Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session P6: Inelastic Deformations, Fracture and Spall VII: Rods and Cylinders |
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Chair: Daniel Eakins, Imperial College London, James Cazamias, Engility Corporation Room: 8/9/10 |
Wednesday, June 17, 2015 11:15AM - 11:30AM |
P6.00001: Damage Development in Rod-on-Rod Impact Test on 1100 Pure Aluminum Gianluca Iannitti, Nicola Bonora, Neil Bourne, Andrew Ruggiero, Gabriel Testa Stress triaxiality plays a major role in the nucleation and growth of ductile damage in metals and alloys. Although, the mechanisms responsible for ductile failure are the same at low and high strain rate, in impact dynamics the time resolved stress triaxiality and plastic strain accumulation at the material point establish the condition for ductile failure to occur. In this work, ductile damage development in 1100 commercially pure aluminum was investigated by means of rod-on-rod (ROR) impact tests. Based on numerical simulations, using a CDM model that accounts for the role of pressure on damage parameters and stochastic variability of such parameters, the impact velocity for no damage, incipient and fully developed damage were estimated. ROR tests at selected velocities were performed and damage distribution and extent was investigated by sectioning of soft recovered samples. Comparison between numerical simulations and experimental results is presented and discussed. [Preview Abstract] |
Wednesday, June 17, 2015 11:30AM - 11:45AM |
P6.00002: Gas Gun Driven Dynamic Fracture and Fragmentation of Ti-6Al-4V Cylinders at Initial Temperatures Between 150K and 750K David R. Jones, David J. Chapman, Daniel E. Eakins We present a study of dynamic fracture and fragmentation in Ti-6Al-4V cylinders at initial temperatures ranging from 150 K to 750 K. Samples with inner diameter of 50 mm and wall thickness of 4 mm were driven into uniform axially-symmetric expansion at radial strain rates of $10^4$ s$^{-1}$ using the ogive-insert gas gun method. Experiments were highly diagnosed, employing a combination of high speed imaging, PDV and fragment recovery. Imaging and PDV provided a record of expansion velocity and failure strain. Recovered fragments were examined with optical, SEM and EBSD techniques to determine the fracture mechanisms occurring for each initial temperature. The failure strain was observed to increase with temperature over the range tested, from 7.4$\pm$5.2 percent at 158 K to 24.1$\pm$2.4 percent at 750 K. In experiments from 158 K up to 609 K the fracture mechanism was found to be ductile tearing under mode II loading, along the planes of maximum shear at 45$^{\circ}$ to the radius. At an initial cylinder temperature of 724 K the fracture mechanism transferred to void nucleation and coalescence along adiabatic shear bands, again oriented at 45$^{\circ}$. The fragmentation toughness was largely independent of temperature with an average value of 101$\pm$13 MPa m$^{-1/2}$. [Preview Abstract] |
Wednesday, June 17, 2015 11:45AM - 12:00PM |
P6.00003: Observation and Simulation of Motion and Deformation for Impact-Loaded Metal Cylinders* R.J. Hickman, J.L. Wise, J.A. Smith, J.P. Mersch, C.V. Robino, J.G. Arguello Complementary gas-gun experiments and computational simulations have examined the time-resolved motion and post-mortem deformation of cylindrical metal samples subjected to impact loading. The effect of propagation distance on a compressive waveform generated in a sample by planar impact at one end was determined using a velocity interferometer to track the longitudinal motion of the opposing rear (i.e., free) surface. Samples (24 or 25.4-mm diameter) were fabricated from aluminum (types 6061 and 7075), copper, stainless steel (type 316), and cobalt alloy L-605 (AMS 5759). For each material, waveforms obtained for a short (2 mm) and a long (25.4 mm) cylinder corresponded, respectively, to one-dimensional (i.e., uniaxial) and two-dimensional strain at the measurement point. The wave-profile data have been analyzed to (i) establish key dynamic material modeling parameters, (ii) assess the functionality of the Sierra Solid Mechanics-Presto (SierraSM/Presto) code, and (iii) identify the need for additional testing, material modeling, and/or code development. The results of subsequent simulations have been compared to benchmark recovery experiments that showed the residual plastic deformation incurred by cylinders following end, side, and corner impacts. *Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Wednesday, June 17, 2015 12:00PM - 12:15PM |
P6.00004: Modeling Periodic Adiabatic Shear Bands Evolution in a 304L Stainless Steel Thick-Walled Cylinder Mingtao Liu, Haibo Hu, Cheng Fan, Tiegang Tang The self-organization of multiple shear bands in a 304L stainless steel thick-walled cylinder (TWC) was numerically studied. The microstructures of material lead to the non-uniform distribution of local yield stress, which plays a key role in the formation of spontaneous shear localization. We introduced a probability factor satisfied Gauss distribution into the macroscopic constitutive relationship to describe the non-uniformity of local yield stress. Using the probability factor, the initiation and propagation of multiple shear bands in TWC were numerically replicated in our 2D FEM simulation. Experimental results in the literature indicate that the machined surface at the internal boundary of a 304L stainless steel cylinder provides a work-hardened layer (about 20 $\mu$m) which has significantly different microstructures from base material. The work-hardened layer leads to the phenomenon that most shear bands are in clockwise or counterclockwise direction. In our simulation, periodic oriented perturbations were applied to describe the grain orientation in the work-hardened layer, and the spiral pattern of shear bands was successfully replicated. [Preview Abstract] |
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