力学学报

SOLUTION OF N S EQUATIONS ON UNSTRUCTURED GRID

A new upwind scheme is presented for solving the N S equations on unstructured grid. Spatial discretion is based on flux splitting of Roe. It can capture the strong shock and discontinuity. Solutions are advanced in time by Runge Kutta time stepping scheme and implicit Gauss Seidel relaxation procedure. The adaptive techniques is given. The numerical experiments for flow in tunnel with step, reflection of shock on a flat and flow in cascades demonstrate the flexibility of the present method.

1996, 28(6): 641-650. doi: 10.6052/0459-1879-1996-6-1995-383

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A THEORETICAL MODEL OF MAGNETOELASTIC BUCKLING FOR SOFT FERROMAGNETIC THIN PLATES

As an essential model of magnetoelastic interaction between magnetic field and mechanical deformation, the study on magnetoelastic buckling phenomenon of soft ferromagnetic plates in a magnetic environment has been conducted. One of the key steps for the theoretical prediction of the critical magnetic field is how to formulate magnetic force exerted on the magnetized medium. Till today, the theoretical predictions, from all theoretical models in publications, to the magnetoelastic buckling of ferromagnetic ...

1996, 28(6): 651-660. doi: 10.6052/0459-1879-1996-6-1995-384

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STUDY OF DYNAMIC FRACTURE BEHAVIOUR ON THREE POINT BEND BEAM WITH OFF CENTER EDGE CRACK

A series of experimental studies on the dynamic fracture behaviour of three point bend beam with off center edge crack under transverse implusive loading are presented with the help of dynamic caustics. The effects of the off center position of the prefabricated cracks on dynamic growth (i.e. the crack initiation, the mixed mode stress intensity factor of the crack tip, the crack speed and crack trajectory, etc.) are analysed. By means of dynamic photoelasticity, the interaction between the stress wave...

1996, 28(6): 661-669. doi: 10.6052/0459-1879-1996-6-1995-385

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SINGULAR SOLUTIONS OF NON-AXISYMMETRIC DYNAMIC PROBLEM IN LAYERED ELASTIC HALF-SPACE

The Fourier transformations about the azimuthal angle and Hankel transformation about the radial direction have been used to convert the basic equations of elasticity into a non-homogenous first-order ordinary differential equation system in cylindrical coordinates. By the use of the matrix method to solve this system of equations, the transmission matrices of the layered medium are established. The singular solution in frequency domain for an arbitrarilly buried source acting in the multilayered elastic ha...

1996, 28(6): 670-681. doi: 10.6052/0459-1879-1996-6-1995-386

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NUMERICAL ANALYSIS OF THE LIMIT LOADS FOR CYLINDRICAL SHELLS WITH PART THROUGH SLOTS

A numerical limit analysis is performed for cylindrical shells with part through slots using a general computational method for limit analysis of 3 D structures. The upper bounds for the limit pressures are given for a comprehensive range of geometric parameters. Some of the calculated results are compared with the results of detailed 3 D elastoplastic finite element analysis and where possible, with existing theoretical, experimental or numerical solutions. The effects of various shapes and sizes of par...

1996, 28(6): 682-691. doi: 10.6052/0459-1879-1996-6-1995-387

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DISTRIBUTED PIEZOELECTRIC ELEMENT METHOD FOR VIBRATION CONTROL OF SMART PLATES

The Distributed Piezoelectric Element (DPE) method for active control of smart plates is presented in which the piezoelectric modal sensor and modal actuator are designed by means of cutting the entire piezoelectric layers into several independent elements. The modal coordinates and the modal velocities can be obtained from the charges and currents generated by the sensor elements, and the modalactuator is designed by modulating the spatial distribution of voltage applied on the piezoelectric actuator. Fin...

1996, 28(6): 692-699. doi: 10.6052/0459-1879-1996-6-1995-388

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FEEDBACK CONTROL OF CLOSELY SPACED MODE SYSTEM

This paper studies closely spaced mode system using feedback control law designed for repeated mode system. The damping factors of close loop system is analysised in three cases, the repeated mode system's feedback controller used in closely spaced mode system, in closely spaced mode system with parameter perturbation, in partly controllable closely spaced mode system.It is shown that with right coordinate transformation in the cases, the error of th...

1996, 28(6): 700-706. doi: 10.6052/0459-1879-1996-6-1995-389

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THE ( n -3) MULTIPLE EIGENVALUES FOR A CLASS OF STRUCTURES AND ITS NON DEFECTIVENESS

Based on the block structure of the assembled system matrix by gyroscopic mode synthesis technique, it is proved constructively that there is a series of the ( n -3) multiple eigenvalues in the spectrum of the gyroscopic eigenvalue problem for the rotarywing type structures, corresponding to the n repeated substructures mounted on the structure. The associated complete eigenvectors or modes are also obtained. The obtained analytical results are extended to the nonrotating, ...

