Premature failure is the major problem encountered in the operation of truck brake discs. Although previous studies have established the global phenomena of such failure, the critical thermomechanical loadings associated with braking remain unknown. Thus, the aim of the study presented in this article was to provide an experimental characterisation of thermal loading fields in order to compute thermomechanical loadings. First, a microstructural investigation of a truck brake disc that had been damaged through road use enabled us to verify the type of damage that it had experienced. Next, several braking cases were identified and reproduced on a bench at full scale so that brake loadings and the ensuing damage could be properly correlated with each other. Thermal localisation and bulk temperatures were used as indicators of the most critical stop-braking. Once the latter was identified, it was analysed by means of a coupled numerical-experimental thermomechanical approach. The temperature evolution during braking was studied in relation to the hoop stress-hoop strain cycle. It was found that residual hoop tensile stresses appeared during cooling, which subsequently led to the development of radial microcracks. Finally, microstructural investigations of a bench-tested disc enabled us to validate the modelling results. Radial microcracks on the disc surface and metallurgical phase transformations were observed. Nevertheless, such damage cannot be solely attributed to critical stop-braking, as some of it is likely to be due to the other braking tests in the sequence as well. Thus, we intend to carry out a similar study on holding braking and a series of slowdowns in order to confirm that stop-braking is truly the most critical process in brake disc damage.
Failure of truck brake discs: A coupled numerical-experimental approach to identifying critical thermomechanical loadings
Zum Versagen der Lastwagen-Bremsscheiben: Eine gekoppelte numerisch-experimentelle Vorgehensweise für die Bestimmung kritischer thermomechanischer Beanspruchungen
Tribology International ; 59 ; 114-120
2013
7 Seiten, 15 Bilder, 5 Tabellen, 19 Quellen
Article (Journal)
English
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