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10 February 2004, Volume 26 Issue 1
Review
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-251
Abstract ( 1251 )   PDF (862KB) ( 718 )
As fiber-reinforced composite are widely used as alternative of conventional materials in the constructions of supersonic airplane, marine, automobile, the knowledge in damping of composites is becoming more important for controlling the noise and vibration in the structures. In recent years the research on composite damping mechanisms and prediction methods have received extensive attention. This paper reviews recent achievements in damping studies for fiber-reinforced composites at both the macro- and micro-mechanical levels. The effects of some important factors such as fiber/matrix interface, interlaminar stresses, and transverse shear deformation on specific damping capacity of composites are also summarized. Finally, improvement and optimization for damping are introduced, and some recommendations regarding future research are prospected.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-252
Abstract ( 1294 )   PDF (262KB) ( 624 )
The mechanical analysis of bottom hole assembly(BHA) is the basis of BHA's design and well-path control in oil and gas drilling engineering. Beam-column theory'' is a typical and effective method in practice, but its application is limited for not solving the initial bending problems. A method, as known as equivalent loading method, for solving beam-column with initial bending is discussed in this paper. The method has been used successfully for solving practical problems in drilling engineering and provides theoretical foundations for downhole tool design and well-path control. Conclusions are given in this paper.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-329
Abstract ( 1227 )   PDF (187KB) ( 565 )
In this paper problems of dynamic stability of members with elastic support had been investigated. The critical frequency and unsteadiness border of bars were derived. The effects of spring stiffness and damping on dynamic stability of bars were studied. Research make know the side direction stiffness of members more greatly dynamic stability of structure more better, the advantageous effect is taked in the vibration to members of damping. Some suggestions were given for reducing the vibration of bars in practical engineering fields.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-346
Abstract ( 1573 )   PDF (237KB) ( 616 )
The purpose of this paper is to present an improved domain decomposition method, and to simulate the flow around a single cylinder and two cylinders in tandem arrangement. For the calculations of flow around a single cylinder, the size of steady vortex at low $Re$ here was close to the results obtained from experiments. For the calculations of flow around two cylinders, research was applied to discuss the lift coefficient, drag coefficient and the frequency of lift curve in various spacing. The results we obtained in this paper are consistent with experiments, and provide us with some basic knowledge about vortex-induced vibration.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-372
Abstract ( 1353 )   PDF (405KB) ( 424 )
In this paper, fuzzy reliability methods in the corrosion pipeline are carefully studied. Determining and fuzzy reliability concepts are put forward for the first time. Three methods are brought forward to calculate fuzzy reliability based on fracture failure criterion, FAD failure assessment diagram and residual strength. Three additional methods are proposed to calculate determining reliability, based on modified JC model, modified Monte-Carlo model and modified GA-JC model. According to the observation in Shengli Oilfield certain experimental zones with corrosion inhibitor, temporal variation of reliability are studied. The case study shows that the method based on residual strength is better than the others for fuzzy reliability and modified Monte-Carlo method is better than the others for determining reliability.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-374
Abstract ( 1240 )   PDF (397KB) ( 522 )
In this paper, the fundamental principle of dynamic photoelasticity is introduced. Some issues concerned such as the applicability of stress-optics law and whether the inertia force can be neglected or not etc., are answered theoretically. Based on summarizing all sorts of identification ways, a method to combine stress wave theory with analyzing isochromatic fringes is proposed. As a result, not only the concept of identification is made more distinct, but also the accuracy of analysis and identification can be increased.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-405
Abstract ( 1376 )   PDF (214KB) ( 496 )
When using FEM to analyze the axisymmetric shell, we not only need to distinguish thin and thick shells, but also to select and use different elements, which seems to be inconvenient for us. In order to solve this problem, it's of great significance for us to build up an element of high precision applicable to both thin and thick shell. For this reason, a new axisymmetric curved shell element with independent deflection and slope is presented by means of introducing generalized conforming condition into shear strain and displacement. Numerical examples show the new element exhibits higher precision and suits to both thin and thick shell. The element is also applicable to the calculation and analysis of the axisymmetric shell structure.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-415
Abstract ( 1157 )   PDF (273KB) ( 422 )
In this paper, the oil film force of finite journal bearing is obtained using averaging natural value method. The nonlinear dynamical behaviors of a rigid rotor-bearing system were investigated with the help of numerical integral, Poinc\'are map and spectrum analysis. Some bifurcation maps about rotating speed and a synthetically parameter which reflected the influence of many factors were drawn. The results show that complicated dynamical behaviors such as Hopf bifurcation, double-period and quasi-period movement are existed. The work above-mentioned lay the basis for averaging natural value method to be applied to engineering structure.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-416
Abstract ( 1048 )   PDF (132KB) ( 523 )
Based on the elastic theory and some assumptions of composite section, the reinforced concrete (RC) beam strengthened with carbon fiber reinforced polymer sheets (CFRPs) is analyzed, and the expression of unit-length adhesive interfacial shears and the differential calculus of axial force in the CFRPs are established. Then, the analytical solutions of the axial force in the CFRPs, the interfacial shear stress in the adhesive layer and the bending moment on the cross-section of RC beam are presented as general forms. A case study shows that the stress concentration at the end of beam may cause bending failure, which can be prevented by the measures proposed in this paper.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-424
Abstract ( 1110 )   PDF (223KB) ( 413 )
This paper performs the limit analysis of a thick wall cylinder of linear strengthened material based on the unified strength theory. The analytic expression of limit pressure is obtained. By using the unified strength theory, more reasonable solutions for different materials can be derived.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-425
Abstract ( 1004 )   PDF (316KB) ( 494 )
In order to reduce the influence of blasting vibration on wall rock and roadbed, the divided charges are used to take place of centralized charge and then the interval between the divided charges is determined by engineering calculation based on stress wave spread in rock. The intreval between the divided charges is calculated based on the relations between cracking circles and folded stress waves and the relations between cracking circles and folded stress are studied by stress wave theory and stress analysis of the folded stress that acted on the rock based on engineering practice. The rule and method for the design of the interval between divided charges are established through mechanism analysis and engineering calculation under common conditions and then validated by engineering practice. The rule and method may serve as a guidance in the congener engineering blasting.
