Compatibility of the λ- Kolmogorov test for the brake disc emissivity factor distribution in thermal imaging studies

A thermal imaging camera is widely used in railway, it allows evaluating the wheel-rail contact while rolling the wheel set on the rails [3], cracks of the railway tracks [22] or identify overheated axle bearings of the wheel sets of the railway cars. In studies of braking systems both railway and vehicular ones on brake positions, the thermal imaging measurements are little used. Only in the qualitative assessment, an IR camera can identify the phenomenon of "hot spots" on the brake disc [1, 12, 15]. When testing the disc brake friction pairs, the most difficult is the brake disc and determination of its actual temperature which, due to the polished smooth surface by friction with the friction pad, is a low-carbon object. This type of objects force the person who makes the measurements to do a very precise configuration of the thermal imaging camera in order to determine the emissivity factor. An additional difficulty in the thermal imaging of braking systems is a dynamically changeable nature of the work associated with changes in the rotational speed of the brake disc and a nonlinear increase in its temperature. The paper presents the results of the studies conducted parallel with the thermal imaging measurements by using thermocouples to determine variability of the experimental emissivity factor of the brake disc supported by the λ-Kolmogorov compatibility test.