力学学报

THE THREE PART DECOMPOSITION OF TURBULENT SIGNAL

The turbulent signal measured by hot wire is decomposed into three parts with the digital filter and the wavelet analysis. First, the turbulent signal is decomposed into the small scale vortex that has approxmate isotropy and the large scale vortex. Then, the large scale vortex isdecomposed into the coherent and the non coherent parts. Compared with the conditional sampling, the decomposition is realiable. The time scale and non conditional mean profile of coherent structure can be obtained with this meth...

1997, 29(5): 519-524. doi: 10.6052/0459-1879-1997-5-1995-261

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A LATTICE BOLTZMANN EQUATION METHOD FOR THE SHALLOW WATER WAVE EQUATIONS

We proposed a lattice Boltzmann equation (LBE) method to simulate the shallow water wave equations. If the viscosity of the gas is negligible, the gas macrodynamical equations are compared with the shallow water equation, and the equilibrium distribution function can be given. Numerical results are compared with the exact solution given by W.C.Thacker.

1997, 29(5): 525-529. doi: 10.6052/0459-1879-1997-5-1995-262

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THE CONVEX RESPONSE SET OF A CLASS OF MDOF VIBRATION SYSTEM

The response reachable set is defined for a linear time invariant vibration system excitation of which is modeled by a convex set. The problem of resolving the convex responses of MDOF vibration system is transformed into that of finding the response reachable set. A support hyperplane method of finding the response reachable set to the excitation modeled by aspecial convex set is presented. An analytical expression is obtained for the boundary point of the finite time response reachable set at a directio...

1997, 29(5): 530-539. doi: 10.6052/0459-1879-1997-5-1995-263

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QUALITATIVE PROPERTIES OF FREQUENCY SPECTRUM AND MODES OF ARBITRARY SUPPORTED BEAMS IN VIBRATION

Some important qualitative properties of the frequency spectra and modes for Euler beams with arbitrary supports are determined. The case of supports free-pinned, free-sliding, free-free and sliding-slinding are considered, the rigid-body modes occur for beams with such supports. In addition, the sufficient and necessary conditions of a mode of the beams are obtained.

1997, 29(5): 540-547. doi: 10.6052/0459-1879-1997-5-1995-264

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A STUDY ON TRANSIENT COMPONENTS OF CRACKED ROTOR VIBRATIONS

Approaches of qualitative analysis, multiple scale analysis and numerical simulation have been used to study properties of cracked rotor vibrations in the present paper. It has been shown that transient components of cracked rotor vibrations are ideal symptoms suited to the early detection of fatigue cracks of rotors. It has also been demonstrated that the method of multiple scales is an effective approach toward the study of parameter excited vibration systems with abrupt parameter variations.

1997, 29(5): 548-554. doi: 10.6052/0459-1879-1997-5-1995-265

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TRANSFORMATION PROPERTIES OF Ce TZP AND Ce TZP/Al 2O 3 LAYERED MICROCOMPOSITES

The real time transformation procedures of three point bending beams with a single edge notch of Ce TZP and Ce TZP/Al 2O 3 layered microcomposites are observed by moire interferometry. Strong autocatalytic effect on Ce TZP stabilized with 12% mol CeO 2 and sintered at 1600°C for 3 h is revealed under room temperature, and the frontal transformation zone appears to beroot like. While the autocatalytic transformation is prevented byAl 2O 3 layers in Ce TZP/Al 2O 3 layered microcomposites, th...

1997, 29(5): 555-562. doi: 10.6052/0459-1879-1997-5-1995-266

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ON CO-DIMENSION 2 BIFURCATION SYSTEM EXCITED PARAMETRICALLY BY WHITE NOISES

In this paper, in order to investigate the sample stability of a class of white noises parametrically excited co-dimension 2 bifurcation system which possesses non-semisimple double zero eigenvalues and then to fix the first bifurcation point, the approach of asymptotic analysis of L. Arnold is used to obtain the asymptotic expression of the maximum Lyapunov exponent of the relevant system. In addition, with the aid of the theory of singular boundary of one-dimensional diffusion process, a further research ...

1997, 29(5): 563-572. doi: 10.6052/0459-1879-1997-5-1995-267

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ANALYTICAL EXPRESSION OF TRANSITION BOUNDARIES OF THE SOLUTION OF DUFFING SYSTEMS

The nonlinear Duffing equation is studied and fold boundaries of period T are obtained by introducing Burton's and Cheung's results and nonlinear frequency. Also, the transition boundaries of symmetric breaking are obtained by general Newton's method. Our results are in good agreement with Leung's by IHB method,and we overcome the difficulty of great quantities of computation by computer.

1997, 29(5): 573-581. doi: 10.6052/0459-1879-1997-5-1995-268

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EXPERIMENTAL STUDIES ON TENSILE STRESS STRAIN RELATION OF SOFT COAL

A test set up for measuring tensile stress strain relation and tensile strength of soft coal or soil is proposed A ring shaped coal sample pressed from coal powder is lined with a pressurized water bag When the water pressure increases to a certain value, the coal sample in circumferential tension breaks down Systematic experiments have been done to show the tensile stress strain relation of the pressed coal sample with various sample density and pore pressure The stress strain relation ...

