Experimental investigation of the shearing resistance of SODA-Lime glass at pressures of 9 GPa and strain rates of 10^6 s^(-1)

Pressure-Shear Plate Impact (PSPI) experiments were conducted to measure the high-rate shearing resistance of soda-lime glass at pressures of 9 GPa and at shearing rates of approximately 10^6 s^(−1). Samples of soda lime glass, 5 µm thick, were sandwiched between pure tungsten carbide (WC) plates and impacted by pure WC flyers. Impacting plates were inclined to the direction of approach by an angle of 18°. Normal stress and shearing resistance of the sample were calculated from measured free surface velocities using 1D elastic wave theory. The experimental results show that, at a pressure of 9GPa, the shear stress increases almost linearly up to 1 GPa and then falls quickly to approximately 0.3 GPa — after which it decreases slowly to approximately 0.17 GPa. Comparisons with results of previous experiments on nominally identical samples, impacted to generate lower peak pressures, showed the peak shearing resistance to be much higher at higher pressures; however, the sharp fall in shearing resistance occurs at comparable shear strains (1.5-2)

Experimental investigation of the shearing resistance of SODA-Lime glass at pressures of 9 GPa and strain rates of 10^6 s^(-1)

Pressure-Shear Plate Impact (PSPI) experiments were conducted to measure the high-rate shearing resistance of soda-lime glass at pressures of 9 GPa and at shearing rates of approximately 10^6 s^(−1). Samples of soda lime glass, 5 µm thick, were sandwiched between pure tungsten carbide (WC) plates and impacted by pure WC flyers. Impacting plates were inclined to the direction of approach by an angle of 18°. Normal stress and shearing resistance of the sample were calculated from measured free surface velocities using 1D elastic wave theory. The experimental results show that, at a pressure of 9GPa, the shear stress increases almost linearly up to 1 GPa and then falls quickly to approximately 0.3 GPa — after which it decreases slowly to approximately 0.17 GPa. Comparisons with results of previous experiments on nominally identical samples, impacted to generate lower peak pressures, showed the peak shearing resistance to be much higher at higher pressures; however, the sharp fall in shearing resistance occurs at comparable shear strains (1.5-2)

A new split Hopkinson tensile bar design

This work presents a new design for a split Hopkinson tensile bar (SHTB) as well as generated representative experimental results. The new design uses a U shaped striker bar as projectile and addresses several shortcomings of classical SHTB designs using hollow striker bars. The results presented show that the non-symmetrical striker bar is capable of generating a clean and virtually oscillation free square pulse signal five times longer than typically achieved by classical striker tubes, whilst at the same time offering superior signal quality. Due to the longer stress pulse duration, the new SHTB design allows for the characterisation of materials at strain rates that were difficult to achieve for hydraulic testing machines and classical striker tube based SHTB designs. In addition, the developed SHTB is based on a simple and modular design and allows for a wide range of pulse shaping methodologies to be applied. Therefore, materials requiring different input stress pulse shapes, such as square (ductile), trapezoid or triangular (brittle), can be experimentally characterised at a large range of strain rates. © 2012 Elsevier Ltd. All rights reserved

Pressure-Shear Plate Impact Experiments at High Pressures

The pressure shear plate impact (PSPI) experiment, developed over 40 years ago by R. J. Clifton at Brown University enables the study of the dynamic strength of materials at high pressures and strain rates. Traditional PSPI experiments were typically conducted at velocities and corresponding pressures, limiting the experimental conditions not to exceed the Hugoniot Elastic Limit (HEL) of the anvil materials, with typical values of 3–7 GPa. In this work, PSPI experiments are extended to higher pressures, significantly beyond the HEL, approaching 50 GPa, using a powder gun facility at Caltech. The high-pressure and high-velocity impact regimes introduce several experimental challenges which must be overcome: (1) the inelastic behavior of the anvils at high pressures precludes traditional elastic analysis to extract the material’s strength; (2) the potential for slip between impact faces as a result of elevated temperatures and shear forces on the impact surfaces due to higher velocities and pressures; and (3) accurate measurement of the transverse velocity at large normal displacements, resulting from the higher impact velocities. New experimental capabilities have been developed to overcome each of these technical challenges, which include a new all fiber-optic heterodyne transverse velocity interferometer system. New analysis methods that account for the inelastic response of the flyer and anvil plates have also been developed for the accurate extraction of material strength properties from PSPI experiments. Friction and slip were examined, pushing to the limits of their knowledge under these extreme conditions. The new PSPI capabilities have been demonstrated using tungsten carbide and D2 tool steel anvils for measuring the strength of soda–lime glass and magnesium