Papers by Keyword: SHPB

Abstract: Studying the dynamic properties of a material are an important method to understand the dynamic processes and deformation mechanism of material at different working conditions, particularly at high strain rate. The constitutive equation of a material has the highest significance to represent the mechanical properties, and is the principal research basis for the numerical simulation. In this paper, an important titanium alloy TC11 was studied through the quasi-static tensile test and the split Hopkinson pressure bar (SHPB) tests. Dynamic compressive behavior of TC11 alloy was discussed. Moreover, this paper gave the constitutive model of TC11 alloy and established the Johnson-Cook (J-C) constitutive equation.

Abstract: In this paper the NHDMOC method which succeeded in studying stress wave propagation with one dimensional strain was applied to study the one-dimensional stress wave propagation. In this paper, the ZWT nonlinear visco-elastic constitutive relationship with 7 parameters to NHDMOC, and corresponding equations were deduced The equations was verified from the comparison of elastic stress wave propagation in SHPB with elastic bar and visco-elastic bar respectively. Finally the dispersion and attenuation of stress wave in SHPB with visco-elastic bar was studied.

Abstract: 7075-T651 aluminum alloy are widely used in aeronautical applications such as wing panels, but there is no corresponding constitutive model for it now. In this paper, the flow behavior of 7050-T651 aluminum alloy was investigated by Split Hopkinson Pressure Bar (SHPB) and quasi-static compression experiment system. The strain hardening parameters were obtained by quasi-static compression experiment data, and the strain rate hardening parameters at various strain rates (1000-3000s^-1) and room temperature, and the thermal softening parameter at various temperatures (20-300°C) where strain rate is 3000s^-1 were obtained by SHPB experiment data. Then the constitutive equation of 7075-T651 aluminum alloy is obtained based on Johnson-Cook constitutive equation model.

Abstract: The dynamic fracture behavior of 7075-T6 aluminum alloy was studied by finite element method to simulate a cracked three-point bending specimen loaded by stress wave loading. In order to determine the elastic-plastic dynamic fracture toughness using quasi-static fracture mechanics theory, the nominal load measured by Hopkinson pressure bar loaded fracture testing system was input into a finite element program to calculate the loading point displacement, and then this displacement was employed to obtain the load-displacement field in the vicinity of the crack tip without the inertia effect, the variation of J-integral as a function of time was established using the load-displacement parameters determined by finite element analysis. The critical J-integral corresponding to crack initiation time detected by a small strain gauge mounted on the three-point bending fracture specimen is determined as an elastic-plastic dynamic fracture toughness (JId). The comparison between the equivalent dynamic fracture toughness(KId) given by the aforementioned procedures and the value measured in previous studies was made to verify the validation of the proposed procedure.

Abstract: The effect of steel, copper and aluminum interlayer on the stress wave propagation of ceramic/ Ti6Al4V armors were studied by traditional Split Hopkinson Pressure Bar system in this paper. Based on the SHPB experimental results, the stress wave propagation mechanism and energy absorption in tri-layered structure were discussed. Compared to ceramic/Ti6Al4V structure without interlayer, the steel, copper and aluminum interlayer could attenuate the transmission stress level and greatly increase the energy absorption of the structure. Due to the high acoustic reluctance of steel and copper interlayer, the reflected shock wave was in compressed situation and extended a tri-axial compressive stress within the ceramic which could improve the anti-penetration properties of ceramic plate. The numerical modeling studies of ballistic testing were carried on, and then the energy densities were compared. The results showed the steel and copper interlayer could increase the energy absorption of ceramic and improve the anti-penetration of ceramic plate. The three kinds of interlayer structures all could attenuate transmitted energy and decrease the residual penetration.

Abstract: Combined with strain gauge measurement method, the modified split Hopkinson pressure bar was adopted to investigate the behavior of normal concrete and steel fiber reinforcement concrete exposed to 400°C and 800°C under axial impact compressive loading. The experimental results show that compared with normal temperature, the compressive strength and elasticity modulus of normal concrete exposed to 400°C and 800°C decrease obviously. The transformation of concrete exposed to high temperature in microstructure is analyzed by SEM. The influence of high temperature on macro mechanics performance is discussed.

Abstract: Combination of different materials used in the liner of the shaped charge is of great importance in designing for maximization of energy transfer. In general, a Cu liner is widely used for the special purpose in military as well as in industry. The reactive Cu liners require excellent mechanical properties and reactivity of the energetic materials. Pure Al powders are widely known as energetic materials. In this regard, the integrated work was done based on the three procedures. First, the kinetic-sprayed Al coating was fabricated on Cu substrate to generate a reactive Cu liner. And the reactivity, bonding and mechanical properties of kinetic-sprayed Al coatings were investigated. Second, the experimental evaluation of kinetic-sprayed Al coatings in terms of the strain rate. Finally numerical modeling and simulation were carried outand discussed for visibility validation.

Abstract: For analyzing the effects of specimen-dimension on dynamic behaviors of fiber-reinforced composites, 4 kinds of CFRP specimens for different dimension were designed and made. The compressive loading tests were conducted by Ф 37mm split Hopkinson pressure bar (SHPB) system. The results show that the dynamic compression effects of specimen-dimension were exposed. An amount of Fiber-reinforced units inside the compressed area of the fiber-reinforced composites, then the experimental data are veracious for the material.

Abstract: Effect of strain rate on mechanical properties of pure iron was studied by compression experiments using Gleebe-1500D thermal simulation testing machine and Split-Hopkinson Pressure Bar, indicating that pure iron only has strain rate hardening effect. Adiabatic temperature rise tends to increase with increasing the strain rate. Work hardening effect is also analyzed. It found that there are only two work hardening regions in static stage (10^-3 to 1 s^-1) while there are three work hardening regions in dynamic stage (650 to 8500 s^-1). It is on account of onset of twining at high strain rates.

Abstract: Laser shock wave oscillation caused by lateral inertia effects of Hopkinson bar in large-diameter SHPB apparatus, and the geometry dispersion effect, particularly, the rise time of the stress wave in different diameters and lengths of Hopkinson bar were investigated. The three-dimensional model of member bar is established by the finite element analysis software ABAQUS, and the different shapes pressure pulses including rectangular, triangular and Gaussian pulses induced by laser shock have been loaded on the end face of the bar, respectively. Results indicate that the triangle pressure pulse and Gaussian pressure pulse show less dispersion effect than rectangle stress pulse on wave shape, and Gaussian stress pulse can keep the morphology better and reduce the dispersion effect more effectively than triangle stress pulse in the propagation process. In addition, as the bar diameter increases and the distance of the propagating stress wave raises, wave oscillation enhances significantly in the bar, the same as the rise time of stress wave increases gradually and the maximum stress also has a certain degree of attenuation, which have influence on laser shock processing or forming.