Analysis Of Strength And Reliability On Coupler Body Of Heavy Haul Train

With the rapid development of Chinese heavy haul railways,the traction tonnage of heavy haul trains has increased,the numbers of vehicle turnovers have increased and the subsequent increase in the longitudinal loads between vehicles has deteriorated the service conditions of the coupler bodies and has caused excessively large abnormal loads.On the one hand,the new operating conditions of heavy haul trains put forward new requirements for the service safety of the coupler body strength.On the other hand,a significant reduction in the fatigue life of the coupler body shortens the maintenance period and increases the maintenance cost.For this reason,it is necessary to carry out the strength safety assessment,fatigue life prediction and reliability analysis under the new operating conditions of the No.17 main type coupler body,used in current heavy haul train.Firstly,the typical representative of Chinese heavy haul railway,the No.17 coupler body of Daqin Railway,is taken as the survey object and the main parts of the fatigue failure of the coupler body and the main causes of the cracks are counted and analyzed.It provides the basis for the subsequent static strength analysis and fatigue life prediction of the coupler body.Secondly,the finite element model of the coupler body is established.According to the load specified in the TB456-2008 standard and the maximum load observed,the static strength analysis and the safety check of the coupler body are performed using ANSYS Workbench software.The analysis results show that the maximum stress values of the coupler body are all less than the E-class steel yield limit of 690 MPa under the working conditions specified in the TB456-2008 standard and actual operating conditions.According to the mechanical properties and fatigue properties of E-grade steel materials,the fatigue strength of the coupler body is evaluated using the modified Goodman-Smith fatigue limit diagram.The six selected fatigue control points were all within the fatigue limit curve,and the fatigue strength of the coupler body meets the requirements of use.In order to carry out the anti-fatigue design of the coupler body,the measured 8-grade coupler body load spectrum of the Daqin Line is converted to the 8-grade stress spectrum based on the load-stress relationship calibrated by the quasi-static method.The defect coefficient is introduced to modify the S-N curve of the coupler body.Combined with Miner fatigue linear cumulative damage theory,it is estimated that the life span of the coupler body is greater than 5×10~6—the design operation mileage of the truck when the defect coefficient does not exceed 2.3.Compared with the life statistics of cracks of the coupler bodies running on the Daqin Line,the defect coefficients of the actual service couplers are determined to be in the range of 1.9 to 2.4,which provides reference for the selection of the defect coefficients when conducting fatigue design.Choose the weak fatigue position of the hook body,traction flange and hook pin hole,to carry out anti-fatigue design.If the coupler body meets the requirements of operating mileage specified in China's truck design standards,the equivalent stress at the traction flange cannot exceed 70.5MPa,the equivalent stress at the hook pin hole can not exceed 26.8MPa.Taking into account the impact of the mechanical properties of the material and the dispersion of the load on the reliability of the coupler body,Monte Carlo method was used to analyze the reliability of the coupler body.The analysis results show that the reliability of static strength of the hook body is 0.999 and the coupler body is safe and reliable.