We present experimental results supporting physics-based ejecta model development, where our main assumption is that ejecta form as a special limiting case of a Richtmyer–Meshkov (RM) instability at a metal–vacuum interface. From this assumption, we test established theory of unstable spike and bubble growth rates, rates that link to the wavelength and amplitudes of surface perturbations. We evaluate the rate theory through novel application of modern laser Doppler velocimetry (LDV) techniques, where we coincidentally measure bubble and spike velocities from explosively shocked solid and liquid metals with a single LDV probe. We also explore the relationship of ejecta formation from a solid material to the plastic flow stress it experiences at high-strain rates () and high strains (700 %) as the fundamental link to the onset of ejecta formation. Our experimental observations allow us to approximate the strength of Cu at high strains and strain rates, revealing a unique diagnostic method for use at these extreme conditions.

Unstable Richtmyer-Meshkov growth of solid and liquid metals in vacuum

The melting curve of Mg, Mn, Cu, Ag, Au, Zn, Cd, Al, In, and Pb has been measured up to 12 GPa using a Bridgman-type cell. Melting at high-pressure was identified detecting discontinuities in the electrical resistance of the studied metals. The results are compared with previous experimental and theoretical studies when possible. A comparison with the Lindemann’s law predictions is also done. In particular we found that among the studied metals Pb has the steepest melting curve (dTM/dP=78 K/GPa). In contrast, Mn has the flattest melting curve (dTM/dP=29 K/GPa). The reported results suggest that the electronic structure of an element might play a key role in determining the pressure dependence of its melting curve.

The melting curve of ten metals up to 12 GPa and 1600 K

This effort investigates the relation between ejecta production and shock-breakout pressure (PSB) for Sn shocked with a Taylor shockwave (unsupported) to pressures near the solid-on-release/partial melt-on-release phase transition region. The shockwaves were created by detonation of high explosive (HE) PBX-9501 on the front side of Sn coupons. Ejecta production at the backside or free side of the Sn coupons was characterized through use of piezoelectric pins, optical shadowgraphy, x-ray attenuation radiography, and optical-heterodyne velocimetry. Ejecta velocities, dynamic volume densities, and areal densities were then correlated with the shock-breakout pressure of Sn surfaces characterized by roughness average of Ra=16 μin or Ra=32 μin.

Effects of shock-breakout pressure on ejection of micron-scale material from shocked tin surfaces

Segmental dynamics of polyurea: Effect of stoichiometry

Rayleigh-Taylor and Richtmyer-Meshkov instabilities: A journey through scales

Using piezoelectric diagnostics, we have measured densities and velocities of ejected particulate as well as “free-surface velocities” of bulk tin targets shock loaded with high explosive. The targets had finely grooved, machined finishes ranging from 10 to 250μin. Two types of piezoelectric sensor (“piezopins”), lithium niobate and lead zirconate titanate, were compared for durability and repeatability; in addition, some piezopins were “shielded” with foam and metal foil in order to mitigate premature failure of the pins in high ejecta regimes. These experiments address questions about ejecta production at a given shock pressure as a function of surface finish; piezopin results are compared with those from complementary diagnostics such as x-ray radiography and time-resolved optical transmission techniques. The mass ejection shows a marked dependence on groove characteristics and cannot be described by a groove defect theory alone.

Piezoelectric characterization of ejecta from shocked tin surfaces

Data on the high-pressure melting temperatures of metals is of great interest in several fields of physics including geophysics. Measuring melt curves is difficult but can be performed in static experiments (with laser-heated diamond-anvil cells, for instance) or dynamically (i.e., using shock experiments). However, at the present time, both experimental and theoretical results for the melt curve of lead are at too much variance to be considered definitive. As a result, we decided to perform a series of shock experiments designed to provide a measurement of the melt curve of lead up to about 50GPa in pressure. At the same time, we developed and fielded a reflectivity diagnostic, and conducted measurements on tin as well. The results show that the melt curve of lead is somewhat higher than the one previously obtained with static compression and heating techniques.

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Measurement of the shock-heated melt curve of lead using pyrometry and reflectometry

