It is observed that T-bolt fracture of DT III fastener affects the safety of railway operations. The present study is aimed at finding solution to this critical issue of DT III T-bolt fracture. The paper is based on outcomes of field studies and analysis of relationship between bolt installation torque and stress. A refined DT III fastener model is established based on test data and nonlinear contact theory as per the actual size of each component. It is being observed that head-shank joint is a critical area during service. With respect to fatigue and stress, when the installation torque is less than 300 KN-mm, the bolt is prevented from yielding during installation. To a certain extent it also improves the fatigue life of bolt. From the frequency spectrum point of view, the vibration sensitive frequency band (1050–1100 Hz, 1230–1270 Hz) of bolt in service is very close to the main frequency of bolt vibration (1200 Hz). It may cause bolt fracture. In order to avoid resonance, the train operational speed should be strictly controlled between 115 km/h and 120 km/h.

据观察，DTⅢ扣件T型螺栓断裂影响铁路运营安全。本研究旨在寻找解决 DT III T 型螺栓断裂这一关键问题的方法。本文基于现场研究的结果以及对螺栓安装扭矩和应力之间关系的分析。根据试验数据和非线性接触理论，根据各部件的实际尺寸，建立了精炼的DT III紧固件模型。据观察，头柄接头是使用过程中的关键区域。就疲劳和应力而言，当安装扭矩小于300 KN-mm时，可以防止螺栓在安装过程中屈服。在一定程度上也提高了螺栓的疲劳寿命。从频谱上看，使用中螺栓的振动敏感频段（1050~1100 Hz、1230~1270 Hz）与螺栓振动主频率（1200 Hz）非常接近。否则可能会导致螺栓断裂。为避免共振，列车运行速度应严格控制在115公里/小时至120公里/小时之间。