Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session Q1: Inelastic Deformation, Fracture, and Spall VIII |
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Chair: Guangli Hu, Johns Hopkins University Room: Grand Ballroom II-III |
Wednesday, June 29, 2011 4:00PM - 4:15PM |
Q1.00001: Calculated Ductile Damage and Stress Histories from Plate Impacts Compared with those from HE Loadings Davis Tonks, Curt Bronkhorst, John Bingert It is well known that the stress profiles involved in plate impacts and HE (High Explosive) loadings differ. The former is often called a square wave profile while the latter is called a triangular wave profile (Taylor HE wave). It is also known from recovery experiments that the spatial damage profile of plate impacts is more concentrated than that of HE loading. This is thought to be the reason why the damage level in plate impacts is higher than with HE loading for the same peak driving pressure. Simple elastic wave models of the loading are useful to mentally visualize the evolution of the loading stress waves, but the effect on damage evolution and damage spatial profile is more difficult to imagine. The purpose of this work is to perform simulations of the two kinds of experiments using an existing ductile damage model for tantalum or copper to better illustrate the history and damage magnitude effects. The model includes void nucleation, time dependent void growth, void coalescence, and fracture. Calculational results will be presented to elucidate and clarify the coupling between the loading profiles and damage. [Preview Abstract] |
Wednesday, June 29, 2011 4:15PM - 4:30PM |
Q1.00002: Comparing CTH Simulations and Experiments on Explosively Loaded Rings C.H. Braithwaite, B. Aydelotte, N.N. Thadhani, D.M. Williamson A series of experiments were conducted on explosively loaded rings for the purpose of studying fragmentation. In addition to the collection of fragments for analysis, the radial velocity of the expanding ring was measured with PDV and the arrangement was imaged using a high speed camera. Both the ring material and the material used as the explosive container were altered and the results compared with simulations performed in CTH. Good agreement was found between the simulations and the experiments. The maximum radial velocity attained was approximately 450 m/s, which was achieved through loading with a 5g PETN based charge. [Preview Abstract] |
Wednesday, June 29, 2011 4:30PM - 4:45PM |
Q1.00003: Ductile damage evolution in high purity copper Taylor impact test Nicola Bonora, Andrew Ruggiero, Gianluca Iannitti Recently, the continuum damage mechanics model proposed by Bonora (Eng. Frach. Mech., 58, 1997) has been updated to account for stress triaxiality effect on model parameters,(Bonora et al., Proc. SCCM 2009). This model enhancement allows to predict ductile damage initiation under varying stress states (uniaxial stress, uniaxial strain, and complex load paths) and dynamic loading conditions. In this work, the model has been used to predict the minimum impact velocity for damage initiation in Taylor impact test. The material investigated in this study is high purity copper with different grain size. Taylor impact tests have been performed at different velocities with the gas-gun facility at the University of Cassino. Evidence of damage development has been given by means of fractographic analysis. Damage spatial distributions along the cylinder axis and across the section have been compared with numerical results [Preview Abstract] |
Wednesday, June 29, 2011 4:45PM - 5:00PM |
Q1.00004: Numerical investigation of multiple shear bands in collapsing Thick-Walled Cylinders Zev Lovinger, Daniel Rittel, Zvi Rosenberg The ability to simulate evolution of shear bands in TWC experiments is a powerful tool for studying the complex problem of multiple adiabatic shear bands' formation and propagation. We carry out 2D numerical simulations to reproduce experimental results of multiple shear bands in cylindrical specimens collapsed by electro-magnetic driving forces. In order to simulate the shear bands we use a shear failure model which incorporates a positive feedback mechanism. Alternatively, we use for the Johnson-Cook strength model an enhanced thermal softening term, reaching similar behavior. We present a detailed study of the numerical model, exploring its ability to properly reproduce the evolution of the multiple shear-bands. The influence of initial perturbations, mesh size and pressure history on the initiation and final stages is investigated. Analyzing the shear band distribution, we use an empirical distribution function (ECDF) to reach a quantitative measure to compare simulation and experimental results. Finally, we compare the experimental shear band distribution to our simulations' results, showing good agreement. [Preview Abstract] |
Wednesday, June 29, 2011 5:00PM - 5:15PM |
Q1.00005: Fractal behavior in the fragmentation of brittle reactive materials Joe Hooper A theoretical formulation for the fragmentation of brittle, granular metal composites is presented. This work is based on our experimentally measured fragment patterns of reactive materials under explosive or high-velocity impact loading. At high strain rates, the fragment distribution displays fractal power-law behavior over at least two orders of magnitude in fragment size. This behavior may arise from side-branching off unsteady high-speed cracks, consistent with other recent work on brittle materials. The observed behavior differs markedly from distributions (such as the formulations by Mott and Grady) based on a Poisson-statistics process of crack nucleation and overlap. We present a theoretical fragment distribution to describe this new behavior; there is initial evidence that the power-law may be similar for several pressed granular reactive materials, in which case the theory requires only a single material parameter. [Preview Abstract] |
Wednesday, June 29, 2011 5:15PM - 5:30PM |
Q1.00006: ABSTRACT WITHDRAWN |
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