On the Double-Point Wheel-Rail Contact Situation Using Simplified Constraints. A Preliminary Study

In this work a smoothed computation of the two-point wheel-rail contact scenario using the simplified Knife-edge Equivalent Contact constraint method (KEC-method) is presented. The procedure that considers the continuous KEC solution of the wheel-rail contact with equivalent profiles (equivalent wheel and single-point rail) proposes a smoothed transition between tread and flange contact in order to reduce the numerical instabilities that abrupt forces in flange may produce when flange contact occurs. This smoothed transition considers a small region in the wheel close to the two-point contact scenario. When contact happens in this region, tread normal contact force is transformed into two normal contact forces: one acting on the wheel tread and the other one acting on the wheel flange where different algorithms for this force transformation are proposed. However, in order to maintain the dynamics of the vehicle, the resultant normal force acting on the wheelsets, which is obtained as a reaction force of the constraint KEC-method, is kept after the force transformation. This procedure is applied to the numerical simulation of a single wheelset and results show that numerical instabilities of the two-point contact scenario using constraints are avoided.