Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session W1: ME.3 Inelastic Deformation, Fracture, and Spall XI |
Hide Abstracts |
Chair: Jean-Paul Davis, Sandia National Laboratories Room: Grand Ballroom III |
Thursday, July 11, 2013 4:00PM - 4:15PM |
W1.00001: Laser Shock-Induced Spalling in Tantalum Tane Remington, Christopher Wehrenberg, Brian Maddox, Damien Swift, Bruce Remington, Marc Meyers The processes of dynamic failure by spalling were established in nano, poly, and mono crystalline tantalum in recovery experiments following laser compression and release. Samples were compressed over a range of energies varying from 50 to 120 J/mm$^{\mathrm{2\thinspace \thinspace \thinspace }}$and initial duration of 3 ns. The waves were allowed to reflect at the back surface (specimen thickness: 250 um) and the process of separation was characterized by different techniques: optical microscopy, SEM, and microcomputerized tomography. Additionally, the pull back signal was measured by VISAR and the pressure decay compared with HYADES simulations. There are clear differences in the microscopic fracture mechanisms, dictated by the grain sizes. In the nano and polycrystals, spalling occurred by ductile fracture favoring grain boundaries. In the monocrystals, these are absent, and the process was of ductile failure by void initiation, growth and coalescence. The spall strengths in laser experiments are compared with those in experiments at much larger durations (us regime). [Preview Abstract] |
Thursday, July 11, 2013 4:15PM - 4:30PM |
W1.00002: X-ray microtomography study of the spallation response in Ta-W Samuel McDonald, Matthew Cotton, Jeremy Millett, Neil Bourne, Philip Withers The response of metallic materials to high strain-rate (impact) loading is of interest to a number of communities. Traditionally, the largest driver has been the military, in its need to understand armour and resistance to ballistic attack. More recently, industries such as aerospace (foreign object damage, bird strike, etc.), automotive (crash-worthiness) and satellite protection (orbital debris) have all appreciated the necessity of such information. It is therefore important to understand the dynamic tensile or spallation response, and in particular to be able to observe in three-dimensions, and in a non-invasive manner, the physical damage present in the spalled region post-impact. The current study presents plate impact experiments investigating the spallation damage response of recovered targets of the tantalum alloy Ta-2.5{\%}W. Using X-ray microtomography the damage resulting from differing impact conditions (impact velocity/stress, pulse duration) is compared and characterised in 3-D. Combined with free surface velocity measurements, the tensile failure mechanisms during dynamic loading have been identified. [Preview Abstract] |
Thursday, July 11, 2013 4:30PM - 4:45PM |
W1.00003: Effect of Pre-Strain on the Twinning Behavior in Tantalum Jeffrey Florando, Nathan Barton, Bassem El-Dasher, Mukul Kumar, Changqiang Chen, Kaliat Ramesh, Kevin Hemker In an effort to understand the relationship between the mobile dislocation density and twinning, polycrystalline Ta samples have been pre-strained to various amount of strain at room temperature, and then tested at liquid nitrogen temperatures at a stain rate of 1/s, and under laser-induced shock wave loading; conditions that promote twinning. Recovered samples were characterized using EBSD orientation mapping along with transmission electron microscopy to assess the occurrence of twinning under each test condition. The results show that as the dislocation density increases, there are discernible differences in the initial portion of the stress-strain and wave profile data which can be linked to the amount of twinning observed. In addition, the experimental observations have been compared with a crystal level twinning model. The implications of these findings on the deformation behavior will be discussed. [Preview Abstract] |
Thursday, July 11, 2013 4:45PM - 5:00PM |
