To investigate the worn-surface microstructure and fatigue cracks in D2 wheel steel under the pure rolling and 0.5% slip ratio conditions,a rolling wear test using a GPM-40 wear machine to simulate the wheel/rail oper...To investigate the worn-surface microstructure and fatigue cracks in D2 wheel steel under the pure rolling and 0.5% slip ratio conditions,a rolling wear test using a GPM-40 wear machine to simulate the wheel/rail operation was performed. After testing,a transmission electron microscope,a scanning electron microscope with electron backscatter diffraction,and micro-hardness testers were used to characterize the microstructure and fatigue cracks.The surface microstrncture and hardness of the pure rolling sample were in a steady state after 8 × 10^4 cycles;however,the 0.5% slip ratio sample reached a steady state after 7 × 10^3 cycles.Regardless of whether the test uses the slip ratio,the orientation of lamellar pearlites gradually became parallel to the surface and a portion of lamellar cementites was fragmented and dissolved during the formation of steady-state microstructure.The slip ratio accelerates this process.The hardening mechanism of the samples shows a decrease in the lamellar spacing of pearlite and the refinement of proeutectoid ferrite (PF).As the number of cycles increased,plastic deformation of samples became increasingly severe and the wear mechanism of the samples was fatigue wear in steady state.The sample surfaces formed shallow cracks,which gradually peeled off.The slip ratio accelerated the initiation and propagation of fatigue cracks because of the high friction stress on the contact surface.Most fatigue cracks initiated at the interface of pearlite and PF and in the PF region.展开更多
Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and st...Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and stability of the vehicle,it is crucial to control it and coordinate the driving force.With this aim,this paper presents a driving force coordination control strategy with road identification for eight-wheeled electric vehicles equipped with an in-wheel motor for each wheel.In the proposed control strategy,the road identification module estimates tire-road forces using an unscented Kalman filter al-gorithm and recognizes the road adhesion coefficient by employing the recursive least-square method According to road identification,the optimal sip ratio under the current driving condition is obtainedand a controller based on sliding mode control with a conditional integrator uses this value for accel-eration slip regulation.The anti-slip controller obtains the adjusting torque,which is integrated with the driver-command-based feedforward control torque to implement driving force coordination control.The results of hardware-in-loop simulation show that this control strategy can accurately estimate tire-roadrces as well as the friction coefficient,and thus,can effectively fulfill the purpose of driving force coordinated control under different driving conditions.展开更多
文摘To investigate the worn-surface microstructure and fatigue cracks in D2 wheel steel under the pure rolling and 0.5% slip ratio conditions,a rolling wear test using a GPM-40 wear machine to simulate the wheel/rail operation was performed. After testing,a transmission electron microscope,a scanning electron microscope with electron backscatter diffraction,and micro-hardness testers were used to characterize the microstructure and fatigue cracks.The surface microstrncture and hardness of the pure rolling sample were in a steady state after 8 × 10^4 cycles;however,the 0.5% slip ratio sample reached a steady state after 7 × 10^3 cycles.Regardless of whether the test uses the slip ratio,the orientation of lamellar pearlites gradually became parallel to the surface and a portion of lamellar cementites was fragmented and dissolved during the formation of steady-state microstructure.The slip ratio accelerates this process.The hardening mechanism of the samples shows a decrease in the lamellar spacing of pearlite and the refinement of proeutectoid ferrite (PF).As the number of cycles increased,plastic deformation of samples became increasingly severe and the wear mechanism of the samples was fatigue wear in steady state.The sample surfaces formed shallow cracks,which gradually peeled off.The slip ratio accelerated the initiation and propagation of fatigue cracks because of the high friction stress on the contact surface.Most fatigue cracks initiated at the interface of pearlite and PF and in the PF region.
基金This work was supported by the Weapons and Equipment Pre-Research Project of China(No.301051102).
文摘Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and stability of the vehicle,it is crucial to control it and coordinate the driving force.With this aim,this paper presents a driving force coordination control strategy with road identification for eight-wheeled electric vehicles equipped with an in-wheel motor for each wheel.In the proposed control strategy,the road identification module estimates tire-road forces using an unscented Kalman filter al-gorithm and recognizes the road adhesion coefficient by employing the recursive least-square method According to road identification,the optimal sip ratio under the current driving condition is obtainedand a controller based on sliding mode control with a conditional integrator uses this value for accel-eration slip regulation.The anti-slip controller obtains the adjusting torque,which is integrated with the driver-command-based feedforward control torque to implement driving force coordination control.The results of hardware-in-loop simulation show that this control strategy can accurately estimate tire-roadrces as well as the friction coefficient,and thus,can effectively fulfill the purpose of driving force coordinated control under different driving conditions.
