The high-speed train transmission system,experiencing both the internal excitation originating from gear meshing and the external excitation originating from the wheel-rail interaction,exhibits complex dynamic behavio...The high-speed train transmission system,experiencing both the internal excitation originating from gear meshing and the external excitation originating from the wheel-rail interaction,exhibits complex dynamic behavior in the actual service environment.This paper focuses on the gearbox in the high-speed train to carry out the bench test,in which various operat-ing conditions(torques and rotation speeds)were set up and the excitation condition covering both internal and external was created.Acceleration responses on multiple positions of the gearbox were acquired in the test and the vibration behavior of the gearbox was studied.Meanwhile,a stochastic excitation modal test was also carried out on the test bench under different torques,and the modal parameter of the gearbox was identified.Finally,the sweep frequency response of the gearbox under gear meshing excitation was analyzed through dynamic modeling.The results showed that the torque has an attenuating effect on the amplitude of gear meshing frequency on the gearbox,and the effect of external excitation on the gearbox vibration cannot be ignored,especially under the rated operating condition.It was also found that the torque affects the modal param-eter of the gearbox significantly.The torque has a great effect on both the gear meshing stiffness and the bearing stiffness in the transmission system,which is the inherent reason for the changed modal characteristics observed in the modal test and affects the vibration behavior of the gearbox consequently.展开更多
Rock excavation in quarries is normally carried out by using explosives. The steps in planning of cutting face are based on the appropriate design for angles of cut and the optimum consumption of charge weights. Prior...Rock excavation in quarries is normally carried out by using explosives. The steps in planning of cutting face are based on the appropriate design for angles of cut and the optimum consumption of charge weights. Priority procedures in planning are the stability of bench excavation,vibration evaluation,and the selection for the blast patterns. The methods of analysis are described and compared with field results. From several cases of trial cut angles and changing geometry of blast dimensions,the result of an optimum pattern in a specific quarry,with respect to the acceptable global unit cost is achieved.展开更多
为降低变速箱的振动噪声,提高整车噪声、振动与声振粗糙度(noise vibration harshness,NVH)性能,通过变速箱下线台架(end of line,EOL)振动测试和整车NVH测试,对比分析正常齿廓齿轮、带S形齿廓的齿轮对整车NVH性能的影响。EOL测试结果表...为降低变速箱的振动噪声,提高整车噪声、振动与声振粗糙度(noise vibration harshness,NVH)性能,通过变速箱下线台架(end of line,EOL)振动测试和整车NVH测试,对比分析正常齿廓齿轮、带S形齿廓的齿轮对整车NVH性能的影响。EOL测试结果表明:装配S形齿廓齿轮的变速箱的振动加速度级明显高于正常齿廓齿轮变速箱,尤其在48阶次处增幅最大。整车NVH测试结果表明,S形齿廓齿轮在发动机舱及车内的声压级分别增大12、7 dB。实际加工制造验证结果表明,正确设定齿轮加工珩磨轮寿命可以有效消除齿廓的S形波动,改善变速箱及整车的NVH性能。展开更多
基金The authors are grateful for the financial support from the National Key Research and Development Program of China(Grant No.2021YFB3400701)the Fundamental Research Funds for the Central Universities(Science and technology leading talent team project,Grant No.2022JBQY007).
文摘The high-speed train transmission system,experiencing both the internal excitation originating from gear meshing and the external excitation originating from the wheel-rail interaction,exhibits complex dynamic behavior in the actual service environment.This paper focuses on the gearbox in the high-speed train to carry out the bench test,in which various operat-ing conditions(torques and rotation speeds)were set up and the excitation condition covering both internal and external was created.Acceleration responses on multiple positions of the gearbox were acquired in the test and the vibration behavior of the gearbox was studied.Meanwhile,a stochastic excitation modal test was also carried out on the test bench under different torques,and the modal parameter of the gearbox was identified.Finally,the sweep frequency response of the gearbox under gear meshing excitation was analyzed through dynamic modeling.The results showed that the torque has an attenuating effect on the amplitude of gear meshing frequency on the gearbox,and the effect of external excitation on the gearbox vibration cannot be ignored,especially under the rated operating condition.It was also found that the torque affects the modal param-eter of the gearbox significantly.The torque has a great effect on both the gear meshing stiffness and the bearing stiffness in the transmission system,which is the inherent reason for the changed modal characteristics observed in the modal test and affects the vibration behavior of the gearbox consequently.
文摘Rock excavation in quarries is normally carried out by using explosives. The steps in planning of cutting face are based on the appropriate design for angles of cut and the optimum consumption of charge weights. Priority procedures in planning are the stability of bench excavation,vibration evaluation,and the selection for the blast patterns. The methods of analysis are described and compared with field results. From several cases of trial cut angles and changing geometry of blast dimensions,the result of an optimum pattern in a specific quarry,with respect to the acceptable global unit cost is achieved.
