Failure Cause Analysis and Optimization Design of the Transmission Shaft for Guideway Rubber-tyred Vehicle

Abstract

[Objective] The structural reliability of the transmission shaft of guideway rubber-tyred train is crucial to the safety of train operation. During the ice and snow test on a certain urban rail transit line, the guideway rubber-tyred train failed several times resulting from the fracture of the transmission shaft. Therefore, it is necessary to analyze the fracture causes of the transmission shaft and optimize its design. [Method] The causes of the fracture of the transmission shaft are analyzed from two aspects: macroscopic detection of the failure shaft section, physical and chemical detection of the failure material. A wireless torque test system is used to test the real-time load of the transmission shaft between stations 5-6 and stations 5-7 on the line. The test results are analyzed, and the structure of the transmission shaft is optimized. The strength test on the optimized transmission shaft bench and the fatigue test on the optimized transmission shaft are carried out respectively. [Result & Conclusion] The causes of transmission shaft fracture are identified as the overload brittle fracture of cross shaft and fatigue fracture of double coupling bushing. The test results from the above two line sections show that all the maximum torques of the shaft occur when the vehicle is slipping. Though the actual torque of transmission shaft is less than the designed maximum working torque, the impact energy on the shaft is much larger than the torque change value under normal working conditions because the torque changes within a very short time. The measures that are taken to optimize the transmission shaft structure are as follows: increasing the shaft diameter of the cross shaft, increasing the chamfer angle of the cross shaft arc transition, and further reducing the stress concentration. The strength of the shaft shoulder of the double coupling bushing is increased by adding the reinforcing rib on it. The strength test on the optimized transmission shaft bench shows that it meets the design requirements and passes its fatigue test.

Keywords

• guideway rubber-tyred vehicle
• transmission shaft
• failure cause
• optimization design