Abstract
The article presents the state of knowledge and research in the field of surface cracks occurring in disc braking systems of rail and car vehicles. The craze formed during the operation of vehicles is particularly dangerous and leads to breaking the disc into several pieces. It may lead to a loss of braking force and damage to the entire disc brake caliper. The main aim of the research is to identify surface cracks in brake discs made of cast iron and use experimental methods to estimate their depth. Research were conducted on the disc braking system developed by the authors. In examining the location and depth of cracks, the penetration method, ultrasound, as well as a special probe were used. This device measures the crack depth based on the electrical resistance between two points on the surface of the metallic object. The tests showed that the first microcracks on the brake discs appeared after 309 braking tests on the test stand. In addition, it was observed that the surface cracks length of the disc increased linearly to depth until they reached about 11.5–12 mm with corresponded to crack lengths in the range of 65–70 mm. However, determination of the regression functions presented in the article allows to estimate the depth of surface cracks up to 70 mm long on cast iron brake discs by measuring their length.
Highlights
Academic Editor: Francesco IacovielloReceived: 23 May 2021Accepted: 7 July 2021Published: 12 July 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Licensee MDPI, Basel, Switzerland.Most of the publications taking thermal phenomena in brake discs into consideration focus on the destructive effects of friction rings on the disc material
309 brakings, combined with non-destructive tests, showed that surface cracks appeared on new discs after hundred several etration) tests, showed that surface cracks appeared on new discs after several tests, showed that surface cracks appeared on new discs after several hundred braking operations
Conducted research and analysis of the results allowed for the creation of a simple tool enabling an easy assessment of the technical condition of the brake disc in terms of its suitability for regeneration and further operation
Summary
Academic Editor: Francesco IacovielloReceived: 23 May 2021Accepted: 7 July 2021Published: 12 July 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Licensee MDPI, Basel, Switzerland.Most of the publications taking thermal phenomena in brake discs into consideration focus on the destructive effects of friction rings on the disc material. It has been shown that changes in the volume of the material due to its thermal expansion in the areas of overheating lead to compressive stresses during heating and tensile stresses during cooling. Multiple repetitions of this cycle lead to a gradual increase in stresses up to the limit of the tensile strength of the disc material. This phenomenon, described in many publications [1,2,3,4,5,6,7,8], causes cracks that grow with each successive braking of the vehicle
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