力学学报

SPECTRAL METHODS INVOLVING THE GENERAL CYLINDER BOUNDARY

Using the Spectral Method, higher precision derivatives can be calculated in numerical computations. After FFT-code was discovered, this method was used popularly in Computational Fluid Dynamics. But till now, problems that can be studied by this method are limited to such boundaries which are either geometrically simple (rectangular, circular and so on) or periodical. Obviously if we break through this limitation, more and more CFD problems can share the advantage of the Spectral Method. In this paper we d...

1993, 25(4): 385-393. doi: 10.6052/0459-1879-1993-4-1995-657

PDF

THE THEORETICAL ANALYSIS OF POLLUTANT DISPERSION IN TIDAL FLOW AND ITS APPLICATION

In this paper a formula is derived for shear dispersion coefficients of two dimensional tidal flow, the velocity distributions of which can be expressed by the product of a space-dependent function and a time-dependent function, by the method of concen-trational moment. The process of dispersion coefficients versus time is calculated in case of sine tidal flow with logarithmic velocity distribution. The relation of dispersion and features of tidal flow, and the phenomenon of negative dispersion are analyzed...

1993, 25(4): 394-403. doi: 10.6052/0459-1879-1993-4-1995-658

PDF

THE HOT ELECTRON AND LINE TYING STABILIZATION OF LOW FREQUENCY PLASMA INTERCHANGE MODES

The dispersion relation for the low-frequency plasma interchange modes in a hot-electron plasma with line-tying function is solved by using the MHD equ. of multiple species. The analytic solution of the real frequency and growth rate is also respectively obtained. The stabilizing effect of hot-electron and line-tying on the low-frequency plasma interchange mode is analysed. When there is no line-tying function, and the density ratio of the hot-electrons to the ions is bigger than , then the plasma interchan...

1993, 25(4): 404-410. doi: 10.6052/0459-1879-1993-4-1995-659

PDF

THE HOPF BIFURCATION OF THE VAN DER POL-DUFFING OSCILLATOR IN THE PRESENCE OF BOTH PARAMETRIC AND THE EXTERNAL INFLUENCE

In this paper, we study the Hopf bifurcations of the van der Pol-Duffing type nonlinear oscillator under the stochastic external influence and the internal parametric excitation. It is shown that the Hopf bifurcation point exhibited in the deterministic system is sensitive to the stochastic external influence and the parametric excitation. The addition of a small stochastic parametric excitation gives rise to a shift of the bifurcation point, which will be earlier than that of the ordinary system for a van ...

1993, 25(4): 411-418. doi: 10.6052/0459-1879-1993-4-1995-660

PDF

STATISTICAL FAILURE THEORY OF BUNDLE-REINFORCED COMPOSITES

The shear-lag model[1] and the geometrical local load-sharing rule[2] are applied for analysis of load concentrations of bundles and fibers in the paper. Based on these studies, the statistical microscopic criteria of failure of small-bundle-(the boundary effects of bundles must be taken into account in this case) and large-bundle-reinforced composites are established by using the method of the critical crack core model[1,3,4] and used for investigation of failure and fracture of bundle-reinforced composite...

1993, 25(4): 419-426. doi: 10.6052/0459-1879-1993-4-1995-661

PDF

AN ACCURATE MODAL SUPERPOSITION METHOD FOR COMPUTING MODE SHAPE DERIVATIVES IN STRUCTURAL DYNAMICS

The modal superposition method is often used to obtain mode shape derivatives. However, it can not give an accurate solution and the errors may become significant, when more high-frequency modes are truncated. This paper deals with the contribution due to the unavailable high-frequency modes to mode shape derivatives, proves that it can be expressed by the available low-frequency modes and the system matrixes, and presents a numerical algorithm. Numerical examples show that the method is correct and can imp...

1993, 25(4): 427-434. doi: 10.6052/0459-1879-1993-4-1995-662

PDF

THE IMPACT BUCKLING OF ELASTIC CYLINDER UNDER STEP TORQUE

Based on the Koiter's initial post-buckling theory and Thompson's discrete coordinate approach, the imperfection sensivity and impact buckling of cylinder under torsion are studied. It is shown that it corresponds to symmetric buckling. By solving the nonlinear dynamic equation numerically, it is found that in the process of post-buckling under step torque, the shell will vibrate with a longer period and its amplitude in increased a bruptly. Also, some experimental results for the impact buckling of cylinde...

1993, 25(4): 435-442. doi: 10.6052/0459-1879-1993-4-1995-663

PDF

SECONDARY BUCKLING OF A STRUT ON AN ELASTIC FOUNDATION UNDER AXIAL COMPRESSION

本文研究弹性基础上受轴向加载的两端铰支杆当其最低两屈曲荷载很近时的后屈曲行为。首先,使用Liapunov-Schmidt约化并借助稳定性分析,揭示了杆的二次屈曲现象;基于分叉方程给出了原始后屈曲分支及二次分支的渐近展开。其次,我们使用作者建立的二次分叉的计算方法对杆的二次屈曲做了数值计算,数值结果与渐近展开符合得很好

1993, 25(4): 443-451. doi: 10.6052/0459-1879-1993-4-1995-664

PDF

A CLOSED FORM SOLUTION ABOUT HIGH CYCLE FATIGUE CRACK INITIATION LIVES OF NOTCHED PLATES BY METHODOLOGY OF DAMAGE MECHANICS

According to methodology of damage mechanics, the conservative integral, stress and strain concentration factors and closed form solution of fatigue crack initiation lives of notched plates are established. For aluminum alloy, the agreement between the results of theoretical predictions and those by experiments is satisfactorily good. This method is very time-saving and a lot of experimental work can be substituted.So this method is in engineering practice.

