Authors: Sang Yeob Oh, Hyung Seop Shin

Abstract: The damage behaviors induced in a SiC by a spherical particle impact having a different material and size were investigated. Especially, the influence of the impact velocity of a particle on the cone crack shape developed was mainly discussed. The damage induced by a particle impact was different depending on the material and the size of a particle. The ring cracks on the surface of the specimen were multiplied by increasing the impact velocity of a particle. The steel particle impact
produced the larger ring cracks than that of the SiC particle. In the case of the high velocity impact of the SiC particle, the radial cracks were generated due to the inelastic deformation at the impact site. In the case of the larger particle impact, the morphology of the damages developed were similar to the case of the smaller particle one, but a percussion cone was formed from the back surface of the specimen when the impact velocity exceeded a critical value. The zenithal angle of the cone cracks developed into the SiC decreased monotonically as the particle impact velocity increased. The size and material of a particle influenced more or less on the extent of the cone crack shape. An empirical equation was obtained as a function of impact velocity of the particle, based on the quasi-static zenithal angle of the cone crack. This equation will be helpful to the computational simulation of the residual strength in ceramic components damaged by the particle impact.

1321

Authors: Kan Huang, Bao Chen Liu, Jian Guo Peng, Fu Huang

Abstract: The collapse surface of surrounding rock induced by the excavation has significant influence on the stability and supporting structures of deep-buried tunnel since located in high in-situ stress field. Based on the assumption of curved velocity discontinuity surface, the internal dissipated power along the surface was calculated in the framework of Power-Law nonlinear failure criterion. In considering the role of supporting forces, an objective function composed of external rate of work and the internal energy rate of dissipation was constructed by using the upper bound theorem of limit analysis, and the analytical expression of collapse surface was obtained with the help of variational calculation. The effect of parameters on the collapse surface was analyzed. It is found that the height and width of the collapse block increased with the rise of nonlinear coefficient *m,* which illustrate that the nonlinear coefficient *m* has significant influence on the shape of collapse block. In the limit state, the height and width of the collapse block increase with the growth of supporting pressure.

962

Authors: Yong Huang, Yue Dong, Xiao Ming Du

Abstract: Filling and solidification for aluminum alloy packing block in die casting were simulated by numerical simulation. Distribution and change of temperature field as well as velocity field were visualized. The desirable processing parameters can be obtained with pouring temperature of 620°C and mould temperature of 180°C as well as shot velocity of 4m/s. The qualified products were obtained on the basis of the optimized die-casting parameters.

2362

Authors: Tao Wang, Fang Li, Wen Li Yu, Jin Tao Wang, Tuo Wang

Abstract: In this paper, the damage patterns of the hexagonal aluminum honeycomb sandwich plate subjected to normal and oblique impact by spherical, cylindrical and cubic fragments at different velocities are simulated using LS-DYNA code. The damage patterns of the sandwich plate and the energy loss ratio of fragment are acquired. In normal and oblique impact for different shapes of the fragment, the damage patterns of the sandwich plate include the plastic deformation, the fracture and the perforation of the face sheet and the tearing of the core or the combination of them. The curve of energy loss ratio waves with the velocity of fragment. And the peak point at the curve of energy loss ratio versus the velocity of fragment denotes the limit velocity of fragment. Furthermore, the energy loss ratios of fragments in oblique impact at the velocity of 500 m•s-1 with the angle of impact of 5°, 10°, 15° and 20° are obtained. The results denote that a fragment with large ratio of length to diameter is easy to perforate the sandwich plate both in normal and oblique impact.

364

Authors: Wei Gao, Lei Zhang

Abstract: In inertial navigation system, gyro is used to measure the angular velocity of carrier relative to inertial space for achieve attitude matrix updated in real time. Gyro difficult to eliminate the error, results in strapdown inertial navigation system precision decrease with time. Star sensor is a high-precision attitude measuring instrument and don’t require any priori information, the attitude date can be provided by star sensor. Thus, gyro is simulated by star sensor in order to improve the precision of strapdown inertial navigation system.

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