Application study
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-438
Abstract ( 1288 )   PDF (207KB) ( 435 )
The effect of negative damping is to force the amplitude to increase gradually. Eventually, the motion gets rid of the potential well and cease to be periodic. The escaping time from the potential well of quadratic nonlinear oscillator is obtained by using the multiple scales method. Approximate potential method is applied to overcome the difficulty caused by nonlinearity. Numerical examples further validate the present method.
Review
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2002-441
Abstract ( 1546 )   PDF (299KB) ( 602 )
PVDF is a kind of gauges used to measure pressure, velocity, and acceleration. The principle of PVDF gauge is systematically described in the paper. Split Hopkinson pressure bar (SHPB) was used to have the dynamic calibration of customized PVDF gauges. It showed that the dynamic frequency response of PVDF gauges were high enough for impact loading and noise signal was smaller compared with the signal from resistance strain gauges. We are used to PVDF gauges to measure the propagation and attenuation of stress wave under impact loading to different assembled layers with different materials by 37\,mm caliber gas gun, including water, aluminum foam, granite and steel fiber reinforced concrete. The experiments show that aluminum foam is a good material for energy absorption and water is a nice material to unload when it overflowed under dynamic loading. We conclude that PVDF gauges are suitable for dynamic stress wave measurement for its small size, high dynamic frequency response and wide linear pressure measurement.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2003-049
Abstract ( 1320 )   PDF (241KB) ( 462 )
As a research tool of the turbulent flow, spectrum analysis can decompose the complex flow into the flows with the various scales. By DNS data, the spectra of fluctuant kinetic energy, velocity and temperature are analyzed in turbulent flow of natural convection between two infinite vertical differently heated walls. Results show that the ranges of all these spectra are very broad from the largest to the smallest scales, time step is small enough to be used in DNS. From the energy distribution, energy region, inertial sub-region and dissipation region can been observed, the characteristics of these regions are concluded. Due to the high anisotropy of this kind of the turbulent flow, inertial sub-region is much small. Further, the influence of the vertical position to the fluctuant kinetic energy and to the energy spectrum is discussed, the characteristic of large-scale structures in the frequency space is showed also in the paper.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2003-193
Abstract ( 1194 )   PDF (423KB) ( 378 )
The flood disaster along the Yangzte river in 1998 which brought about enormous economic losses to Chinese people shows that the flood control system of the Yangzte River is still very weak despite of enhanced capabilities of flood prevention in these years. Focusing on the Jingjiang River and Dongting Lake area, a numerical FVM model is established to study flood routing in this complicated water system consisting of one-dimensional rivers and two-dimensional lakes. By applying this model, the simulation of flood motion in the river network owing to geographical environment factors are analyzed in detail. Two important factors that may cause high stages in the Jingjiang River during the 1998 Yangzte River flood period have been identified. They are, the blockage of the dividing rivers and shrink of the Dongting Lake. According to this research, a number of measures can be adopted to mitigate the flood disaster in the Yangtze River valley.
2004, 26(1):  0-0.  doi:10.6052/1000-0992-2003-380
Abstract ( 1188 )   PDF (881KB) ( 502 )
This paper analyzes the classification and characteristics of medical waste, chemical warfare agents and hazardous waste, and compares the fundamental requirements, classifications, and specialties of different incinerators with equipment for pyrolysis and plasma treatment technologies. This paper also discusses the requirements of pre-treatment technologies and off-gas treatment for thermal treatment technologies to avoid the secondary pollution, and introduces the properties of Dioxin (PCDD/Fs) and relative technologies. This paper also introduces the situation of medical waste and hazardous waste management, disposal and pollution control technologies in developed countries.