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Sandia National Laboratories' origin began during World War II. In July 1945 our forerunner, Sandia Base, was established to develop, test, and assemble non-nuclear parts of weapons. Shock wave research became essential in the 1950s with the advent of supersonic and exoatmospheric missiles. A major concern was effects of radiation-produced shocks on materials. As a result, we developed a wide range of experimental, diagnostic, modeling, and computational capabilities. These have addressed complex issues related to both weapons and basic science. Notable applications have included analysis of the cause of the turret explosion aboard the USS Iowa and predicting the response to the Shoemaker- Levy comet impact on Jupiter. Six decades later, our research encompasses all aspects of material science from high energy density physics to low density plasma surface interactions.

The synopsis of shock wave science presented in this book describes the pioneering research conducted at Sandia over the past 60 years. The shock wave program was organized and conducted rather differently from that of similar research programs at other institutions. Two separate shock wave research efforts were established in the 1950s, one focused on scientific understanding of shock compression processes and the other on engineering applications.

After the turn of the century, dramatic changes occurred in experimental and theoretical shock wave research at Sandia. In the 1950s and 1960s, computational capabilities to design and interpret shock wave experiments were extremely limited. Use of slide rules and small desktop calculators was common. In the 1950s instruments to measure the fine details of shock compression and dynamic material response were limited. In those early decades, the innovation and intuition of experimentalists and modelers were critical in advancing shock wave research in spite of these constraints. By the late 1960s, dynamic phenomenological models to describe the shock compression of complex materials such as composites and porous materials were beginning to be established. The pioneering loading and diagnostic technology developed in the 1960s was instrumental in advancing knowledge in the later decades. This was especially true for high-pressure applications until the mid-1970s, when time-resolved gauges became available for routine use at Sandia. Bob Graham and his team concentrated on developing the piezoelectric gauge, which is also known as the quartz gauge (Graham 1961a, b; Graham 1975; Neilson and Benedick 1960; Neilson et al. 1962; Graham and Ingram 1968; Graham and Reed 1978). Meanwhile, Lynn Barker and his team concentrated on developing optical interferometric gauges and, in particular, the velocity interferometer system for any reflector (or VISAR), which grew out of a wide-angle version of the Michelson interferometer (Barker and Hollenbach 1965, 1972; Barker 1968, 2000a). This allowed considerable progress in understanding dynamic compression processes. Among early researchers, there was an excitement in developing pioneering new capabilities and solving complex dynamic material problems using the new gauges.

These individual recollections present a window into the personal experiences of people who participated in the shock wave research program at Sandia. We made a strong effort to contact and encourage as many people as possible to participate. Over 80 people were contacted and about 40 provided recollections of their personal experiences. Each contributor was asked to provide a summary of their role in shock wave research at Sandia, bringing out any interesting events or anecdotes that happened along the way

In 1973 a laboratory-wide reduction in Sandia staff was implemented that caused major reverberations in shock wave research. As Barry Butcher stated in his recollections

The 1960s witnessed phenomenal growth of shock wave capabilities at Sandia. Along with rapidly evolving techniques for producing precisely controlled loading at ever-increasing shock pressures, pivotal improvements in precision diagnostics were occurring at a record rate. The goal was to probe the detailed structure of shock waves to understand specific aspects of dynamic material response, such as the ubiquitous two-wave structure observed in materials that exhibit both elastic and plastic response under shock loading. This information was needed for the new material models being developed. It was important, as well, to apply this new technology to the pressing requirements of the nation’s defense community. In particular, it was necessary to understand the stress response of materials in nuclear environments, such as the stress wave response of materials subjected to pulsed radiation sources, so that appropriate experimental techniques and material models could be developed to simulate effects on weapon components and systems.

The main objective of the current study was to gain a detailed understanding on the rate-dependent strength behavior under ramp and shock wave loading. A forward, numerical-simulation-based cause and effect analysis was used to address the research objective. The apparent strength associated with shock and ramp wave loadings with different risetimes and shapes was investigated. It was shown that intrinsic material strength could vary with pressure, temperature, and deformation history, but the apparent strength, which was larger than the intrinsic strength, was a result of the interaction between the rate sensitivity of the strength and the rate of the external loading. The degree of interaction led to different levels of mechanical and thermal dissipations and their partition, which was manifested by different temperature, stress, and deformation histories. The knowledge and foundation established in this study should provide some guidance in the proper interpretation and analysis of the measured wave profiles obtained from ramp and shock wave experiments, instead of simply by trial and error of applying an arbitrary model without a sound physical justification. As also demonstrated in this study, different types and degrees of material dissipations result in much more dramatic changes in temperature than mechanical response. In other words, temperature could provide a direct measurement of material dissipation and provide a distinct signature of the actual material response. This study also shows that by varying the risetimes and/or shapes of ramp waves, different strain rate histories can be produced. Thus, the ramp wave experiment is potentially a very effective tool to investigate the rate sensitivity of material strength.

