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A series of heated reverse Taylor impact experiments have been undertaken on pure polycrystalline tantalum to investigate the individual and interdependent effects of strain-rate and temperature. Impact velocities and initial temperatures in the ranges 112-185 m/s and 293-954 K were studied. Velocimetry and high-speed imaging were used to record time-resolved deformation of the rods. The data is compared to Lagrangian hydrocode simulations and the performance of three strength models (Steinberg-Guinan, Preston-Tonks-Wallace and the LMS13 multiscale model) are assessed. Overall, the LMS13 model was able to reproduce the deformed rod profile and the velocimetry most accurately. [ABSTRACT FROM AUTHOR]

The effect chemical composition on the shock response of two bulk metallic glass (BMG) alloys with slightly different elemental compositions (Zr55Cu10Ni5Al30 and Zr46Cu38Ag8Al8) has been investigated. Plate-impact experiments were conducted at a peak compressive stress of ~10GPa, above the expected elastic limit of these alloys (~7GPa). Velocity interferometry was used to measure the particle (up) and free surface velocity (FSV) histories. These measurements allowed calculation of the Hugoniot elastic limits and onset stresses of fracture (i.e. spall strength) for each alloy. The soft recovered specimens were characterized by means of optical and electron microscopy. It was found that the Zr55Cu10Ni5Al30 exhibited a higher HEL and spall strength and a smooth fracture surface morphology consisting of dimple-like features. Conversely, the lower spall strength of the Zr46Cu38Ag8Al38 alloy seems to correlate with rougher fracture surface that shows cup-cone features associated with a predominantly brittle dynamic fracture. [ABSTRACT FROM AUTHOR]

Expanding cylinder experiments using a gas gun technique allow investigations into the ductility of metals and the fracture and fragmentation mechanisms that occur during rapid tensile failure. These experiments allow the radial strain-rate of the expansion to be varied in the range 102 to 104 s-1. Presented here is a comparative study of the fracture and fragmentation behaviour of rapidly expanded stainless steel 316L cylinders manufactured from either a wrought bar or additive manufacturing techniques. The results show that in the strain-rate regime studied, an additively manufactured cylinder failed at a higher strain and produced larger fragment widths when compared to cylinders manufactured from a wrought bar. In addition, an investigation into the role of macroscopic elongated voids that were introduced into the cylinder wall, at an angle of 45° to the cylinder radius, was undertaken. A comparison between experimental and simulated results (using the Eulerian hydrocode CTH) was also completed. [ABSTRACT FROM AUTHOR]

When a shock wave is incident on a free surface, micron sized pieces of the material can be ejected from that surface. Phase Doppler Anemometry (PDA) is being developed to simultaneously measure the sizes and velocities of the individual shock induced ejecta particles; providing an important insight into ejecta phenomena. The results from experiments performed on the 13 mm bore light gas gun at the Institute of Shock Physics, Imperial College London are presented. Specially grooved tin targets were shocked at pressures of up to 14 GPa, below the melt on release pressure, to generate ejecta particles. These experiments are the first time that PDA has been successfully fielded on dynamic ejecta experiments. The results and current state of the art of the technique are discussed along with the future improvements required to optimise performance and increase usability. [ABSTRACT FROM AUTHOR]

Using a gas gun to create rapid expansion in metal cylinders to investigate fracture and fragmen-taion has been commonplace for the last several decades. Results from such experiments alongside data from explosive and electromagnetic expansion techniques have produced several models for fragment size and mass distributions. We present a new geometry for expansion that can be applied to cylinders at elevated & reduced temperatures whilst keeping the drive mechanism constant, enabling us in the future to experiment over a range of sample temperatures at a fixed strain rate and loading path. This new geometry has been investigated through a series of gas gun experiments employing X-ray radiography and AUTODYN simulations to reveal the deformation and failure behaviour within the cylinder. [ABSTRACT FROM AUTHOR]

