Papers by Author: Hui Qun Yuan

Abstract: Based on multi-fractal theory, the generalized fractal dimensions of acoustic emission (AE) signals during cutting process were calculated using improved box-counting method. The generalized dimension spectrums of AE signals for different tool wear condition were gained, and the relation between tool wear condition and generalized dimensions was analyzed. Together with cutting process parameters, the generalized fractal dimensions were taken as the input vectors of BP neural network after normalization. The initial weight and bias values of BP neural network which was used to classify the tool wear condition were optimized with Genetic Algorithm. The test results showed that the method can be used effectively for the identification of tool wear condition.

Abstract: Considering the drawbacks of existing dynamics research of gearbox system, the dynamic analysis method based on perfectly elastic body is presented. A certain type of marine gearbox is taken as investigation object based on Abaqus/Explicit dynamic finite element program, the dynamic contact nonlinear model of gearbox system is established considering the coupling effect of each component, dynamic simulation of the gearbox system is carried out. The results show that, in the gearbox coupling model, the coupling effects among the bearing, the housing and the gears cause the dynamic characteristic of the gear transmission system more complex, which exacerbates shock effect of the gearbox, the model which considered coupling among the components is closer to the real working condition. The research has certain reference value for gearbox dynamic characteristic optimization.

Abstract: To valve leakage in working process of diesel engine, the corresponding fault simulation is an important measure for finding a diagnostic method. By the Law of Conversation of Energy, Conversation of Mass and the Classical Equations, mathematical model of working cycle of diesel engine is reasonably built and calculated. Through analyzing valve leakage fault, the single Weber-function is used as a combustion model in fault simulation. Fault diagnosing of valve via the energy parameters of cylinder head vibration signal is proposed. The key to diagnose valve leakage closely lies in analyzing its high frequency components through selecting the cylinder head vibration signal close to the maximum burning and exploding pressure step and proposing spectrum analysis.

Abstract: Using the basic finite element theory, 3D finite element models of flexible membranous disc coupling with different disc thickness is built by ANSYS ，and then the dynamic characteristics are analyzed in working conditions. In particular, the analysis of static stress and harmonic response to the thickness of 0.85 model is done for getting the stress variation under a rated condition. The date calculated by dynamic characteristics and stress analysis can satisfy the design requirements. Those researches and analysis provide a theoretical consideration for complex vibration situation of flexible membranous disc coupling and for the improvement and optimization of coupling product.

Abstract: In this paper, through generally using basic priniciple of heat transfer and gear, established the transient conduction differential equation and its definite conditions. On the basis of tribology and engagement theory, established the periodical boundary condition. Using ANSYS Programm, we analyzed temperature distribution of a spur gear operating under transient friction heat, and its periodical change. Simultaneously, we get the flash temperature distribution on the engaged surface of spur gear and its change curves. The basis for precisely studying its thermal deformation and profile modification is also established.

Abstract: A new twenty-freedom non-linear dynamic model for two-span dissymmetric elastic rotor system was established by considering the crack fault, rub-impact fault and oil film force. The complex motion characteristics of this system were numerically studied and the effect of different parameters on the system is investigated. Moreover, the both cases with and without crack fault were discussed in detail. The results indicate that the system has obvious single-period, period-doubling bifurcation and chaos phenomena. There are marked influences of the crack faults on the nonlinear characteristics of the system, especially under some the rotating speed. The case considering crack faults has different chaos region from the case without crack fault. The chaos phenomenon appears at lower rotating speed, and when the chaos comes again, the corresponding rotating speed extends backwards. Synchronously, the influence of crack fault increases along with the depth of crack. The results may provide theoretical references for rotor fault diagnosis.