Using intense magnetic pressure, a method was developed to launch flyer plates to velocities in excess of 20 km s−1. This technique was used to perform plate-impact, shock wave experiments on cryogenic liquid deuterium (LD2) to examine its high-pressure equation of state (EOS). Using an impedance matching method, Hugoniot measurements were obtained in the pressure range of 22–100 GPa. The results of these experiments disagree with the previously reported Hugoniot measurements of LD2 in the pressure range above ~40 GPa, but are in good agreement with first principles, ab initio models for hydrogen and its isotopes.

The intense magnetic field generated by the 20 megaampere Z machine [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories is being used as a pressure source for material science studies. An application we have studied in great detail involves using the intense magnetic field to accelerate flyer plates (small metal disks) to very high velocities (>20 km/s) for use in shock loading experiments. We have used highly accurate velocity interferometry measurements (error ∼1%) in conjunction with one-dimensional magnetohydrodynamic (MHD) simulation to elucidate details of the flyer dynamics. One-dimensional MHD simulations are able to produce experimental results with a high degree of accuracy, thereby revealing otherwise unobtainable, but useful information about magnetically accelerated flyers on Z. Comparisons of simulation results with time-resolved measurements of velocity from a shock loading experiment involving a 925 μm aluminum flyer are presented. Results show that Joule ...

In this paper, we describe a new technique for using a pulsed power source (Z pinch) to produce planar shock waves for high-pressure equation of state (EOS) studies. Initial EOS experiments indicate that these sources are effective for shock wave studies in samples with diameters of a few millimeters and thicknesses of a fraction of one millimeter, and thus provide the possibility for achieving accuracy in shock and particle velocity measurements of a few percent. We have used the Z pinch source to produce the first in-situ time-resolve particle velocity profiles obtained with pulsed radiation sources in the Mbar regime. Particle velocity profiles obtained with a VISAR interferometer are compared with 1-D numerical simulations performed with a radiation-hydrodynamics code, ALEGRA. Good agreement with experimental results was achieved in the simulations and suggests that the Z pinch source should be a valuable tool for high-pressure EOS studies in thermodynamic regimes important to hypervelocity impact.

In the presentation we report on experiments at the Karlsruhe Light Ion Facility KALIF employing high-resolution laser-Doppler velocimetry. The schemes of possible EOS experiments using interferometry and the dynamics and the limiting factors of the ablative hypervelocity launching are discussed as well as advantages of the ion beam technique for investigations in the field of hypervelocity impacts and equations of state. So far, we have accelerated aluminum foils of 10 to 30 μm thickness to velocities beyond 12 km/s. Besides the beam power, the limiting factors for the launching are melting of the accelerated flyer plate as a result of shock-wave heating and the heat transfer from the energy deposition zone. The experiments considered include the Hugoniot measurements and measurements at unloading of shock-compressed state down to the vaporization region. Parameters of shock waves that cause melting of aluminum, copper, molybdenum and titanium in release have been measured with a pulse proton beam on KALIF. A way of measurements in the vaporization region has been tested with explosive facilities.

Shock and shockless compression methods were used to examine the loading path and rate dependence of single crystal x‐cut quartz. Analysis of the transmitted wave profiles show remarkably different behavior between shock and shockless loaded samples. Shock loaded x‐cut quartz shows inelastic deformation below 5 GPa. Ramp loaded samples do not show inelastic behavior until approximately 9 GPa, with the onset of this behavior dependent on sample thickness. The results demonstrate that both loading path and rate play important roles in the inelastic behavior of materials.

A systematic study is described which addresses the technical issues associated with launching plates to hypervelocities using compressed helium gas as the driving medium. Similar acceleration rates are used to drive constant-mass flier plates, while the material properties such as the shock impedance, yield strength, and spall strength are varied. Results of these experiments indicate that, due to the severity of loading, the flier plates have a tendency to fragment following peak acceleration. Each material has its own unique fragment distribution. More significantly, these experiments suggest a direct dependence of the mean fragment size to its normalized spall strength, i.e., the spall strength divided by its density. A method is also proposed for successfully launching intact plates to hypervelocities.

