Abstract
The contact fatigue of aviation gears has become more prominent with greater demands for heavy-duty and high-power density gears. Meanwhile, the coexistence of tooth contact fatigue damage and tooth profile wear leads to a complicated competitive mechanism between surface-initiated failure and subsurface-initiated contact fatigue failures. To address this issue, a fatigue-wear coupling model of an aviation gear pair was developed based on the elastic-plastic finite element method. The tooth profile surface roughness was considered, and its evolution during repeated meshing was simulated using the Archard wear formula. The fatigue damage accumulation of material points on and underneath the contact surface was captured using the Brown-Miller-Morrow multiaxial fatigue criterion. The elastic-plastic constitutive behavior of damaged material points was updated by incorporating the damage variable. Variations in the wear depth and fatigue damage around the pitch point are described, and the effect of surface roughness on the fatigue life is addressed. The results reveal that whether fatigue failure occurs initially on the surface or sub-surface depends on the level of surface roughness. Mild wear on the asperity level alleviates the local stress concentration and leads to a longer surface fatigue life compared with the result without wear.
Highlights
Gears are extensively utilized in numerous machines such as helicopters, ships, wind turbines, and vehicles
Gear contact fatigue life is one of the main factors determining the time between overhauls (TBO) of aviation transmissions
When the surface roughness Rq was less than 0.2 μm, the gear contact fatigue life was very high, and the failure occurred in the subsurface area
Summary
Gears are extensively utilized in numerous machines such as helicopters, ships, wind turbines, and vehicles. Ringsberg et al [21] combined a multiaxial fatigue crack initiation model with the damage accumulation theory to form a fatigue life prediction strategy for rolling contact fatigue crack initiation This theory considers fatigue failure as a process of damage, it neglects the gradual deterioration of material properties during repeated loading. Based on the CDM theory, Leonard et al [37], Ghosh et al [38], and Shen et al [39] simulated the combined process of fretting wear and fatigue damage and discussed the effects of the surface roughness, frictional coefficient, material hardness, and Young's modulus on fretting wear. To describe the interaction between wear and fatigue damage of the gear tooth and to identify failure modes under real tooth surface micro-topography, the elastic-plastic finite element model of an aviation gear pair was established. Variations in wear volume and fatigue damage on the near-surface and sub-surface areas around the pitch point area are described, and the effect of surface roughness on fatigue life and failure mode is discussed considering the coupled mechanism of wear damage
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