Railway operational benefits from bogie rotation friction management: Numerical simulations of bogie dynamics

 The purpose of this project was to prove or disprove the hypothesis that wheel and rail wear, and incidents of wheel squeal increase with increasing bogie rotation friction, while decreasing bogie rotation friction leads to increased incidents of hunting and increased wheel and rail wear. Therefore for any given combination of factors (vehicle type, curve radius, wheel profile, etc) an optimal bogie rotation friction level should exist at which incidents of hunting and wheel squeal are eliminated and wheel and rail wear is minimised. 

In order to test the hypothesis a literature review was first undertaken. The purpose of the review was to examine the results from previous similar projects and identify any areas that may be improved upon in order to achieve the most accurate results. As a result of the literature review the simulation vehicle model was designed. Past studies featured a three-dimensional wagon body with the centre bowl connection modelled as a single spring, or the centre bowl was modelled in isolation. However for this project the vehicle included a centre bowl connection modelled using centre plate springs evenly distributed across the top centre, and plate and rim friction on the centre bowl, radial bumpstops around the rim and a vertical restraint from the cotter pin. Additional features of the simulation vehicle model were friction wedges, in order to properly represent the damping present at the spring nest connection, and a non -circular top centre, to reflect the design currently used by QR (Queensland Rail). 

The remainder of the project focussed on computer simulations of the vehicle model using different combinations of parameters (vehicle type, curve radius, wheel profile, centre bowl friction and loading condition) to examine the way that the vehicle behaviour responded. The vehicle response was determined by measuring the wheelset lateral position, wheelset angle of attack and wear index (calculated using creep force and creepage). 

The first series of simulations were used to prove that the centre bowl friction levels could be determined using wayside monitoring equipment provided that particular conditions were met. Provided that the vehicle was travelling through an area of constant curvature (not in transition or tangent), in 75% of cases the centre bowl friction level to lateral position relationship was relatively linear. Therefore after initial studies to calibrate the system according to the curve radius and type of vehicle it would be possible to calculate the centre bowl friction using wayside monitoring equipment. However if the system was limited to curves with a radius larger than 800m, the accuracy of the system increased to 83% of cases following a linear relationship.