The high-pressure response of cryogenic liquid deuterium $(L{\mathrm{D}}_{2})$ has been studied to pressures of $\ensuremath{\sim}400\mathrm{GPa}$ and densities of $\ensuremath{\sim}1.5{\mathrm{g}/\mathrm{c}\mathrm{m}}^{3}.$ Using intense magnetic pressure produced by the Sandia National Laboratories $Z$ accelerator, macroscopic aluminum or titanium flyer plates, several mm in lateral dimensions and a few hundred microns in thickness, have been launched to velocities in excess of 22 km/s, producing constant pressure drive times of approximately 30 ns in plate impact, shock wave experiments. This flyer plate technique was used to perform shock wave experiments on $L{\mathrm{D}}_{2}$ to examine its high-pressure equation of state. Using an impedance matching method, Hugoniot measurements of $L{\mathrm{D}}_{2}$ were obtained in the pressure range of $\ensuremath{\sim}22--100\mathrm{GPa}.$ Results of these experiments indicate a peak compression ratio of approximately 4.3 on the Hugoniot. In contrast, previously reported Hugoniot states inferred from laser-driven experiments indicate a peak compression ratio of approximately 5.5--6 in this same pressure range. The stiff Hugoniot response observed in the present impedance matching experiments was confirmed in simultaneous, independent measurements of the relative transit times of shock waves reverberating within the sample cell, between the front aluminum drive plate and the rear sapphire window. The relative timing was found to be sensitive to the density compression along the principal Hugoniot. Finally, mechanical reshock measurements of $L{\mathrm{D}}_{2}$ using sapphire, aluminum, and \ensuremath{\alpha}-quartz anvils were made. These results also indicate a stiff response, in agreement with the Hugoniot and reverberating wave measurements. Using simple model-independent arguments based on wave propagation, the principal Hugoniot, reverberating wave, and sapphire anvil reshock measurements are shown to be internally self-consistent, making a strong case for a Hugoniot response with a maximum compression ratio of $\ensuremath{\sim}4.3--4.5.$ The trends observed in the present data are in very good agreement with several ab initio models and a recent chemical picture model for $L{\mathrm{D}}_{2},$ but in disagreement with previously reported laser-driven shock results. Due to this disagreement, significant emphasis is placed on the discussion of uncertainties, and the potential systematic errors associated with each measurement.

Wave structure methods have played an important role in probing mechanical and physical states of matter under dynamic loading. Applications cover a broad spectrum of research, including dynamic yielding; shock‐induced phase transformations; energetic reactions, tensile and compressive strength; and viscoplastic deformation. A large variety of experimental configurations have been developed to explore these phenomena using an extensive range of time‐resolved diagnostics. These methods were developed on single‐stage light gas guns for the most part, but extended to higher‐pressure capabilities, including explosive loading, propellant guns and two‐stage light gas guns. More recently, peak pressures accessible with these methods have been extended to even higher impact velocities and pressures through novel experimental platforms, including a modified two‐stage light gas gun that increases impact velocities to about 15 km/s, magnetically driven flyer plates that extend the velocities above 20 km/s, and laser...

Summary form only given. Recent developments in fast pulsed power have enabled an innovative approach for obtaining accurate high-pressure equation-of-state (EOS) data. The new method, referred to as the Isentropic Compression Experiment (ICE), uses the large currents produced over time intervals of 200-300 ns on the Z Accelerator to perform EOS experiments. Sample configurations have been developed on the accelerator to continuously load planar specimens with a magnetic field to peak pressures exceeding 200 GPa (2 Mbar). Time-resolved velocity measurements performed on the specimen are then used to extract EOS data along a material path that is quasiisentropic. The ability to perform quasi-isentropic EOS experiments over this pressure range has been a goal of the shock wave community for several years because these measurements provide unique EOS data previously unavailable. This loading condition is also useful for studying other physical effects, such as pressure-induced phase transitions or compressive material strength that are not easily studied with other methods. The ICE technique represents a major advance in shock physics and has opened a new sub-field of high-pressure research. This paper will review development of the ICE technique, including use of MHD codes to design and analyze ICE and flyer plate experiments. Several recent examples will be presented to illustrate the versatility of the method. Finally, prospects for increasing peak pressures and flyer plate velocities achievable with the technique will be discussed.

