Papers by Author: Ruo Ze Xie

Abstract: Compression experiments of spruce along axial, radial and tangential loading directions are implemented by INSTRON equipment. Mechanical properties of spruce along three directions are gained. Spruce microscopic cell failure modes under axial, radial and tangential compression condition are observed by scan electron microscope. Results show that failure modes of spruce are fiber buckling and wrinkle when loading direction is along the grain. When loading direction is along radial or tangential across to the grain, failure modes are wood fiber slippage and delamination. Theory analytic solution to single wood cell failure under different direction compression is done. The obtained expression shows that mean limit loading is relative to yield stress, cell structure dimension and wrinkle length for complete wrinkle cases.

Abstract: The curves of stress versus strain along spruce wood axial, radial and tangential directions are gained by static compression experiments. Moisture content and density of the spruce wood are 12.72% and 413 kg/m³ respectively. The results indicate that spruce compression process includes elastic, yield and compaction phases. Failure modes of spruce subjected to axial compression are fiber buckling and wrinkle. And failure modes under radial or tangential compression are wood fiber slippage and delamination. Axial compression yield strength is about nine times as that of radial and tangential compression. Radial and tangential compression yield strengths are almost equal. Energy absorption efficiency and ideality energy absorption efficiency of spruce along different loading directions are analyzed. And theory analytic solution to single wood cell buckling under axial compression is done. The obtained expression shows that the mean limit loading is relative to yield stress, cell structure dimension and wrinkle length for complete wrinkle cases.

Abstract: Numerical simulation on container cushion behavior in three impact loading directions is implemented in the present work. The results show that the energy absorption abilities are different in axial, radial and tangential loading directions. For certain deformation condition, energy absorption in axial loading is the most. And energy absorption abilities along radial and tangential loading are nearly equal. For certain energy absorption quantity, the deformation in axial loading is the least and the deformations in radial and tangential loading are larger. It can be concluded that wood grain should be perpendicular to protected object for low velocity, small energy absorption case. And wood radial or tangential direction should be perpendicular to protected object for high velocity, large energy absorption case.

Abstract: In this work the static and dynamic properties of vanadium alloy V-5Cr-5Ti over a wide range of temperature from 20 to 1000 degree at strain rates ranged from 10-4/s~103/s were studied experimentally under uniaxial quasi-static tension with MTS universal testing machine, uniaxial dynamic compression and tension with split Hopkinson bar system with temperature control. The stress-strain curves of V-5Cr-5Ti at various temperatures and various strain rates were obtained. Experimental data show that V-5Cr-5Ti behaves strain-rate sensitive and temperature dependent, for instance the material parameters yield stress, tensile strength and failure strain. And fracture mode of the material is also dependent on strain-rate and temperature. Based on experimental data the temperature-rate-dependent constitutive relations were established in the form of Johnson-Cook and Cowper-Symonds models which are widely used in numerical simulation of dynamic processes of structures under impact loading. The material microstructures and failure modes were analyzed using optical microscope, TEM etc, and results shows that the yield stress and strength are increased with strain rate. The brittle-ductile transition strain-rate is from 101/s to102/s.

Abstract: For researching the terminal ballistic effect of the Fragment Simulation Projectile (FSP), the experiments that A3 steel cylindrical projectiles of 25mm diameter impacting 45 steel plates are conducted. The intensity of A3 steel is less than that of 45 steel. In the velocity ranges of 200m/s～ 800m/s, Taylor impact, petal-cap failure of Sunflower alike and plugging perforation are observed, respectively. Complicated material failures of projectile and target conflict with the various penetration mechanisms.