모노레일 주행 롤러 지지용 볼 베어링 리테이너의 파손 원인 분석

Abstract

This study evaluates the structural stability of the drive system of a monorail and investigates the causes of derailment accidents using finite element analysis. We assume a scenario where the gear pitch decreases by 1 mm owing to construction defects and perform dynamic analysis as the pinion gear traverses the abnormal pitch interval of the rack gear. The contact analysis between the rack and pinion gears reveals that the pinion gear collides in the abnormal pitch range due to the construction defect at the rack gear connection. The collision generates stresses exceeding the yield strength of the gear and rail materials, leading to plastic deformation. This study additionally investigates the bearings where the actual damage occurs utilizing the load data derived from the analysis. Findings indicate that plastic deformation and fatigue damage occurs in the bearing retainer and balls owing to the impact load, leading to ball detachment and retainer failure. Moreover, repetitive impact loads can rapidly degrade bearing durability, directly contributing to accidents. The findings of this study should be considered during the design, manufacturing, assembly, and maintenance processes of monorail system components, enhancing the safety through precise manufacturing and assembly practices.