars was measured using a VISAR in a series of unconfined and confined alumina bar-on-bar impact experiments at impact speeds from 100 m/s to 500 m/s. A high speed camera was used to photograph impactor and target bars during impact. Velocity history data from an unconfined bar-on-bar impact at 100 m/s show the material response as elastic. Velocity history data on unconfined bars at higher impact velocities of 200 m/s and 300 m/s suggest an inelastic material response. Velocity histories from four shots at impact velocities of 203 m/s, (two at) 293 m/s, and 511 m/s on confined alumina bars exhibit inelastic material response. Axial velocity history data on confined and unconfined bars clearly suggest that confinement marginally enhances the compressive strength of alumina in the 1-d impact configuration. [Preview Abstract] |
Thursday, August 4, 2005 1:45PM - 2:00PM |
T4.00004: Evidence of anisotropic wave propagation in laser shock-loaded quartz Thibaut de Resseguier, Patrick Berterretche, Martine Hallouin The response of brittle single crystals to shock loading and their spallation under short pulsed loads are subjects of constant interest. Here, we show that the anisotropy of single crystal quartz has a major influence on stress wave propagation and spall fracture in that material. Post-test observations of laser shock-loaded samples cut out from single crystal quartz reveal spall damage in unexpected locations as well as a strong dependence of the observed behaviour on the direction of shock application versus crystal orientation. For instance, the propagation of a laser shock applied along the electrical (x) axis leads to a damaged zone of elliptical shape in the opposite free surface, with two spalls near its extremities. When a similar shock is applied along the mechanical (y) axis, spall damage consists in a single crater, with a strong lateral shift which indicates an oblique propagation of the stress pulse. Three-dimensional computations involving the elastic rigidity matrix of quartz have been performed to simulate those experiments. Despite the model limitations, they provide a good prediction of the observed positions, shapes and sizes of the spalled zones for the three crystallographic orientations. [Preview Abstract] |
Thursday, August 4, 2005 2:00PM - 2:15PM |
T4.00005: Stabilization of Wave Formation on a Contact Boundary of Metal Layers at an Oblique Impact during Kelvin - Helmholtz Instability Development Oleg Drennov Plane metal layers loading by an oblique shock wave during explosive welding and various shields' effects on a contact boundary state after the loading were experimentally investigated. The stabilizing effect of thin metal coating on the explosive welding and disturbance evolution at a contact boundary was experimentally found. For example for copper -- copper contact boundary disturbance amplitude is $a \quad \approx $ 350 $\mu $m. For contact boundary for the same pair, but under the loading through a zinc layer $\Delta \quad \approx $ 22 $\mu $m thick, the disturbance amplitude decreased up to $a \quad \approx $ 15 $\mu $m. Thermophysical properties of a coating material affect the stabilization. The phenomenon of perturbation attenuation can be explained by the character of occurred hydrodynamic flow and complicated stress -- strain state of substance. [Preview Abstract] |
Thursday, August 4, 2005 2:15PM - 2:30PM |
T4.00006: High-Explosive Shock Compression of Aluminum through Smooth and Corrugated Interfaces J.D. Molitoris, R.G. Garza, W.M. Howard, H.G. Andreski, L.D. Crouch Detonating HMX based energetic materials were used to shock compress Aluminum. The primary diagnostic on these experiments was a new high-resolution radiography system that obtained a set of time sequence images of the dynamic process. X-Ray material penetration was sufficient to image density structure in the shocked material in addition to shock propagation and overall material deformation. As this diagnostic typically has 25 ns temporal resolution and spatial resolution of less than 1 mm, a high level of detail was obtained. The corrugated interface experiments show perturbation growth at the interface and internal density structure that will be discussed in terms of the Sakharov viscosity technique. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. [Preview Abstract] |
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