Pitch deviation at rack joints(PDRJ) is a common error in rack railways. It directly affects the contact characteristics between the rack and gear and leads to accelerated surface wear. This threatens the stability an...Pitch deviation at rack joints(PDRJ) is a common error in rack railways. It directly affects the contact characteristics between the rack and gear and leads to accelerated surface wear. This threatens the stability and service life of the rack system, and the theoretical understanding of this issue remains limited. To address this gap, this study develops an improved tooth wear model that simultaneously accounts for the instantaneous variations in meshing stiffness and dynamic transmission error(DTE) induced by PDRJ, as well as the real-time correlation between gear-rack contact position and meshing excitation. Subsequently, the rack tooth load and wear characteristics are evaluated through the rack vehicle-track coupled dynamics and gear-rack contact model. The model's reliability is verified through field measurements. Moreover, the influence of varying PDRJ levels on load sharing factors, surface wear depth, and rack displacement is investigated. The results show that PDRJ disrupts the theoretical gear-rack meshing process, resulting in non-uniform load distribution and accelerated wear, particularly in the addendum and dedendum regions of the rack teeth. This study provides valuable insights into the rack surface wear mechanism under PDRJ.展开更多
Pitch deviation,a type of longwave deviation,has been demonstrated to be a significant contributor to noise generation in the drive trains of motor vehicles operating at relatively high speeds.To date,numerous studies...Pitch deviation,a type of longwave deviation,has been demonstrated to be a significant contributor to noise generation in the drive trains of motor vehicles operating at relatively high speeds.To date,numerous studies have investigated the effects of pitch deviation on the dynamic characteristics of gear systems.However,these models often exhibit inconsistencies with real-world observations due to the simplification of the contact between teeth pairs.This simplification ignores clearance compensation and damping of the oil film.To fill this gap,a new numerical model of spur gear systems with pitch deviation considering lubrication is proposed.An analytical model of the time-varying mesh stiffness(TVMS)and meshing impact force for spur gear pairs is proposed,in which the geometric relationship and iterative solution process are investigated.An improved tribodynamic model is established to investigate the excitation behavior of gear pairs with pitch deviation under lubrication.The accuracy of the proposed model is verified through comparisons with references and experimental results.The results show that the random impact phenomenon of the TVMS is significantly suppressed by the oil film,and the meshing impact force is also reduced.The transmission stability of spur gear pairs with tooth pitch deviation is improved under lubrication.The research results provide theoretical support for accurately predicting the dynamic responses of spur gear pairs with different precision levels while considering lubrication.展开更多
We present the spatial resolution estimation methods for a photon counting system with a Vernier anode.A limiting resolution model is provided according to discussions of surface encoding structure and quantized noise...We present the spatial resolution estimation methods for a photon counting system with a Vernier anode.A limiting resolution model is provided according to discussions of surface encoding structure and quantized noise. The limiting resolution of a Vernier anode is revealed to be significantly higher than that of a microchannel plate. The relationship between the actual spatial resolution and equivalent noise charge of a detector is established by noise analysis and photon position reconstruction. The theoretical results are demonstrated to be in good agreement with the experimental results for a 1.2 mm pitch Vernier anode.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.52388102)the Sichuan Science and Technology Program (Grant No.2024NSFTD0011)the Fundamental Research Funds for the State Key Laboratory of Rail Transit Vehicle System of Southwest Jiaotong University (Grant No.2023TPL-T11)。
文摘Pitch deviation at rack joints(PDRJ) is a common error in rack railways. It directly affects the contact characteristics between the rack and gear and leads to accelerated surface wear. This threatens the stability and service life of the rack system, and the theoretical understanding of this issue remains limited. To address this gap, this study develops an improved tooth wear model that simultaneously accounts for the instantaneous variations in meshing stiffness and dynamic transmission error(DTE) induced by PDRJ, as well as the real-time correlation between gear-rack contact position and meshing excitation. Subsequently, the rack tooth load and wear characteristics are evaluated through the rack vehicle-track coupled dynamics and gear-rack contact model. The model's reliability is verified through field measurements. Moreover, the influence of varying PDRJ levels on load sharing factors, surface wear depth, and rack displacement is investigated. The results show that PDRJ disrupts the theoretical gear-rack meshing process, resulting in non-uniform load distribution and accelerated wear, particularly in the addendum and dedendum regions of the rack teeth. This study provides valuable insights into the rack surface wear mechanism under PDRJ.
基金funded by the Chongqing Natural Science Foundation(No.CSTB2022NSCQMSX1243)the National Natural Science Foundation of China(No.52035002).
文摘Pitch deviation,a type of longwave deviation,has been demonstrated to be a significant contributor to noise generation in the drive trains of motor vehicles operating at relatively high speeds.To date,numerous studies have investigated the effects of pitch deviation on the dynamic characteristics of gear systems.However,these models often exhibit inconsistencies with real-world observations due to the simplification of the contact between teeth pairs.This simplification ignores clearance compensation and damping of the oil film.To fill this gap,a new numerical model of spur gear systems with pitch deviation considering lubrication is proposed.An analytical model of the time-varying mesh stiffness(TVMS)and meshing impact force for spur gear pairs is proposed,in which the geometric relationship and iterative solution process are investigated.An improved tribodynamic model is established to investigate the excitation behavior of gear pairs with pitch deviation under lubrication.The accuracy of the proposed model is verified through comparisons with references and experimental results.The results show that the random impact phenomenon of the TVMS is significantly suppressed by the oil film,and the meshing impact force is also reduced.The transmission stability of spur gear pairs with tooth pitch deviation is improved under lubrication.The research results provide theoretical support for accurately predicting the dynamic responses of spur gear pairs with different precision levels while considering lubrication.
基金supported by the National Natural Science Foundations of China under Grant Nos.10878005/A03 and 61007017
文摘We present the spatial resolution estimation methods for a photon counting system with a Vernier anode.A limiting resolution model is provided according to discussions of surface encoding structure and quantized noise. The limiting resolution of a Vernier anode is revealed to be significantly higher than that of a microchannel plate. The relationship between the actual spatial resolution and equivalent noise charge of a detector is established by noise analysis and photon position reconstruction. The theoretical results are demonstrated to be in good agreement with the experimental results for a 1.2 mm pitch Vernier anode.
