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08 April 2010, Volume 32 Issue 2
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    Application study
    2010, 32(2):  32-34.  doi:10.6052/1000-0992-2007-221
    Abstract ( 1894 )   PDF (500KB) ( 871 )  
    In this letter, the model of elastic catenary is established by introducing a transformation parameter $u$ (${\rm sinh} u=\d y/\d x$), and the corresponding parametric equation is obtained. The tension of the mooring line in ocean engineering can be calculated by the model. The algorithm is simple and effective, and easy to program in computer language.
    2010, 32(2):  35-38.  doi:10.6052/1000-0879-2008-301
    Abstract ( 1314 )   PDF (607KB) ( 621 )  
    Traditional analyses of circular concrete tanks without prestressing suffer from some drawbacks, such as complicated computation and unsatisfactory accuracy. In this paper, a pseudospectral method based on barycentric Lagrange interpolation for linear elastic static analysis of tank is proposed. The differentiation matrix for the unknown function is constructed by using barycentric Lagrange interpolation. The governing equations of equilibrium, in terms of stress resultants and couples, are put into a generalized displacement form by the use of strain-displacement relationships and constitutive equations. The governing equation of tank wall can be expressed as a set of algebraic equations by the pseudospectral method. With boundary conditions, the algebraic equation system is solved to obtained the deflections at discrete points. The principle of this method is simple and ease to program. The accuracy and the numerical stability are good.
    Education Study
    The People and Stories in Mechanics of Materials Teaching
    li min jia lijie wang mingchun
    2010, 32(2):  114-115.  doi:10.6052/1000-0879-2008-335
    Abstract ( 1391 )   PDF (659KB) ( 780 )  
    The people and stories in the history of mechanics of materials are talked about in this paper. The role utilizing these stories on method of teaching and how to give students a course of character training are shown.
    2010, 32(2):  128-131.  doi:10.6052/1000-0879-2008-361
    Abstract ( 1262 )   PDF (808KB) ( 557 )  
    On the base of the principle of matrix transformation of three-dimensional diagram,the scaling,rotation and translation for the element drawing data about internal force and displacement are carried out,and the diagram of internal force and displacement of space frame have been drawn with the transformed data by Matlab.The method and programme established in this paper can be applied to display of the analysis of space frame FEM in graphics mode.
    2010, 32(2):  137-138.  doi:10.6052/1000-0879-2008-467
    Abstract ( 1093 )   PDF (955KB) ( 519 )  
    In order to maximize the performance of large-scale experimental device and promote the materials mechanics experiment open,allow students according to their own personal circumstances experiment,but the teachers to monitor in the background,this paper want to put forward a flexible mechanics experiment platform which based on the number of machine for the logo and the computer network communication technology to support .Through this flexible open platform , variety of materials mechanics experimental , in particular, students design their own personalized type of experiment can be orderly, and efficient implementation.When technology is mature, it can be extended to other disciplines to the management of the laboratory.
    2010, 32(2):  119-120.  doi:10.6052/1000-0879-2008-529
    Abstract ( 1250 )   PDF (401KB) ( 755 )  
    2010, 32(2):  139-141.  doi:10.6052/1000-0879-2008-579
    Abstract ( 1251 )   PDF (1502KB) ( 571 )  
    Application study
    2010, 32(2):  76-81.  doi:10.6052/1000-0879-2008-598
    Abstract ( 1080 )   PDF (972KB) ( 530 )  
    An efficient precise time-step integration algorithm to solve large-scale transient problems is presented. The Krylov subspace method, the Pad\'{e} approximations and the dimensional expanding method of ordinary excitations are applied to modify the original precise time-step integration algorithm in order to improve the computational efficiency. The problems of arbitrary complex excitations can also be solved. For a large-scale system, the efficiency of the algorithm would be influenced because the dimension of system extended by the dimension expanding method becomes higher, especially, for the complex excitations. The present algorithm can solve the large-scale system without difficulty by using the decreasing dimension analysis of the Krylov subspace method. The efficiency of the new algorithm can be improved by analyzing the exponentional matrix in a subspace instead of the original large space. More computational cost can be saved by selecting the parameter $N$ carefully.
