高速铁路WJ-8型扣件螺旋道钉锤击松动机理研究OA

The WJ-8 fastener system is widely deployed on high-speed railway trunk lines in China with satisfactory overall service performance.Nevertheless,abnormal loosening of screw spikes under accidental hammer impact was found during track fine adjustment,posing potential hazards to the safe operation of high-speed railways.Aiming at this problem,this paper firstly investigates the fastening balance conditions of screw spikes under normal service conditions.Based on vibration theory,the mechanical variation of screw spikes subjected to hammer impact is analyzed,and the effects of key parameters including thread lead angle,equivalent friction coefficient and thread meshing force on the anti-loosening performance are evaluated.Accordingly,a theoretical calculation formula for characterizing the anti-loosening capacity of screw spikes is established.Furthermore,the finite element method is adopted to calculate the vibration response of screw spikes after hammer impact;meanwhile,a drop hammer test rig is designed and relevant impact tests are conducted.The results reveal that the decrease in fastening torque after hammer impact is the primary cause of spike loosening when the thread fails to achieve self-locking.The anti-loosening capability against hammer impact can be enhanced by increasing the thread meshing force,thread equivalent friction coefficient,contact friction coefficient and contact radius between flat washers and spikes,while reducing the thread lead angle,thread pitch diameter,vertical linear stiffness of threads,and contact stiffness between flat washers and spiral spikes.The critical loosening amplitude of WJ-8 fastener screw spikes is determined as 0.670 mm via high-speed photography,which deviates merely by 7.8％from the theoretical prediction,thereby validating the rationality of the proposed formula.