Investigating the effect of the equivalent conicity function's nonlinearity on the dynamic behaviour of a rail vehicle under typical service conditions

Generally, the equivalent conicity function (ECF) is denoted by equivalent conicity at 3mm (lambda(3mm)) and a Nonlinearity Parameter (NP). NP describes the nonlinearity of the ECF and its influence on a vehicle design is explored thoroughly, however, NP's role in vehicle and track maintenance is not researched yet. This paper investigates the influence of track maintenance actions on vehicle dynamics with help of NP vs lambda(3mm) scatter plots of ECF database. The ECF database is constructed by combining measured worn wheel and rail profile pairs of the Swedish high-speed vehicle and rail network, respectively. The ECF database revealed an inverse relationship between lambda(3mm) and NP, i.e., NP is negative for larger lambda(3mm) values. The combination of negative NP and high lambda(3mm) causes reduction in the vehicle's nonlinear critical speed and vehicle often exhibit the unstable running on the Swedish rail network. Thus, the occurrence of ECF with negative NP and high lambda(3mm) is undersirable and the undesirable ECF can be converted into desirable ECF by grinding the rail, which converts ECF's into positive NP and low lambda(3mm) combinations. Thus, the NP parameter along with the lambda(3mm) must be considered in track maintenance decisions.