Jack LeRoy Wise

Dynamic behavior of tungsten carbide and alumina filled epoxy composites

The dynamic behavior of a tungsten carbide filled epoxy composite is studied under planar loading conditions. Planar impact experiments were conducted to determine the shock and wave propagation characteristics of the material. Its stress-strain response is very close to a similar alumina filled epoxy studied previously, suggesting that the response of the composite is dominated by the compliant matrix material. Wave propagation characteristics are also similar for the two materials. Magnetically driven ramp loading experiments were conducted to obtain a continuous loading response which is similar to that obtained under shock loading. Spatially resolved interferometry was fielded on one experiment to provide a quantitative measure of the variability inherent in the response of this heterogeneous material. Complementing the experiments, a two-dimensional mesoscale model in which the individual constituents of the composite are resolved was used to simulate its behavior. Agreement of the predicted shock an...

Microstructure and Mechanical Properties of Precipitation Hardened Aluminum Under High Rate Deformation

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.

Shock-vaporization studies on zinc and porous carbon

Experiments probing the shock-induced vaporization of zinc and porous carbon yielded time-resolved data suitable for evaluation of equation-of-state (EOS) models and computations that describe expanded-state material behavior. In these tests, partial vaporization of the target material occurred as the initial shock stress ({approx gt}100 GPa) was released through a rarefaction originating at the target free surface. The target expansion products traversed a gap and impinged on a witness plate that was backed by a transparent window. A velocity interferometer recorded histories of the witness-plate/window interface velocity which were compared to one-dimensional wavecode (CTH) calculations based on selected multiphase EOS treatments. 10 refs., 4 figs.

Dynamic, multiaxial impact response of confined and unconfined ceramic rods

A new configuration for impact testing was implemented which yielded time‐resolved measurements of the dynamic response of materials undergoing multiaxial strain. With this method, one end of an initially stationary rod (i.e., right circular cylinder) of test material was subjected to planar impact with a flat‐faced projectile. The test rod was either free (unconfined) or mounted within a close‐fitting sleeve which provided lateral confinement. Velocity interferometer diagnostics monitored the axial (longitudinal) velocity of the rod free end, and the transverse (radial) velocity for one or more points on the periphery of the rod or confinement sleeve. Analysis of the resultant velocity records allowed assessment of material properties, such as wave speeds and compressive yield strength, without the requirement of intact recovery of the rod. Data were obtained for alumina (Coors AD‐99.5) rods in a series of tests involving variations in confinement and peak impact stress.

Experimental Technique for Measuring the Isentrope of Hydrogen to Several Megabars

The experimental measurement of the EOS of hydrogen has been of interest for some time because of the theoretical expectation of a transition to the metallic state in the multi-megabar pressure regime. Previous experiments [1–4] have reported results which are consistent with a metallic transition, but experimental uncertainties have precluded positive identification of the metallic phase.

Comparative Shock Response of Additively Manufactured Versus Conventionally Wrought 304L Stainless Steel.

Gas-gun experiments have probed the compression and release behavior of impact-loaded 304L stainless steel specimens that were machined from additively manufactured (AM) blocks as well as baseline ingot-derived bar stock. The AM technology permits direct fabrication of net- or near-net-shape metal parts. For the present investigation, velocity interferometer (VISAR) diagnostics provided time-resolved measurements of sample response for one-dimensional (i.e., uniaxial strain) shock compression to peak stresses ranging from 0.2 to 7.0 GPa. The acquired wave-profile data have been analyzed to determine the comparative Hugoniot Elastic Limit (HEL), Hugoniot equation of state, spall strength, and high-pressure yield strength of the AM and conventional materials. The possible contributions of various factors, such as composition, porosity, microstructure (e.g., grain size and morphology), residual stress, and/or sample axis orientation relative to the additive manufacturing deposition trajectory, are considered...

Development of a system to provide diagnostics-while-drilling.

This report describes development of a system that provides high-speed, real-time downhole data while drilling. Background of the project, its benefits, major technical challenges, test planning, and test results are covered by relatively brief descriptions in the body of the report, with some topics presented in more detail in the attached appendices.

Design of a sample recovery assembly for magnetic ramp-wave loading.

In order to generate new properties of metals exposed to high pressure states, it is desirable to study samples loaded in one‐dimensional strain. Previous work to obtain these ideal conditions, involve a technique where the sample was recovered at late times to examine its microstructure. In those experiments, the shock‐loading was produced by impacting the sample with a flyer plate. In the present work, we modified the sample recovery assembly and optimized it for ramp wave loading. We describe the 2‐D calculations performed with the ALEGRA MHD code that led to improved recovery assembly efficiency. Preliminary comparisons of the simulations with measurements of the sample deformation from an experiment indicate excellent agreement.

DYNAMIC RESPONSE OF KOVAR TO SHOCK AND RAMP‐WAVE COMPRESSION

Complementary gas‐gun and electromagnetic pulse tests conducted in Sandias Dynamic Integrated Compression Experimental (DICE) Facility have, respectively, probed the behavior of electronic‐grade Kovar® samples under controlled impact and intermediate‐strain‐rate ICE (Isentropic Compression Experiment) loading. In all experiments, velocity interferometer (VISAR) diagnostics provided time‐resolved measurements of sample response for conditions involving one‐dimensional (i.e., uniaxial strain) compression and release. Wave‐profile data from the gas‐gun impact experiments have been analyzed to assess the Hugoniot Elastic Limit (HEL), Hugoniot equation of state, spall strength, and high‐pressure yield strength of shocked Kovar®. The ICE wave‐profile data have been interpreted to determine the locus of isentropic stress‐strain states generated in Kovar® for deformation rates substantially lower than those associated with a shock process. The impact and ICE results have been compared to examine the influence of loading rate on high‐pressure yield strength.Complementary gas‐gun and electromagnetic pulse tests conducted in Sandias Dynamic Integrated Compression Experimental (DICE) Facility have, respectively, probed the behavior of electronic‐grade Kovar® samples under controlled impact and intermediate‐strain‐rate ICE (Isentropic Compression Experiment) loading. In all experiments, velocity interferometer (VISAR) diagnostics provided time‐resolved measurements of sample response for conditions involving one‐dimensional (i.e., uniaxial strain) compression and release. Wave‐profile data from the gas‐gun impact experiments have been analyzed to assess the Hugoniot Elastic Limit (HEL), Hugoniot equation of state, spall strength, and high‐pressure yield strength of shocked Kovar®. The ICE wave‐profile data have been interpreted to determine the locus of isentropic stress‐strain states generated in Kovar® for deformation rates substantially lower than those associated with a shock process. The impact and ICE results have been compared to examine the influence of...

Effects of Annealing and Preheating on the Impact Response of Selected Braze Materials

A series of gas‐gun experiments has probed the planar (uniaxial strain) impact response of six different commercial brazing alloys that were subjected to a peak shock stress in the range of 5.5 – 7.2 GPa. The alloys studied were copper + gold (65/35 wt%), copper + gold (50/50 wt%), Cusil®, Nicusil®‐3, Nicoro® + titanium (98/2 wt%), and silver zirconate. Both as‐received and annealed samples of each alloy were tested under ambient (room temperature) and preheated (100 C) initial conditions. Velocity interferometer data acquired during this investigation have been evaluated to determine the dynamic yield strength (i.e., Hugoniot Elastic Limit), shock Hugoniot state, and spall strength for baseline alloy samples (i.e., unheated, as‐received material) and for samples whose initial condition involved annealing and/or preheating.