Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session C6: Focus Session: Ejecta Physics II |
Hide Abstracts |
Chair: Fady Najjar, Lawrence Livermore National Laboratory Room: Regency Ballroom E |
Monday, July 10, 2017 11:15AM - 11:30AM |
C6.00001: Picosecond radiography combined with other techniques to investigate microjetting from calibrated grooves in laser shock-loaded metals. Thibaut De Resseguier, Caroline Roland, Gabriel Prudhomme, Erik Brambrink, Jean-Eloi Franzkowiak, Didier Loison, Emilien Lescoute, Arnaud Sollier, Laurent Berthe Debris ejection upon shock breakout at a rough surface is a key issue for many applications. For a few years, we have used laser driven shocks to study microjetting in metallic samples with calibrated grooves in their free surface. Fast transverse optical shadowgraphy, time-resolved measurements of both planar surface and jet tip velocities, and post-recovery analyses have provided data over ranges of small spatial and temporal scales, short loading pulses (ns-order) and extremely high strain rates. The new experiment presented here involves two laser beams in a pump-probe configuration. Picosecond laser irradiation of a thin copper wire generates x-rays which are used to radiograph the microjets expanding from single grooves in tin and copper samples shock-loaded by a longer, nanosecond laser pulse. Such ultrashort radiography can be used to infer the density gradients along the jets as well as inside the samples deep beneath the grooves. It is combined with the techniques mentioned above to provide a more complete insight into the physics of microjetting. [Preview Abstract] |
Monday, July 10, 2017 11:30AM - 11:45AM |
C6.00002: Formation, instability and fragmentation of shock-produced jets Vasily Zhakhovsky, Sergey Dyachkov, Nail Inogamov Formation and evolution of shock-induced ejecta from metal surface are studied by molecular dynamics and smoothed particle hydrodynamics methods. Simulation of ejecta was divided onto two parts: the short-time formation of jet until it reaches its final mass and the long-time evolution of jet towards its fragmentation. The second part utilizes the mass and velocity distributions obtained at the end of the first part of simulation. MD simulation results for liquid jets of tin with different surface tensions, obtained using two EAM potentials, are presented. We show that fragmentation of ejecta in forms of cylindrical and planar jets happens via different pathways. While the cylindrical jets decay to droplets after reaching a critical length due to Savart--Plateau--Rayleigh instability, the plane jets are stable against the small perturbations of jet shape. We found a more complicated fragmentation mechanism via boundary instability of plane jets. [Preview Abstract] |
Monday, July 10, 2017 11:45AM - 12:00PM |
C6.00003: Ballistic properties of ejecta from a laser shock-loaded groove: smoothed particles hydrodynamics compared with experiments Caroline Roland, Thibaut De Resseguier, Arnaud Sollier, Emilien Lescoute, Diouwel Tangiang, Marc Toulminet, Laurent Soulard The interaction of a shock wave with a rough free surface may lead to micrometric material ejection of high velocity (km/s-order). This microjetting phenomenon is a key issue for many applications, such as industrial safety, pyrotechnics or inertial confinement fusion experiments. We have studied this process from single V-shaped grooves of various angles in copper and tin samples shock-loaded by a high energy laser. Experimental details are presented elsewhere in this conference [T. de Ress\'{e}guier, C. Roland et al., abstract {\#}000154]. As the Smoothed Particles Hydrodynamics formulation is well-suited for the high strains involved in jet expansion and for subsequent fragmentation, this mesh-free method was chosen to simulate microjetting. Computed predictions are compared to experimental results including jet tip and planar surface velocities, spall fracture, and size distribution of the fragments inferred from both fast shadowgraphy and post-recovery observations. Special focus is made on the dependence of the ballistic properties (velocity and mass distributions) of the ejecta on numerical parameters such as the initial inter-particular distance, the smoothing length and a random noise introduced to simulate inner irregularities of the material. [Preview Abstract] |
Monday, July 10, 2017 12:00PM - 12:15PM |
C6.00004: Study the fragment size distribution in dynamic fragmentation of laser shock loding tin. Weihua He, Jianting Xin, Genbai Chu, Min Shui, Tao Xi, Yongqiang Zhao, Yuqiu Gu Characterizing the distribution of fragment size produced from dynamic fragmentation process is very important for fundamental science like predicting material dymanic response performance and for a variety of engineering applications. However, only a few data about fragment mass or size have been obtained due to its great challenge in its dynamic measurement. This paper would focus on investigating the fragment size distribution from the dynamic fragmentation of laser shock-loaded metal. Material ejection of tin sample with wedge shape groove in the free surface is collected with soft recovery technique. Via fine post-shot analysis techniques including X-ray micro-tomography and the improved watershed method, it is found that fragments can be well detected. To characterize their size distributions, a random geometric statistics method based on Poisson mixtures was derived for dynamic heterogeneous fragmentation problem, which leads to a linear combinational exponential distribution. Finally we examined the size distribution of laser shock-loaded tin with the derived model, and provided comparisons with other state-of-art models. The resulting comparisons prove that our proposed model can provide more reasonable fitting result for laser shock-loaded metal. [Preview Abstract] |
Monday, July 10, 2017 12:15PM - 12:30PM |
C6.00005: Ejecta from periodical grooves in tin foils under laser-driven shock loading Gabriel Prudhomme, Jean-Eloi Franzkowiak, Thibaut de Ress\'eguier, Erik Brambrink, Caroline Roland, Didier Loison, Emilien Lescoute, Arnaud Sollier Laser-driven shocks are versatile, low destructive method to study material dynamic behaviors with an efficient repetitive rate. In these experiments, compared with the more conventional high-explosive or impact-based techniques, all the scales are reduced (few ns shock duration, a few mm planar loaded area) while the shock pressure may reach several tens of GPa. This configuration enables the use of many diagnostics with limited exposition to generated fragments. We present recent experiments of material ejection under laser-driven shock loading. The target is a thin plate of Tin with periodical grooves of about tens of $\mu$m in its rear surface in order to induce solid or liquid micro-jetting. These jets transform into a cloud of $\mu$m-sized particles. Depending on surface roughness, the velocity and the density of the cloud vary. The velocities are estimated using Photonic Doppler Velocimetry (PDV). The density of the cloud is estimated thanks to a new high-resolution X-ray imaging with a laser-driven source of the particle cloud; while optical shadowgraphy observes the displacement of the fastest particles. $\mu$m-structures in the particles cloud and in the target can be revealed. [Preview Abstract] |
Monday, July 10, 2017 12:30PM - 12:45PM |
C6.00006: Experimental investigation of dynamic fragmentation of laser shock-loaded by soft recovery and X-ray radiography. Jianting Xin, Weihua He, Genbai Chu, Yuqiu Gu Dynamic fragmentation of metal under shock pressure is an important issue for both fundamental science and practical applications. And in recent decades, laser provides a promising shock loading technique for investigating the process of dynamic fragmentation under extreme condition application of high strain rate. Our group has performed experimental investigation of dynamic fragmentation under laser shock loading by soft recovery and X-ray radiography at SG¢ó prototype laser facility. The fragments under different loading pressures were recovered by PMP foam and analyzed by X-ray micro-tomography and the improved watershed method. The experiment result showed that the bilinear exponential distribution is more appropriate for representing the fragment size distribution. We also developed X-ray radiography technique. Owing to its inherent advantage over shadowgraph technique, X-ray radiography can potentially determine quantitatively material densities by measuring the X-ray transmission. Our group investigated dynamic process of microjetting by X-ray radiography technique, the recorded radiographic images show clear microjetting from the triangular grooves in the free surface of tin sample. [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