    Education Study
    2010, 32(2):  125-127.  doi:10.6052/1000-0879-2008-602
    Abstract ( 1068 )   PDF (632KB) ( 420 )  
    Abstract: Taking the centered-fan fields for example, the application of an orthogonal net of circles for construction of the complex slip-line fields are discussed. The results of this method are compared with the results of the numerical method and the matrix-operator method. The calculation shows that result of above three methods proffers a good approximation.
    2010, 32(2):  116-118.  doi:10.6052/1000-0879-2008-605
    Abstract ( 1369 )   PDF (416KB) ( 632 )  
    This paper analyzes relationship between shear stress and normal stress. The conditions for introducing shear stress formulation were discussed, and a method to solve elastic mechanics problem using shear stress was introduced. It is proved that the problems, where the shear stress is zero or for beams having an independent on x, can be solved using shear stress. This method is simpler than conventional methods. Three examples were provided using shear stress to solve elastic mechanics problems.
    Application study
    2010, 32(2):  51-54.  doi:10.6052/1000-0879-2008-609
    Abstract ( 1228 )   PDF (632KB) ( 589 )  
    A research method for the deflection of throttle slice under the local distribution of variable load is presented. The analytical equation is deduced using the plate theory according to the physical model of throttle slice, which is convenient for the theoretical analysis and engineering application. The equation is validated by finite element calculation results. The relations between different loads, structure parameters, materials characteristics of throttle slice and the deflections are studied. The analytical equation and conclusions offer some guidance to design throttle valve of shock absorber.
    2010, 32(2):  26-31.  doi:10.6052/1000-0879-2009-006
    Abstract ( 1247 )   PDF (995KB) ( 552 )  
    Practicable loss and deviation models for transonic and subsonic axial compressors are established. They are combined with the blade row-by-blade row cascade model. A method for calculating off-design performance of multi-stage axial compressors is developed, based on those models. Box's optimization technique is then used to optimize the stator vane stagger setting. The methodology has been incorporated into a computer program and is validated by using data from an eight-stage transonic axial compressor. Results show that the variable stator stagger setting is a powerful method to rematch stages, which can be used to enlarge aerodynamic stability range of multi-stage compressors.
    2010, 32(2):  82-84.  doi:10.6052/1000-0879-2009-023
    Abstract ( 1095 )   PDF (499KB) ( 794 )  
    A relational equation between the torsion angle of a torsion bar and the roughness of a road is obtained by analyzing a torsion bar road wheel dynamics model for a simplified tracked vehicle. Based on the equation, the torsion angle is calculated against the roughness of the road and vise versa. A numerical example combined with the ADAMS simulation verifies the feasibility of the method to calculate the roughness of a road upon the measured result of a torsion angle.
    2010, 32(2):  95-99.  doi:10.6052/1000-0879-2009-095
    Abstract ( 1562 )   PDF (1098KB) ( 607 )  
    Based on the distribution of the three-dimensional holes in human bones, we propose a method to establish the mechanical model for human radius scaffold. Mechanical model of human radius is established in this paper by this method, together with a viscoelastic constitutive model. According to mechanical properties of the mechanical model, we reach the following conclusions: when given a uniaxial pressure, the maximum stress appears in the hole wall, and the relationship between stress and strain is non-linear.
    2010, 32(2):  90-94.  doi:10.6052/1000-0879-2009-114
    Abstract ( 1719 )   PDF (3429KB) ( 729 )  
    Mosquitoes can pierce their fascicle into human skin with a micro-Newton force by using a natural ultimate painless microneedle. Firstly the structure of the {\it Aedes albopictus} mosquito fascicle is obtained using a scanning electron microscope, and then the simulation model of the mosquito fascicle tip is built based on the structure obtained from the SEM observation. A numerical simulation is conducted to analyze the insertion process of the mosquito fascicle tip into a human skin using a nonlinear finite element method based on ABAQUS. The mechanical properties of different skin layers are taken into account. The deformation and failure of the skin and the insertion force are discussed. A good agreement is obtained between the numerical results and the experimental measurements.
