Papers by Author: San Min Wang

Abstract: As one of the important components of aviation and space transmission systems, dynamic characteristics of involute spline couplings influence its lifetime and reliability seriously. Here, taking the backlash of spline joint into account, considering the meshing stiffness varying with the teeth engaged, established the dynamic model with varying stiffness and dynamic equations, and calculated the number of actual meshing teeth and comprehensive meshing stiffness while bearing the varying torque, then, solved dynamic equations using the fourth order Runge - Kutta method, finally, get the teeth meshing number is 23,and the maximum dynamic load coefficient gets smaller from 1.19 to1.15 with the decrease of . This provides a numerical basis for wear`s studying and lifetime`s forecasting of involute spline coupling.

Abstract: The surface dynamometer card is considered as the primary data for a computer analysis of a sucker rod pumping well. There are many problems in the information retrieved from the surface dynamometer card involving duplicated data and reverse direction data (RDD) ,and discontinuous data of the upstroke or the downstroke , etc. This paper presents a simple method for data processing of surface dynamometer card,it is very useful for the dynamics analysis and structural optimization design of pumping unit (PU).

Abstract: Centric slider-crank mechanism forms the main mechanism of slider-crank type cluster well pumping unit (SCTCWPU). The kinematic analysis is the basis of structure design of SCTCWPU. The kinematic analysis based on Pro/Mechanism is simple, intuitive ,reliable,accurate and easy to be modify. This paper presents the mechanism kinematics simulation of SCTCWPU based on Pro/Mechanism. In addition,a comparative motion analysis of SCTCWPU in Pro/Mechanism and MATLAB is made on the basis of actual working conditions.

Abstract: Centric slider-crank mechanism forms the main mechanism of slider-crank type cluster well pumping unit(SCTCWPU). The friction and wear is the core problem of (SCTCWPU). The pressure of the slide upon the rail is one of the major factors of the friction and wear between the roller and rail.This paper presents the static analysis and optimization of the structure of the slide. In addition,a comparative analysis of the two types of the slide’s structure is made on the basis of actual working conditions.

Abstract: Combined gear drive is a common transmission form for high power drive systems. In order to study its behaviors of redundant drive, which improve the system reliability but lead to a problem of inter-excitation of vibrations, dynamic analysis becomes very necessary. First, considering the influences of gear meshing errors, backlashes and time-varying meshing stiffness, a nonlinear dynamic model of sixteen degrees of freedom is developed by using lumped parameter method. Then a nonlinear differential equation set is derived for calculating the steady-state forced response to the internal sinusoidal excitation. After that, time history wave of displacement responses, phase graphs, Poincaré maps and FFT (Fast Fourier Transform) spectra are analyzed. Finally, some useful conclusions are obtained.

Abstract: Transmission influences on the performance and the security of tilt-rotor directly. A transmission-wing coupling dynamic model including time-varying mesh stiffness and static transmission error was proposed, then calculated the dynamic loads of the transmission-wing coupling system under two flight modes: aircraft and helicopter. Then, computed the life of transmission under different system reliability based on the dynamic loads. This paper presents a more accurate transmission life estimation method. The results present some useful informations for dynamic optimization of the transmission and provide a theoretical basis for the transmission design.

Abstract: Gear dynamics model and 16-degree of freedom nonlinear vibration equations of the combining gear drive system are established considering backlash, transmission error and time-varying mesh stiffness, the equations are solved thanks to the fourth-order Runge-Kutta method, and the gear dynamic responses are analyzed, the vibration performances of this system affected by the dimensionless vibration frequency are investigated. The results show when the dimensionless frequency is 0.687, the system appears harmonic response; when the dimensionless frequency is 0.868, the system appears quasi-periodic response; when the dimensionless frequency is 0.889, the system appears chaos.

Abstract: Microelectromechanical system (MEMS) and nanotechnology are important directions on the development of the science in twenty-first century. Some of the effects, such as viscous force, surface force, electrostatic force, friction etc., which can be usually ignored on the traditional scale, have become noticeable when the scale has turn to micro or nano scale. Nanotribology is one of the main areas of the indispensable researches on the basic theory and methodology of the effects. The micro/nano adhesive contact which is the foundation of nanotribology is studied in this paper. The earliest study on adhesive contact was done by Bradley. He presented an expression of adhesive force of two contacting rigid spheres. Derjaguin, Muller and Toprov (DMT) gave the relation of the contact area and the applied load of the adhesive contact of two spheres, but they did not consider the elastic deformation due to the adhesive force of the bodies. Johnson, Keudall and Roberts (JKR) provided a theory of the adhesive contact of two elastic spheres. Tabor gave a parameter (Tabor parameter) to interpret the ratio of the elastic deformation with the adhesive force of two contacting bodies. That is to say the DMT model corresponding to small Tabor parameter(<0.1) and the JKR model to large Tabor parameter(>5). Maguis gave a DMT-JKR transition using the Dugdale model in fracture mechanics (M-D model) in the intermediate region between the DMT model and the JKR model. A numerical algorithm of elastic adhesive contact based on the meshless method is presented in this paper. This make it possible to solve the adhesive contact with more complex surface topography and to consider more intricate factors, such as thermal stress, friction, elasto-plastic deformation etc. in the further studies on micro/nano scale adhesive contact problems. The meshless method seems to be a promising approach for contact analyses because of its flexibility in domain descritization and versatility in node arrangements. It can be used to solve a variety of complicated engineering problems. A numerical example of adhesive contact between a micro elastic cylinder and a rigid half-space is carried out to show the feasibility of the algorithm. In the simulation, an effective method of the M-D model is used to save the cost of computation. Compared with the existed solutions, the results solved by the presented algorithm are reasonable.

Abstract: To study the stability margin sensitivity to the parameters of the geared rotor system is prerequisite to carry on structure optimization design and vibration control. The global dynamic equations of the geared two rotor system are set up through the coupled matrix of the spiral bevel gear pairs, and the stability margin is obtained by analyzing the global dynamic equations. To enhance the damping of the bearings and to enhance the module and mesh damping of the gear pairs can improve the stability margin of the geared rotor system. The method for the stability margin sensitivity analysis of the geared multi-rotor system is feasible. The conclusions from the numerical example are useful to improve the stability margin of the geared multi-rotor systems.

Abstract: In a turbofan engine, the high pressure rotor and the radial driveshaft, which transmit the power from the internal gear-box to the external gear-box, are geared by a spiral bevel gear pair. In this paper, a reasonably simplified dynamic model of the coupled rotors system is established, and then, the coupled stiffness matrix and coupled damping matrix of the spiral bevel gear pair are deduced. A shaft element method is proposed to investigate the lateral-torsional coupled vibration equations of the gear-rotor system. Furthermore, the mode shapes and unbalance responses of this two rotors coupled system are simulated. The results indicate that the system derives many new modes and the exciting forces on a rotor of the system would be passed to the other rotor for the gears meshing. When the rotor dynamics of a turbofan engine is being analyzed, the high pressure rotor and the radial drive shaft must be viewed as a whole. The dynamic balance precision of the rotors should be qualified properly, in order to improve the dynamic quality of the turbofan engine.