Papers by Author: Bang Chun Wen

Abstract: This paper proposes an analytical approach to study self-synchronous motion and stabilizing conditions of a novel vibrating mechanism excited by two unbalanced rotors. This approach begins with utilizing Lagrange equation to establish differential motion equations of the system, and then obtains the dimensionless coupled equation of the unbalanced rotors with a modified average small parameter method. The zero solutions of dimensionless coupled equations are used to achieve the condition to implement self-synchronization of the vibrating system, and finally the Routh-Hurwitz criterion is used to derive the conditions of self-synchronous motion stability.

Abstract: A dynamic model of the single vertical centrifugal pump was established to avoid seismic disadvantageous direction towards the direction of continually occurring earthquake during the designing and the installing. Finite element method was used to analyse the single vertical centrifugal pump and educe the first 20 natural frequencies and vibration shapes. Response spectrum method was adopted to do earthquake analysis. Response spectrum was inputted from different directions for getting different displacements and loads. According to the results, model’s direction of 45°~75° should be located at the direction of continually occurring earthquake to avoid the maximum vibration.

Abstract: In this paper, we analysed the level of radiation noise and distribution of noise sources of car’s engine and front panels by using sound intensity method. To get the nephogram of sound intensity and sound power spectrum, we used the sound intensity probe and Multi-channel Data Acquisition Regulation System B&K 3560-D and Pulse Data Processing Analysis Software. By analysing experimental results, we can conclude the location of noise sources of these parts. The measurement results will serve as a reference for the car noise reduction.

Abstract: To reduce noise and make the structure of the car more rational, we established modal test system of car's body-in-white in this paper. Car body-in-white was mounted on rigid platform with four coil springs. The car was excited by an electromagnetic exciter. The method of single-point excitation and multi-point collecting vibration was used in this test. Excitation point was chosen in the bearing beam. Signals picked up by the acceleration sensors were processed in the software of Mescope. With this system, different modal frequencies and modal characteristics of the car are acquired. The results show that modal parameters are effective and reliable and those parameters can be basis for the designer to improve the structure of the car.

Abstract: Design and R&D (Research and Development) of products play an important role in development and competitiveness of enterprise. How to do the works better We think that most advanced product design methodology should be used on design, research and development of products. So-called most advanced product design methodology is that based on “the Scientific Outlook on Development” that we set up recent years. New developments of product design methodology include: At first it has been classified that more than seventy theories and methods proposed by domestic and overseas scholars in recent 100 years; QCTES was instead of IQCTES including six requirements of product design; traditional design stages were replaced with four new stages including investigation, planning, implement and inspection; green design was replaced with harmonious design; traditional design method was replaced with deep-layer design method; concept and connotation of product top-layer design were proposed; more detailed contents of product systematic design were advanced; formulas of complete system and product design quality, and connection equation between design objective, design content and design method were submitted. We got good effects to apply above product design methodology on many product designs recent years.

Abstract: Transient Statistic Energy Analysis (T. S. E. A.) for transient response of a vibration system is investigated in this paper. Mathematical expressions of the rise time and the peak energy were derived. Numerical modeling of the system was also made. It showed that the peak energy decrease as the internal loss factor and the coupling stiffness decrease, the rise time decease as the internal loss factor and the coupling loss factor increase. It was found that the results of TSEA and the traditional methods are identical.

Abstract: The stability and bifurcation behavior of Jeffcott rotor with local rubbing are investigated in terms of Hartman-Grobman theorem in this paper. The case with double zero real part of eigenvalues is analyzed by means of the theory of center manifold and n-dimension Hopf bifurcation. Along with discussion for the effects of parameters on system stability and bifurcation behavior, numerical simulation of rotor locus is conducted and the stability condition is derived.

Abstract: Continuous attribute discretization based on rough set is to got possibly minimum number of cuts, and at the same time it should not weaken the indiscernibility ability of the original decision system. In order to obtain the optimal cut set of the continuous attribute system, based on research the choice of candidate cut set, this paper presents a heuristic genetic algorithm for continuous attribute discretization to decision tables. In this algorithm making the importance of the continuous cut as heuristic message, a new operator is constructed to not only maintain the discernibility of the cuts selected, but also improve local search ability of the algorithm. Compared the performance of this method with the others’, this method is proved effective and superiority.

Abstract: The model based fault identification method was used to identify the two unbalance faults in two-span rotor system. The unbalance location and magnitude were identified using least squares fitting approach by the system’s transient residual vibration. The all-phasic FFT technique was used to analyze the original phases of vibration signals. The unbalance location and magnitude of the rotor system can be detected by using only a few sensors. Numerical simulations and experiment on rotor system with two unbalance faults were used, which proved the efficiency of the method.