A review of dynamics modelling of friction draft gear

Abstract

Longer and heavier trains mean larger in-train forces and more complicated force patterns. Practical experience indicates that the development of fatigue failure of coupling systems in long heavy trains may differ from conventional understanding. The friction-type draft gears are the most widely used draft gears. The ever developing heavy haul transport environment requires further or new understanding of friction draft gear behaviour and its implications for train dynamics as well as fatigue damage of rolling stock. However, modelling of friction draft gears is a highly nonlinear question. Especially the poor predictability, repeatability and the discontinuity of friction make this task more challenging. This article reviews current techniques in dynamics modelling of friction draft gears to provide a starting point that can be used to improve existing or develop new models to achieve more accurate force amplitude and pattern predictions.

Advanced dynamic modelling for friction draft gears

“…[9] Therefore, further or even new understanding of draft gear behaviour and the implications for longitudinal train dynamics as well as for fatigue damage of rolling stock is required. Friction draft gears have been commercially applied for more than a century [13]; some designs have remained unchanged since they were patented 60 or 70 years ago. At that stage, freight trains were much lighter, shorter and slower.…”

Influence of resistance to motion of railway vehicles on the longitudinal trains dynamics

“…Nowadays, these devices are worldwide classified into two main categories: lateral buffers, traction devices and hand couplings (screw and traction hook coupling) and automatic couplings. A famous study that focuses on the work of all researchers on modeling buffer and draw-gear devices is performed by Qing Wu, Colin Cole et al [9]. In this paper the authors show how different these devices are in the world, the researchers' concerns and the importance of evaluating the longitudinal forces, but also the complex or simple mathematical models used in these programs.…”

About the influence of wheel slide protection devices action on longitudinal dynamic of trains

“…Mechanical and pneumatic modelling of trains has been discussed in an extensive of publications, see for instance [1][2][3][4][5][8][9][10][11][12].…”

“…Considering the vehicles designed for a specific running speed V max ≥ 160 km/h equipped with disc brakes, the brake force is described accounting the dependency on instantaneous air pressure in brake cylinders p BC and the wheel-rail adhesion coefficient in normal conditions [8,13]:…”

“…This results in a pronounced sensitivity of the braking system to degraded adhesion [8]. Consequently, all passenger vehicles are featured with WSPD that, in case of important sliding, rapidly diminish the air pressure in brake cylinders until the affected wheelset returns to normal rotational speed according to the translational speed of the vehicle.…”