    2010, 32(2):  39-41.  doi:10.6052/1000-0879-2009-126
    Abstract ( 1319 )   PDF (705KB) ( 499 )  
    The thermal dissociation scope of gas hydrate in deposit around heat conductor is very important for either gas hydrate exploitation or related hazard prevention. Maximum dissociation scope based on planar heat dissociation under the boundary condition of constant temperature is obtained and compared with that obtained in heat dissociation experiments of THF hydrate in deposit in this paper. It is shown that the maximum dissociation scope is determined by the difference between the temperatures of heat source and surrounding environment. The theoretical results of the maximum dissociation scope are in agreement with those of experiments, with errors less than 5%.
    2010, 32(2):  85-89.  doi:10.6052/1000-0879-2009-136
    Abstract ( 1199 )   PDF (896KB) ( 575 )  
    In this paper, the kinematics and dynamics of the free-floating space robot system with dual-arms are analyzed. The closed-loop dynamic error equation considering uncertainties for such system is derived by using the PD type computed torque method. A new learning control method using real coded genetic algorithm (GA) is used to control the system with its controller structure designed. A compensating learning control term is added to the error equation to deal with the uncertainties by evolutionary learning. Then, the computed torque method and the GA learning control are combined to realize the perfect trajectory tracking. Simulation results show the efficiency of the control method.
    2010, 32(2):  42-46.  doi:10.6052/1000-0879-2009-148
    Abstract ( 1019 )   PDF (1512KB) ( 513 )  
    To study the axial energy-absorption performance of thin-walled tubes of energy absorbing elements in a vehicle body, thin-walled tubes with single and double hat and with stiffeners were designed. Then the quasi-axial compression tests were carried out. Test results show that the energy-absorption performance of the thin-walled tubes is increased when the number of stiffeners is increased, but the quasi-axial steady ability is decreased.
    2010, 32(2):  108-111.  doi:10.6052/1000-0879-2009-157
    Abstract ( 2169 )   PDF (578KB) ( 709 )  
    Five gabled frames with hinges are analyzed by the equilibrium method and the effective length factors of coulumns are determined by solving stability equations, theoretical analysis and codes for design or technical specifications. The calculation results show that the results of the equilibrium method and the finite element method are consistent; the effective length factors of leaning columns are equla to one by codes for design or technical specifications, but greater than one by the equilibrium method; for frame columns, the calculation results of codes for design or technical specifications are different from those obtained by equilibrium method. It is shown that the code method is not suitable to analyze the frame stability, the effective length factors of the frame columns should be obtained by the second order analysis.
    2010, 32(2):  60-64.  doi:10.6052/1000-0879-2009-172
    Abstract ( 1299 )   PDF (755KB) ( 540 )  
    In order to reveal fully the characteristic of thermal self-stress distribution in beams with wide flange under nonlinear thermal differential and improve the currently used thermal self-stress analysis method, a refined analytical method is presented which is based on the mechanics of elasticity. The flange and web plates are considered to be in a state of plane stress under nonlinear thermal differential. The conditions of deformation compatibility and equilibrium at the connection of flange and web plates are used to establish additional equations by which the constants of integration in Airy stress function can be evaluated. The analytical expressions of stresses and displacements in flange and web plates are derived. In the normal stress formula of flange, non-uniform distribution of thermal differential self-stress is taken into account automatically. Numerical results of a tee beam with wide flange show that, the self-stress in flange plate under thermal differential is distributed very non-uniformly along its width. Greater compression stress occurs near the fixed edge while much smaller stress at the free edge in the flange plate. This characteristic of thermal self-stress can’t be revealed by using the common analytical method.
