Please wait a minute...
All
Member of CSTAM
 
 
Dynamics>>More
Table of Content
15 April 2012, Volume 34 Issue 2
For Selected: Toggle Thumbnails
    Around the mechanics
    A SURVEY OF AUTONOMOUS NAVIGATION FOR DEEP SPACE EXPLORATION
    LI Junfeng, CUI Wen, BAOYIN Hexi
    2012, 34(2):  1-9.  doi:10.6052/1000-0879-20120201
    Abstract ( 1954 )   PDF (3364KB) ( 1029 )  
    Due to the advantages of reducing the burden of ground station support, enhancing the viability and expanding the special application of spacecraft, autonomous navigation has been successfully validated and begun to apply in foreign deep space missions. It will be a key technology for deep space missions in future. As the lack of ground station tracking resources, the development of autonomous navigation will become more important for Chinese deep space exploration program. Based on the upcoming Chinese Mars mission and asteroids mission, the application and development of autonomous navigation for deep space mission is reviewed and analyzed. Then, the optical sensor used in autonomous navigation system of different deep space mission is recapitulated. Finally, according to the asteroids based optical autonomous navigation of "Deep Space 1" mission, the critical techniques associated with its study of autonomous navigation are summarized.
    THE APPLICATIONS OF SHAN-CHEN-TYPE LATTICE BOLTZMANN METHOD IN MICROFLUIDICS SIMULATION STUDY
    ZHANG Renliang, DI Qinfeng, WANG Xinliang, DING Weipeng, GONG Wei
    2012, 34(2):  10-18.  doi:10.6052/1000-0879-20120202
    Abstract ( 2024 )   PDF (3154KB) ( 953 )  
    In a numerical simulation of microscale flow, it is difficult to reasonablly handle the interaction between microscopic particles and to improve computational efficiency. This paper discusses the Shan-Chen-type lattice Boltzmann method and its implementation. The applications of the model in various microfluidic situations are reviewed, and the effectiveness of the model is analyzed. The simulations show that Shan-Chen-type lattice Boltzmann method is easy to be implemented with the micro force and has capability and efficiency in computational microfluidics, and its applications are prospected. At the same time, because of easiness in dealing with wettability boundary, Shan-Chen-type lattice Boltzmann method has experienced tremendous advances in microstructure simulation with slip effect.
    2012, 34(2):  19-23.  doi:10.6052/1000-0879-20120203
    Abstract ( 1438 )   PDF (1355KB) ( 682 )  
    The finite integral method is a numerical solution by which Brown and Trahair analyzed some differential equations. The kernel mechanism of the finite integral method is how to calculate z = z(x) numerically when some values of z′ = z′(x) are known. Function z′ = z′(x) is the derivative of z = z(x). Essentially, the deflection calculation by curvatures φ is a mathematical process to calculate z from z″. Based on the relations between z-z″ and z′-z″ in the finite integral solutions, the deflection-curvature matrix is derived by matrix operations, and the curvature-deflection equation is derived by the relation φ = - z″. The curvature-deflection equations for some kinds of common boundary conditions are discussed. The finite integral solution for deflections of structures with complicated distribution of curvature is obtained.
    2012, 34(2):  24-28.  doi:10.6052/1000-0879-20120204
    Abstract ( 1151 )   PDF (1522KB) ( 787 )  
    This paper numerically analyzes the effects of elastic modulus, yield stress and elongation percentage on the post-buckling of spherical-cone diaphragms for positive expulsion tanks based on orthogonal tests. With orthogonal tests, the number of tests is greatly reduced, without affecting the validity of results. Numerical results are as follows: according to the specific diaphragm considered in the paper, its elastic modulus and yield stress have a marked effect on its post-buckling, while the elongation percentage hardly affects the post-bucking of the structure. The top node displacement of diaphragms increases with the increase of the elastic modulus and the decrease of the yield stress. As a result, large elastic modulus, small yield stress and about 20% of elongation will be optimal for diaphragm expulsion.
    2012, 34(2):  29-33,28.  doi:10.6052/1000-0879-20120205
    Abstract ( 1283 )   PDF (1738KB) ( 843 )  
    The analytical solutions of plates, based on deflection shape functions of beams in form of separation of variables are proposed. Several typical examples are given to validate the present method. The results from the present method agree with those obtained by FEM. This indicates the accuracy of the method, and its applicability in solving special-shaped plates. Instead of those of ordinary beams, the deflection shape functions of beams on elastic foundation are used in the method, which can simulate the more complex deformation of plates better. This research provides a simple and convenient tool for analysis of plate deformations.
