Study On Dynamic Behavior Of Axle Box Bearing Of High Speed Train

With the rapid development of high-speed trains,the independent innovation of key parts of high-speed trains is an important support for the implementation of the strategy of "manufacturing power" and "one belt along the road" strategy.As one of the key components of high-speed train,axle box bearings are liable to cause axle temperature alarm if there are faults in the operation process,leading to train speed reduction or even emergency stop,thus affecting the normal operation of the line and causing economic losses.At present,all axle box bearings of high-speed trains are imported products,and the localization of axle box bearings is one of the urgent issues to be solved in the development of high-speed trains.During the operation of axle box bearings,the inner ring is connected with the wheelset,the outer ring is matched with a series of suspensions in the axle box seat or the box body,and then connected with the frame beam.The dynamic characteristics of these components are coupled with each other.This paper studies the interaction between vehicle and bearing from the perspective of vehicle system dynamics and bearing dynamics.The main research work and conclusions are as follows:1.The dynamics of vehicle-track system including axle box bearings is established.Bearings are considered as 6-DOF roller and 6-DOF cage models,car body,frame and wheelset are considered as rigid models,and rails are considered as continuous discrete support beam models of Euler beam.Modal superposition method is used to solve the problem.The credibility of the model is verified by comparing it with the traditional model.Because the traditional vehicle-track coupling model takes wheelset and bearing as a whole,this model separates wheelset and axle box.The comparative study shows that the vibration acceleration amplitude of wheelset and axle box is close,but the vertical acceleration amplitude of axle box is slightly larger than the vertical acceleration amplitude of wheelset,and the lateral acceleration amplitude of axle box is slightly smaller than the lateral acceleration amplitude of wheelset.2.The vibration characteristics of axle box bearing of high-speed train are studied.The results show that the track excitation has an effect on the contact load of the roller raceway,and in the non load area,the roller and the outer raceway will contact,and the contact load is square with the speed.At different speeds,the mean value of contact load on the outer ring is not significantly different,but the standard deviation is significantly different,and the faster the speed is,the greater the standard deviation is.The impact force between roller and cage will be increased due to the wheel rail excitation,especially the radial impact between roller and cage.At the same time,the wheel rail excitation will also aggravate the skid of cage,and even lead to negative skid.3.Combining damage theory and contact load value of roller raceway,fatigue life calculation model of axle box bearing based on cumulative damage is proposed.The results show that the faster the vehicle speed,the greater the damage growth rate,and the shorter the bearing life.The influence of track excitation on the cumulative damage and fatigue life of axle box bearing is obvious.The greater the track excitation,the greater the damage and the greater the damage growth rate,the shorter the bearing life.Compared with vehicle speed and track excitation,the influence of curve radius on cumulative damage and fatigue life of axle box bearing is smaller.4.Based on the wheel tread defect model,the impact response of axle box bearing with tread defect is studied.The model of wheel tread defect is established by the method of wheel radius change.The results show that the wheel flat scar will affect the contact load of the outer ring raceway.The impact load generated when the wheel enters the flat scar area is to reduce the contact load of the outer ring of the roller,and the impact load generated when the wheel leaves the flat scar area is to increase the contact load of the outer ring.With the increase of the length of the flat scar,the impact load on the outer ring of the roller increases when the wheel enters and leaves the flat scar area.Under the condition of non-circular excitation,the contact load of the outer ring of the roller increases by 21.5% compared with that without non-circular excitation.5.The response of vehicle system to local failure of bearing raceway and surface waviness is studied.The bearing fault is reflected by the change of roller raceway surface position.The results show that under local fault,the bearing will have one or two impact phenomena because of the difference of defect length,defect width and defect depth.During one impact,the roller in the defect area still bears the load.During the second impact,the roller in the defect area is not loaded,which leads to the increase of the roller load in the rest of the bearing area of the raceway.When the outer ring has waviness,the vertical vibration acceleration of the axle box includes the outer ring fault frequency fbsfo and its double frequency.When the degree of corrugation is equal to the integral times of the number of rollers,the amplitude of vertical vibration acceleration of axle box is the largest at the fault frequency fbsfo of outer ring.When there is corrugation in the inner ring,the vertical vibration acceleration of the axle box includes the combination frequency of inner ring fault frequency fbsfi and inner ring rotation frequency fi and its octave frequency.When the degree of corrugation is close to the multiple of the number of rollers,the vertical vibration acceleration of the axle box increases obviously.6.Based on the measured changes of the outer ring contour,the non Hertz contact between roller raceways and the bearing life are studied.The results show that when the profile of roller and raceway is not modified,there will be obvious stress concentration at both ends of roller,and the contact stress at the small end of roller is greater than that at the large end of roller.When both the roller and the outer ring raceway are reshaped,the roller and the outer ring raceway are convex-convex contact when the bearing is first used.With the increase of train operation mileage,when the bearing is running for more than 1.2 million kilometers,the roller and the outer ring raceway change from convexconvex contact to convex-concave contact.The contour shape of roller raceway has an obvious influence on the bearing life.The larger the contact stress of roller raceway,the shorter the bearing life.