Abstract
Research and /or Engineering Questions/Objective: Among noise, vibration, and harshness problems concerning automobiles, brake squeal still annoys consumers, OEMs, and brake-component suppliers. Its propensity depends significantly on the vibrational characteristics of brake discs, particularly their natural frequencies. Accordingly, our previous studies on natural frequencies are integrated into a total approach based on advanced product quality planning (APQP) and quality function deployment (QFD) for brake-disc rotors (covering initial design through to manufacturing and quality control). Methodology: First, a rough APQP flow and QFD process focusing on disc natural frequencies are introduced, and then the disc-design process is explained. Second, to determine significant quality characteristics of brake discs for controlling natural frequencies, macroscopic factorial effects of material properties and dimensions were analysed by conducting CAE experiments. Third, to reduce variations in natural frequencies of brake discs, key process operations affecting natural frequencies in regular production were identified from significant quality characteristics of discs and further broken down into process-control factors. Fourth, microscopic factorial effects of dimensions were analysed in order to control modal alignment more freely at design stage and maintain frequency variation less than ±3.0%. And finally, the effectiveness of natural frequency and its controlling process on other important quality characteristics of brake discs, namely, thermal strength and thermal coning, was investigated. Results: An integrated approach for brake-disc rotors–covering design through to manufacturing and quality control— was established with special focus on reducing brake squeal by controlling natural frequencies. Through this approach, a ±3.0% variation in disc natural frequencies was attained. Macroscopic analysis confirmed that Young’s modulus significantly affects the frequencies in all modes and the dimensions of the ventilation paths affect disc-plate bending stiffness and thus out-of-plane-circumferential mode frequencies. Microscopic analysis showed that the effects of disc dimensions on natural frequencies depend on the vibration modes and basic design of disc rotors. Finally, natural frequency is confirmed to be a total index for brake-disc quality that covers not only natural frequencies but also other requirements, for example, thermal strength and thermal coning. Limitations of This Study: Aiming to reduce frequency variation in regular production to less than ±1.5%, the authors are further improving key process operations in casting by applying the results obtained from the present study. What Does the Paper Offer That is New in the Field in Comparison to Other Works of the Author: Our previous studies are integrated into a total approach based on APQP and QFD (covering initial design through to manufacturing and quality control) for brake-disc rotors. The effect of natural frequency and its controlling process on other important quality characteristics of brake-disc rotors (namely, thermal strength and coning) was investigated. Conclusion: Based on two typical methodologies for quality control, namely, APQP and QFD, an integrated approach for brake-disc rotors—covering design through to manufacturing and quality control—was established with special focus on reducing brake squeal by controlling natural frequencies. Through this approach, variation in disc natural frequencies has been kept below ±3.0%. Natural frequency is confirmed to be a total index for brake-disc quality, which includes not only natural frequencies but also other requirements, for example, thermal strength and thermal coning.
KEYWORDS – brake disc, brake squeal, eigen-mode alignment, natural frequency, variety reduction