1996, 28(6): 707-716. doi: 10.6052/0459-1879-1996-6-1995-390

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IMPLICIT NUMERICAL ALGORITHM FOR MULTIBODY DYNAMICS WITH OPEN LOOP SYSTEMS

Qi Wang

The implicit algorithm of multibody systems with topological tree configuration is studied. The canonical equations of the system and the general form of Jacobian matrix of the equations are obtained in the form of matrix. The paper presents the algorithm of Jacobian matrix divided into several submatrices and the diagonal implicit Runge-Kutta method( DIRKM) and implicit symplectic Runge-Kutta method (ISRKM) of canonical equations of the multibody system. The methods are suitab...

1996, 28(6): 717-725. doi: 10.6052/0459-1879-1996-6-1995-391

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1996, 28(6): 726-729. doi: 10.6052/0459-1879-1996-6-1995-392

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NUMERICAL SOLUTION OF THE EULER EQUATIONS FOR THE TRANSONIC FLOW ABOUT THE COMPLETE AIRCRAFT AT HIGH ANGLES OF ATTACKE

In this paper, the conformal mapping technique combined with the algebraic method is used, the unified body fitted orthonormal O H mesh is generated. The Euler equations are solved by finite volume method, the transonic flow about the fighter like aircraft and wing body configuration at high angles of attack can be simulated. The results of the computations show good agreement with experimental normal force coefficients, aerodynamic center position and surface pressure distributions.

1996, 28(6): 730-735. doi: 10.6052/0459-1879-1996-6-1995-393

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NUMERICAL SIMULATION OF INCOMPRESSIBLE VISCOUS FLOW OVER A DELTA WING AT HIGH ANGLE OF ATTACK

The choice of the pseudo compressiblility parameter β is investigated and a function form of β which accelerates the convergence effectively is presented. The numerical simulation of vortical flow about a 70° delta wing is made by solving the incompressible Navier Stokes equations. The agreement of calculated results with the experimental data is favourable. The physical aspects of vortical flow of the delta wing at high angles of attack are analysed.

1996, 28(6): 736-740. doi: 10.6052/0459-1879-1996-6-1995-394

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CML MODELS FOR SPATIOTEMPORAL CHAOS

Some new coupled map lattice (CML) models are developed. Numerical results show that the new models not only are effective to study both weakly and strongly coupled systems spatiotemporal chaos but also reveal abundant spatiotemporal pattern evolution in different nonlinear dissipative dispersive terms.

1996, 28(6): 741-744. doi: 10.6052/0459-1879-1996-6-1995-395

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AN ELASTO PLASTIC CONSTITUTIVE EQUATIONS FOR THE STAINLESS STEEL UNDER COMBINED AXIAL AND TORSIONAL LOADS II. THEORY

This paper proposed that stress may be expressed as a functional of the intrinsic geometry parameters of plastic strain space. In general, the plastic strain space is not an Euclidean geometric space and its measure tensor is a function of not only coordinates (plastic strain) but also plastic strain history. However, it can be taken as an Euclidean one for the case when the material is initial isotropic and plastically incompressible. Based on the theories of Ilyushin and Valanis, a new integral elasto pl...

1996, 28(6): 745-750. doi: 10.6052/0459-1879-1996-6-1995-396

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THE SPHERICAL CAVITATION BIFURCATION IN SUPERELASTIC MATERIALS

The problem for spherical cavitation bifurcations in superealstic materials is formulated in the first section of the paper. Then, two new exact solutions of the spherical cavitation bifurcation for the modified Blatz Ko material are obtained. The stress concentration factor and discontinuity at the vavitation are given when the cavity appears. Finally, the cavitation bifurcation solutions are numerically computed. One can see that the stress concentration near the cavitation is an important cause of the g...

1996, 28(6): 751-755. doi: 10.6052/0459-1879-1996-6-1995-397

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GENERAL THEORY FOR STEADY DYNAMIC PROBLEM OF INFINITE PLATE ON AN ELASTIC FOUNDATION

Integral transform method is used to obtain general solution for steady dynamic response of infinite plate on an elastic foundation causing by a moving arbitrary load. Dynamic response of plate suffering with a moving stationary random load is also discussed. It's found that the plate is not a linear time-variant system in this case. Even if the excitation of plate is a stationary process, the output of it is still a non-stationary process.

1996, 28(6): 756-760. doi: 10.6052/0459-1879-1996-6-1995-398

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1996 Vol. 28, No. 6

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