Principles of the implementation of wheel-rail friction measurements and friction mapping in rail digital twins

Considering recent rapid developments in the use of rail digital twins, it is necessary to clearly understand the basis for such developments . Digital twins are commonly built in a complex modelling environment and their modelling concepts are based on physical-based models. This process requires great precision with the introduction of non-linear modelling components that have many uncertainties that cannot be described by purely physical models. One such component in the modelling involves the wheel-rail contact couplings that require the introduction of friction characteristics to calculate creep contact forces at the wheel-rail interfaces. The modelling concept assumes that a rail digital twin for a heavy haul line should be supplied with a friction map that allow modification of the friction characteristics at the wheel-rail couplings based on the variations of wheel-rail contact point locations along the track, which take into account the real train operational scenarios and tribological aspects observed in the field. In this paper, the methodology for the development of such a friction map and principles for its implementation are proposed and the existing limitations are discussed in detail.