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 U3: Materials Science V: Dynamic Effects II |
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Chair: Vitali Nesterenko, University of California, San Diego Room: Hyat Regency Constellation D |
Thursday, August 4, 2005 3:00PM - 3:15PM |
U3.00001: Dynamic Characterization of Epoxy-Cast Al+Fe$_{2}$O$_{3}$ Mixtures Louis Ferranti, Jr., Naresh Thadhani Dynamic mechanical properties experiments were conducted on epoxy-cast Al+Fe$_{2}$O$_{3}$ specimens using the classic Taylor anvil test at relatively low impact velocity (100m/s). Reverse Taylor anvil impact experiments were also conducted using a single stage gas gun by impacting a rigid anvil onto a stationary target at relatively high velocity (200 to 400 m/s). Dynamic deformation and fracture response of the epoxy-cast thermite were captured in real time utilizing high-speed photography. Strain, strain-rate, and stress were measured from the captured images. Plate-impact experiments were also performed to determine the P-V/V$_{0}$ compressibility. Postmortem analysis of recovered fragments was conducted using differential thermal analysis (DTA) to determine impact-induced material alteration. The presentation will describe the results obtained to date. Funding for this research was provided in part by AFOSR/MURI under grant No. F49620-02-1-0382; and by a graduate research internship grant (for L. Ferranti) provided by EGLIN/AFRL through contract No. F08630-03-C-001. [Preview Abstract] |
Thursday, August 4, 2005 3:15PM - 3:30PM |
U3.00002: Observation of Shock-Induced Failure of Diamond Particles using High-Speed Photography Geoff Willmott, Field John Failure of shocked diamond particles has been observed using high-speed photography with an exposure time of 50 ns and an interframe time of 100 ns. The diamonds, which were each embedded in a transparent polymethylmethacrylate matrix,~were approximately discs of diameter~$\sim $5 mm and thickness 1~-~2 mm. Shock waves were induced in plate impact experiments. Three broad categories of failure were observed in the first microsecond after shock wave arrival. Diamonds containing pre-existing weaknesses and birefringence at crystal centres were prone to comminution.~These diamonds also developed large internal single fractures, which propagating at up to 14~$\pm $~1~mm~$\mu $s$^{-1}$, faster than the Rayleigh wave velocity. Smaller cracks observed near particle edges suggest that the flaws of dimensions up to at least 5~$\mu $m are present near unpolished diamond surfaces. The size distribution of fragments recovered from these experiments indicates that fractures interact with each [Preview Abstract] |
Thursday, August 4, 2005 3:30PM - 3:45PM |
U3.00003: Features of the Shock and Detonation Waves in Cylindrical Explosive Compaction Jose Ribeiro, Ricardo Mendes, Igor Plaksin, Jose Campos It is believed that many of the essential features of the explosive compaction process are due to the micromechanical behaviour of the powder. However, despite of the significant amount of the work done in the area, there is a considerable lack of experimental data obtained at a suitable length scale to be used in the increase of the knowledge of the referred behaviour; moreover, many of the attempts made to overcome this problem were done in conditions far way from the ones used in real compaction experiments. To fill that gap is necessary to perform the characterization of both, the compaction and the detonation waves, in conditions close to the ones used in real experiments and with a spatial resolution approaching the characteristic size of the powder. Using a standard experimental technique developed at our laboratory - LEDAP, based on the used of a 64 channels optical fiber strip connected to a electronic streak camera, spatial and temporal resolved details of the compaction and detonation waves shape and intensity, were obtained and are presented. The results refer to a cylindrical configuration set-up and alumina powder, several values of the E/M relation and two characteristic sizes of the powder particles. [Preview Abstract] |
Thursday, August 4, 2005 3:45PM - 4:00PM |
U3.00004: Reverse Taylor Tests on Ultra-fine Grained Copper Anuj Mishra, Morgana Martin, Fabienne Gregori, Marc Meyers, Naresh Thadhani Reverse Taylor Tests have been carried out on ultra-fine grained copper processed by Equal Channel Angular Pressing. The samples were processed using route B$_{C}$ with a channel angle of 102$^{o}$. Tests were carried out after sequential ECAP passes (from 1 to 8) providing shear strains of up to 8. The average grain size ranged from 30.6 $\mu $m for the initial unprocessed sample to less than 0.5 $\mu $m for the samples processed by 8 passes. The microstructure was characterized by EBSD and TEM. Experimental results, captured by high speed camera (viewable through a timeline as opposed to an initial and final state) are compared with computer simulations run in Autodyne to model the impact. The constitutive response was obtained through quasistatic and dynamic mechanical tests and incorporation into constitutive model. This research is supported by the National Science Foundation under Grant CMS-0210173 (NIRT). [Preview Abstract] |
Thursday, August 4, 2005 4:00PM - 4:15PM |
U3.00005: Explosive forming of aerospace components Erik Carton, Marianne Stuivinga, Cyril Wentzel TNO is involved in development of the explosive forming technology for the fabrication of metal sheets and plates. This technology is labor intensive, but requires only single-sided tooling. Therefore, it can be used economically for small series of hard to deform metals, like nickel, titanium and aluminum alloys that are generally used in aerospace applications. As the alloys can be explosively formed in their hardened (tempered) condition, these formed components do not need a heat-treatment after forming, preventing unwanted deformations to occur. At TNO this forming process is under development both experimentally and theoretically. Results of computer simulations and in-situ measurements of strain, strain rate and forces will be presented, compared and discussed. Examples are given of aerospace components of aluminum, nickel and titanium alloys made at TNO for reasons of process development and the generation of demonstrators. [Preview Abstract] |
Thursday, August 4, 2005 4:15PM - 4:30PM |
U3.00006: Investigation of dynamic friction induced by shock loading conditions Antoine Juanicotena, Stephanie Szarzynski Modelling the frictional sliding of one surface against another under high pressure is often required to correctly describe the response of complex systems to shock loading. In order to provide data for direct code and model comparison, a new dynamic friction experiment investigating dry sliding characteristics of metal on metal at normal pressures up to 10 GPa and sliding velocities up to 400 m/s has been developed. The test consists of a specifically designed target made of two materials. A plane shock wave generated by plate impact results in one material sliding against the other. The material velocity of the rear surface of the target is recorded versus time by Doppler Laser Interferometry. The dynamic friction coefficient $\mu $ is then indirectly determined by comparison with results of numerical simulations involving the conventional Coulomb law. Samples can also be recovered in order to carry out metallographic analyses of sub-surface deformation at the interface. Using this new experimental configuration, three dynamic friction experiments with various impact speeds were performed on AA 5083-Al (H111) / AISI 321 stainless steel tribo-pair. Results suggest a decrease in the friction coefficient with increasing sliding velocity, a classic experimentally observed phenomenon. [Preview Abstract] |
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