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10 December 2007, Volume 29 Issue 6
Application study
2007, 29(6):  56-59.  doi:10.6052/1000-0992-2006-340
Abstract ( 1045 )   PDF (585KB) ( 1039 )
A given length thin-wall member, under axial or lateral loads below its material limit strength, may under go elastic flexural and torsional buckling. An analysis is carried out for the I-section cantilever steel beam in this paper. Equilibrium method and energy method are used to obtain the differential equation of the elastic flexural and torsional buckling under the axial pressures and transverse loads, and Ritz method is used to solve the derived differential equation and obtain critical values and the limit characteristics of the fixed beam section.
2007, 29(6):  27-31.  doi:10.6052/1000-0992-2006-342
Abstract ( 902 )   PDF (637KB) ( 609 )
The stability of thin-walled structures is an important problem in civil engineering. In this paper, the nonlinear elastic buckling of the open thin-walled curved-beam is analyzed by using the finite element method. Through the nonlinear regression computation for a great number of Finite-Element results, a practical and simple formula is obtained, which can be used to estimate the ultimate bearing capacity of the open thin-walled curved beams.
2007, 29(6):  51-55.  doi:10.6052/1000-0992-2006-360
Abstract ( 1493 )   PDF (777KB) ( 533 )
It is important to deal with the material interfaces appropriately in multimaterial flows. ALE based on moving grids is applied to solve 1-D multi-material Riemann problems and three methods of dealing with the numerical flux on the material interface are proposed in this article: Lagrange method, GFM and HLLC method. According to the results obtained with these methods, the performance of GFM and HLLC method is better and they give more accurate results than Lagrange method at the material interface with high grades of pressure.
2007, 29(6):  44-47.  doi:10.6052/1000-0992-2006-404
Abstract ( 1014 )   PDF (667KB) ( 637 )
During the process of aero-dynamical computation for wind turbine rotor, one has to solve an integral equation with respect to the radial circulation distribution. Within its integrand, however, an unknown circulation is included so that it becomes an integral-differential equation. This paper proposes a numerical method to obtain a comparatively accurate result for the aerodynamic computation for wind turbine rotors. The history of this integral-differential equation is briefly described first. Then two numerical computational methods are given. With respect to the singularity of the integrand, an appropriate approach is also proposed. Finally, the results from aero-dynamic computation for a wind turbine rotor by using the numerical method presented and other two methods are compared in order to illustrate the effectiveness of the method presented, as well as to show some problems in the method with possible improvement in future.
2007, 29(6):  60-63.  doi:10.6052/1000-0992-2006-423
Abstract ( 972 )   PDF (736KB) ( 469 )
In this paper, a dynamic stress test on the headstock of the residue film recycling machine is presented. By processing and analyses of data, headstock's operational stress state is obtained, which provides a basis for its improving design.
2007, 29(6):  23-26.  doi:10.6052/1000-0992-2006-428
Abstract ( 1455 )   PDF (560KB) ( 832 )
Boundary value problems for dynamical systems with periodic solutions can be turned into initial value problems. With this point in mind, the paper improves the shooting method. In the process of computing derivatives of boundary conditions' algebraic equations, which are functions of unknown initial value parameters, the node function values are obtained through Runge-Kutta method, and by using Runge-Kutta method once more, the derivatives can be obtained. The validity of such a method is verified by using it to obtain periodic solutions of Duffing equation and nolinear rotor-bear system, and comparing the results with those computed by traditional method. Meanwhile, we discuss the stability of the solutions by Floquet theory.
2007, 29(6):  32-36.  doi:10.6052/1000-0992-2006-485
Abstract ( 1026 )   PDF (901KB) ( 617 )
Rotary kiln is a key equipment in the production of metals, cement and refractory materials. For studying bending vibration of its body system related with its axis movement, the method of transfer matrix is developed to set up the body system's dynamical model with the anisotropy equivalent stiffness equation of the wheel-bearing system. An example is given to illustrate why there are dynamical errors in the common axis measurement methods. The transfer matrix model provides a basic equation for computing dynamical stresses of roller and dynamical errors in the axis measurement.
