| Trucks play an important role in China’s transportation.NVH(Noise,Vibration and Harshness)performance is a key indicator to measure its quality,and the dynamic characteristics of bending-torsion coupling of transmission shafting directly affect NVH performance.Therefore,this thesis takes the truck drive shafting as the research object,establishes the bending-torsion coupling dynamic model of the drive shafting based on the finite element method considering mass eccentricity and middle bracing rigidity,obtains the dynamic response of the drive shafting under different loads through numerical calculation,and analyses the influence of system parameters.The research results reveal the deep vibration mechanism of the truck drive shafting and provide a theoretical basis for improving NVH performance of the vehicle.Firstly,the dynamic model of truck drive shaft is established based on finite element method and the modal parameters are solved by MATLAB software.Based on Workbench platform,the natural frequency and mode shape of the truck drive shaft are obtained,and the correctness of the truck drive shaft dynamic model is verified by comparative analysis.Modal test is carried out on the truck drive shaft.15 measuring points are evenly arranged on the drive shaft.Modal parameters of the drive shaft are obtained by steady-state calculation.Based on the modal frequency criterion,modal mode criterion and modal confidence criterion,the finite element model based on MATLAB is validated from the point of view of experimental modal analysis.Secondly,based on coordinate transformation method,the unequal velocity formula of the cross-axle universal joint is deduced,which is verified by simulation with Adams software.The influence of different angles between shafts on the angle difference between master and slave shafts,the angular velocity of driven shafts,and the angular acceleration of driven shafts are analyzed using MATLAB mathematical software.The equal velocity condition of the double-cross-axle universal joint is obtained,and the dynamic characteristics of the double-cross-axle universal joint are studied.The torque curve of the driven shaft is given and the mathematical relationship between the angle between the shafts and the additional bending moment at the fork of the active shaft cardan joint is derived.Thirdly,conduct a three-dimensional modeling of the intermediate support of the transmission shaft,mainly including three parts: the bracket,rubber sleeve,and rolling bearing.According to the deformation coordination condition,considering the radial clearance equal to zero and greater than zero,the calculation formula of the maximum load of the rolling body is derived.The contact stiffness of the bearing was derived based on Hertz contact theory,and the oil film stiffness of the bearing was derived based on the theory of elastohydrodynamic lubrication.The comprehensive stiffness of the bearing was obtained by connecting the contact stiffness and oil film stiffness in series,and the influence of system parameters was explored.The stiffness of the rubber sleeve was obtained based on vibration isolation theory,and the stiffness of the intermediate support was obtained by connecting it in series with the comprehensive stiffness of the bearing.Finally,considering mass eccentricity and stiffness of intermediate support,a bending-torsion coupling dynamic model of truck drive shafting is established,and the numerical solution is obtained by Newmark-β method.The dynamic response characteristics of the drive shafting under different combinations of radial excitation,torsional excitation and additional bending moment of universal joint are obtained.Through the amplitude-frequency characteristic curve,it is found that the bending vibration will cause torsional vibration to generate new frequency components.Torsional vibration will cause bending vibration to produce new frequency components,and the influence of system parameters on the dynamic characteristics of transmission shafting bending-torsion coupling is analyzed.The thesis has 113 figures,11 tables,and 107 references. |
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