Thermal coupled structural analysis of a brake disc

Abstract

Designing a brake disc is a very challenging job. Besides to being a key item in vehicle safety, we are referring to a product that goes through several manufacturing processes and during its application it is exposed to extreme conditions of mechanical stress, temperature and vibration. The raw material for a large portion of commercial brake discs is normally gray cast iron with the possibility of adding alloy elements. This material is characterized by having high resistance to wear due to friction and having practically zero plasticity. As it is a material without a plastic working regime, it is very important to properly size the product for use, once the material’s resistance limit is reached, a catastrophic failure in operation may be inevitable. Quality control systems in casting and machining have great importance in the development of the disc, but physical tests are always essential in this type of product. Dynamometer tests are great options for validating brake discs, due to their ability to simulate practically all the severe conditions to which they will be exposed in real application. However, it is possible to predict possible disc failures even before subjecting them to the dynamometer, using numerical analyzes through the finite element method, a methodology that ensures that we are more assertive in the project, reducing time and money spent. In view of this challenging scenario, this work presents the results of a thermal analysis (CFD) of a brake disc, coupled with a structural analysis (FEA), with the objective of predicting a possible failure in the product and finally correlating the numerical results data with data from physical tests obtained on a dynamometer. At the end of this work, it was possible to determine the thermal distribution of the disc at the thermocouple installation point with an accuracy of 95% and find tensile stresses in the order of the yield stress of the disc material, thus predicting a probable breakage.