Figure 1 shows a railroad wagon axle and forces acting over it. There are two disc brakes on the wagon axle. Since the wagon wheels are not driven wheels, the load bearing element to which the wheels are connected is called axles. The axle is supported at both ends with bearing A and bearing B and the the weight of the wagon (G) is evenly distributed on both bearings (as G/2). During braking, two disc brakes on the axle are applied Ff force and Ft friction forces are formed on the wheels. Therefore the axle is forced to bend in the vertical direction with the effect of wagon weight (G) and wheel reaction forces (Rt), and in horizontal direction with the effect of braking (Ff) and wheel friction (Ft) forces. At the same time, the axle is forced under torsion because of Ff and Ft forces. GIVEN: Shaft material : 50CrMo4 Wheel material : GS 60 Brake discss material: 15Cr3 All the radiuses : 5 mm Average roughnesses for press fit surfaces: Ra =6.3 m Wheel speed: =100 d/d Wagon weight per one axle: G=6 tons Wheel rail friction forces: Ft=(5)kN. Note1- Lateral forces acting on the wagon axle and all other dynamic effects are neglected. Note2: Choose the ungiven values. ASKED: 1. Determine the critical cross section of the axle and control that if it is safe or not. 2. Calculate that how many kilometer the axle can travel through its life. 3. The wheel is fastened to the axle with a tightening of 0.3 mm. Check that the connection is proper or not so that it can carry the transmitted torsional moment. 4. The brake discs are fastened to the axle with press fit. Calculate the required tightness.

Figure 4. Technical drawing of axle Tablo 2 Axle dimensions