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The microstructural and mechanical response of materials to shock loading is of the utmost importance in the development of constitutive models for high strain-rate applications. However, unlike a purely mechanical response, to ensure that the microstructure has been generated under conditions of pure one dimensional strain, the target assembly requires both a complex array of momentum traps to prevent lateral releases entering the specimen location from the edges and spall plates to prevent tensile interactions (spall) affecting the microstructure. In this paper, we examine these effects by performing microhardness profiles of shock loaded copper and tantalum samples. In general, variations in hardness both parallel and perpendicular to the shock direction were small indicating successful momentum trapping. Variations in hardness at different locations relative to the impact face are discussed in terms of the initial degree of cold work and the ability to generate and move dislocations in the samples.

Manganin stress gauges are used to monitor the behavior of pure tungsten under conditions of one-dimensional shock loading, which are mounted in longitudinal and lateral orientations. The results have shown that the decrease in shear strength behind the shock front is related to both the innate influence of the high Peierls stress in tungsten on dislocation generation, motion and storage and the nucleation and growth of grain boundary cracks that gradually degrade the material's strength.

Lateral stresses generated by shock loading in tantalum have been determined using manganin stress gauges. The shock-wave response of tantalum is discussed in the context of a previous weak-shock wave-profile analysis of tantalum, and in terms of defect generation and storage response of pure face-centered- versus body-centered-cubic metals

The shock response of the aluminum alloy 7010-T6, induced by the technique of plate impact, is investigated as a function of orientation to the loading axis to the rolling direction. A simulation using finite-element modeling has shown that while the model can reproduce the dependency of the Hugoniot elastic limit on orientation, the degree of success with the spall strength has not been so great.

The Hugoniot of the fluorinated tripolymer Viton B has been quantified in terms of shock stress, shock velocity, and particle velocity. The shock velocity—particle velocity curve was found to be linear, thus suggesting no changes in phase occurred in the experimental stress range investigated. Comparisons of the calculated hydrodynamic pressures and measured stresses also showed close agreement, with only small differences apparent at the highest stresses. It is believed that this shows Viton B has a low shock-induced shear strength that only becomes significant at high impact stresses. Comparison of the Hugoniots of Viton B, polytetrafluroethylene, and polyvinylidene difluoride shows that the former is slightly steeper. The authors suggest that this is due to the -CF3 side group having a strengthening effect. [ABSTRACT FROM AUTHOR]

The shock response of the aluminum alloy 6061 and its variation according to heat treatment are monitored by the placement of stress gauges in such orientations, which is sensitive to the lateral component of stress and the shear strength. Microstructural analysis postshock has shown a more randomized dislocation distribution, with little or no postshock hardening occurring once the shock induced strain is accounted for, which is attributed to the presence of fine [Mg.sub.2]Si precipitates inhibiting the motion and generation of dislocations.

The response of four cubic metals to shock loading analyzed in order to understand the effects of microstructure on continuum response. The studies have illustrated the role of defect generation, transport, storage and interaction in determining the response of materials to shock prestraining.

Lateral stress and shear strength behind the shock front are measured in three face centered cubic alloys. The aluminum alloy 6082-T6 has shown a low degree of hardening behind the shock front, which is due to the presence of fine intermetallic particles suppressing the formation of dislocation cells but rather forming a random distribution throughout the microstructure.

A series of plate impact experiments are performed to analyze the role of anisotropy on the response of the titanium alloy Ti-6Al-4V to shock loading. It is shown that extensive deformation twinning during the early stages of deformation in the shock and thereafter c + a slip and dislocation tangling have built up over a longer time period, which has resulted in the higher degree of hardening.

The effect of dynamic, high-pressure loading in the regime of the phase II to phase III pressure-induced crystalline phase transition in polytetrafluoroethylene (PTFE) is examined. Taylor impact has highlighted continuum behavior that has origin in mesoscale response and there is a rapid transition from ductile to brittle behavior, which has occurred at a pressure consistent with this phase transition.

Manganin stress gauges sensitive to lateral component of stress are used for examining deviatoric response of a particulate alumina-epoxy composite to shock loading. Results show that lateral stress and shear strength are near constant behind shock front, thus showing that presence of alumina has a diluting response of the epoxy resin.

An investigation on the shock response of the intermetallic compound Ni3Al is conducted to determine equation of state and shock induced mechanical properties, and the response is compared to that of pure nickel. Results reveal that the spall strength of Ni3Al reduces with pulse duration, and that although it initially increases with shock stress amplitude, it reaches a peak in the range of 6-7 GPa before reducing again.

The shock response of a NiTi alloy is investigated in terms of its equation of state, dynamic tensile strength and shear strength. Manganin stress gauges are used to measure the longitudinal and lateral stresses.

The shock response of a silicon carbide is investigated using the methods of plate impact, and monitored using manganin stress gauges mounted to be responsive to lateral stress. A two-step stress response is observed, indicating the presence of delayed failure at the impact face.

The deviatoric response of the dense ceramic, tungsten carbide is investigated under shock loading conditions, using laterally mounted stress gauges. The results indicate that lateral stress increases, and thus shear strength decreases behind the shock front.

Reports on the results of experiments conducted on metals subjected to planar impact loading in which a biaxial stress state and a uniaxial strain state is induced. Measurement of the longitudinal and transverse stresses in copper, iron, and mild steel specimen used in the study; Use of the results in calculation of shear stress.

The stress, shock velocity, and particle velocity measurements are conducted on the shape memory NiTi alloy. An inflection at lower stresses are found in the stress-particle velocity, and are ascribed to the martenstic phase transformation that is the characteristic of the shape memory effecting this alloy.

Manganin stress gauges are placed in potassium chloride plates, in such orientation that they are sensitive to the lateral component of stress during shock loading. Impact conditions are chosen such that measurements are made both above and below the stress.

Abstract: The effect of the addition of an alloy element to a pure metal upon its behaviour under shock loading had been investigated. Two materials had been chosen: nickel, a face centred cubic material, and nickel–60wt% cobalt, also a face centred cubic material but with a much reduced stacking fault energy (SFE). The influence on the shock response of cobalt additions had been studied by the plate impact technique (uniaxial strain). The experimental results allowed the determination of characteristic properties of both materials. The Hugoniots of pure nickel and its alloy were established and compared, for the range of stress 0–20GPa. The dynamic tensile stress (pull-back stress) was then investigated at low-stress amplitudes as a function of specimen thickness to investigate the nucleation of damage. The Hugoniot elastic limit (HEL) was investigated and the dynamic tensile stress under different incident conditions was presented and discussed. The cobalt additions did not modify the shock properties in compression. The sensitivity to the pulse length duration was observed for the alloy in tension. [Copyright &y& Elsevier]

Abstract: Right cylinders of the thermoplastic polyether ether ketone have been impacted onto a hardened steel anvil at velocities from 152 to 408ms−1. The resultant deformation showed the expected ‘mushrooming’ behaviour up to impact velocities of 303ms−1, before the impact face began to fracture. No evidence of brittle failure was observed, but rather a ductile process was noted. Discolouration behind the impact face gave evidence of high temperatures in this region, believed to be due to adiabatic heating as the material flowed across the impact face. The concave nature of the impact face after recovery showed that the material had relaxed after the loading had been removed, mostly likely due to the viscoplastic nature of the material. [Copyright &y& Elsevier]