Identification of the hot spots phenomenon in brakes by using a thermal imaging camera

Abstract

A long operation of the brake pads of the brake disc causes uneven wear of the friction surface. This applies both to the friction pads of organic material and from sintered metal. For larger braking power is the reason for overheating the blade, resulting in varying temperature distribution on the brake disc cooperating with the friction pad. The first study of this phenomenon has shown that it is highly speed-dependent braking. Therefore, it was observed during the train's braking from a speed of 300 km/h. At these speeds the brake disc there are known. Hot spots between which are areas with a substantially lower temperature. However, in areas of high temperatures it occurs following the formation of the protrusions due to the expansion of the target material. This phenomenon is further enhanced during each rotation of the disc, while on each bulge of material stresses acting on each surface of the friction pad. Occurring grooves on the facing (the space between the surfaces of friction) have proved insufficient to absorb the heat produced during braking. They take a small part of the thermal energy, which on the face have areas with different temperatures, 100 °C at the periphery of the disc 800 and 900 °C protrusions. This phenomenon is very complicated because it involves in addition to the properties of the material for brake discs presented and described dependency of the breaking function of temperature. Thus, many manufacturers brake disc determines the maximum mean temperature of the disc at 400 °C in cooperation with the organic friction pad and 550 °C in cooperation with the pad of sintered metal. Type of braking understood speed beginning of braking pressure to the brake disc pads and the mass of the slowdown and the strength properties of the target material impact on the number of hot spots on the disc, ie. The distance between hot spots. In order to eliminate the phenomenon, the manufacturers of friction pads modify the shape of the contact surface pads of brake discs to ensure even distribution of pressure on the dial. However, during the long service there is a phenomenon of laying a liner with respect to the brake disc, the reasons for the backlash in the mechanism of the brake lever which, due to wear of the brake disc itself. Then, in some cases, a phenomenon arises hotspots. Cladding without causing the phenomenon is facing divided into several friction elements hinged. This solution will ensure even distribution of the pressure of all the friction elements on the shield throughout the life of the pad. As a result, the brake disc does not tend to create "hot" areas that are the reason the formation of bulges in the material of the disc.The article presents the possibility of using the thermal imaging camera studies disc brakes in order to identify the phenomenon of hot spots. The results allow to evaluate the temperature distribution on the brake disc in which there is a tendency to create hot spots.