    2012, 34(2):  34-37,53.  doi:10.6052/1000-0879-20120206
    Abstract ( 1090 )   PDF (1464KB) ( 644 )  
    This paper studies the deformation mechanism and the damage features of the large-section roadway surrounding rock under the conditions of soft rock, to determine reasonable and effective supporting forms and parameters, with the large-section gate of Gaojialiang coal mine as an example. Based on the roadway section shape and size, using the site monitoring and numerical simulation methods, the anchor, the net and the cable combined supporting system are designed. The results show that the supporting forms and parameters are effective to control the deformation of the surrounding rock, and the supporting is good, economic, reasonable, and reliable; the supporting system provides a basis for similar projects and some new ideas for resolving the difficult problems of large surrounding rock deformation and of poor stability, in supporting the soft rock roadway.
    2012, 34(2):  38-42.  doi:10.6052/1000-0879-20120207
    Abstract ( 1101 )   PDF (1654KB) ( 809 )  
    The flexural property of RC beams with high-strength steel wire mesh and polymer mortar overlay is analysed, and a unified formula is proposed for design of strengthened beams made of different materials. It is shown that the ultimate flexural capacity and the crack resistance property of the strengthened beam are greatly influenced by the initial stress state of the original beam and the U-style strengthening. An ultimate flexural capacity calculation formula for the RC beams with high-strength steel wire mesh and polymer mortar overlay is obtained by the limit equilibrium method on the normal section. Based on the concrete structure design codes, modified calculation formulas of crack width and crack space are obtained. The calculation results agree well with the test values.
    2012, 34(2):  43-48.  doi:10.6052/1000-0879-20120208
    Abstract ( 1159 )   PDF (2086KB) ( 596 )  
    In view of the importance of the permeability of top coal to the safety of the working face of fully mechanized caving mining, the variation of the permeability of top coal is studied and analyzed in the limit equilibrium zone. Vertical and horizontal strains are determined through damage mechanics and mathematical statistics with a mathematical model. The relationship between the volume strain and the permeability of coal is determined with the method of the triaxial compression test. The fluid used in experimentation is methane. The piecewise fitting is used to analyze the experimental data. The results show that according to the mathematical model for the volume strain, the volume strain at any point of top coal can be obtained. The horizontal strain of top coal is not related with the distance from the calculated point to the coal floor. The permeability at any point of top coal can be obtained from the relationship between the volume strain and the permeability. The relationship is obtained through test and fitting. The computing model is checked in practice.
    2012, 34(2):  49-53.  doi:10.6052/1000-0879-20120209
    Abstract ( 1212 )   PDF (1536KB) ( 640 )  
    A novel fluid-type floating raft vibration isolator based on anti-resonance principle is designed in this paper. The mathematical model of the floating raft is built based on the fluid momentum equation and the vibration theory. The isolation behavior of the floating raft is analyzed. The relationship between the optimum isolation frequency and the immersed depth of the floating body is obtained. It is found that the anti-resonance occurs over a wide band from lower to higher frequencies with the immersed depth of the floating body in a limited range. Utilizing the anti-resonance, the force transmissibility of the fluid-type floating raft can be reduced at very low levels. The raft enjoys an excellent performance of vibration isolation especially for low frequency vibrations.
    2012, 34(2):  54-57.  doi:10.6052/1000-0879-20120210
    Abstract ( 1147 )   PDF (1204KB) ( 516 )  
    A formula of the self-rotating kinetic moment is derived theoretically for the self-cleaning and rotating steel spiral with plastic coat. The moment is proportional to d (spiral wire diameter), sin2α (α: the helical angle), D2 (D: the spiral O.D), u2 (u: the flow velocity) and ρ (fluid density). The results of the formula agree with experimental results. Therefore, the formula can serve as the theoretical foundation in optimal design of the steel spiral with plastic coat. The spiral is thick with coat but the experiment results show that the flow resistance is still in the range of the general industrial limitation.
    Around the mechanics
    2012, 34(2):  58-60,63.  doi:10.6052/1000-0879-20120211
    Abstract ( 856 )   PDF (1136KB) ( 889 )  
    To avoid the repeated mechanical experiments to determine the mechanical strength of wheat straw stalk, the neural network technology is adopted to build the prediction model for the mechanical strength of wheat straw stalk using neural network multiple geometric parameters. The prediction results show that the method is effective.
    2012, 34(2):  61-63.  doi:10.6052/1000-0879-20120212
    Abstract ( 1225 )   PDF (805KB) ( 885 )  
    Experiments are carried out to obtain transfer functions for torsional vibration absorber (TVA). The natural frequencies of TVA are deduced for different test methods. The calculation results of different test models are compared with accurate values, and good agreements are found.