In this paper we discuss a series of experiments to extract data relevant to the loading of geological materials by explosives. Metre cube blocks of limestone were subjected to explosive loading from a borehole. Stress gauges, accelerometers and a multi-point VISAR system were used to monitor material behaviour at a variety of distances from the loading point, in order to provide a robust data set for modellers. Through the use of two separate target geometries the effect of jointing in geological materials was investigated and shown to have a significant effect on the attenuation of the stress pulse passing through the material. [ABSTRACT FROM AUTHOR]

An optical system was developed to allow the accurate focussing and alignment of small samples for velocity analysis with streak photography Even at low magnifications, a narrow streak slit means that any vibration or instability in the system greatly reduces the accuracy of the velocity measurements achieved. The optical system was designed to reduce the effects of such vibration. A spatial mount and rotation stage were modified to allow three spatial axis and rotational freedom of a custom-made sample mount. Markers within the sample mount were used to achieve precise alignment of the sample with the optical axis of the streak camera. [ABSTRACT FROM AUTHOR]

Through the use of laterally mounted stress gauges the Hugoniot Elastic Limits (HELs) of various geological materials have been measured. These materials, kimberlite, basalt, siltstone, quartz/feldspathic gneiss and amphibolite show a range of HEL values, from 1.3 GPa to 5 GPa. The value of the HEL appears to be influenced strongly by the grain size of the material, whereas, for example, it would appear to be independent of both the elastic properties and the measured Hugoniot slope in σ-up space. The current experimental data has been supplemented with relevant literature data. [ABSTRACT FROM AUTHOR]

A problem has recently been reported concerning the use of manganin gauges as a diagnostic in certain geological materials in that excessive noise can limit usability. A number of plate impact experiments have been performed with un-powered gauges to examine the extent to which electromagnetic emission from piezoelectric materials within the rocks affects gauge performance. It has been shown that materials with higher quartz content produce significantly more noise in the gauge traces. Mineral analysis has also been conducted to identify possible gauge straining due to different impedances of minerals within the rock types investigated. [ABSTRACT FROM AUTHOR]

A robust experimental technique to measure the shock response of compacted granular materials is demonstrated. The Hugoniot curve for a quasi-statically compacted soil (∼14% porous) is presented in the stress range 0.7–4.3 GPa and compared to that of similar un-compacted materials. The soil investigated was a mixture of silt and sand in a 2:1 ratio by volume, with compacted density 2290±40 kg m-3. The Hugoniot data was generated using a plate-impact reverberation technique similar to that used by other authors. [ABSTRACT FROM AUTHOR]

The shock response of geological materials is of interest to many industries, in particular oil and gas exploration. The porous inhomogeneous composition of geological materials complicates characterisation under dynamic loading. The behaviour of dry limestone has been investigated under the condition of uniaxial strain using a plate impact facility. Manganin gauges were used to measure both longitudinal and lateral stresses within the limestone. The Hugoniot and shear data obtained are compared with that available in the open literature. [ABSTRACT FROM AUTHOR]

Porous and granular materials are widely found in a number of environments. One of the most important groups both geographically and in the construction industry are the sands. A review of the response of sand (42% porous) over a wide range of strain rates is presented. Factors such as water content and density variation are addressed. In addition a very low-density silica dust (95% porous) is also discussed in relation to its contrasting behaviour. [ABSTRACT FROM AUTHOR]

A series of plate impact experiments have been performed to assess the dynamic behaviour of dry and water saturated concrete under shock-loading. Information was obtained on the Hugoniot curve and dynamic shear properties using manganin gauges. This extends our previous data obtained on cement paste, mortar, and micro-concrete to full-size concrete. Despite the varying heterogeneous composition of concrete it has been found that all materials Hugoniot curves lie within a close range in Stress—Particle Velocity space (σ-up). [ABSTRACT FROM AUTHOR]

A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University’s one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were modeled with CTH, a 3D Eulerian hydrocode developed at Sandia National Laboratory. Simulated pressures at two test locations are presented and compared with measurements. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The response of a commercially available silica powder at low density to shock loading has been investigated. Hugoniot data were obtained for samples from two initial densities. The shock velocity particle velocity dependence was found to be linear for both densities. The data is modelled using a P-α model and reported in a companion paper. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]