A novel approach was developed to probe density compression of liquid deuterium ($L\mathrm{\text{\ensuremath{-}}}{\mathrm{D}}_{2}$) along the principal Hugoniot. Relative transit times of shock waves reverberating within the sample are shown to be sensitive to the compression due to the first shock. This technique has proven to be more sensitive than the conventional method of inferring density from the shock and mass velocity, at least in this high-pressure regime. Results in the range of 22--75 GPa indicate an approximately fourfold density compression, and provide data to differentiate between proposed theories for hydrogen and its isotopes.

Shock compression science is a relatively new discipline that enables studies of materials in thermodynamic regimes inaccessible by other methods. The underlying motivation for these studies is to promote a physical understanding of dynamic material response. A fundamental understanding of material compression allows development of material models used to predict the response of materials subjected to dynamic loading. The past fifty years have produced a challenging research environment, resulting in the discovery and implementation of a broad spectrum of experimental, theoretical, and computational methods for this purpose. As a result, a large variety of phenomenological models have been developed for use in numerical simulations of material response under complex loading conditions. Even after a half-century of intensive research, however, there are still a large number of shock processes that cannot be resolved a priori with our existing level of understanding. A few examples include the prediction of shock transition times, compressive or tensile strengths under shock loading, and the kinetics of shock-induced phase transitions. This has led us to examine the issue of “what is a shock?” in tllis chapter by looking at the fundamental assumptions. These include assumptions of uniaxial displacement for applied planar loading, steady shock wave propagation, homogeneous shocked states, and thermodynamic equilibrium in tile shocked state. We examine the traditional approaches used for describing shock processes in solids, including the apparent anomalous observations resulting from these interpretations. Both experimental and computational results are used to show that shocks produce highly heterogeneous states of compression, which strongly influence observable material properties in the shocked state. Understanding these effects will require improved experimental diagnostics to probe deformation mechanisms in situ and in real time. We conclude by discussing what kinds of measurements will be needed to resolve these issues.

The intense magnetic field generated in the 20 MA Z-machine is used to accelerate flyer plates to high velocity for EOS experiments. A peak magnetic drive pressure on the order of 2 Mbar can be generated, which accelerates an approximately 0.2 g aluminum (Al) disc to 21 km/s. In a planned refurbishment of Z, called ZR, it is expected that up to 26 MA will be delivered to certain loads (e.g., dynamic hohlraums). We have used magneto-hydrodynamic (MHD) simulations to predict the peak magnetic drive pressure (and flyer velocity) that can be generated in a shock physics load on ZR. MHD simulations show that motion of the electrodes during the rise to peak current significantly increases the load inductance, which limits the peak current to values less than the expected maximum. This reduces the peak drive pressure to a value below what would be estimated using the expected peak current in a static geometry. However, MHD simulations also show that starting with a load geometry that maximizes magnetic flux on one wall of the anode, it is possible to reduce dynamic geometry effects by tapering the rise of the voltage pulse in combination with using a stiff material for the cathode. Simulations predict that peak magnetic pressures of 6 Mbar in Al, and 10 Mbar in tungsten are possible on ZR. In addition, it is predicted that flyer velocities of 40 km/s and larger can be achieved.

Three sets of LX‐04 samples of 0.18 and 0.49 mm nominal thicknesses were all dynamically loaded by Sandia’s Z‐accelerator with a ramp compression wave with a 200 ns rise time and about 160 kb peak stress. The LX‐04/lithium fluoride samples interface velocities were measured using VISAR’s. Comparisons of experimental and computational results will be given. Compression and release isentropes both show some reaction and kinetic behavior of the LX‐04. Experiments were also performed on ultra‐fine TATB where PMMA windows were used. Future experiments on single crystals of HMX that are designed to measure the phase transition at high pressures will be discussed.

Modern shock wave applications require prediction of material response under complex loading conditions and are often solved with numerical simulations. Even though many of the fundamental problems have been addressed, there are still a large number that cannot be solved from a first‐principles approach. To attain a fully predictive capability for these phenomena, it is necessary to understand the physical processes occurring during the shock process itself and to critically examine the fundamental postulates used to interpret shock wave phenomena. This paper examines the basic assumptions for describing shock processes in solids.

