# Assessment of Uneven Wear of Freight Wagon Brake Pads
## 3 Results and Discussion  
Field experiments were carried out to investigate the uneven wear of brake pads. The wagons that worked in different operating conditions (loaded and empty runs, technical condition and track profile, weather conditions, etc.) were observed. Private fleet wagons (open wagons, box wagons and hopper wagons for the transportation of cement) were experimentally studied. They were separated from the state-owned fleet wagons and belonged to \"Ivano-Frankivskcement\", a private joint-stock company (IFCEM). Unlike the wagons of Ukrainian Railways (Ukrzaliznytsia), the IFCEM wagons operated only along at a fixed 1173 km long route from the Yannrytsia station (the Lvivska Zaliznytsia regional branch) to the Osnova station (the Pivdenna Zaliznytsia regional branch), as was stipulated by the contracts for the supply of cement. Production studies of a relatively small number of the IFCEM wagons were carried out in accordance with the developed \"Program and techniques of production inspections of brake systems and wagon wheels\". The route under observation was not changed over the period of inspection, thus, the wagons worked in the same operating conditions. It should also be noted that in one direction, the wagons ran loaded, and in the other direction, they ran empty along the same tracks, thus the coefficient of empty mileage was 50%. Experimental studies were carried out during the inspection of the brake systems of wagons at subdivisions of the wagon industry and at sorting stations. 2 TE116 locomotives were used for the braking of the wagons under observation and they were changed within the guaranteed sections. The wagons under observation also included two box wagons with the air distributors No. 483 set to the empty mode. In accordance with the regulatory and technical documents, the load on the composite brake pad in the empty mode is 17.5 kN, and the its average value is 34.34 kN. All inspections and measurements of the brake lever transmission elements of the wagons were carried out with tools, measuring instruments, and technological equipment, as stipulated by the appropriate regulatory and technical documents. The obtained statistical data on thicknesses of composite brake pads at the control points of wagon bogies were processed. Based on the obtained data, graphical dependencies for the average wear value of the pads of wagon bogies were built (Figures 3 and 4). Figure 2: Dependence of brake pad wear on mileage. The results of calculations for loads of 35 kN and 17.5 kN showed a significant dependence of the wear of the pad on the pressure force value and the force distribution between the pads. Optimization of the weight coefficient \(k_{i}\) made it possible to consider the uneven distribution of the pressure force caused by the imperfection of the lever transmission design. For the load of 35 kN, the weight coefficients were as follows: \(k_{1}\) = 0.28 (Pad 1), \(k_{2}\) = 0.26 (Pad 2), \(k_{3}\) = 0.24 (Pad 3), \(k_{4}\) = 0.22 (Pad 4) (Figure 5). Figure 4: Dependence of the wear of the wagon bogie pads on the mileage when the air distributor is in the average mode. Figure 5: Pads in the brake lever transmission. Figure 3: Dependence of the wear of the wagon bogie pads on the mileage with the air distributor in the empty mode. For a load of 17.5 kN, the corresponding weight coefficients were as follows: \(k_{1}=0.3\), \(k_{2}=0.27\), \(k_{3}=0.23\), \(k_{4}=0.2\). The maximum wear of some pads was 38.04 mm for a pressure force of 35 kN and did not exceed 28 mm for 17.5 kN during a run of 74,400 km. The built dependencies demonstrate that the lower pressure force proportionally reduces the wear rate, which provides a longer service life of the pads, provided that the weight coefficients are correctly optimized. Dependencies of the wear of the pads on the mileage, built on the basis of these weight coefficients, demonstrate a gradual increase in wear for each pad in accordance with its position in the bogie.