    2010, 32(2):  100-102.  doi:10.6052/1000-0879-2009-188
    Abstract ( 1324 )   PDF (613KB) ( 698 )  
    A new composite geophone, with a number of advantages such as high sensitivity, heavy damping ratio and low output impedance, is developed based on micro-electronic technology, which is adopted to modify the geophone frequency characteristics in the main frequency region to approach the acceleration characteristics by increasing damping of the geophone. The in-situ testing results show that the data recorded by the composite geophone have high S/N ratio, high visual frequency and strong energy, and the geophone has the ability to compensate the high frequency energy and to widen the bandwidth of seismic wavelet, and can be used for high resolution seismic explorations.
    2010, 32(2):  103-107.  doi:10.6052/1000-0879-2009-197
    Abstract ( 1328 )   PDF (732KB) ( 489 )  
    Based on the nonlinear magnetic-elasticity kinetic equations, physical equations, electrical kinetic equations and the expression of Lorentz force, a nonlinear dynamic model of Euler pole is established by using the Lagrangian description method. After the simplifications of the nonlinear dynamic model, the bifurcations of a nonlinear static model, a linear dynamic model and a simplified nonlinear dynamic model with a cubic nonlinear item are analyzed, respectively. As an example, the curves of the critical buckling load vs. related the relative parameters are obtained when a pole is applied with compressive force in a magnetic field. The calculated results are discussed.
    2010, 32(2):  47-50.  doi:10.6052/1000-0879-2009-264
    Abstract ( 1462 )   PDF (746KB) ( 492 )  
    In order to analyze the crack growth by the cohesive zone approach in a general structure, the concept of generalized cohesive interface is proposed. Based on the principle of the energy release rate and the linear elastic equivalence of the cohesive interface, the element's stiffness matrix is obtained. On this basis, the load/displacement function of the double cantilever beam(DCB) is obtained, under pure mode I condition. With the software BAQUS, the numerical simulation of delamination's growth is carried out. Analytic functions and numerical simulation's results show that the generalized linear elastic cohesive zone equivalence is valid.
    2010, 32(2):  55-59.  doi:10.6052/1000-0879-2009-292
    Abstract ( 1367 )   PDF (1016KB) ( 607 )  
    The fracture mechanics method is used to analyze crack propagation characteristic of rubber sheet with the oblique edge crack under uniaxial tension.With the application of ABAQUS software, we have founded element models of two-dimensional rubber sheet with oblique edge crack at different angles of 0°、15°、30°、45°and 60°;and calculated the J-integral in the different orientation for the different models under simple tension.The J-integral parameter has been used to analyze the crack propagation orientation. It is shown that the crack propagation orientation isn’t along with the initial orientation of crack but with a certain angle, and the angle is gradually decreasing with the initial angle of oblique crack increasing.
    2010, 32(2):  65-70.  doi:10.6052/1000-0879-2009-335
    Abstract ( 1237 )   PDF (966KB) ( 515 )  
    In order to obtain a general analytical solution of three types of anchors, an analytical solution of inner-bonded anchor under tensile load is obtained by assuming displacement consistency between anchor and soil, based on Mindlin solution of force at a point in the interior of a semi-infinite solid. Then the analytical solution is extended to the full-bonded anchor and compression anchor. Further, a general analytical solution of the three types of anchors under tensile load is obtained. The effect of anchor type, soil elastic modulus and anchor diameters on shear distribution between anchor and soil is evaluated by using the general analytical solution. The results show that (1) there is only one stress peak along the shear distribution curve of the three types of anchors; (2) as the elastic modulus of soil increases, the magnitude of shear increases while the distribution length of shear decreases; (3) as the anchor diameter increases, the magnitude of shear decreases while the distribution length of shear is almost not changed.
