Papers by Keyword: SHPB

Abstract: The strength and deformation properties of carbon fiber reinforced concrete under different fiber volume loadings under impact loading were studied by using the ɸ100 mm split Hopkinson pressure bar (SHPB) test system. The results show that after the carbon fiber is added, the stress-strain curve of the specimen shows the platform section at the peak stress. The strength and peak strain of the concrete under the impact load increase first and then decrease with the increase of the carbon fiber volume. Trend, when the carbon fiber volume is 0.2%, the impact mechanical properties of concrete are significantly improved.

Abstract: In this paper, the effects of temperature and strain rate on the plastic deformation behavior of 5052 aluminum alloy were investigated by quasi-static tensile test and split Hopkinson pressure bar (SHPB) experiments. Meanwhile, the stress-strain relations obtained through these experiments were employed for calibrating Johnson-Cook (J-C) plastic flow constitutive parameters of 5052 aluminum alloy. The results show that the strain rate sensitivity of 5052 aluminum alloy is insignificant in the range of 0.001s^-1~3000s^-1, while temperature has a great effect on the material plastic behavior. The experimental data are basically consistent with the predicted outcome of J-C constitutive model.

Abstract: The dynamic compressive mechanical behavior of railway wheel steel at room temperature was investigated experimentally for strain rates up to ~2300/s, by using a split Hopkinson pressure bar (SHPB) apparatus. Experimental results indicate that the wheel steel exhibits an obvious strain rate-dependence; both yield strength and flow stress enhance with the increase of strain rate. Based on experimental data, an empirical dynamic constitutive model was used to describe the strain rate effect of wheel steel. These research results could provide reliable and accurate material constitutive parameters for wheel-rail impact simulations, to guide the design and assessment of the safety of the wheel-rail system.

Abstract: Finite element simulation of high speed machining of Ti6Al4V alloy was carried out based on the software of Abaqus. The Johnson-Cook constitutive model was chosen for the material of Ti6Al4V, the parameters of the model were obtained through the SHPB (Split Hopkinson Pressure Bar) experiment. The similarity of the chips obtained from the simulation and that obtained from the experiment indicated that the parameters of the Johnson-Cook constitutive model for Ti6Al4V alloy were reliable. Different cutting parameters and different tool geometric parameters were used in the simulations to find out their effects to the simulation results. Also a comparison was made between the results got form the simulations results and the experimental results, a good agreement between them indicated that the finite element simulation of high speed machining of Ti6Al4V is reliable, so it can be concluded that the finite element simulations of high speed machining can be widely used in practice to study the more about the machining process and reduce the experimental expenses.

Abstract: The SHPB loading three-point bending specimen is a popular way for measuring the dynamic fracture toughness of the material. The wedge shapes on the loading end of the incident bar have necessary effects on the propagation of the stress wave. The dynamic mechanical response and the fracture toughness of the aluminum alloy were measured by SHPB with different wedge shapes, and the influences of wedge shape on determination of dynamic fracture toughness was analyzed in this study. The investigation result can be used to provide reference for the design of a new Hopkinson apparatus for dynamic fracture testing.

Abstract: The effect of multi-wall carbon nanotubes and nanoSiO₂ content on physico-mechanical properties of glass microspheres-epoxy resin composite, designed for blast energy absorbing applications, was evaluated experimentally. Specific porous lightweight foam with high volume fraction of microspheres (70 vol.%) was prepared and modified by 1 to 5 vol.% of multi-wall carbon nanotubes and nanosilica (nanoSiO₂). Two types of microsperes with different wall thickness and strength were used. The quality of dispersion of nanoparticles was evaluated in relation to the mixing procedure using scanning electron microscope observation. The compressive and flexural strength tests were conducted at quasi-static load. The mixtures containing nanosilica exhibited an increasing trend in both flexural and compressive strength with increasing nanoparticle content up to 4 vol.%. The addition of carbon nanotubes also increased flexural strength (again up to 4 vol%, crossing this concentration, the significant drop was observed), whereas the compressive strength was affected at lower level. Nanoparticle modification is more effective in the foams with higher thickness and thus strength. The evaluation of test results showed that the properties of glass/epoxy foams can be tailored by adding nanoscale fillers.

Abstract: In this paper, the shock phase transformation of β phase in Ti-5Al-5Mo-5V-3Cr-0.5Fe (Ti-5553) was investigated. Split Hopkinson Pressure Bar (SHPB) and light gas gun were employed to investigate the dynamic properties under high strain rates from 1000s^-1 to 3500s^-1. Microstructure characterization was carried out by optical microscopy (OM), scanning electronic microscopy (SEM) and transmission electron microscope (TEM). The experimental results demonstrate that the Ti-5553 alloy with β phase exhibit no obvious strain rate hardening effect with the high strain rate from 1000s^-1 to 3000s^-1. However, compared with the quasi-static compression test results (10^-3s^-1), this alloy shows an evident strain rate hardening effect, with the yield strength significantly improved. Second time loading indicates light gas gun dynamic tensile loading and then SHPB dynamic compression loading in Ti-5553 alloy with β phase. The results show that the shock-induced β to αʺ martensite phase transformation dramatically influences the postshock mechanical properties of these alloys. The yield strength of this alloy decreased after the shock wave effect of light gas gun, its ductility increasing. Higher shock pressures yielded an increased dislocation density and a gradual increase in the yield strength. Adiabatic shear band (ASB) exists in second time loading Ti-5553 alloy under 10³s^-1 strain rate. SHPB loaded the alloy: The results show that the Ti5553 alloy with β phase is adiabatic shear failure in high strain rate (3000s^-1).

Abstract: In this study, the strains of artificial rock were analyzed in order to estimate the deformation behavior of rock-like materials in the SHPB test. The axial strain measured directly from the strain gage and obtained from the process analysis of three-wave method were compared. The analysis results show that: (1) the measurements of dynamic strains of material obtained from the strain gage method are feasible; (2) the axial strains and strain rates analyzed from the strain gage records are less than those obtained from the three-wave method; (3) the dynamic/static deformation modulus ratio E_d/E_s has the increasing tendency with the raising of stress rate, and the modulus ratio obtained from the strain gage method is more than that obtained from the three-wave method.

Abstract: The paper used the numerical software of RFPA^2D-Dynamic to build the numerical simulation model of the Brazilian disk and study the initiation, propagation, coalescence of the crack and eventually fail through setting different compression stress waves, and analyzed the failure mechanism and process of the rock. The results showed: (1) With the increase of the stress rate, the tensile strengthen of the rock also increases and has a logarithmic growth. (2) Under the higher stress rate, the time of the damage, crack initiation, and coalescence are in advance comparatively. At the same loading time, the damage and failure scale are more obvious. (3) The failure model of the Brazilian disc is splitting along loading path and appears “V-shaped” failure zone at the contact area .

Abstract: In order to analyze the effect of RDX-based thermobaric explosive on strain rate, the stress-strain curves with different strain rates were measured by using the Split Hopkinson Pressure Bar (SHPB) and resistive strain testing technology. The different strain rates were obtained by changing the length to diameter ratio (L/D=0.46~0.92) and speed of the bullet (10~18m/s). The results showed that it is obvious to change the strain rate by the change of the L/D and speed of the bullet with different functional relationship; RDX-based thermobaric explosives have the evident strain rate: failure stress and strain are increased with the increase of strain rate.