Prediction Method of Contact Fatigue Behavior of High-speed Train Transmission Gears Considering Wheel Rail Service Status 核心 · 已核验

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With the increase in the operating speed of high-speed trains, the wheel-rail excitation leads to a sharp increase in the contact load of the transmission gears, making traditional quasi-static contact fatigue strength assessment methods unable to accurately reflect the transient contact characteristics of the gears. On the other hand, the current heat treatment processes for high-speed train transmission gears are still mainly based on standard specifications for qualitative design, with weak correlation between the hardened layer parameters and actual service conditions. To address this issue, a vehicle dynamics model considering the local contact characteristics of gears was established to obtain the transient contact mechanical parameters of the transmission gears under wheel-rail excitation. A contact fatigue model based on the distribution of tooth surface hardness was developed, and the fatigue safety margin of the tooth surface along the depth direction is quantitatively represented by the fatigue damage index.Taking a 400 km/h high-speed train as the research object, a vehicle dynamics model considering the local contact characteristics of gears was established. The basic structure of the train mainly includes key subsystems such as the body, bogie, wheelset, suspension system, and gearbox. The full vehicle dynamics model was built using SIMPACK software. In the vehicle dynamics model, measured track irregularities from the Wuhan-Guangzhou high-speed railway were applied, including complete vertical and lateral track irregularities of both the left and right rails, simulating the train’s operation in a real-world environment. Wheel flats usually represented by edge wear on the wheel, can be characterized by the distance from the wheel's center, while wheel polygons refer to periodic wear along the circumference of the wheelset, which was typically simulated by a harmonic function representing the diameter variation of the wheelset. During gear meshing, the actual contact area between teeth is much smaller than the overall size of the gear, so the local contact of the tooth surface can be approximated as a line contact problem between two parallel cylinders with specific radii of curvature. Based on Hertzian contact theory, the local contact stress of the gear can be solved. To verify the accuracy of the established gear contact model, a straight tooth gear pair contact model was built using gear parameters from literature, and the Hertzian contact pressure and contact half-width during gear meshing were compared with the analytical solutions in the literature, validating the effectiveness of the gear contact model. Furthermore, a dynamic model of a double helical gear pair for a certain high-speed train was constructed to analyze the distribution characteristics of local contact mechanical parameters of the tooth surface.During each meshing process, the contact stress on the gear tooth surface gradually increases from zero to a peak value and then decays back to zero, forming a complete stress cycle. This periodic contact stress change generates alternating shear stress beneath the contact point, driving dislocations in the tooth surface material and initiating small fatigue cracks. Under sustained cyclic loading, these cracks gradually propagate towards the tooth surface, eventually causing localized material spalling and pitting damage. Therefore, to assess the gear's contact fatigue performance, accurate subsurface stress field parameters are required. The analytical expression for the Hertzian subsurface stress field was provided, and the distribution characteristics of the subsurface stress field were analyzed. At the surface, both normal stresses σx and σz are compressive, with σz monotonically decreasing with depth, while σx remains compressive at shallow depths but turns tensile after a certain depth. Shear stress is symmetrically distributed on both sides of the contact center, and its direction undergoes periodic reversal as the contact load rolls through the meshing process. The maximum alternating shear stress amplitude occurs at a subsurface depth approximately 0.5 times the contact half-width, and this alternating shear stress is a significant driving force for surface pitting cracks. The maximum shear stress is located directly beneath the contact center, and although its absolute value is high, its contribution to fatigue damage is usually lower than that of alternating shear stress because its direction remains largely unchanged during the loading cycle. The Matake criterion, as an infinite fatigue life evaluation method, posits that the initiation of fatigue cracks is primarily controlled by alternating shear stress on the critical plane. This assumption is highly consistent with the damage mechanism of gear contact fatigue. Based on the Matake criterion, a fatigue damage index was developed to reflect the impact of tooth surface hardness gradient distribution on contact fatigue performance, and the transient contact mechanical parameters of the tooth surface were combined with heat treatment process parameters, providing a theoretical basis for the quantitative design of tooth surface hardened layer parameters.To explore the impact of track irregularities on the gear's contact fatigue characteristics, transient contact loads of the gears were obtained under 0x, 0.5x, 1x, 1.5x, and 2x track irregularity excitation while the train operates at 400 km/h. Under conditions of no track excitation, single and double track irregularity excitation, the most dangerous point’s contact fatigue damage index is 4.6, 4.0, and 3.4, with the most dangerous point’s distance from the surface being 0.15 mm, 0.17 mm, and 0.20 mm, respectively. Compared to the no-track-excitation case, track irregularities increase the gear contact fatigue damage, but the increment of fatigue damage becomes smaller as the track irregularity amplitude increases, and the location of crack initiation does not significantly change. This analysis suggests that controlling track irregularities will not significantly improve the contact fatigue performance of high-speed train transmission gears.To explore the impact of wheel defects on transmission gear contact fatigue characteristics, transient contact loads of the gears were extracted under wheel flat lengths of 20 mm, 40 mm, 60 mm, 80 mm, and 100 mm, as well as under 20th-order wheel polygon amplitudes of 0.02 mm, 0.04 mm, 0.06 mm, 0.08 mm, and 0.10 mm. Under wheel flat excitation, as the flat length increases, the average contact load remains nearly unchanged. When the flat length is less than 60 mm, the standard deviation of the contact load increases only slightly, but when the flat length exceeds 60 mm, the increase in standard deviation is significant. When the flat length is 60 mm and 100 mm, the standard deviation of the contact load increases by about 9% and 26%, respectively, compared to the undamaged case. The fatigue damage index at the most dangerous position decreases from 4.0 to 3.3, and the maximum fatigue damage depth increases from 0.17 mm to 0.20 mm. Under wheel polygon excitation, as the polygon amplitude increases, both the average contact load and the standard deviation show a significant upward trend. When the polygon amplitude is 0.10 mm, the average contact load and standard deviation increase by approximately 14% and 130%, respectively, compared to the undamaged case. The fatigue damage index at the most dangerous position decreases further to 2.7, and the corresponding maximum fatigue damage depth increases from 0.17 mm to 0.26 mm. Overall, under the excitation of wheel flat and polygon defects, the degree of fatigue damage significantly increases as the degree of wheel damage intensifies. Specifically, when the wheel flat length exceeds 60 mm or the 20th-order wheel polygon amplitude exceeds 0.04 mm, the degradation of the tooth surface contact fatigue performance is notably enhanced. Therefore, the contact fatigue performance of high-speed train transmission gears can be significantly improved by controlling the level of wheel tread defects.

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国内直连:可达 (2026-07-11 检测) 非直连:可达 (2026-07-11 检测)
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设备类型

gearbox

PHM 任务

health_state_assessment

故障工况

运行工况