Contact Analysis And Dynamical Characteristic Of Marine Gearbox With Small Down Angle

This subject of the thesis stems from the subtopic"Key technologies and the industrialization of the marine gearbox"of the project"The study of key technologies of high-speed heavy-duty precise transmission"(2006BAF01B07-02) in the National Science and Technology Pillar Program during the Eleventh Five-year Plan Period of China.The gearbox with small down angle is applied extensively in marine industry, like on the high-speed yacht, etc. Due to the formed intersecting transmission and the crossed transmission, a necessary water-entry angle for the propeller is provided. Due to the large dynamic response, high noise, and early wear, etc., the further industrial application of the gearbox with small down angle. In the current study the meshing characteristic of the noninvolute beveloid gear is proposed based on the engagement theory through the numerical simulation with the FEM package ABAQUS. Natural characteristic and the dynamic response of the gearbox system are investigated and the experimental test is conducted for the verification of the theoretical analysis. The maincontents of this thesis are as follows:①Derivation of the surface equation of the noninvolute beveloid gears applied on the transmission system. Surface equations of the noninvolute beveloid gears are derived through coordination transformation based on the meshing involute beveloid gear, and the 3D solid model is generated through the surface reconstructing.②Contact analysis of the meshing gear pair taken the assembly error into consideration is proposed based on the nonlinear finite element analysis software Abaqus. The effects of these errors, the center distance error, axial position error and the angular error, on the contact characteristic are discussed. Modification investigation on the beveloid gears is conducted. The axial modification and the profile modification are proposed based on the maximum deformation of the gear surface with the comprehensive assembly error.③Investigation on the internal dynamic excitation of the gear system is proposed. Time dependent meshing stiffness of the beveloid gears is calculated and the internal excitation of each transmission stage is generated by taking the manufacture error, variant meshing stiffness, impact effect into consideration. A discretization approach is applied here for the internal excitation calculation of the beveloid gear. ④Dynamic analysis of the gear-shaft-bearing-case coupled system is presented. Based on the set up of the coupled dynamic model of the gearbox system, natural characteristic of the system is conducted and the dynamic response of the system is investigated under the ahead condition and the astern condition, respectively.⑤Experimental investigation of the marine gearbox is conducted for the comparison with FEA results. A test rig is built for the investigation of the contact behavior, transmission efficiency of the beveloid gears and the experiment modal analysis is conducted to validate the correctness of the FEA result. The dynamic response of the system is analyzed through the vibration acceleration of those measure points on the case. Experimental results are in close corresponding with theoretical analysis.