| Straight bevel gears are widely applied in automobile, aero-space and petrochemical industries to transmit power and motion between intersecting shafts instead of straight bevel gears due to their advantages such as large contact ratio, smooth transmission, high load-carrying capacity, etc. the complicated gear mechanism assembled by straight bevel gears inherits the characteristic of single pair tooth meshing and double pair tooth meshing lead to the complexity of meshing performance. For example, automotive differential in driving axle transmission system usually operate at a relatively high rotational speed and transmit substantial power. Accurate predicting these change rules of contact stress, bending stress and circumferential displacement of tooth is beneficial to improve gear manufacturing processes and prolong the service life of gear. Moreover, in modern industry, the designer is commonly restricted by the requirement that gears should carry high loads at high speed with both size and weight kept to a minimum. For this demand, it is crucial to investigate the contact fatigue and the bending fatigue to ensure the reliable design of gears. Therefore, analyzing fatigue failure of straight bevel gear is helpful to confirm the main component in gear pairs and to understand the influences of contact fatigue stress and bensing fatigue stress on fatigue lives of gears, which provides useful guidelines for the design of gears.According to the manufacturing process and the gear meshing theory in this paper, firstly establishing the accurately3D parameterized geometrical model of straight bevel gears using the spherical involute equation under the PRO/E software environment, then performing virtual assembly of automotive differential and motion simulation, which are the foundation of FE analysis of automotive differential.A theoretical assembling3D elastic FE model of symmetrical bevel gear differential is developed under the ANSYS software environment. Based on the valid3D FE model, the variation rule of maximum surface contact stress of tooth, the distributions of tooth surface contact stress and tooth root bending stress, the phenomena of stress concentration, tooth end effect, transmission error, symmetry of symmetrical bevel gear differential and equivalence of planetary pinions are investigated in detail. Furthermore, based on the cumulative fatigue standard, the significant meshing state of the straight bevel gear pair is investigated for the analysis of contact fatigue and bending fatigue and the reliability of the proposed3D FE model is proved by comparing the calculation result with the simulation result. On the basis of the reliable3D FE model, the contact fatigue stress and the bending fatigue stress of gear teeth are analyzed under the different load. The contact fatigue life and the bending fatigue life are also studied using the stress-life equation. The obtained results provide useful guidelines for better understanding the fatigue failure of gear tooth, it is also helpful for acknowledging the effect of fatigue stress on the fatigue life of gear tooth. |
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