Advanced Materials Research Vols. 211-212

Abstract: The prototype testing of penetration requires a large amount of manpower, material and financial resources. So computer simulation technoolgy is used to save the resource.The process of high-speed penetration is simulated based on nonlinear dynamic analysis software ANSYS/LS-DYNA, and especially the simulation process of ANSYS/LS-DYNA is stated. Firstly, the theoretical analysis of material model and state equation are completed in the process of simulation. And by using the post-processor LS-PREPOST of LS-DYNA, the effective stress curve and acceleration changing curve were obtained. Simulation results show that: JOHNSON_COOK material model is correct in solving the problem of high-speed penetration, and the stress of internal projectile is decreasing along the axial direction.

Abstract: Ceramic insulating tile is the main insulation material used on space shuttle thermal protection system at present, but this material has low strength, high brittleness and easy to be damaged. So the study of thermodynamic response of damaged rigid ceramic insulating tiles is very important. In this paper the temperature field and thermal stress field of the damaged ceramic insulating tiles under aerodynamic heating are simulated by ABAQUS code. The analyzed results indicate that the sharp degree of the damage shape has minor influence on the temperature field, but is more significant for the maximum thermal stress. Meanwhile the larger loading is, the bigger influence is.

Abstract: Preparation and performance testing methods of short carbon fiber reinforced wood(SCFRW) were briefly introduced and utilized. Mechanical properties and electric conductivity of SCFRW veneering sample boards were analyzed with carbon fiber and woodiness fiber in different quality ratios, moreover, conductivity models were put forward according to the temperature influence on surface resistivity of composites. The experimental results showed that the performance of woodiness fiber boards were effectively improved by joining of carbon fiber, especially the modulus of elasticity. Meanwhile, it also endowed composites good electric conductivity, and nonlinear least squares fitting models was intuitively suitable for the negative effect relationship between surface resistivity and temperature, which provided basis and guidance for preparation and processes optimization of conductive woodiness functional composites.

Abstract: To further study the field of the mixed-mode interface crack tip under compression and shear, we analyze the problem on the quasi-static propagating of the interface crack theoretically and numerically.In this paper,we assumes that the artifical viscosity cofficient is in inverse proportion to power law of the plastic strain rate,and the stress of the interface crack possesses power law singularity. The viscosity of material,the friction touch effection of the crack-tip surface and the load hybrid parameter are considered. The asymptotic solution is established for elastic-viscoplastic field at the mixed-mode propagating crack-tip under comprission and shear.It is shown in numerical results and analysis that for the mixed-mode crack-tip field under compressing and shear is whole plastic without elastic unloaded section;viscosity effection is an important factor when propagating crack-tip field is studied; viscosity coefficient, mach number and singularity exponent are the control factors of singular field at the crack-tip.

Abstract: The present study applied genetic programming (GP) to estimate the slump flow of high-performance concrete (HPC) using seven concrete ingredients. GP optimizes functions and their associated coefficients simultaneously and is suitable to automatically discover complex relationships between nonlinear systems. The results demonstrated that GP generates a more accurate formula and has lower estimating errors for predicting the slump flow of HPC than multiple linear regressions (MLRs).

Abstract: The present study applied genetic programming (GP) to estimate the slump flow of high-performance concrete (HPC) using seven concrete ingredients. GP optimizes functions and their associated coefficients simultaneously and is suitable to automatically discover complex relationships between nonlinear systems. The results demonstrated that GP generates a more accurate formula and has lower estimating errors for predicting the slump flow of HPC than multiple linear regressions (MLRs).

Abstract: In order to reduce the production cost of Microbial Flocculation，this article uses the cheap straw-inorganic nitrogen medium，directly domesticated and screened out a stable and efficient microbial flocculant producing strain B-15，which has better flocculation on kaolin clay suspension system. Preliminary identify as bacillu, the strain produce flocculant has flocculating rate of 81.08% for suspension.

Abstract: Sight-stabilizing mechanisms controlled by diaphragm springs and other damping elements is an important subordinate system of airborne sight stabilizing System. The performances of sight-stabilizing system depend on the characteristics of kinematics and dynamics of the system in a great extent. Among various external moments acting on the rod of the manipulator, such as those moments caused by damper, positioning spring, and restoration spring, the forces by diaphragm springs are most obvious. According to the structure form and motion peculiarity, the rod can be equivalent to a rigid body turning around a fix point. Simulation results reveal that the moment of the restoration spring to the rod is proportional to the angular displacement, and that the moment is the most prominent factor influencing the operating performances among all these moments. Through reasonable adjustments of structural parameters of the restoration spring, the performances of the sight-stabilizing system can be improved greatly; the analysis method provides a basis for guiding the design of concerned structural parameters of sight-stabilizing system.

Abstract: In the same conditions, the transformer on-line monitoring and off-line chromatographic analysis should be consistent, but the actual on-line monitoring is effected by the ambient temperature to make it is different from the off-line chromatographic measurement. this paper analyzes the theory of oil-gas separation, and develops a gas-oil separation test platform first, conducts an experiment about the changes of temperature based on the device, and then compares with the data of off-line measurement, gets the law of temperature affection on the oil-gas separation process, Finally gives the reason of influence of ambient temperature on oil-gas separation in on-line monitoring.

Abstract: DC-DC converters have some inherent characteristics such as high nonlinearity and time-variation, which often result in some difficulties in designing control schemes. RBF neural network sliding-mode control method is applied to PWM-based DC-DC converters in this paper. As the control input is duty cycle, the control inputs are in the scopes between 0 and 1. A general RBF neural network can not be suitable to control the PWM-based DC-DC converters, because the output layer of such network uses a linear function, and that the outputs of the network are between -∞ and +∞. Sigmoidal function is used instead of the output layer function in this paper to make the outputs are between 0 and 1. This sliding mode control method based on neural network can not only control the scope of the network output, but also eliminate the system chattering. Simulation experiments verify that this method can control the DC-DC converters well.