In view of over-limit reduced value of switch rail of No 42 high-speed turnouts,a train-turnout dy-namic simulation model was established based on the theory of train-turnout dynamics to investigate the effect of over-limit reduced value of switch rail on the dynamic characteristics of switch.In the model,the field meas-ured reduced value of switch rail was used as a calculation condition.The results showed that the over-limit re-duced value of the switch rail caused the starting point of wheel load transfer of the switch to move backwards, resulting in significant increase in the length and width of wheel hunting motion.The maximum lateral dis-placement of the wheelset and lateral acceleration of the vehicle body were 2 times of the design conditions, likely to cause vehicle vibration.With the maximum lateral wheel-rail additional force increasing from 6.29 kN to 46.28 kN and the maximum vertical wheel-rail additional force increasing from 5.73 kN to 20.04 kN,a sharp deterioration occurred in the dynamic interactions in wheel-rail system.With little change of the load shedding rate of wheel,when the maximum derailment coefficient of wheel reached 0.65,6.5 times of the de-sign conditions,which was close to the safety limit value of 0.8,the traffic safety would be endangered.The o-ver-limit reduced value of switch rail,if it arises on site,should be adjusted in time to avoid further deteriora-tion of dynamic characteristics of the switch.%针对42号高速道岔尖轨降低值超限问题,基于车辆-道岔系统动力学的理论,建立车辆-道岔动力仿真模型,分析尖轨降低值超限对转辙器动力特性的影响。模型中采用现场实测的尖轨降低值作为计算条件。结果表明：尖轨降低值超限导致转辙器轮载过渡的起点后移,使得轮对蛇行运动的距离和幅度发生较大程度地增大；轮对横向位移和车体横向振动加速度为设计条件下的2倍,容易引起晃车现象；轮轨横向动力附加力由6.29 kN 增大至46.28 kN,垂向动力附加力由5.73 kN 增大至20.04 kN,轮轨动力作用急剧恶化；车轮减载率变化不大,车轮脱轨系数最大值为0.65,是设计条件下的6.5倍,接近安全限值0.8,将危及行车安全。现场出现尖轨降低值超限时,应及时进行调整,以避免转辙器动力特性进一步恶化。
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