Cause Analysis and Solution for Vertical Damper Mounting Bolt Loosening in High-Speed Railway EMU
Journal Title: Urban Mass Transit - Year 2025, Vol 28, Issue 2
Abstract
［Objective］ During the operation of a certain type of high-speed EMU (electric multiple units) in China, the mounting bolts at lower rubber joint of the secondary vertical damper (hereinafter referred to as the ′lower joint′) experience loosening. It is necessary to identify the cause of the bolt loosening and propose effective solutions. ［Method］ The structural composition of the damper is briefly described. To address three potential causes of bolt loosening, the damper design structure is checked and the production process is inspected. It is found that the torsional stiffness of the lower joints exceeds the maximum permissible value during operation. Reverse verification reveals the conditions triggering bolt loosening under calculation working conditions. Bench tests and field trials under actual EMU operating conditions are conducted to verify and identify the specific causes of bolt loosening. Based on the identified causes, three corresponding solutions are proposed and their effectiveness are verified through bench tests. ［Result & Conclusion］ The loosening of the damper mounting bolts is attributed to a combined effects of the adverse conditions including reduced tightening torque, decreased friction coefficient of the contact surface, and increased torsional stiffness of the lower joint. Optimizing the application process of assembly paste, reducing the torsional stiffness of the lower joint, and increasing the nominal tightening torque can effectively prevent bolt loosening.
Authors and Affiliations
Guangxu HAN, Jun FAN, Hao LIU, Yuanyuan FU
Keywords
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- EP ID EP759801
- DOI 10.16037/j.1007-869x.2025.02.004
- Views 23
- Downloads 0
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