Dynamic Characteristics Analysis And Performance Optimization Of Marine Gearbox Under Complex Excitation

Gear transmission is a most widely used transform type of power and motion in allkinds of mechanical equipment of which the dynamic characteristic has significantinfluence on gear device and the entire mechanical system. With the rapid developmentof mechanical industry, gear equipment is developing towards the direction ofhigh-power, high-speed, low-noise and light-weight. Noise and vibration reduction ofthe high-speed and heavy-load gear system has been paid full attention. In this paper, amarine gearbox is taken as the research object. Principle of gear engagement, nonlineardynamic, and optimization design method are utilized to carry out the dynamicproperties analysis and dynamic performance optimization of the high-speed andheavy-load gear system under complex excitation. The study has important theoreticalsignificance and application prospects for the low-noise and light-weight design ofgearbox.The thesis is supported by National Natural Science Foundation of China. Themain research work in this paper can be summarized as follows:(1) Taking time-varying mesh stiffness, mesh damping, tooth composite error,backlash and tooth surface friction into consideration, a nonlinear dynamic model ofmarine gearbox under complex excitation is established based on lumped parametermethod. The dimensionless dynamic differential equations are solved by Runge-Kuttamethod. Then the time history curves, spectrum, phase traces, Poincaré, bifurcationmaps, and dynamic load coefficient curve are analyzed to study the effect of differentparameters on nonlinear dynamics characteristics of gear transmission system.(2) The internal dynamic excitation of multi-stage gear pair of marine gearbox issimulated consisting the stiffness excitation, the error excitation and the mesh impactexcitation. By means of ANSYS/APDL language, the parametric dynamic finiteelement model for the gearbox is constructed. The modal analysis using the blockLanczos method and the dynamic response analysis using the full method of gearboxare carried out, after which natural frequency, natural mode, vibration displacement,vibration velocity and vibration acceleration response are obtained.(3) Based on multi-objective optimization design theory, a dynamic performanceoptimization method of gearbox considering modal parameters and dynamic responseparameters is proposed. Setting the targets of minimizing the root mean square of vibration acceleration of evaluating points on the surface of housing and avoiding thenatural frequencies from the excitation frequencies, the linear weighted multi-objectiveoptimization model of gearbox is established in ANSYS. Though the zero-orderoptimazition solution, the conclusions that after optimazition the RMS of vibrationacceleration of evaluating points on the surface of housing reduces16%, the staticstrength improves39%and the static stiffness improves53%are drawn. Consequentlythe dynamic optimazition of the gearbox reaches a good effect.