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Fan F.-L.,PLA Air Force Aviation University | Xu J.-Y.,PLA Air Force Aviation University | Xu J.-Y.,Northwestern Polytechnical University | Li W.-M.,Center South Airport Construction Company | Zhang J.,Airport and Barracks Office
Binggong Xuebao/Acta Armamentarii | Year: 2010

In order to study the dynamic constitutive relation of concrete, the impact compression tests on concrete were carried out with a 100 mm split Hopkinson pressure bar(SHPB)device. The dynamic stress-strain curves were obtained, and the experiment data was analyzed. Based on the test results and a kind of static constitutive model of concrete, i.e. the Ottosen model, considered the strain rate effect and damage weakening effect, a dynamic constitutive model for concrete was built. The parameters in the model were confirmed and the theoretical curves were compared with the test curves. It is concluded that there is obvious strain rate strengthening effect in the dynamic mechanics performances of concrete, there are approximate function relations among the dynamic strength increase factor DIF, the peak strain and the logarithmic strain rate, the method used to constitute the model is feasible, the constitutive model can be used to describe the impact mechanics behavior of concrete and can provide an important reference for further research and engineering application.


Xu J.,PLA Air Force Aviation University | Xu J.,Northwestern Polytechnical University | Lu X.,PLA Air Force Aviation University | Zhang J.,Airport and Barracks Office | And 2 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2010

Dynamic mechanical performance experiments were carried out for three types of rocks under different confining pressures and cyclical impact loadings by using split Hopkinson pressure bar with confining pressure device. The stress-strain curves of specimens under cyclical impact loadings were obtained. According to theoretical analysis, a determinant criterion of damage degree of rock was established; and the accumulative specific energy absorbency was defined to describe energy properties of rock dynamic damage. The studies of the relationships among damage degree of rock, accumulative specific energy absorbency and confining pressure under cyclical impact loadings show that accumulative specific energy absorbency could well describe the damage degree of rock. When the confining pressure increases gradually, the incremental tendency of damage becomes slow along with the accumulative specific energy absorbency, i.e., the higher the confining pressure is, the more energy for rock to reach the same damage level is needed. The formulae of rock damage degree and accumulative specific energy absorbency are put forward under confining pressures. When the damage threshold is reached, the growth rate of accumulative specific energy absorbency of sandstone is the largest along with the increase in confining pressure, the rate of sericite quartz schist is the smallest, and the rate of plagioclase amphibolite is between ones of sandstone and sericite quartz schist.


Liu J.-Z.,PLA Air Force Aviation University | Xu J.-Y.,PLA Air Force Aviation University | Xu J.-Y.,Northwest University, China | Lv X.-C.,Airport and Barracks Office | And 2 more authors.
International Journal of Nonlinear Sciences and Numerical Simulation | Year: 2012

In order to investigate rock dynamic mechanical properties of amphibolites, sericite-quartz schist and sandstone under the different strain rates varying from 30 s -1 to 150 s -1, the specimens were subjected to axial impact at different projectile speeds by using the split Hopkinson pressure bar (SHPB) of 100 mm in diameter. The optimal experimental size of rock samples is verified by analyzing the stress equilibrium of cylindrical rock samples in different thicknesses. It has studied the mechanic properties of these three rocks which under impact loadings; and analysed the dynamic compressive strength, failure modes, energy dissipation variation with the strain-rate and the strain-rate hardening effect from the perspective of material microstructure. Experimental results show that the dynamic Young's modulus of rock samples increase with strain-rate slightly. The dynamic failure modes of different rock samples are always different. When at a lower strain-rate, the damage of sandstone takes a peeling off the external radial tensile failure mode, but that of amphibolites takes axial splitting mode; when at a higher strain-rate, sandstone takes granular crushing failure mode, and that of amphibolites and of sericite-quartz schist take massive crushing mode. Significant strain-rate effect can be represented by a linear relation between the specific energy absorption and the strain-rate ε̇, or between the dynamic strength increase factor η and ε̇ 1/3. © 2012 by Walter de Gruyter Berlin Boston.


