Papers by Author: Shang Jun Ma

Abstract: To improve the car's active safety, studies on electromechanical brake (EMB) system have been taken in recent years. The principle and characteristics of EMB are investigated in this paper. An EMB system is designed, and a ballscrew/ballnut assembly is used as the transmission device. The comparison of hydraulic brake (HB) and EMB shown that EMB could regulate brake force more quickly and accurately.

Abstract: Based on the current study of planetary roller screw(PRS), a summary of how to match the main parameters of the PRS is obtained. A mathematic model for contact analysis is developed, where series of equivalent balls are used to replace the rounded profile of the roller. At the same time, the formula of axial contact deformation of the PRS is derived. Then a simplified finite element model of the PRS is established and the contact analysis is conducted by FEA. The FEA results and the theoretical ones agree well with each other, so the accuracy of the calculation method and the validity of the equivalent method are verified.

Abstract: Based on the meshing principle of Planetary Roller Screw (PRS), the meshing clearance of screw pair is minimized by taking the half of thread angle, and the pitch diameter tooth thickness, e, as the optimization variables. Optimal structural parameters are obtained by using optimization module of the software Matlab. The 3D model of PRS structures are established with Solidworks and the finite element contact analysis is carried out with Ansys. The contact deformation and stress distribution are calculated among screw, rollers and nut. The results can be used for PRS design.

Abstract: A multiscale method coupled molecular dynamics simulation and finite element method is used to investigate two dimensional nanoscale sliding contacts between a rigid cylindrical tip and an elastic face centered cubic copper substrate with textured surface, in which adhesive effects are considered. Two series of nanoscale surface textures with different asperity shape, different asperity heights and different spacing between asperities are designed. Through the friction forces comparisons between smooth surface and textured surfaces, a better shape is advised to indicate that asperity shape plays an important role in friction force reduction. With proper asperity height and proper spacing between asperities, surface textures can reduce friction forces effectively.

Abstract: A torsional and translational vibration dynamics model for serial herringbone planetary gear train, which considers the effects of the time-varying errors and meshing stiffness as well as elastic coupling between two stage trains at the same time, was established by using lumped mass method. Time domain dynamic load excitation which derived from dynamics equation is taken as the input of steady-state response solution. The steady-state response of gear structure was solved with mode superposition method combined with external judgment program. The effects of rim thickness for thin wall herringbone planetary gear and single-stage internal gear were also analyzed. Through the comparison, the displacement and stress results of key locations on structure have reached the satisfying and disirable values when the rim thickness of planetary gear is greater than 4.0 mn and rim thickness of internal gear greater than 6.5 mn.

Abstract: The dynamic model of the gear transmission system is built in consideration of the time-varying mesh stiffness and the gear errors. Then the time history of the dynamic load of system is calculated. The gearbox structural-acoustic coupling system is built and its noise radiation is calculated by using BEM. The noise spectrum of the gearbox and the panel contribution are obtained. The influence of the gearbox structure improvement, structure damping and different gear style on the noise radiation is analyzed. The study provides useful theoretical guideline to the design of the gearbox.

Abstract: The dynamic load sharing characteristic of the 2K-H-type planetary gear system with floating center gear is researched in consideration of the manufacturing errors, assembly errors, time-varying mesh stiffness. The nonlinear dynamic model is set up and solved by using Newmark’s method. Then the time history of load sharing factor of the system with load balancing mechanism are obtained, and the effects of the floating clearance， the load torque, and the way of planetary gears assembled on load sharing factor are researched. The sensitivity analysis of load sharing factor is done by using finite differential method. The study provides useful theoretical guideline to the design of planetary gear system.