The plateau stress and energy absorption of low density (≤300 kg/m3) polyurea (PU) foams expanded polystyrene (EPS) were measured at deformation rates ranging from 0.004 s−1 to 5000 s−1. Low (≤10−1 s−1) strain rate testing was performed using an Instron load frame, intermediate (101–102 a drop-weight impact tower, high (≥103 conditions modified split-Hopkinson pressure bar. PU exhibit strong dependence across all rates. This result has been previously unreported for polymer under sensitivity...

Self-assembled nanotubular arrays on Ti alloys could be used for more effective implantable devices in various medical approaches. In the present work, adhesion of TiO2 nanotubes (TiO2 NTs) Ti-6Al-4V (Ti64) was investigated by laser spallation and scratch test techniques. At first, electrochemical anodization performed an ammonium fluoride solution dissolved a 90:10 ethane-1,2-diol (ethylene glycol) water solvent mixture. This process at room temperature (23?C) steady potential 60 V 1 h....

Shock deformation of copper nano-films and nano-rods is examined with Molecular Dynamics (MD) simulations. The influence the small system size on onset plasticity, its origin resulting from nucleation dislocation loops, reversible nature are determined. While simulations large systems periodic boundary conditions indicate that tremendous axial stresses needed to induce plastic in perfect crystals, present results suggest stress levels initiate irreversible plasticity more than one order...

Dynamic compaction of granular materials is a complex process, wherein the material response at continuum scale arises from fracture, comminution, and fragment flow grain scale. Granular have heterogeneity due to variation in properties as well local packing density structure. These heterogeneities may affect dynamic response, producing structured time-varying front. The methodology used characterize shock behavior solid be inappropriate for because this unsteady interactions between...

An apparatus and test procedure for fabrication loading of single crystal metal nanopillars under extremely high pressures (>1 GPa) strain rates (>107 s-1), using laser-generated stress waves, are presented. Single-crystalline Cu pillars (∼1.20 μm in tall ∼0.45 diameter) prepared via focused ion beam milling Cu(001) substrates shock-loaded this approach with the dilatational waves propagating along [001] axis pillars. Transmission electron microscopy observations show that dislocation...

An outstanding challenge in developing a complete equation of state for materials at elevated pressure and temperature is robust method determining the bulk under dynamic conditions. In metals, determination states by optical pyrometry complicated small depth thermal conduction effects. These effects lead to observed temperatures differing 20% or more from state. this work, we show presence measurements tin iron coatings during compression experiments. We demonstrate that tin, contrast iron,...

In this work we provide direct evidence of shock-induced melting and associated kinetics in a porous solid (aluminum powder) using time-resolved x-ray diffraction. Unambiguous 50% aluminum (Al) powder samples, shocked to peak pressures between $\ensuremath{\sim}13\text{\ensuremath{-}}19\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, was provided by the broadening Debye-Scherrer ring corresponding (111) peak. Shocked Al did not melt completely any our experiments within durations measurement....

Understanding the particle-scale dynamics of granular materials during rapid compaction and flow is fundamental importance for manufacturing, planetary science, geology, defense applications. Time-resolved 2D radiography static 3D x-ray tomography are powerful in situ tools studying but provide detail only or with significant time-scale limitations, respectively. Here, we introduce a new method that uses imaging determining time-resolved rapidly compressed materials. The employs initial...

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements dispersion. Laser generated rarefacted exceeding 3 GPa rise times 10 ns were introduced samples material Galfenol. The resulting reveal evolution into a compressive acoustic front lateral release...

This article presents a concept and implementation of calibrated streaked spectral pyrometer (SSP) temperature diagnostic used in dynamically driven shock experiments on two-stage gas gun. system relies upon measuring the total response using tunable monochromator, NIST-traceable power meter, SSP. The performance is validated against previously measured temperatures z-cut quartz at 99 GPa 93 GPa. results are found to agree with literature within 5% discussed this manuscript. experimental...

To date, temperature and conductivity have many outstanding implications in extreme environments but are yet to be fully understood under high pressure dynamic conditions. Here, we introduce an approach provide quality electrical results loading Emphasis is given address the skin depth effect's influence a experiment by using thin films. The film samples this study were at least 100 times thinner than previous experiments, increasing current density its full potential across sample's entire...

Mesoscale simulations of a LiF impactor colliding with PMMA capsule containing aluminum powder (ρ00 = 1.5 g/cc) have been performed to investigate shock-induced melting in porous metals. Impact velocities 1-2.5 km/s are chosen coincide situ X-ray diffraction experiments, which provide direct evidence powders. show shock heating within the is highly nonuniform and remains incomplete over hundreds nanoseconds behind front despite equilibrium pressure-temperature states from continuum lying...

The response of particulate materials to impulsive loading includes complex interactions between grains due fracture and comminution the presence interstitial material. quasi-static strength saturated powders is related concept "effective stress" in which fluid stiffens material reduces shear strength. However, detailed information regarding effects saturation under dynamic lacking since static equilibrium phases cannot be assumed interaction becomes more complex. Recent experiments on...

The temperature of shock-compressed z-cut quartz was determined at 99 and 93 GPa using a calibrated streaked spectral pyrometry system for use in high-pressure gas-gun experiments. temperatures obtained are found to agree with the majority previous literature values within 5%. Sensitivities various error sources, including geometric corrections, response-measurement errors, wavelength-assignment errors discussed. combined uncertainties due these estimated be 0.7-1.1%, substantial improvement...

We perform a gas gun experiment by shock loading tantalum samples of varying grain structures to assess the suitability numerical model for simulating spall behavior. The observed differences in strength, as well spallation and re-compression history, are not captured uncalibrated hydrodynamic simulations. An optimization is performed on Johnson determine best parameters that fit trends. Linear stability analysis employed motivate bounds those parameters. Herein, optimized simulations agree...

This paper explores a fundamental connection between ductility and domain size in metallic solids under extreme conditions of cryogenic temperatures strain rates (10 8 s -1 ).A series novel experiments, backed by multiscale modelling transmission electron microscopy (TEM) analysis, are presented that involve loading TEM-ready single crystal nanopillar samples Cu varying lengths (50 nm to 1 mm) aspect ratios 100 diameter) laser-generated stress waves sub-nanosecond rise times, rate (>10 )...