Isentropic ramp‐wave loading of materials is a novel method to study the kinetics of phase transitions, particularly in regimes that cannot be accessed by shock‐loading techniques. The Sandia Saturn accelerator produces magnetically driven planar ramp waves of 200–300 ns rise time in an aluminum drive plate, which then propagate into a material sample. In this way, molten tin initially at 600–700 K was isentropically loaded to 160–220 kbar, driving it across the liquid‐solid phase boundary. VISAR measurements at a sapphire window interface show possible evidence of nonequilibrium freezing in tin with a characteristic transition time around 100 ns. Improved experimental techniques are needed to verify this conclusion.

Using intense magnetic pressure, a method was developed to launch flyer plates to velocities in excess of 20 km/s. This technique was used to perform plate-impact, shock wave experiments on cryogenic liquid deuterium (LD{sub 2}) to examine its high-pressure equation of state (EOS). Using an impedance matching method, Hugoniot measurements were obtained in the pressure range of 30-70 GPa. The results of these experiments disagree with previously reported Hugoniot measurements of LD{sub 2} in the pressure range above {approx}40 GPa, but are in good agreement with first principles, ab-initio models for hydrogen and its isotopes.

Using intense magnetic pressure, a method was developed to launch flyer plates to velocities in excess of $20\mathrm{km}/\mathrm{s}$. This technique was used to perform plate-impact, shock wave experiments on cryogenic liquid deuterium ( $L\ensuremath{-}{\mathrm{D}}_{2}$) to examine its high-pressure equation of state. Using an impedance matching method, Hugoniot measurements were obtained in the pressure range of $30--70\mathrm{GPa}$. The results of these experiments disagree with previously reported Hugoniot measurements of $L\ensuremath{-}{\mathrm{D}}_{2}$ in the pressure range above $\ensuremath{\sim}40\mathrm{GPa}$, but are in good agreement with first principles, ab initio models for hydrogen and its isotopes.

In many technological and scientific applications it is desirable to accurately determine the off-Hugoniot isentropic response of materials at ultra-high pressures. Although unloading isentropes can be determined from unloading profiles, experimental techniques for measuring compressive isentropic response have been extremely limited. A brief summary is presented of the various techniques that have been developed for isentropically compressing materials to high pressure. A new technique is also discussed, which shows considerable promise for performing isentropic compression experiments with smooth ramp waves to multi-Mbar pressures. This approach uses the high current densities produced with fast pulsed power accelerators to create continuous magnetic loading to a few hundred kbar in the present study over time intervals of 100 ns. The method has been successfully applied on copper and iron to determine the isentropic compression curve in copper and evaluation of the kinetic properties of the alpha-epsil...

The thin foil acceleration method was tested in explosively-driven experiments with shock compressed PMMA and polyethylene at shock pressures up to 35 GPa. A transition was observed from the behavior expected for condensed matter to the gas-like response of the PMMA samples. Measurements of the PMMA unloading isentrope have been completed by modification of the equation of state in the vaporization region.

Recent developments have demonstrated the use of pulsed power for producing intense radiation sources (z-pinches) that can drive planar shock waves in samples with spatial dimensions significantly larger than possible with other radiation sources. In this paper, we will discuss the use of z-pinch sources for shock wave studies at multi-Mbar pressures. Experimental plans to use the technique for absolute shock Hugoniot measurements and with accuracies comparable to that obtained with gun launchers are discussed.

An optically recording velocity interferometer system (ORVIS) can be operated in a line-imaging configuration that effectively combines subnanosecond temporal resolution with high spatial resolution (length scales

Unloading from a plastically deformed state has long been recognized as a sensitive measure of a material's deviatoric response. In the case of a ramp compression and unload, time resolved particle velocity measurements of a sample/window interface may be used to gain insight into the sample material's strength. Unfortunately, measurements of this type are often highly perturbed by wave interactions associated with impedance mismatches. Additionally, wave attenuation, the finite pressure range over which the material elastically unloads, and rate effects further complicate the analysis. Here, we present a methodology that overcomes these shortcomings to accurately calculate a mean shear stress near peak compression for experiments of this type. A new interpretation of the self-consistent strength analysis is presented and then validated through the analysis of synthetic data sets on tantalum to 250 GPa. The synthetic analyses suggest that the calculated shear stresses are within 3% of the simulated values obtained using both rate-dependent and rate-independent constitutive models. Window effects are addressed by a new technique referred to as the transfer function approach, where numerical simulations are used to define a mapping to transform the experimental measurements to in situ velocities. The transfer function represents a robust methodology to account for complex wave interactions and a dramatic improvement over the incremental impedance matching methods traditionally used. The technique is validated using experiments performed on both lithium fluoride and tantalum ramp compressed to peak stresses of 10 and 15 GPa, respectively. In each case, various windows of different shock impedance are used to ensure consistency within the transfer function analysis. The data are found to be independent of the window used and in good agreement with previous results.

