Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session Q2: BL-1: Ballistics |
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Chair: Charles Anderson, Southwest Research Institute Room: Hermitage AB |
Wednesday, July 1, 2009 9:30AM - 10:00AM |
Q2.00001: Some Recent Results on Propagation of the Failure Front Associated with Rod Penetration of Borosilicate Glass Invited Speaker: Propagating failure fronts (FF), often termed failure ``waves'', have been observed for a variety of impact/shock conditions and geometries. An FF is inferred from VISAR particle velocity measurements and longitudinal and transverse stress gage measurements in uniaxial strain (plate impact). Failure fronts are observed optically in uniaxial stress (plate-glass bar impact, bar-bar impact, Taylor impact), Edge-on Impact and 3 dimensional divergent (two-dimensional axial symmetry) rod impact geometries. This paper presents some recent results for the FF associated with rod impacts and penetration of borosilicate glass. Specifically, experiments were performed to address the questions: 1) Does the FF stop propagating after the stress at the rod-glass interface is removed? 2) Can the FF propagation be reinitiated by the impact of a second rod? And, if so, 3) is the propagation velocity the same as for the original FF? The results of these experiments and what they suggest regarding the physical mechanism(s) underlying FFs in glass are presented. [Preview Abstract] |
Wednesday, July 1, 2009 10:00AM - 10:15AM |
Q2.00002: Index of Refraction of Shock Loaded Soda-Lime Glass Scott Alexander Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to approximately 25 GPa) where the material remains transparent. In order for SLG to be practical as a VISAR window, the correction factor, which describes the frequency correction related to the strain dependence of the refractive index, and hence the index of refraction itself, must be characterized as a function of pressure. Characterization data are reported in this paper and compared to previous results. The present data show good agreement with those of Dandekar [\textit{J. App. Physics}, \textbf{84}, 6614 (1998)] and separate study results by Gibbons and Ahrens [\textit{J. Geophys. Res.}, \textbf{76}, 5489 (1971)] up to 7 GPa. However, at stresses over 7 GPa, marked discrepancies are evident between the present data and that of Gibbons and Ahrens. Differences in test methods may explain these discrepancies. [Preview Abstract] |
Wednesday, July 1, 2009 10:15AM - 10:30AM |
Q2.00003: Modeling Impact Behavior of Glass with Peridynamics S. Satapathy, A. Dawson, S. Bless, I. Polyzois, G. Rodin Glass is being considered for various transparent armor applications due to its high compressive strength. However, its low tensile properties lead to cracks and fractures if significant tensile stresses are present. Presence of surface cracks in combination with high tensile stresses lead to dynamic failure, sometimes in an explosive manner. We have conducted bar impact experiments as well as ballistic tests to study their penetration behavior. Numerical simulation of these experiments is a challenge. The existing hydrocodes do not provide satisfactory results for brittle materials. This can be attributed to significant differences in constitutive behavior between brittle and ductile materials and the need to account for many fracture surfaces. A new numerical method, peridynamics---a meshless Lagrangian method solving the equation of motion in integral form---has been proposed by Stewart Silling that appears to be more suitable for modeling brittle materials. We use this method to examine the response of glass to impact loads in both bar impact and penetration experiments. This paper will discuss advantages and difficulties in modeling glass with peridynamics. [Preview Abstract] |
Wednesday, July 1, 2009 10:30AM - 10:45AM |
Q2.00004: Impact Response of Laminate Metal Honeycomb Sandwich Structure Xiaodong He, Xianghao Kong, Liping Shi The ARMOR TPS is one of important candidate structure of RLV. It will be the best selection for all kinds of RLV. So the ARMOR thermal protection system will be used in aviation and spaceflight field more and more widely. ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction and impact load. The metal honeycomb sandwich structure is made of upper faceplate, lower faceplate and honeycomb core. In the course of the reusable launch vehicle working, it is possible that the space chips impact its outer surface. The main problem is what impact the metal honeycomb sandwich structure can stand and how many times it can stand. In the high speed impact experiment we choose different quality and velocity to simulate real space environment. This paper will analyze the mechanics behaviour of metal honeycomb sandwich structure in the course of impact, then we make sure the limit impact load and get the effect of impact flaw. [Preview Abstract] |
Wednesday, July 1, 2009 10:45AM - 11:00AM |