1993, 25(4): 452-459. doi: 10.6052/0459-1879-1993-4-1995-665

PDF

Dynamic buckle propagation on Chater's beam

In this paper, a sweeping investigation on dynamic buckle propagation on Chater's beam is performed by using the general nonlinear finite element methods (FEM)instead of any quasi static or dynamic steady propagation assumptions, With the help of the arbitrary Lagragian -Eulerian boundary element method (ALE-BEM) and the weighted residual methodology,the effect of interaction between the beam and the fluid flow inside is also reconsidered based on the two-demensional potentional flow theory.How the structur...

1993, 25(4): 460-467. doi: 10.6052/0459-1879-1993-4-1995-666

PDF

CRACK TIP SUPERBLUNTING: EXPERIMENT, THEORY AND NUMERICAL SIMULATION

Experimental revelation of superblunting along plane strain predominant crack tip segment is reported here for modified polyproplene. As elucidated by a heuristic model of progressive circumferential cold-draw the formation of superblunting crack tip depends critically on the ratio between the cold -draw propagation speed and the loading speed, and contributes significantly to the material toughening,especially for the improvement on impact toughness. Detailed numerical calculations are conducted based on a...

1993, 25(4): 468-478. doi: 10.6052/0459-1879-1993-4-1995-667

PDF

DYNAMIC STRAIN ANALYSIS METHOD USING ONE-BEAM SHEARING MOIRE INTERFEROMETRY

This paper developed a new dynamic analysis method based on the principle of one beam shearing Moire interferometry.The method can be used to measure the full strain field of dynamic problems. It is characterised by simple optical arangment,excellent fringe contrast and high sensitivity, etc. Besides, as it uses a portable multiple pulsed - ruby -laser as light source,the method is particularly suitable for field measurement.In the paper, a problem of stress propagating in a rectangle is studied with the ab...

1993, 25(4): 479-484. doi: 10.6052/0459-1879-1993-4-1995-668

PDF

APPLICATION OF MOIRE INTERFEROMETRY TO TECHNOLOGICAL STRESS DISTRIBUTION MEASUREMENT

An experimental study was conducted to measure residual stress distribution around cold-expanded fastener holes and interference stress distribution near interference fit fastener holes. Investigated stresses were relieved by cutting specimens along a radial direction, and additional strain fields created by relieving the stresses were measured using moire interferometry. Relaxation of the residual stress caused by circular loading was investigated experimentally. The results of typical test are presented a...

1993, 25(4): 485-491. doi: 10.6052/0459-1879-1993-4-1995-669

PDF

THE EFFECT OF PROPORTIONAL OVERLOAD ON THE LOW CYCLE TENSION-TENSION FATIGUE LIFE OF ALUMINIUM ALLOY PLATE WITH CIRCULAR HOLE

It is presented in this paper the experimental study of low-cycle fatigue with constant amplitude and overload for aluminium alloy plate with circular hole.During the research six different over load ratios have been selected and different over load cycles have been carried out.It is concluded that for each given over load ratio, the over load fatigue life ratio(ratio of fatigue life for over loaded specimen over the fatigue life for constant amplitude specimen)increases with the increase of over load cycle...

1993, 25(4): 492-495. doi: 10.6052/0459-1879-1993-4-1995-670

PDF

A RESEARCH APPROACH BASED ON THE EXHAUSTION MODEL OF MATERIAL DUCTILITY FOR FATIGUE DAMAGE

Considering the fact that the material ductility may be decreased in cycle fatigue process, a new damage variable based on the exhaustion model of material ductility is defined for low-cycle fatigue , and measured experimentally. It is shown that this damage variable has a definite physical meaning and can be measured by a simple procedure. The relationship between the damage variable and mechanical property of material is establised.

1993, 25(4): 496-499. doi: 10.6052/0459-1879-1993-4-1995-671

PDF

THE DYNAMIC STABILITY ANALYSIS FOR THE BULLET BY THE NONAUTONOMOUS SYSTEMS MODEL

This paper presents the analysis of the dynamic stability of a bullet by use of the nonautonomous nonlinear model which is closer to reality, and by application of the theorems author published before, the theorem of evalution of the state transition matrix and the formulas of the matrix measure.The paper introduces a new theory and method to investigate the stability in the exterior ballistics.

1993, 25(4): 500-504. doi: 10.6052/0459-1879-1993-4-1995-672

PDF

GEOMETRICALLY NONLINEAR ANALYSES FOR 2-D PROBLEMS BASED ON THE INCOMPATIBLE FINITE ELEMENTS WITH INTERNAL PARAMETERS

1993, 25(4): 505-513. doi: 10.6052/0459-1879-1993-4-1995-673

PDF

1993 Vol. 25, No. 4

NoticeMORE+

Exquisite ArticlesMORE+

Download Center

Author Center