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08 February 2008, Volume 30 Issue 1
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    Application study
    2008, 30(1):  47-51.  doi:10.6052/1000-0992-2006-481
    Abstract ( 1207 )   PDF (2531KB) ( 1613 )  
    In the light weight design of truss-like landing-gear structure, the related specification on strength is considered. The bars' strength and critical loads are used as constraints and the minimum structural weight design is achieved by shape and size optimization. The data obtained from an example agree with the results of static force test. Theoretical analysis and the flight of model planes carrying load show that the approach is not only feasible but also effective. It can be used to design the landing-gear structure of a small or super light-weighted vehicle. %Finally, three conclusions have been drawn from this paper.
    2008, 30(1):  57-61.  doi:10.6052/1000-0992-2007-021
    Abstract ( 1084 )   PDF (912KB) ( 653 )  
    Air flow bifurcations often occur in a room with mechanical ventilation system, and will change the velocity and temperature fields in the room. The main influencing factors of air flow bifurcations in rooms with mechanical ventilation system are studied in this paper. First, with the jet theory and the results of computer simulation, the paper explains why bifurcation occurs with plane jet but not with centralized jet by analyzing Coanda effect. It is shown that Coanda effect is the main mechanism of bifurcation. Second, the key parameters affecting bifurcations are analyzed using the theory of orthogonal test and variance analysis. The relations between bifurcation intensity and the key factors are obtained.
    Education Study
    2008, 30(1):  84-85.  doi:10.6052/1000-0992-2007-061
    Abstract ( 1111 )   PDF (460KB) ( 646 )  
    Application study
    2008, 30(1):  35-40.  doi:10.6052/1000-0992-2007-074
    Abstract ( 1114 )   PDF (905KB) ( 1013 )  
    With bending, shear and tension deformations being considered in the thin-walled beams within aluminum honeycomb cores under in-plane loadings, the analytical formulas for the in-plane elastic moduli of the aluminum honeycomb cores are derived based on Timoshenko beam theory. The finite element simulation methods for calculating these moduli for a representative unit cell are proposed based on shell elements. The calculations on the elastic moduli of two kinds of aluminum honeycomb cores are carried out, respectively, by using the theoretical and finite element methods. The agreement between the calculated results and the experimental data has verified the theoretical formulas and finite element simulation method. Finally, the effects of aluminum honeycomb cores' configuration parameters on their material efficiency are analyzed.
    2008, 30(1):  41-43.  doi:10.6052/1000-0992-2007-079
    Abstract ( 1342 )   PDF (588KB) ( 725 )  
    This paper disscusses the design principle of the gas actuator used as the aerodynamic simulation load device, and the calculation of the aerodynamic simulation load by using the inclined plane and ascending method. It is shown that the scheme of the aerodynamic simulation load device is practicable; the aerodynamic loads of missile wings can be simulated in a practical and equivalent way, which may greatly reduce the time and expense for related development.
    2008, 30(1):  75-78.  doi:10.6052/1000-0992-2007-124
    Abstract ( 1112 )   PDF (1231KB) ( 864 )  
    This paper proposes a method of measuring displacement by ultrasonic speckle interferometry. Base on the digital interferometry method and phase-shift---frequency-shift principle, formulas for the ultrasonic speckle digital interferential measurement are deduced. In order to verify the theoretical results, an experiment of measuring in-plane and out-of-plane displacements of an aluminous specimen is performed. The experimental results indicate that the theoretical analyses are correct and the method can be applied in measuring displacements and deformations.
    2008, 30(1):  27-30.  doi:10.6052/1000-0992-2007-136
    Abstract ( 1133 )   PDF (692KB) ( 558 )  
    Based on Brinson's one-dimensional thermo-mechanical constitutive relations of shape memory alloys and the von K\'{a}rm\'{a}n theory of thin plates, the bending response of a uniform heated circular plate embedded with SMA fibers in the radial directions and subjected to a uniform distributed mechanical load is studied. The characteristic curves of the deflection at the center versus temperature rise of the circular plate with both clamped and simply supported boundary conditions are obtained. The numerical results show that, the recovery forces of the pre-strained SMA caused by the phase transformation from martensite to austenite can modify the bending deformation significantly. So, it is concluded that the bending deformation can be adjusted effectively and actively by embedment of the SMA fibers into the circular plates.
    2008, 30(1):  18-22.  doi:10.6052/1000-0992-2007-189
    Abstract ( 1236 )   PDF (1201KB) ( 800 )  
    The development of studies on passive dynamic walking is reviewed briefly. The nondimensional equations of a planar straight leg passive dynamic biped model with round feet are derived and a simulation is carried out. The basin of attraction of the model obtained by the cell mapping method is larger than that of point feet models, proposed by other researchers. These results indicate that the model can walk stably from an initial state far from the fixed point.
    2008, 30(1):  79-81.  doi:10.6052/1000-0992-2007-192
    Abstract ( 1136 )   PDF (991KB) ( 1399 )  
    By means of experimental modal analysis for a joint cantilever plate with one end fixed, the first natural frequency and modal shape are determined. The joint plate is treated as a joint cantilever beam. The transfer matrix method is implemented with the computer algebra language. The equation for the angle stiffness is obtained. With the first natural frequency of the joint plate as an input, the angle stiffness can be determined. The validity of this method is shown by experiment.
    2008, 30(1):  52-56.  doi:10.6052/1000-0992-2007-193
    Abstract ( 1155 )   PDF (805KB) ( 704 )  
    This paper studies the Foucault pendulum movement under the influence of air damping. Dynamic simulations are carried out by the use of the numerical and analytical methods, and comparisons are made for the Foucault pendulum movement with and without the influence of air damping.