Liu S.,PLA Air Force Aviation University | Xu J.,PLA Air Force Aviation University | Xu J.,Northwest University, China | Liu J.,PLA Air Force Aviation University | Lu X.,Airport and Barracks Office
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

By using the hydraulic and servo-controlled pressure testing machine and the split Hopkinson pressure bar(SHPB) testing apparatus of 100 mm in diameter, which is improved by pulse shaping technique, the experimental tests of sericite-quartz schist and sandstone with strain rate varying from 50-160 s-1 under shock compression loading are carried out to study the quasi-static mechanical properties and relationship among wavy curves, dynamic compressive strength, specific energy absorption and strain rate effect of fracture forms of the two rocks. The experimental results show that the dynamic compressive strength, specific energy absorption and fracture forms of sericite-quartz schist and sandstone have significant correlation with strain rate. However, there is no significant correlation with strain rate can be seen for elastic moduli of the two rocks. The dynamic mechanical comparison results of sericite-quartz schist and sandstone show that sandstone is more sensitive to strain rate than sericite-quartz schist. In the sight of microstructure characteristics and energy absorption of sericite-quartz schist and sandstone, dynamic fracture process is analyzed;and crucial factors influencing the characteristics of fracture are discussed. The research method and conclusions can provide references for analyzing dynamic mechanical behavior of other kinds of brittle materials.


Ren W.,PLA Air Force Aviation University | Xu J.,PLA Air Force Aviation University | Xu J.,Northwest University, China | Zhang Z.,Airport and Barracks Office | Zhu J.,PLA Air Force Aviation University
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2014

The deformation properties of basalt fiber reinforced concrete(BFRC) after exposure to different temperatures and subject to impact loading were investigated by using a 100mm diameter split Hopkinson pressure bar(SHPB) apparatus. The experimental results indicate that with the rise of temperature and impact velocity, the crushing degree of BFRC becomes greater and stress-strain curves exhibit plasticity features. Under the same temperature, the peak strain and average strain increase with increase of average strain rate with obvious strain rate dependency. Under a fixed impact velocity, an increase in temperature results in a larger peak strain and average strain and enhances the strain rate sensitivity of peak strain, but after exposure to 200℃, the average strain of BFRC under a lower impact velocity is lower than that at room temperature. The addition of basalt fiber can efficiently improve the deformation performance of BFRC after exposure to elevated temperatures, and the impact deformation capability of BFRC is the best with 0.3% basalt fiber(volume fraction), but under lower temperature and impact velocity, the average strain of BFRC is lower than that of plain concrete. ©, 2014, Tongji University. All right reserved.


Xu J.-Y.,PLA Air Force Aviation University | Xu J.-Y.,Northwestern Polytechnical University | Lu X.-C.,PLA Air Force Aviation University | Zhang J.,Airport and Barracks Office | And 2 more authors.
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2010

Dynamic mechanical performance experiments were carried out for amphibolite specimens under cyclical impact loadings by using the SHPB. The changes of characteristics of stress-strain curve with the variation of cycles number of impact load were analysed and the relationships among dynamic modulus, strain rates and confining pressures were discussed. It is demonstrated that the Young's modulus of amphibolite decreases along with the increase of cyclies number of impact load, under certain confining pressure and impact loading. The normal stress on rupture surface will be enhanced with the increase of confining pressure, and white rock powder will come forth on the rupture surface under the action of cranny friction and slippage. When the rock specimen being shattered, with the same accumulative absorption energy, the higher the confining pressure, the smaller the total area of rupture. Energy absorbency ratio increases with the augment of strain rate, and decreases with the augment of confining pressure. The expressions were put forward for illustrating the relationships among energy absorbency ratio, strain rate and confining pressure.


Liu J.-Z.,PLA Air Force Aviation University | Xu J.-Y.,PLA Air Force Aviation University | Xu J.-Y.,Northwest University, China | Lu X.-C.,Airport and Barracks Office | And 3 more authors.
Gongcheng Lixue/Engineering Mechanics | Year: 2012

In order to test the impact mechanical properties of rock, the amphibolites are subjected to impact loads with different confining pressures (0 MPa-6 MPa) and strain rates (50 s -1-170 s -1) by using the improved SHPB of 100 mm diameter. The SHPB has confining pressure device. Experimental results show that under the same confining pressure, the dynamic compressive strength of amphibolites are strain-rate dependent, and the strain-rate effect can be expressed by linear approximations, so the relationship between the dynamic increase factor and the logarithm of strain-rate is approximately linear. The strengthening effect gets more prominent with the increase of confining pressure at the same range of strain rates. The damage constitutive model of rock under dynamical load based on weibull distribution is established through combining statistic damage model and visco-elastic model. It is found that the theoretical curves and experimental curves are in good agreement, indicating the constitutive model is reliable. It can offer reference for further research on rock mechanical properties and engineering application in underground engineering.

Loading Airport and Barracks Office collaborators
Loading Airport and Barracks Office collaborators