Coupler jack-knifing and derailment of slave control locomotives in 20,000-tonne heavy-haul trains usually occur due to the combinations of large in-train forces with poor track conditions. This paper presents an experimental investigation on the dynamic performance of slave control locomotive couplers in 20,000-tonne heavy-haul trains. A field test method for measuring and monitoring the dynamic behavior of heavy-haul locomotive couplers is proposed. The on-track tests involved coupler forces, coupler yaw angles, and coupler dynamic motion monitoring of the test locomotive in the whole traveling process. The dynamic process of coupler jack-knifing is exhibited, and the distribution characteristics of the coupler forces and yaw angles are investigated. The test results indicate that the front and rear couplers of the slave locomotive group respectively suffer the largest draw (tensile) and buffing (compressive) forces, and the maximum yaw angle appears at the middle coupler between the slave locomotives. The maximum draw and buffing forces attain 1551 kN and 2067 kN, respectively. The maximum absolute yaw angle is about 13 degrees. During the cycle braking operation conditions, the intense buffing forces and the excessive coupler yaw angles are more likely to appear in the release process. The coupler instability generally occurs under train run in buffing forces. Moreover, the coupler status, the track conditions as well as the duration of buffing forces are also supposed to have an important effect on the coupler stability of slave control locomotives.
