The mesh stiffness and contact ratio of gear drive are very important factors which have a great impact on the dynamic load. Contact ratio also affects the fluctuation and the mode of change of the mesh stiffness. In this research, a novel high contact ratio internal gear with a circular arc contact path is introduced. However, the irregular tooth profile of non-involute gear usually causes the numerical calculation to be more complex. To get the torsional mesh stiffness of a pair of internal spur gear, the two-dimensional finite element models of involute internal gear and high contact ratio internal gear are presented and compared. In addition, the influence of input torque on torsional mesh stiffness and contact ratio are analyzed. The mesh stiffness of a single tooth pair and the effect of different engagement positions on mesh stiffness are obtained and compared. Finally, experimental measurement of contact ratio is established by strain gauge technique. It is shown that the torsional mesh stiffness increases with the increase of input torque, and the greater the contact ratio, the smoother the gear drive.
Contact characteristics of friction pair play a crucial role in the torque transmission capacity and temperature rise prediction of automotive clutches. In this study, a Multi-cone friction pair used in wet clutches has been proposed. Each pair of conical contact is considered as the contact between a finite stiffness punch and an elastic half-plane, and 2D finite element (FE) models are developed to calculate the contact load assignments. Considering the capsizing moment and stress singularity at the end of the contact interface, an analytic model is established to obtain the contact pressure distribution on each conical contact interface based on the results of contact load assignments. Finally, the numerical examples are given, and the influences of axial load, mating material characteristics, friction coefficient, and cone angle on contact pressure distribution have been discussed in detail, which supplies the guidance of parameters design for Multi-cone friction pair.
Non-return mechanism is the key device that plays the role of braking in the opening and closing electric actuator of amphibious aircraft hatch door, in which there are two core components, namely ball-and-socket contact pair and multi-disc friction pair. The braking response characteristics of non-return mechanism directly determine the performance and operation safety of the hatch door. In this paper, the dynamic model of non-return mechanism is established considering the freedom of rotation-translation. Based on MATLAB/Simulink, the solution framework of the overall dynamic model is built. The dynamic response characteristics of non-return mechanism in the process of reverse load braking, forward load braking and continuous closing are analyzed. The braking time and the angular displacement of the output shaft in the braking phase have been presented. The simulation demonstrates that three pairs of friction pairs can realize effective braking under the given working conditions. Compared with the forward load braking, the reverse load braking has longer braking time and smaller angular displacement of the output shaft. This study provides a theoretical basis for the design and optimization of non-return mechanism.
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