In a previous study by Asay et al. [J. Appl. Phys. 106, 073515 (2009)], the inelastic response of annealed and cold-rolled pure polycrystalline tantalum at intermediate strain rates was characterized with ramp wave loading to peak longitudinal stresses of 17 GPa. It was found that the annealed Ta at strain rates of about 106/s exhibited pronounced elastic overshoot, followed by rapid stress relaxation and the amplitude of the elastic precursor depicted essentially no dependence on sample thickness for samples with controlled initial properties, in contrast to the precursor attenuation typically observed in shock wave experiments. The precursor for the cold-rolled sample was more dispersive and did not exhibit the characteristics depicted by the annealed samples. A principal objective of the present study was to gain some insights into this behavior and its implication on the deformation mechanisms for tantalum. Another objective was to gain a fundamental understanding of the dynamic inelasticity of polycr...

Shock wave techniques have been used for decades to study the dynamic states of matter in temperature and pressure regimes inaccessible by other methods. These techniques have been employed in a wide variety of scientific and commercial applications. A principal scientific objective has been to determine high-pressure equations of state (EOS) to ultra-high pressures; pressures of a few TPa have been reported for several materials. Most recently, these methods have been used for studies of thermophysical properties under shock compression, including phase transition kinetics, and mechanical properties, such as the high-pressure yield strength. In this paper, a brief discussion of recent developments in high velocity launchers is given. Advances in techniques for subjecting materials to a wide range of loading conditions are presented, including selected illustrations of shockwave measurements to Mbar pressures.

Time‐resolved measurements of shock‐wave rise times have been accomplished for aluminum, copper, and steel to stress levels of 41, 96, and 139 GPa, respectively, using velocity‐interferometer techniques. To within the time resolution of the technique, the shock transition is found to occur within 3 ns in all materials. Based on this upper limit for the transition time, limiting viscosity coefficients of 1000, 3000, and 4000 P are obtained for 6061‐T6 aluminum, OFHC copper, and 4340 steel, respectively, at strain rates above 108 s−1. It is found that the effective viscosity can be expressed as parameters in a Maxwellian relation for an elastic‐plastic solid, in which the viscosity is related to an effective relaxation time. It is also shown that viscosity is inversely proportional to mobile‐dislocation density, which implies that the density of mobile dislocations obtained during shock compression in these materials is well over 109/cm2.

Shock waves have been used to determine material properties under high shock stresses and very-high loading rates. The objectives of the present experiments were to obtain information on the mechanical response of aluminum at shock stresses approaching and in the solid–liquid mixed phase regions, which is not routinely available with other methods. The accurate determination of compressive strength under shock compression has proven to be difficult due to the need for accurate reshock experiments from the initial shock state, with the consequence that estimates of shear strength have been limited to relatively low stresses. In this investigation, we have significantly improved the shock/reloading technique to obtain high quality data on reloading from the shocked states for initial shock stresses up to about 80 GPa. This has allowed the first self-consistent determination of the shear strength and the initial shear stress state of aluminum in the shocked state in this stress region. In addition, unloading experiments have been extended to over 140 GPa to understand how the strength of the material behaves when shocked beyond the solid–liquid mixed phase boundary. The combined wave velocity and strength data provide estimates of the onset and completion of shock-induced melting.

In recent years the shock deformation properties of a precipitation-hardened aluminum alloy (6061-T6) have been investigated extensively with time-resolved wave profile gauges. Studies have revealed complicating features of the shock deformation process not easily explained by existing theories of plastic deformation. Specifically, unusual behavior in the dynamic hardness or strength, post-shock hardness, steady wave viscosity, and post-shock microstructure has been observed over the shock pressure range of range of 1–15 GPa. The deformation structure suggests that microscopic heterogeneity in the deformation and temperature state during dynamic compression may be responsible for the observed effects. We have undertaken a study to correlate the shock compression and quasistatic deformation of 6061-T6 aluminum. Recovered specimens which have been shock loaded are examined metallurgically, and results are compared with both static and dynamic mechanical property measurements. Illuminating correlations are emerging from this study, although an unambiguous determination of the importance of heterogeneous effects is yet to be achieved. A modeling effort of dynamic deformation in aluminum based on heterogeneous deformation and adiabatic thermal trapping is being pursued to guide the experimental effort.