Dynamic Characteristics of Metro Trains under Rescue Conditions

In order to study the dynamic characteristics of metro train under rescue conditions, a detailed dynamic model with different train formations is established, taking into account the characteristics of wheel-rail contact, nonlinear characteristics of suspension components, and nonlinear hysteresis characteristics of the draft gear systems. To verify the accuracy of the simulation results, field tests are carried out and comparison is made between simulation and test results. Then, simulation analyses are conducted under the condition of AW0 rescues AW0, AW0 rescues AW3, and AW3 rescues AW3. Based on the simulation results, the longitudinal dynamic characteristics of the train under different rescue conditions are compared, and the influence of the longitudinal impulse on the dynamic performance of coupler and vehicle is analyzed. Finally, some suggestions are put forward to improve the draft gear as well as the rescue method

Effects of Filler–Bitumen Ratio and Mineral Filler Characteristics on the Low-Temperature Performance of Bitumen Mastics

This study analyzed the effects of the filler–bitumen interaction of the content and the meso powder characteristics of the mineral filler on the low-temperature performance of bitumen mastics. Control strategies for the mineral filler content (filler–bitumen ratio (RFB)) were also determined. Panjin #90 bitumen and styrene–butadiene–styrene polymer-modified bitumen were used in the experiment. Four kinds of limestone powder were used, all of which satisfy the Chinese standard for powder particle size but exhibit different meso characteristics. Each kind of limestone powder was used to prepare bitumen mastic samples under five different RFBs. The meso voids in the unit mass (Vg) of the four kinds of mineral filler were tested on the basis of the principle of the Rigden void ratio. The fixed bitumen–free bitumen ratio in the bitumen mastic samples was determined using Vg, bitumen density, and RFB. The low-temperature cohesive strength of the bitumen mastics was used as the control index for critical failure, whereas variation rates of bending creep stiffness at low temperature were used as the control index for fatigue failure. Results showed that the effects of the filler–bitumen interaction of the content and the meso characteristics of the mineral filler are significant and such effects are determined by the fixed bitumen–free bitumen ratio. The optimal fixed bitumen–free bitumen ratio in the bitumen mastics under two low-temperature conditions (−30 °C and −10 °C) can be determined on the basis of the influence of the fixed bitumen–free bitumen ratio on the critical and the failure control indices. Moreover, RFB can be obtained through reverse calculation. The mineral filler content can therefore be precisely controlled, which is crucial for the rational use of mineral filler and for the improvement of the pavement performance of bitumen mastics at low temperatures

Research on the compression stability mechanism and its optimisation of coupler with arc surface contact

Cole, CR ORCiD: 0000-0001-8840-7136; Wu, Q ORCiD: 0000-0001-9407-5617In order to improve the adaptability of the coupler with arc surface contact to the demanding operating environment of heavy-haul trains, the compression stability mechanisms were analysed. The angle evolution process of the force transmission line when the coupler is gradually rotated from the centring state to the maximum structure angle is derived, as well as a proposal for the coupler self-stabilising ability. Based on the theoretical analysis, a more detailed dynamic model of the coupler with arc surface contact has been established in which the friction and contact characteristics of both coupler tail and coupler head are considered. Then the model is used to simulate the dynamic behaviour of the coupler with different radius matching relationships. The research results indicate that the effective way to improve the running safety of a heavy-haul locomotive under buff condition is to make full use of the self-stabilising ability of the coupler on the premise of not affecting the adhesion ability of the coupler tail. Based on the above research work, an improved scheme is proposed in this paper. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group