W1.00004: The Influence of Shock-Loading Path on the Spallation Response of Ta George Gray III, Neil Bourne, Veronica Livescu, Carl Trujillo, Sam MacDonald Spallation is well known to be a complex process strongly influenced by microstructure, loading path, and the loading profile yet often a singular``spall strength'' is utilized in hydrocodes to quantify the dynamic fracture behavior of a material. In the current study the influence of loading path on the ``spall strength'' and damage evolution in high-purity Ta is presented. The Ta samples where shock loaded to three peak shock stresses using both symmetric impact and two different composite flyer plate configurations such that upon unloading the three samples displayed nearly identical``pull-bac'' signals as measured via rear-surface velocimetry. While the ``pull-bac'' signals observed are similar in magnitude, the highest peak stressed sample resulted in complete spall scab separation while the two lower peak stresses resulted in incipient spall. The damage evolution in the ``soft'' recovered Ta samples was quantified using optical metallography, electron-back-scatter diffraction, and tomography. The effect of loading path on spallation and its ramifications for the stress and kinetic dependency of dynamic damage evolution is discussed. [Preview Abstract] |
Thursday, July 11, 2013 5:00PM - 5:30PM |
W1.00005: Plastic flow, inferred strength, and incipient failure in BCC metals at high pressures, strains, and strain rates Invited Speaker: Hye-Sook Park We present our extensive experimental results from the Omega laser to test models of high pressure, high strain rate strength at $\sim$ 1 Mbar peak pressures, strains \textgreater 10{\%}, and strain rates of $\sim$ 10$^{7}$ s$^{-1}$ in Ta, V, and Fe, using plastic flows driven by the Rayleigh-Taylor instability. The observed time evolution of the plastic deformation is compared with 2D simulations incorporating a strength model. This methodology allows average values of strength at peak pressure and peak strain rate conditions to be inferred. The observed values of strength are typically factors of 5-10 higher than ambient strength, with contributions coming from pressure hardening (via the shear modulus), and strain rate hardening. For Fe, there is the added contribution from the alpha-epsilon phase transition. Ta has been studied as a function of grain size, and at the high strain rates and short durations of the experiments, no grain size dependence was observed; the observed deformation and inferred strength were independent of grain size. Both Ta and V have been driven to large enough strains that incipient failure (softening) has been observed. Both the Ta and V experiments were compared favorably with multiscale strength models, with the conclusion that the Ta deformation was in the thermal activation regime, whereas the V deformation was in the phonon drag regime. Finally, preliminary results of new iron RT strength experiments done at $\sim$ 1 Mbar pressures, and $\sim$ 10$^{7}$ s$^{-1}$ strain rates, well beyond the alpha-epsilon phase transition, will be given. [Preview Abstract] |
Thursday, July 11, 2013 5:30PM - 5:45PM |
W1.00006: ABSTRACT WITHDRAWN |
Thursday, July 11, 2013 5:45PM - 6:00PM |
W1.00007: Study of Materials at High Negative Pressures Using Picosecond Laser Pulses I.K. Krasyuk, S.A. Abrosimov, A.P. Bazhulin, P.P. Pashinin, A. Yu. Semenov, I.A. Stuchebryukhov, V.V. Voronov, K.V. Khishchenko In the present work, the dynamic strength of Al, Pb, Cu, and Ta was studied by the method of generation of shock waves under the action of laser pulses of 70~ps duration. The use of such short pulse make it possible to realize in the experiments strain rates exceeding $10^7$~s$^{-1}$. We have used an approach that is based on both the measurement of the spallation depth after the laser-pulse action on the target and the subsequent numerical simulation of the shock-wave process in the matter under study. The obtained data show that, at moderate amplitudes of shock loading, spall strength values are in a good agreement with the known functional dependencies of the strength upon the rate of deformation. With greater loading pressure, a sharp growth of spall strength, that indicates the strengthening of the material as a result of loading, takes place. The registered growth of spall strength of the metals is connected with the fact that, in the experiments, the increase of the rate of deformation was achieved not only by shortening of the pulse duration, but also by the increase of the amplitude of loading. The latter increase leads to hardening of the material under study. In this case, defects, which cause the premature spallation of the material, may be disappeared. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700