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In this paper, Split Hopkinson Bar technique was used to investigate the shear behaviour of adhesively bonded assemblies at high rates of loading. New sample geometry was adopted so that the compressive wave is transformed in a shear loading in the sample. Samples are conditioned at 20°C and 50% of hygrometry to eliminate any interference with temperature and humidity effects. The new technique is applied to an assembly built with a cyanoacrylate based adhesive and a metallic (Steel) adherent. They are found to be highly rate sensitive.

To estimate the strain rate dependence of the dynamic flow stress of aluminum alloys, 2017-O and - T4, high strain rate and rate reduction tests are performed at strain rates ranging from about 1000/sec to 30000/sec. A steep increase in the flow stress is observed for 2017-O at the strain rate of about 3000/sec. For 2017-T4, the above phenomenon is observed at the strain rate above about 10000/sec. A simplified model for dislocation kinetics under dynamic plastic deformation is employed which can represent a transition in the rate controlling mechanism of dislocation motion from a thermally activated process to a viscous drag. It is expected that the steep increase in the flow stress observed at high strain rates is attributed to the rate dependence of the viscous drag on the dislocation motion.

The strain hardening part of the Preston-Tonks-Wallace (PTW) model, developed for the description of the plastic constitutive behavior of materials at wide ranges of strain, strain rate, and temperature, has been modified by employing the Voce equation. The prediction capability of the modified PTW (MPTW) has been investigated with reference to Taylor impact test results in the literature, and comparison has been made with the models of Johnson-Cook (JC), Steiberg-Guinan (SG), Zerilli-Armstrong (ZA), and PTW. Of the compared existing models, no model was appropriate for describing the results of various Taylor impact tests. However, the modified PTW is shown to predict fairly accurate results in terms of the length, diameter, and shape of the deformed specimen tested at different temperatures and impact velocity.

The grain size of as-extruded AZ31 magnesium alloy was refined by isothermal annealing pretreatment through orthogonal experiment. By using the Gleeble-3800 thermal simulator, the compression superplasticity of as-extruded AZ31 magnesium alloy was studied. The high strain rate superplastic compression was realized. The process parameters of the superplastic compression were established and the mechanism of the superplastic deformation was analyzed. The effects of deformation temperature and strain rate on the superplastic flow were investigated. The results indicated that at 250°C–300°C and strain rate at 1×10^-2s^-1, the true strain values were all more than 2.03. As the temperature was 300°C and the strain rate was 1×10^-2s^-1–1×10 s^-1, the true strain values were all more than 2.18. The results showed that the as-extruded AZ31 magnesium alloy being refined presented good compression superplasticity. The main mechanism for the superplastic compressive deformation of the as-extruded AZ31 magnesium alloy was grain-boundary sliding, meanwhile, dynamic recrystallization also played a harmonious role during the superplastic deformation.

At high strain rates, the dynamic response of cement mortar, a heterogeneous material with damage, was experimentally studied under three different stress states: (1) one-dimensional stress state by using the SHPB technique, (2) one-dimensional strain state at high pressures from 1 to 5 GPa by using a one-stage gas gun, and (3) quasi one-dimensional strain state by using an improved passive confining SHPB technique. The experimental results indicate that cement mortar is a kind of nonlinear rate-dependent material with internal damage evolution, and that the confining pressure greatly influences its ductility and strength. The main results are given and discussed.

A plasticity-based approach has been proposed for reinforced concrete (RC) subjected to impact and blast loading. The proposed approach includes a new failure surface together with modified descriptions related to equation of state, strain rate effect and damage taken from literature. These selective descriptions in numerical analysis have been found to give better results than the existing models. A user-defined UMAT subroutine for the commercial software LS-DYNA has been developed for the proposed model. Dynamic analysis for both blast and impact type of loading on RC slabs are performed. The results are compared with an in-built material model in commercial software LS-DYNA, namely the Winfrith concrete model (WCM) and with experimental results taken from literature. A parametric study is carried out by analyzing the mechanical and damage response by varying parameters such as concrete strength, slab thickness and reinforcement ratio. The proposed approach is found to be effective in predicting the behavior under both impact and blast analysis.

