Development of a magnetorheological elastomer rubber joint with fail-safe characteristics for high-speed trains

The stiffness of the train's rubber joint at the primary suspension system has a crucial influence on the operation stability and curve-passing performance. As traditional rubber joint only provides unadjustable parameters, they cannot meet the conflicting stiffness requirements when the train is running at high speed on straight track and passing through the curve track. To solve this problem, this paper proposed a new rubber joint with fail-safe characteristics based on magnetorheological elastomer (MRE). The joint stiffness is controlled by a hybrid magnetic field generated by permanent magnets and electromagnets. With this hybrid magnetic field, the initial stiffness of the MRE joint can be designed to be hard so as to suppress the hunting motions and vibrations of wheelsets and thus keep the trains' high-speed stability; furthermore, the stiffness can decrease by energizing the electromagnets when passing through a curve track. With this characteristic, the joint can guarantee the safety of the train at high operation speed even when the joint control system fails. The prototype of the MRE joint was fabricated and assembled. Stiffness controllability of the MRE joint was tested using a Material Testing Systems machine. The result reveals that the stiffness of this MRE joint can be controlled effectively. According to the testing results, a new phenomenological model was built to predict the joint's dynamic performance. Then this established model was integrated into dynamic models of trains to numerically evaluate the new joint's influence on the train's stability and trafficability. The evaluation result shows that the proposed MRE joint is fully effective on providing controllable stiffness to satisfy the conflicting stiffness requirement with fail-safe characteristics.