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 D5: Focus Session: Failure Wave II |
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Chair: Dennis Grady, Applied Research Associates Room: Hyatt Regency Constellation F |
Monday, August 1, 2005 1:30PM - 2:00PM |
D5.00001: Time dependent inelastic deformation of shocked soda-lime glass Invited Speaker: Shock wave compression of soda-lime glass (SLG) has received considerable attention in recent years. To understand inelastic deformation in shocked soda-lime glass between 3 and 10.8 GPa, we have carried out plate impact experiments. In-material, time-resolved, measurements were obtained using longitudinal and lateral stress gauges (4.6 to 10.8 GPa), and electromagnetic particle velocity gauges (2.9 to 6 GPa) at comparable sample thicknesses. The 4.6 and 6 GPa experiments revealed time-dependent inelastic response along with time-dependent loss of material strength. The combination of our experimental results and related analyses demonstrate that previous interpretations of shocked SLG response in terms of a propagating failure wave are not valid. At higher peak stresses ($\sim $ 10GPa), the SLG results do not display time-dependent strength loss. The shock response of SLG over the 4-10GPa range is complex and depends significantly on the peak stress. The experimental results and simulations from a phenomenological continuum model will be discussed. Work supported by DOE. Much of this work was carried out by Dr. Hari Simha. [Preview Abstract] |
Monday, August 1, 2005 2:00PM - 2:15PM |
D5.00002: A study of the failure wave phenomenon in glasses at peak stresses exceeding the HEL G.I. Kanel, S.V. Razorenov, A.S. Savinykh, A. Rajendran , Zhen Chen Shock-wave experiments with two glasses of different hardnesses have been carried out at shock stress levels above the Hugoniot elastic limit. A comparison between the measured wave profiles (VISAR signals) from two plate impact experiments performed at approximately the same shock stress level (one with a single thick target plate, and the other with several adjacent target plates of total thickness equal to that of the thick target plate) revealed: 1) at shock loading the failure wave is not formed at stress levels above the HEL, indicating suppression of the fracture process by plasticity, 2) at gradual compression the failure wave process occurs as the stress increases above the failure threshold up to the stress at which plastic deformation begins. These experiments unambiguously demonstrate the role of surfaces in the overall response of glass to shock compression loading and provide an effective tool to reveal and diagnose the failure wave process. [Preview Abstract] |
Monday, August 1, 2005 2:15PM - 2:30PM |
D5.00003: Effect of Shock Induced Shear on Spall Strengths of Materials Dattatraya Dandekar This work examines the effect of shock induced shear under simultaneous compression-shear loading on spall strengths of ductile and brittle materials. The working assumption is that if deformation of a material is dominantly ductile i.e., elastic-plastic, then magnitude of its spall strength under normal shock, and under simultaneous compression-shear loading may not differ significantly. On the other hand, if deformation of a material is dominantly brittle i.e., through crack propagation, then magnitude of its spall strength under simultaneous compression-shear loading may be significantly less than its value under normal shock wave loading. The results of a few spall experiments conducted on Ti-6Al-4V, tungsten carbide, and silicon carbide appear consistent with the above stated assumption. [Preview Abstract] |
Monday, August 1, 2005 2:30PM - 2:45PM |
D5.00004: Failure Fronts in Brittle Materials and Their Morphological Instabilities Michael Grinfeld, Scott Schoenfeld, Tim W. Wright There are various observations and experiments showing that in addition to standard shock-wave fronts, which propagate with trans-sonic velocities, other much slower wave-fronts can propagate within glass or ceramic substances undergoing intensive damage. These moving fronts propagate into intact substance leaving intensively damaged substance behind them. They have been called failure waves. In this paper we model them as sharp interfaces separating two states: the intact and comminuted states. The approach is based on an analogy between failure fronts and fronts of slow combustion. In this presentation we announce two main theoretical results that require experimental verification. One of them concerns the speed of a failure wave driven by oblique impact of a brittle target. The other establishes a criterion for morphological instability of failure fronts. [Preview Abstract] |
Monday, August 1, 2005 2:45PM - 3:00PM |
D5.00005: A Rate-Dependent Damage Model and its Application to Uniaxial Strain Martin N. Raftenberg, Michael A. Grinfeld Our analysis is based on a damage model discussed in [1] in which the internal energy density $W$ depends on strain \textbf{E} and damage \textit{$\kappa $} : $W({\rm {\bf E}},\kappa )=\phi (\kappa ){\kern 1pt}{\kern 1pt}{\kern 1pt}\mu {\kern 1pt}{\kern 1pt}{\kern 1pt}\left( {\frac{\nu }{1-2\nu }E_{kk} E_{ll} +E_{ij} E_{ij} } \right)$; \textit{$\mu $} is elastic shear modulus, \textit{$\nu $} is Poisson's ratio. The factor $\phi (\kappa )=1-\left( {1-\phi _{\min } } \right)\frac{\kappa }{\kappa _{\max } }$ describes degradation of elastic modulus due to damage; \textit{$\phi $}$_{min}$ and \textit{$\kappa $}$_{max }$are material constants.$_{ }$ The system of evolution includes \[ \rho \frac{\partial ^2u}{\partial t^2}=\nabla \frac{\partial W}{\partial {\rm {\bf E}}},\quad \;\frac{\partial \kappa }{\partial t}=-K\frac{\partial W}{\partial \kappa } \] where$ K$ is (for now) a material constant. The above model was installed into LS-DYNA using the User Material Interface. The model was applied to a finite-element simulation of a rod under uniaxial strain, with a prescribed-velocity boundary condition at one end and a stress-free condition at the other. The resulting initial-value boundary-value problem was scaled to reveal the presence of the dimensionless group $\Pi =\frac{\rho _0 }{2}\sqrt {\frac{(1-2\nu )\rho _0 }{2{\kern 1pt}{\kern 1pt}{\kern 1pt}(1-\nu )\mu }} \cdot \frac{\left( {1-\phi _{\min } } \right)K}{\kappa _{\max } ^2}\cdot L\cdot \dot {u}_0 ^2$, where $\rho _0 $ is the material density, $L$ is the length of the rod, and $\dot {u}_0 $is the prescribed velocity. Solutions were obtained for a range of $\Pi $ values. The progression of contours of \textit{$\kappa $}($x$,$t)$ was observed. [1] Grinfeld, M.A., and Wright, T.W., \textit{Metallurgical and Materials Transactions A}, Vol. 35A, 2651-2661, 2004. [Preview Abstract] |
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