2007, 29(6):  17-22.  doi:10.6052/1000-0992-2006-491
Abstract ( 1049 )   PDF (2933KB) ( 882 )
A mechanical model of membrane wrinkle is established in this paper. Relationship between the strains and the stresses in the wrinkled regions is analyzed based on the tension field theory and the stability theory. The NBA-UM (nonlinear buckling analysis-update matrix) method is proposed for the dynamic analysis of membrane wrinkles, and the study on the vibration characteristics of the membrane. The result shows that excess shrink'' phenomena is due to wrinkles, which in turn change the stress distribution in the membrane. Wrinkles greatly influence the vibration characteristics of the membrane, and large amplitude wrinkles will change the natural frequencies and modal forms of the membrane. In conclusion, it is shown that the NBA-UM method can effectively predict the dynamic behaviors of membrane wrinkles.
Review
2007, 29(6):  9-12.  doi:10.6052/1000-0992-2007-019
Abstract ( 1577 )   PDF (1085KB) ( 734 )
The impact and contact dynamics is a hot topic in the field of dynamics of multi-rigid-body systems in recent years. The related methods are reviewed. The energy inconsistency due to Coulomb-type friction, Painlev\'{e}'s paradox and the restitution coefficient of impact are discussed in detail, together with progress made in those problems. The future research directions in this field is pointed out.
Application study
2007, 29(6):  37-40.  doi:10.6052/1000-0992-2007-062
Abstract ( 1124 )   PDF (584KB) ( 478 )
The hybrid boundary node method (HBNM) and the dual reciprocity method (DRM) are combined for solving potential problems in this paper. As a boundary-type meshless method, the HBNM is based on a modified variational principle and moving least squares (MLS) approximation, with the advantages of both BEM and meshless methods. The solution of potential problems is expressed as the sum of a particular solution and a homogeneous solution. The homogeneous solution is solved by means of HBNM, and the particular solution is approximated by using radial base functions. Only for discretely distributed nodal points on the boundary surface of the domain input data are required and without other extra equations to compute internal parameters in the domain. The postprocessing is very simple. Numerical examples show high accuracy and high convergence rates of the presented scheme.
2007, 29(6):  41-43.  doi:10.6052/1000-0992-2007-068
Abstract ( 1070 )   PDF (547KB) ( 582 )
On basis of concepts of population and adaptive degree, a new method is proposed to identify parameters in the constitutive model used to improve Particle Swarm Optimization Algorithm starting from a stochastic solution. This method can solve difficult problems of identifying parameters in a constitutive model for hardening rubber-like materials with large strain. Firstly, by a constitutive model test of uniaxial tension, a point of inflexion in the experimental curve is obtained, the PSO is used to identify the parameter, and then the result is testified by a simple shearing test. The result shows that the PSO method enjoys efficiency, high precision and quick convergence, in identifying constitutive parameters and it can be widely used for various complex materials.
2007, 29(6):  13-16.  doi:10.6052/1000-0992-2007-088
Abstract ( 1192 )   PDF (884KB) ( 651 )
Shear stress on the surface of columns and the low $Re$ flow field of interstitial flow in column array is studied numerically in this paper, with focuses on the difference of shear stress on the column surface between solid body and permeable body. The porous models are used to simulate the region between the columns, and the structure of columns. Shear stress is calculated based on Brinkman equation using the finite volume method with proper boundary conditions. The numerical results show that the penetration structure of columns can inflect the flow field and significantly reduce the shear stress and effective permeability.
2007, 29(6):  48-50.  doi:10.6052/1000-0992-2007-233
Abstract ( 1050 )   PDF (502KB) ( 621 )
Due to the influence of the exhaust gas produced by airborne weapons on engine's operational parameter, a micro-differential pressure sensor is developed to measure the signal when the pressure in the air compressor falls suddenly. The system of antisurge can open in time to prevent the engine surge or stop. This paper discusses the sensor structure, the principle of work, the design principle and the main part parameter design method. And the test results show that the design requirement is satisfied.
Review
2007, 29(6):  1-8.  doi:10.6052/1000-0992-2007-438
Abstract ( 1062 )   PDF (3085KB) ( 891 )
Recent developments in the field of machine tools are summarized, and issues of basic research associated with machine tool materials and structures are discussed. The materials/structures used over the years in machine systems are reviewed, with emphasis placed upon the application of novel lightweight materials/structures in ultra-high precision machine tools.