    2008, 30(1):  44-46.  doi:10.6052/1000-0992-2007-258
    Abstract ( 1078 )   PDF (1288KB) ( 676 )  
    On the basis of the finite element model of a whole aircraft, the paper simulates a crack with a length of 150mm in a place between No.2 and No.3 walls of the upper wing panel before and after it is repaired. The results give a quantitative relationship between rivet rows and residual load factor, and the influences of the damaged stringer, before and after it is repaired, on the force-bearing ability of aircraft structure are compared. The results can be used in a rapid assessment of a battle-damaged aircraft repair and as a reference for the usual repair of aircraft.
    2008, 30(1):  66-69.  doi:10.6052/1000-0992-2007-261
    Abstract ( 1125 )   PDF (1682KB) ( 580 )  
    The production casing stress inside steam-injection wells is analyzed with a casing temperature field. The commercial software, ANSYS, is used to simulate the casing stress under different conditions, and the results indicate that the highest thermal stress is at the internal wall, exceeding the elastic yield ultimate stress of N80 casing, while the maximum thermal expansion occurs in the temperature-transition area. In case that the surrounding area of casings is emptied, the thermal strain will be much higher than the elastic strain limit, and should be mainly responsible for the deformation failure of casings. Based on the results, some preventive measures for casing deformation are proposed, which are verified through the application of TP120TH casings during the well completion in Liao'he oilfield.
    2008, 30(1):  31-34.  doi:10.6052/1000-0992-2007-264
    Abstract ( 1846 )   PDF (618KB) ( 1135 )  
    Rational FEM is used in Timoshenko beam problems. A kind of rational Timoshenko beam element is proposed, to avoid shear locking. In deriving the governing equations, some basic analytic solutions of Timoshenko beam problems are used to approximate the inner field of the element. This method is different from Lagrange interpolation used in the conventional FEM. The rational Timoshenko beam element can avoid shear locking without a reduced integration. Numerical results show that the element's precision is very high. It is shown that the rational FEM has a very wide application.
    2008, 30(1):  70-74.  doi:10.6052/1000-0992-2007-265
    Abstract ( 1021 )   PDF (3042KB) ( 550 )  
    The packing-fixer was designed to replace the packing material for nose to keep breathing, fix the nasal septum and arrest bleeding after nasal septum mucous membrane surgery. Numerical simulation was performed to study the functions of the packing-fixer and the traditional expansive sponge in nasal cavity by finite element method. The compression stress and the first principal stress were compared. It is demonstrated that the packing-fixer can produce larger compression stress and first principal stress than the expansive sponge in the mucous membrane of nasal septum without breaking the mucous membrane of nasal septum. The packing-fixer designed in this paper can keep breathing, fix the nasal septum and arrest bleeding after nasal septum mucous membrane surgery without breaking the nasal septum mucous membrane. The packing-fixer can help to alleviate the pain of patients.
    2008, 30(1):  62-65.  doi:10.6052/1000-0992-2007-270
    Abstract ( 1506 )   PDF (690KB) ( 715 )  
    The security of waxy crude oil pipeline in the process of stop-restart is severely affected by the rheological properties of gelled crude oil, expecially the viscoelastic creep property. The parameters such as stress, time and temperature have to be considered at the same time in describing the viscoelastic behavior of gelled crude oil. Creep experiments are conducted under different stresses and temperatures. The results indicate that the changes of stress and time have similar effects on the creep characteristic time of gelled crude oil. Nonlinear creep behavior is analyzed by means of the equivalence principle of time-temperature-stress. The main creep curve under reference stress and reference temperature is obtained, by fitting with the viscoelastic rheological model. So the long-term creep behavior under lower temperature and stress can be predicted by short-term creep behavior under higher temperature and stress.
    Review
    2008, 30(1):  10-17.  doi:10.6052/1000-0879-2007-430
    Abstract ( 1009 )   PDF (1821KB) ( 817 )  
    This paper presents a brief introduction to the objective, characteristics and the disciplinary content of rational mechanics, as well as its relationship with other disciplines, and its history of development. The activities of the Committee of Rational Mechanics and Mathematical Methods in Mechanics are reviewed, especially, the academic activities organized by the Committee, the dissemination and development of Rational Mechanics in China, in cluding the significant contributions made by Professor Wei-Zang Chien in promoting the development of Rational Mechanics in China, as well as the achievements of Rational Mechanics accomplished in China.
    2008, 30(1):  1-9.  doi:10.6052/1000-0992-2007-449
    Abstract ( 1281 )   PDF (4827KB) ( 1020 )  
    The multifunctional properties of highly porous cellular metals see attractive industrial and military applications. Recent developments in the theoretical determination of effective stress-strain relations using the method of homogenization and the multifunctional optimal design of these novel materials are reviewed. The multifunctions include load bearing, thermal/noise management, blast resistance and structural actuating. Metallic foams with random cellular topologies and periodic lattice metals are respectively considered.
    Application study
    2008, 30(1):  23-26.  doi:10.6052/1000-0992-2007-553
    Abstract ( 1039 )   PDF (583KB) ( 584 )  
    Based on the three-dimensional theory of elasticity and the state space approach, this paper studies the free vibration and forced vibration of an isotropic multilayered rectangular plate with four edges simply supported. Firstly, on the basis of the theory of elasticity, the governing equations of a multilayered plate are established and the free vibration response of the laminated panel is obtained by the state space approach. Then the dynamic response of the multilayered plate subjected to an impact loading is obtained from Lagrangian dynamic formulations.