1997, 29(5): 582-589. doi: 10.6052/0459-1879-1997-5-1995-269

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AN OPTICAL FIBER STRAIN SENSOR METHOD IN VARYING TEMPERATURE ENVIRONMENT

The principle of the additional phase produced by transmissive light in conducting and sensory optical fibers is studied in this paper when variation of temperature is present Formula of additional phase with temperature changes were given in theoretical analysis A new compensatory method of eliminating the effect of additional phase is also presented The strain of a cantilever beam is measured to make use of all fiber Mach Zehnder interferometric sensor with compensative function It is verefied ...

1997, 29(5): 590-594. doi: 10.6052/0459-1879-1997-5-1995-270

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A GENERAL SOLUTION OF THE PLANE STRESS PROBLEMS IN PIEZOELECTRIC MEDIA WITH LINE CRACKS

Considering continuous boundary condition of electric field at the cracks, a general solution of the plane stress problems in piezoelectric media with line cracks is provided by using function of complex variable and solving Riemann-Hilbert problems Solution in closed form and field intensity factors are given for problems of a single crack and two cracks It is shown from the solution that the stresses and electric field intensity and electric displacement have (1/2) type of singularity at the crack tip...

1997, 29(5): 595-599. doi: 10.6052/0459-1879-1997-5-1995-271

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ANALYSIS OF NONLINEAR VIBRATION FOR ELASTIC SHELLS IN A NON NEWTONIAN REFERENCE FRAME

The kinetic description of elastic shell is presented under a non Newtonian reference frame Based on the Hamilton's principle, a system of nonlinear equations governing the motion of the moderate thick shells are set up in a non Newtanian reference frame By using the multiply scale method and the harmonic balance method, the nonlinear vibration of circular cylindrical shells are analyzed

1997, 29(5): 600-605. doi: 10.6052/0459-1879-1997-5-1995-272

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AN ELASTODYNAMICS SOLUTION FOR ANISOTROPIC AXIALLY SYMMETRIC PROBLEMS

This paper presents a simply analytic method to solve axisymmetrically elastodynamic problems for an anisotropic structure In practical example, the histories and distributions of the dynamic stresses in an anisotropic circular plate are computed

1997, 29(5): 606-611. doi: 10.6052/0459-1879-1997-5-1995-273

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SOLUTION OF MULTI POINT ELASTIC IMPACTS OF STRUCTURES

The method of solving the multi point elastic impacting problems of structures is investigated by taking the impact problem of several particles on a beam as an example.The validity of the given method is verified by illustrative examples.

1997, 29(5): 612-616. doi: 10.6052/0459-1879-1997-5-1995-274

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ANALYTICAL SOLUTIONS ON SAINT VENANT PROBLEM OF LAYERED PLATES

The Hamiltonian system theory is introduced into elasticity problem of layered plates, therefore the eigenfunction expansion method based on horizontal Hamiltonian operator matrix are derived to solve this problem. The analytical solutions on Saint Venant problem of layered plates are obtained by this method. It demonstrates further the potential of the Hamiltonian system theory and symplectic mathematics.

1997, 29(5): 617-626. doi: 10.6052/0459-1879-1997-5-1995-275

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A TIME DOMAIN BOUNDARY ELEMENT METHOD FOR SYSTEMS WITH DAMPING

A new damping model (Proportional Decay Damping) is presented and employed in a time domain boundary element method. This is the first attempt to take the effects of material damping, which is one of the most important factor in dynamic analysis, into account in a time domain boundary element procedure. The damping model and the presented time domain boundary element procedure are verified by comparison with theoretical solutions and numerical results of finite element method in a simple benchmark problem.

1997, 29(5): 627-630. doi: 10.6052/0459-1879-1997-5-1995-276

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AN ADAPTIVE CONTROL STRATEGY FOR DIRECTING CHAOTIC MOTION TO PERIODIC MOTION

The paper presents an adaptive control strategy for directing the chaotic motion of a nonlinear system to a periodic motion through the linear feedback of a control parameter. The key problem solved is to choose the control stiffness in the feedback by means of the pole assignment of linearized controlled system in an extended state space spanned by the system state and the system parameter. The paper gives the simulations of recovering the fixed point of the Logistic map and the periodic orbit of a harmon...

1997, 29(5): 631-635. doi: 10.6052/0459-1879-1997-5-1995-277

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MEASUREMENT OF STRAIN FACTOR OF COMPOSITES PLATE USING MOIRE INTERFEROMETRY

The moire interferometry method was used to study the strain concentration factor of a carbon fiber composite plate with a centrical hole. The rules of the strain concentration factors were determined under different loads.

1997, 29(5): 636-640. doi: 10.6052/0459-1879-1997-5-1995-278

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1997 Vol. 29, No. 5

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