Suppression of high frequency brake squeal using a centre slotted pad

Brake squeal remains a critical noise–vibration–harshness (NVH) problem in automotive disc brakes because it arises from friction-induced mode coupling and is highly sensitive to contact, boundary, and operating conditions. This study aims to develop and validate a finite-element-based complex eigenvalue analysis (FE–CEA) workflow for predicting high-frequency squeal and identifying an effective structural countermeasure using a centre-slotted brake pad. A three-dimensional finite element model of a hydraulic disc brake assembly was developed and validated using experimental modal analysis (EMA). The validated model was then used to perform complex eigenvalue analysis after static preloading and contact linearisation. Parametric studies were carried out to examine the effects of friction coefficient and brake pressure, followed by numerical screening of ten rotor and pad geometric configurations. The most effective design was experimentally validated using dynamometer tests under controlled operating conditions. The FE model showed good agreement with EMA results, with rotor mode-shape correlation values of MAC ≥ 0.85 and an assembled-system frequency mismatch below approximately $$3.5%$$ . The parametric study identified a critical friction coefficient near μ ≈ 0.27 for instability onset, while increasing brake pressure mainly amplified the instability growth factor. Among the ten configurations, the 10 mm centre-slotted pad suppressed the dominant unstable mode by weakening rotor–pad mode coupling. Experimental validation at 300 rpm, 4 bar, and 45\,∘C to 55\,∘C confirmed that the centre-slotted pad eliminated the 6.31 kHz squeal tone and reduced the peak sound pressure level by more than 20 dB(A) over five repeated tests. The results demonstrate that FE–CEA, when supported by modal and acoustic validation, can be used as an effective screening tool for brake squeal mitigation. The proposed centre-slotted pad provides a practical structural modification for suppressing high-frequency squeal while reducing reliance on trial-and-error prototyping.