A numerical analysis of the contact stress distribution and physical modelling of abrasive wear in the tram wheel-frog system

Abstract

The condition of track infrastructure has direct influence upon the safety and comfort of tram transport. The sections of tram tracks which demand the closest attention are tram turnouts with frogs as integral elements. The purpose of this work was a thorough analysis of the most significant factors that influence the degradation of tram turnout frogs. Numerical simulations of contact stresses distribution in the tram wheel-frog system were performed under this research. It also included physical modelling of abrasive wear and operating tests in the real working conditions of frogs. On the basis of the results, the most important causes of the fast wear of tram turnout frogs were defined.Investigations performed in the operating conditions showed that tram frogs are the elements which are the most exposed to fast wear and withdrawal from usage. It was also shown that the increment of wear in the grooves of common crossings (frogs) was ca. 0.37mm/month. On the basis of the numerical calculations it was observed that the values of contact stresses depend on both the shape of the wheel flange and load value. The distribution of contact stresses in the plane transverse to the track axis is not elliptical, contrary to Hertz׳s theory. The abrasive wear resistance tests proved that slippage is the factor with a major impact on the intensity of frogs׳ abrasive wear. The second, and also significant factor worsening tribological durability is increase in the load value.