### DETERMINATION OF THE WHEEL TEMPERATURE, DURING STOPPING BRAKING OF RAILWAY VEHICLES, AT POINTS LOCATED AT THE DISTANCE XR FROM THE WHEEL-SHOE FRICTION SURFACE

Liviu Sevastian BOCÎI

#### Abstract

During stop braking, from high speeds, by means of the brake with shoes, the rolling surfaces of the wheels withstand thermal regimes that generate forces that affect driving safety.In this work, the calculation of the wheel temperature is presented using a calculation program (non-commercial), prepared by the author. After entering the initial data: the wheel load GR [daN]; the mass factor g [non-dimensional]; the initial speed of braking V [km / h]; the width of the shoe [m]; the thickness of the shoe [m]; braking deceleration [m / s2]; the conductivity
coefficient for the two materials of the friction coupling elements lR, lK [W/(m°C)]; the density of the two materials rR, rK [kg/m3]; the specific heat cR, cK [J/(kg °C)]) can be calculated, in addition to other parameters, the temperature of the friction surface of the wheel (xR = 0) also the temperature at different points located at a distance xR = 5; 10; 15 mm, from the wheel tread. The values obtained by the calculation represent the variation in temperature at different points located at a distance xR from the friction surface of the wheel vs. time (duration of braking). Figures 2-11 have represented, in temperature (f (x)) - time (x) coordinates, the variation of the temperature at the points located at the distance xR (xR = 0; 5; 10; 15 mm) , considering the following braking
speed values: V = 160; 200 km / h, the load per wheel GR = 7000; 9000 daN (Figures 2-5) and three values of the deceleration: a = 0.8; 1.1; 1.2 m / s2 (Figures 6-11). Results obtained have made it possible to observe that at the
same load per wheel, the increase in the initial braking speed leads to an increase in the wheel temperature. Also, at the same initial braking speed and the same load per wheel, a decrease in tread temperature is observed as deceleration decreases.

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