Mitigating of Low Frequency Squeal Noise by Optimize the Pressure Pattern with Shim Geometry in Noise Dynamometer and Corelating to FEA

• Main Authors: Anand, Ramamoorthy, Rakesh, Sadhasivam, Kitchana, Venkatesh
• Format: Report
• Language: English
• Subjects: CAE; low frequency squeal; Shim & chamfer selection; shim slot; uneven pressure distribution; uneven wear
• ISSN: 0148-7191; 2688-3627
• DOI: 10.4271/2023-01-1871

Despite efforts to reduce disc brake noise occurrence, it remains a significant concern in the automotive industry, particularly in the current era of electric vehicles, where it can be an intermittent issue. There is no standard solution available for every noise frequency, as it depends on various conditions and parameters that need to be experimentally identified and addressed. This paper specifically focuses on addressing low-frequency noise. During dynamic conditions, the contact pressure becomes uneven, leading to uneven pad wear and making the disc brake system susceptible to noise. In noise rigs, the paper selects the most suitable shim and pad geometry based on trials that analyze the interaction between the shim and pad. In conventional practice, shim modification was performed using computer-aided engineering, but obtaining accurate pressure patterns in dynamic conditions with CAE is challenging due to certain assumptions. Through dynamometer trials, the paper identifies that the critical frequency is caused by the coupling of the disc and pad mode shapes. Wear analysis reveals greater wear on the leading side of the piston, which can contribute to noise at critical frequencies. Pressure patterns were examined using Tekscan™ across different pressure ranges from 10 bar to 50 bar to understand the cause of uneven wear, confirming the bias in the caliper loading pattern. Consequently, the details of piston contact pressure were investigated, indicating higher pressure distribution on the leading end of the piston compared to the trialing side. Further analysis using finite element analysis (FEA) confirms a similar bias towards the caliper on the leading side. To modify the pressure pattern and reduce noise, a half-moon cut profile was introduced in the shim, resulting in the elimination of occurrences at 3.9 kHz.