Comparative analysis of wheel-rail adhesion degradation and contact stress distribution on typical metro tracks

Metro line has the characteristics of short station distance, low operating speed, frequent traction /braking, high acceleration and deceleration, small curve radius and various track types. The wheel-rail low adhesion behavior, wear and damage problems are prominent under such a complicated operation condition. This article compares and analyzes the wheel-rail adhesion characteristic on four kinds of tracks, including the concrete slab bed track, steel-spring floating slab track, elastic support block track and trapezoidal sleeper track, revealing the adhesion degradation mechanism of metro wheel-rail system under different operating conditions, such as traction and braking. The results indicate that there are differences in the creepage response and the lowest limit of the wheel-rail adhesion coefficient on different track structures, while the maximum adhesion coefficient of the four track structures under traction/braking conditions shows a similar trend with the variation in speed and adhesion conditions. Traction and braking loads, as well as wheel-rail adhesion conditions, exert a relatively minor influence on the normal contact stress distribution of the wheel-rail interface, but significantly affect shear stress distributions. This study is shown to enhance the understanding of the combined effects of adhesion degradation and track types on the wheel-rail contact stress and surface damage.