Research progress on safety of heavy-haul locomotive and bearing stability of couple and buffer system

In response to the service safety of heavy-haul locomotive and its coupler and buffer system, based on the systematic review of relevant line tests and theoretical simulations, the causes, mechanisms, and influencing factors of three main problems were systematically summarized, including the compressed stability of coupler, the safety of lateral crossing turnout for heavy-haul locomotive and the coupler separation, the improvement technologies for locomotive safety and coupler and buffer system stability were proposed, and the future research focus and development direction were forecast. Research results indicate that under the in-train longitudinal forces, the main safety issues of locomotive are the stability of coupler under compression on straight line or large curve, the safety of lateral crossing turnout for heavy-haul locomotive during electric braking, and the coupler separation in the middle of combined train. For the stability of coupler and buffer system, flatten pin coupler can maintain alignment stability by relying on the contact friction effect between coupler tail and follower plate under general longitudinal forces, but will be prone to lateral deflection instability under extreme compressed forces. The stability of coupler and buffer system can be improved by optimizing the secondary lateral stiffness, lateral stop clearance and stiffness of locomotive. The coupler with circular pin can resist the large longitudinal forces by relying on the mechanical stopper from coupler tail and shoulder, and will maintain a stable state by improving the secondary lateral stiffness of locomotive and reasonably matching with the suspension parameters. However, when coupler deflects to shoulder to play a role, excessive secondary lateral stiffness will strengthen the lateral constraint effect of wheel and rail. For the safety problem that locomotive crosses the branch line of 12-type switch or small curve, the coupler with circular pin can follow curve direction, and the safety of locomotive can be effectively improved by controlling electric braking force and optimizing operation. For the coupler separation in the middle of combined train, the mechanism is that the coupler force of middle locomotive experiences a "zero crossing" state, the releasing of vertical component of traction or electric braking force causes coupler head to bounce upwards, and following large pulling force immediately separates trailer coupler at an angle. Although some measures such as optimizing train operation and controlling coupler height difference can be taken to mitigate coupler separation, the fundamental measure is still adding anti-detachment device. The research work provides technical support for the safety improvement of China's heavy-haul railway transportation and the successful operation of 30 000-ton or even higher heavy-haul combined train. The further research should be carried out in the aspects of system simulation model correction, multi-objective optimization of structural parameters, refined train handling optimization, and safety monitoring and evaluation methods of locomotive. 27 figs, 81 refs.