s submission deadline has been postponed New abstracts submission deadline: 15.01.2016. Registration and Abstracts submission are open!!! Important date Conference registration 10.09.2015 20.06.2016 Abstract submission deadline 15.01.2016submission deadline 15.01.2016 Notification of acceptance 31.01.2016 Paper submission 01.02.2016-20.04.2016 Early bird registration and Author registration deadline for conference paper publication 20.04.2016 Main Topics • Analytical, computational and physical Models; • Biomaterials and Wood Fracture and Fatigue; • Biomechanics; Ceramics Fracture and Damage; • Composites; • Computational Mechanics; • Concrete & Rocks; • Creep Fracture; • Damage Mechanics; • Damage and fracture in materials under dynamic loading; • Durability of structures; • Environmentally Assisted Fracture; • Failure Analysis and Case Studies; • Fatigue Crack Growth (all materials); • Fatigue Resistance of metals; • Fatigue of Metals – Very High Cycle; • Failure Analysis and Forensic Engineering; • Fractography and Advanced metallography; • Fracture and Fatigue at Atomistic and Molecular Scales; • Fracture and fatigue testing systems; • Fracture under Mixed-Mode and Multiaxial Loading; • Fracture vs. Gradient Mechanics; • Functional Gradient Materials; • Impact & Dynamics; • Fundamentals of cohesive zone models; • History of Fracture Mechanics and Fatigue; • Innovative Alloys; • Linear and Nonlinear Fracture Mechanics; • Materials mechanical behavior and image analysis; • Mesomechanics of Fracture; • Micromechanisms of Fracture and Fatigue; • Multi-physics and multi-scale modelling of cracking in heterogeneous materials; • Multiscale Experiments and Modeling; • Nanostructured Materials; Nondestructive Examination; • Physical Aspects of Brittle Fracture; • Physical Aspects of Ductile Fracture; • Polymers Fracture and Fatigue; • Probabilistic Fracture Mechanics; • Reliability and Life Extension of Components; • Repair and retrofitting: modelling and practical applications; • Sandwiches, Joints and Coatings; • Smart Materials; • Structural Integrity; • Temperature Effect; • Thin Films http://www.ecf21.eu/site/ APS-GSCCM Newsletter December 2015 Page 9 of 14 You are cordially invited to submit an abstract to the Symposium “Dynamic Deformation and Fracture”, which is organised within the framework of the ICCES16 to be held in Madeira, Portugalon September 59, 2016 The topics of the Symposium include, but are not limited to, the following: • highstrain rate loading and deformation; • dynamic fracture; • impact and blast loading; • highspeed penetration; • impact fatigue; • damping properties of advanced materials; • thermomechanics of dynamic loading; • stress waves in microstructured materials; • simulation of failure and damage in materials under dynamic loading; • response of components and structures to harsh environment; • improving the resistance of materials to highrate mechanical loading. The materials of interest range from traditional ones such as metals, alloys, ceramics, polymers and composites to advanced and emerging materials as well as bioand biomedical materials. To submit your abstract (or extended abstract), please visit http://www.icces.org/guide.html. www.icces.org 18th International Electromagnetic Launch Technology Symposium

SHOCK COMPRESSION OF CONDENSED MATTER 2009: Proceedings of the American Physical Society Topical Group on Shock Compression of Condensed Matter

Basic Principles of Continuum Mechanics.- Methods and Devices for Producing Intense Shock Loads.- Recording Fast Processes in Dynamic Studies.- Determination of Hugoniots and Expansion Isentropes.- Studies of Phase Transformations.- Dynamic Strength of Materials.- Estimation of Temperatures in Shock-compressed Transparent Material.- Determination of Detonation Parameters and Efficiency of Solid HE Explosion Products.- Laser Doppler Measuring Systems and Their Use in Shock-Wave Studies.

Material Properties under Intensive Dynamic Loading

Pyrometry measurements on shock-heated metals are often performed through a transparent window acting as a shock anvil Sapphire is an interesting anvil because of its rather high shock impedance but is also known to emit light when shocked above its Hugoniot elastic limit (HEL) To study its optical response, we have carried out experiments in which c -cut sapphire (ie crystal orientation { 0 0 0 1 } ) was in contact with a metallic sample (tin or bismuth) or a lithium fluoride (LiF) window The measurement of emitted light was performed using multi-wavelength pyrometry In the experiments performed in the vicinity of the HEL of sapphire, the use of a LiF-sapphire compound window proved beneficial Even though a significant amount of light is emitted over a large wavelength range by sapphire above its HEL, we notice that the signal rise is directly related to the volume of sapphire under shock-loading Consequently, the light emitted by sapphire can be subtracted, allowing us to infer the true thermal radiation originating from the metal under study A theoretical calculation of the expected pyrometry signals supports this point of view These results give evidence that sapphire, despite its significant shock-induced optical emission above the HEL, can be used as a transparent anvil for quantitative pyrometry measurements at medium and high shock pressures

William W. Anderson

Papers

Piezoelectric characterization of ejecta from shocked tin surfaces

Measurement of the shock-heated melt curve of lead using pyrometry and reflectometry

SHOCK COMPRESSION OF CONDENSED MATTER 2009: Proceedings of the American Physical Society Topical Group on Shock Compression of Condensed Matter

Material Properties under Intensive Dynamic Loading

Investigation of shock-induced light from sapphire for use in pyrometry studies