    2010, 32(2):  71-75.  doi:10.6052/1000-0879-2009-337
    Abstract ( 1238 )   PDF (887KB) ( 667 )  
    From the moment-independent importance measure of basic variable effect on response distribution, an importance measure is defined to describe the effect of basic variable on failure probability. Compared with the importance measure of the basic variable effect on the response distribution, this measure can directly provide the global effect of the variables on the structural safety, so can provide more guidance in engineering design than the former. The basic properties of the importance measure of the basic variable effect on the failure probability are discussed in this paper. Since the saddlepoint based line sampling method is independent of the distribution types of the random variables, and has the advantages of high accuracy and efficiency, this method is employed to estimate the defined importance measure.
    Review
    2010, 32(2):  9-15.  doi:10.6052/1000-0879-2009-464
    Abstract ( 1438 )   PDF (2112KB) ( 560 )  
    The applications of X-ray CT technique to detect the internal meso cracks in concrete are reviewed in this paper, including real time detection, CT image analyses, the law of crack growth, the evolution of damage and damage variables, and 3-D reconstructions. The result shows that the CT technology is an effective observation method. The existing problems are how to obtain precise CT images under various experimental conditions. Finally a new approach is proposed.
    Interesting mechanics story
    2010, 32(2):  147-149.  doi:10.6052/1000-0879-2009-501
    Abstract ( 1527 )   PDF (937KB) ( 766 )  
    Mechanicist
    2010, 32(2):  150-153.  doi:10.6052/1000-0879-2009-518
    Abstract ( 1612 )   PDF (653KB) ( 883 )  
    Maxwell not only holds a great position in classical physics, but also made important contributions to applied mechanics. His research on mechanics deals with elastic mechanics, photo-elasticity, structural mechanics, visco-elastic mechanics, celestial mechanics, fluid mechanics, and dynamic stability. During the process of research on applied mechanics, he can grasp the proficient mathematics and the physical nature of the problem, which is consistent with the spirit of engineering science and applied mathematics.
    Review
    2010, 32(2):  1-8.  doi:10.6052/1000-0879-2010-037
    Abstract ( 1497 )   PDF (1513KB) ( 610 )  
    Artificial boundary conditions are necessary in finite domain approximations of wave propagation simulations over an infinite medium. In this survey, we briefly introduce some typical conditions for continua and lattices, including exact artificial boundary conditions and local approximate ones.
    Application study
    2010, 32(2):  21-25.  doi:10.6052/1000-0879-2010-059
    Abstract ( 1119 )   PDF (750KB) ( 729 )  
    The fluid-structure interaction (FSI) of the wind-induced vibration of cable structures is studied in this paper. The basic theory of FSI and the analysis procedure of the weak coupling are discussed. An example of the wind-induced vibration in laminar wind model and turbulence wind model of a 100 m long cable with different parameters such as inclined angle and yaw angle is computed with the ANSYS-CFX software. The numerical results agree well with the theoretical analysis.
    Mechanics History
    2010, 32(2):  144-146.  doi:10.6052/1000-0879-2010-104
    Abstract ( 1690 )   PDF (1341KB) ( 673 )  
    Application study
    2010, 32(2):  16-20.  doi:10.6052/1000-0879-2010-109
    Abstract ( 1262 )   PDF (2197KB) ( 428 )  
    Numerical simulation method is adopted to simulate the mean wind pressure of Shanghai EXPO Meteo World Pavilion. Four turbulence models (RNG k-ε, SST-k-ω, SSG-RSM and BSL-RSM), appropriate for structural wind engineering, are applied in this paper and compared shape coefficient, overall superficial forces and moments, and turbulence energy. In addition, with the analysis on regularity and difference of wind flow characteristics, conclusion is obtained that SST-k-ω ,BSL-RSM and SSG-RSM has different advantage but RNG - k-εis the worse. Finally, mean wind pressure coefficient of the pavilion is researched under the conditions of with and without interference. The reason of wind interference is also analyzed.