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Background/Introduction <p>Noise pollution from railway braking systems is a major concern due to vibrations and high-frequency sounds generated by frictional interactions. Natural fibers such as coconut shells have emerged as eco-friendly, biodegradable alternatives to commercial materials for brake pads, but their performance concerning brake noise remains underexplored.</p> Purpose <p>This study aims to compare the brake squeal performance of commercial and coconut shell–reinforced friction materials in solid railway brake discs, seeking to reduce vibrational instability and noise through finite element and complex eigenvalue analyses.</p> Method <p>An iterative numerical approach was developed using the Finite Element Method (FEM) and Complex Eigenvalue Analysis (CEA) to correlate material and geometric parameters, such as Young’s modulus, thicknesses, and friction coefficient, with instability indicators, including Total Unstable Frequency (TUF), First Unstable Frequency (FUF), and Noise Index (NI). Parametric simulations were conducted varying friction coefficient, stiffness, and geometry for both materials.</p> Results <p>The coconut shell–reinforced material consistently exhibited fewer unstable modes and lower noise indices than the commercial material. For example, TUF decreased from 120 to 65 and NI from 3.3 to 1.4 when replacing the commercial with the reinforced material under similar conditions. The reinforced pads also shifted unstable frequencies (FUF) to higher values, indicating enhanced vibrational stability. In contrast, the commercial material showed greater instability and higher noise, particularly under increased friction and stiff ness conditions.</p> Conclusion <p>The proposed numerical method successfully correlated material and geometric parameters with instability phenomena in railway brake systems. Coconut shell–reinforced materials demonstrated superior stability and reduced noise generation compared to commercial pads, confirming their potential as sustainable alternatives for railway braking applications. Future work should include experimental validation and evaluation under thermal and wear conditions.</p>

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Comparative Analysis of Brake Squeal Performance in Solid Railway Brake Disc using the Complex Eigenvalue Method: Commercial vs. Coconut Shell-Reinforced Friction Materials

  • 期刊论文

  • 发表日期：

    2025年11月21日

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  • Romulo do Nascimento Rodrigues,
  • Gabriela Achtenová,
  • Roberto de Araujo Bezerra,
  • Vanessa Vieira Gonçalves

摘要

Background/Introduction

Noise pollution from railway braking systems is a major concern due to vibrations and high-frequency sounds generated by frictional interactions. Natural fibers such as coconut shells have emerged as eco-friendly, biodegradable alternatives to commercial materials for brake pads, but their performance concerning brake noise remains underexplored.

Purpose

This study aims to compare the brake squeal performance of commercial and coconut shell–reinforced friction materials in solid railway brake discs, seeking to reduce vibrational instability and noise through finite element and complex eigenvalue analyses.

Method

An iterative numerical approach was developed using the Finite Element Method (FEM) and Complex Eigenvalue Analysis (CEA) to correlate material and geometric parameters, such as Young’s modulus, thicknesses, and friction coefficient, with instability indicators, including Total Unstable Frequency (TUF), First Unstable Frequency (FUF), and Noise Index (NI). Parametric simulations were conducted varying friction coefficient, stiffness, and geometry for both materials.

Results

The coconut shell–reinforced material consistently exhibited fewer unstable modes and lower noise indices than the commercial material. For example, TUF decreased from 120 to 65 and NI from 3.3 to 1.4 when replacing the commercial with the reinforced material under similar conditions. The reinforced pads also shifted unstable frequencies (FUF) to higher values, indicating enhanced vibrational stability. In contrast, the commercial material showed greater instability and higher noise, particularly under increased friction and stiff ness conditions.

Conclusion

The proposed numerical method successfully correlated material and geometric parameters with instability phenomena in railway brake systems. Coconut shell–reinforced materials demonstrated superior stability and reduced noise generation compared to commercial pads, confirming their potential as sustainable alternatives for railway braking applications. Future work should include experimental validation and evaluation under thermal and wear conditions.