Study On Modeling And Nonlinear Dynamic Characteristics Of High-speed Train Rolling Bearing With Pedestal Looseness

According to the national “Medium and Long-term Railway Network Plans (which wasamended in2008)”, by2020, the national high-speed railway mileage will be above16000kilometers. To ensure such a massive high-speed rail network system security and sustainab-ility is a major challenge which is faced by China high-speed rail. High-speed trains is thecore of the system of high-speed railway technology, the dynamic behaviors, characteristicsand function laws of the train driving with a high speed formed the most important basicscience problems. Rolling bearings as the key parts and components of train, which subjectedto looseness faults on the fitting surface of inner ring and shaft neck frequently. It would makethe fitting surface heat rapidly once the inner ring creep to spin state, and even cause a hotaxle accident. Therefore, it is necessary to study on nonlinear dynamic characteristics ofhigh-speed train rolling bearings with pedestal looseness, and know how the looseness faultsinfluence the dynamic characteristics of system and its evolution mechanism. In order torealize the real-time monitor of the working state of high-speed train rolling bearing, andachieve the goal of early fault diagnosis of looseness.In this paper, the fault reasons and forms of typical mechanical looseness phenomenonwere concluded by some fault cases at first. The mathematical models of looseness problemswere reviewed. Aiming at a model of single disk rotor system with pedestal looseness fault,the solution procedure of incremental harmonic balance method was inferred. Then theFloquet theory was utilized to judge the stability of periodic solution. The time-frequencyspectrograms, phase path diagrams and Poincare sectional drawings were obtained to analyzethe fault characteristics of rotor system with pedestal looseness.On the basis of studying on rotor system with pedestal looseness, the vertical coupleddynamic model of high-speed train car body-frame-suspension-rolling bearing-wheel/rail wasestablished while the high-speed train rolling bearing existing looseness fault. Thelongitudinal irregularity time series of German track spectrum was simulated to be theexternal disturbance of dynamic model. And the normal rolling bearing’s stiffness anddamping were calculated in accordance with the structure parameters of a certain type ofdouble-row tapered roller bearing which was applied on the high-speed train axle box.An optimized Runge-Kutta numerical integral method was constructed to solve thecoupled system of high-speed train rolling bearing with pedestal looseness. The nonlineardynamic characteristics of system was studied while taking the looseness gap value of rollingbearing as controlling parameter. Further considering the condition of looseness stiffness and damping changing with the looseness gap value, the research about how looseness gap valueor train speed affects the nonlinear dynamic characteristics of the system has accomplished,respectively. Conclusion: with the increasing of looseness gap value, the system’s movementbifurcated, the vibration velocity and the vibration amplitude of high frequency componentalso increased gradually, but the low frequency component of the system’s vibration responsewas determined by the train speed and would not change with the looseness gap value. Thelooseness gap value made more influence to the system’s dynamic characteristics than thetrain speed did.Finally, two measurement experiments, included the bearing inner ring revolving speedand bearing pedestal vibration signal of two shaft ends, which were implemented with the aidof high-speed train bearing looseness simulation test rig designed and manufactured by ourown subject group. The validity of the theoretical study was validated by the comparison ofexperimental results with theoretical analysis.