Strain rate is essential in study of the physics of fluids and solids undergoing deformation. State-of-art high strain rate tests have mainly been in macro-scale with an upper limit of $10^8{\mathrm{\text{s}}}^{-1}$. A graphene-based layered system is proposed to conduct nanometer-scale high strain rate testing. The process is investigated by molecular dynamics simulations. Accelerated single ion or group of ions are used to impact on the proposed system to generate ballistic or plate-like impact scenarios. The effects of impact energy, shape of impact absorber and the impaction location are investigated. The graphene layer is the key of the proposed system to spread the load and protect the sample. The results indicate that ion group and single ion impacts produce strain rates of $5.0$–$5.2\times 10^{11}{\mathrm{\text{s}}}^{-1}$ and $0.9$–$1.2\times 10^{11}{\mathrm{\text{s}}}^{-1}$, respectively. Ion group impact produces a more significant signal than single ion impact on the sensing nano-layer in the system. The ultimate strength of an Al-Cu alloy sample during ion impact is estimated to be 215MPa to 251MPa, significantly lower than predicted by the Johnson–Cook model because of the rapidly increased temperature and melting in the sample. The results demonstrate new possibilities for understanding high strain rate effects at nano-scale.

The present work investigates the novel impact loading response of two-dimensional graphene oxide (GO) reinforced epoxy nanocomposites at high strain rate. The testing was performed up to 1000s${}^{-1}$ of high strain rate, where maximum damage occurs during the impact loading conditions. The Split Hopkinson Pressure Bar (SHPB) was used for the impact loading of the composite specimen. The nanofiller material GO was synthesized by chemical oxidation of graphite flakes used as the precurser. Synthesized GO was characterized using FTIR, UV-visible, XRD, Raman Spectroscopy and FE-SEM. Solution mixing method was used to fabricate the nanocomposite samples having uniform dispersion of GO as confirmed from the SEM images. Strain gauges mounted on the SHPB showed regular signal of transmitted wave during high strain rate testing on SHPB, confirming the regular dispersion of both the phases. Results of the transmission signal showed that the solution mixing method was effective in the synthesis of almost defect-free nanocomposite samples. The strength of the nanocomposite improved significantly using 0.5wt.% reinforcement of GO in the epoxy matrix at high strain rate loading. The epoxy GO nanocomposite showed a 41% improvement in maximum stress at 815s${}^{-1}$ strain rate loading.

Mechanical properties tests of quenched hot stamping panel under six strain rate were carried out in this paper to investigate its failure mode combination with microscopic microstructure. Test showed that: In the six strain rate, elastic modulus of the material has no significant changes in the yield strength, the tensile strength increased with increasing strain rate, the materials uniform elongation declined with increasing strain rate after the first rise occur, the angle between fracture direction and the parallel segments direction was 45°, subject to ductile fracture criterion, fracture showed significant orthogonal dimple.

The high strain rate tensile behaviors of epoxy resin filled with Polyaryletherketone (PAEK) powders have been studied on TS-1000 model high speed material apparatus under dynamic loading conditions. Stress-strain curves of epoxy resin system under high strain rate loading were obtained. The results of the study indicated that the fracture elongation and the tensile strength of epoxy resin casting system which toughened by the PAEK powders are higher than those of pure epoxy resin matrix at the strain rate of 3500/s.

The strain hardening part of the Preston-Tonks-Wallace (PTW) model, developed for the description of the plastic constitutive behavior of materials at wide ranges of strain, strain rate, and temperature, has been modified by employing the Voce equation. The prediction capability of the modified PTW (MPTW) has been investigated with reference to Taylor impact test results in the literature, and comparison has been made with the models of Johnson-Cook (JC), Steiberg-Guinan (SG), Zerilli-Armstrong (ZA), and PTW. Of the compared existing models, no model was appropriate for describing the results of various Taylor impact tests. However, the modified PTW is shown to predict fairly accurate results in terms of the length, diameter, and shape of the deformed specimen tested at different temperatures and impact velocity.