ABSTRACT
The wheel polygonalization has become a great concern for the high speed rail vehicle owing to its highly adverse effects in high speed condition. Such periodic distributed wear along the wheel can give rise to high magnitude of high frequency impact loads at the wheel/rail interface and further contribute to severe fluctuations in axle box acceleration and the self-loosening for axle box bolts. In this study, the wheel polygonalization-induced axle box vibrations and bolt self-loosening are thus initially investigated by the field tests and the roller test rig. Subsequently, a coupled vehicle/track dynamic model integrating a typical high speed rail vehicle and a flexible slab track is formulated to identify the mechanism of bolt self-loosening in the presence of wheel polygonalization. The results suggest that the wheel polygonalization can result in high magnitude accelerations in the axle box, and excite some of vibration modes of the axle box and the axle box end cover. The accelerations on the axle box end cover are much larger than those obtained on the axle box, which is also comparable to the experimental results. It is thus believed that the self-loosening of axle box end cover’s bolts are mainly attributed to the severe oscillations on the axle box due to the wheel polygonalization.