Q2.00005: Numerical and experimental investigation for assessing the high strain rate response of nickel based multi-layered honeycomb sandwiches Zhenqi Yang, Baojun Pang, Liwen Wang The mechanics behaviors of a multi-layered nickel based honeycomb sandwich at quasi-static and high strain rate ranging from 800/s-6500/s were determined by a Instron and uniaxial dynamic compression SHPB experiment respectively. The results of experiment showed strain rate sensitivity at low strain rate portion (0-800/s) while by increasing the strain rate (3400/s- 6500/s); the samples no longer showed noticeable rate sensitivity. Dynamic strain-stress curves showed clearly initial peak strength, flat flow potion and totally compressed ascending part process while a littler peak was appeared during the flat flow potion. A numerical model was developed using LSDYNA software, for investigating the different deformation model under various strain rates with modified by experimental strain-stress curves. Steinberg-Guinan constitution model was utilized to simulate plastic deformation and in-stability status of multi-layered nickel based honeycomb under dynamic compression. In this work the influence of cell wall thickness; layer numbers of sandwich structure; length and height rate of hexahedron cell and influence of skin sheets for dynamic behavior was studied by various finite element models. [Preview Abstract] |
Wednesday, July 1, 2009 11:00AM - 11:15AM |
Q2.00006: Comparison of Breakout Modes in Analytic Penetration Modeling James Walker, Rory Bigger, Sidney Chocron When a projectile approaches the back surface of a target, complicated mechanics and different failure modes can ensue that lead to perforation. There have been a number of attempts to model these different failure modes, for example models due to Ravid and Bodner (1983) and Walker (1999). Of particular interest are analytic models (as opposed to hydrocode models) where the model attempts to explicitly identify relevant failure modes and back surface breakout modes. This paper examines back surface breakout and target failure models with different failure modes to see how they are invoked in specific impact geometries and scenarios. Comparisons are made of thresholds and sensitivities for the different failure modes to gain a greater understanding of their usefulness and applicability. The model results are compared to data to ensure reasonableness of the computations. For example, good agreement is shown with a relatively simple back-surface-strain target failure mode for predicting ballistic limit velocity for large aspect-ratio projectiles and relatively thick targets as compared to the projectile diameter. [Preview Abstract] |
Wednesday, July 1, 2009 11:15AM - 11:30AM |
Q2.00007: ABSTRACT WITHDRAWN |
Wednesday, July 1, 2009 11:30AM - 11:45AM |
Q2.00008: Effects of Titanium Nitride Surface Coating on High Speed Impact Induced Damage of Magnesium Alloys at Cryogenic Temperature K. Takayama, D. Numata, R. Kubota, A. Shimamoto This reports a summary of our recent high speed impact tests aiming to clarify the impact characteristic of magnesium alloy with titanium nitride coating. We placed 100 mm x 100 mm and 3 mm thick magnesium alloy plates, ZK60A-T5 at 298 K, 223 K and 153 K, which were coated with 1 micron thick titanium nitride layer based on a hollow cathode discharge method. We also tested with uncoated magnesium plates. The plates were impinged by 8 mm diameter aluminum alloy (Al2017-T4) spheres at impact speeds of 0.5 to 1.7 km/s in a two-stage light gas gun in the SWRC, IFS, Tohoku Univ. Two specimens were installed at 100 mm interval vertically to the spheres in a cryogenic test chamber [1]. Impact phenomena were visualized with shadowgraph arrangements and recorded with ImaCon 200. As a result, the effect of surface coating on surface fracture was examined. We found the increase of hole areas in proportional to the impact speed and a clear difference of penetration hole and fracture patterns between impact speed of 0.5 km/s and higher impact speeds.~The titanium nitride coating was effective to favorably control the damage process. [1] Numata,D. et al., Shock Waves (2008), 18:169-183. [Preview Abstract] |
Wednesday, July 1, 2009 11:45AM - 12:00PM |
Q2.00009: Instability of an Interface Between Steel layers Acted Upon by an Oblique Shock Wave Oleg Drennov The results of experiments in which development of instability was observed on the interface between two identical metals in tight contact wich passage of an oblique shock wave through it are presented. Numerical modeling of experimental results was performed by a two--dimensional lagrangian procedure using an elasto plastic model with a functional dependence of the dynamic yield point on the state variables of the material. The calculations showed that perturbations develop only in the presence of a technological microgap of several micrometers between the metal layers. Unloading of the material behind the oblique shock front into the gap gives rise to considerable short -- term velocity gradient (t $\le $0.2 $\mu $s; $\Delta $U $\ge $3 $\mu $mm/$\mu $s). Simultaneously, near the interface behing the wave front there is a short--term loss of strength of the material due to thermal softening and the heterogeneous nature of the deformation. [Preview Abstract] |
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