Kinetics of Moisture Adsorption and Its Impact on Brake Pad Compression Modulus and Compressibility: Static Modulus of Compression vs. Dynamic Modulus of Compression vs. Hardness vs. Friction Coefficient

Rhee, Seong Kwan; Rathee, Aman; Singh, S.R.; Sharma, Devendra

doi:10.4271/2022-01-1165

SAE Technical Paper Series

2022

DOI: 10.4271/2022-01-1165

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Kinetics of Moisture Adsorption and Its Impact on Brake Pad Compression Modulus and Compressibility: Static Modulus of Compression vs. Dynamic Modulus of Compression vs. Hardness vs. Friction Coefficient

Seong Kwan Rhee¹,

Aman Rathee²,

S.R. Singh³

et al.

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2023

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Cited by 2 publications

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Effect of Moisture Adsorption on Low-Speed and Moderate-Speed Braking: Effect on In-Stop Friction Coefficient and Low Frequency Noise

Sriwiboon,

Koetniyom,

Rhee

et al. 2023

SAE Technical Paper Series

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<div class="section abstract"><div class="htmlview paragraph">Copper-free NAO disc pads of passenger cars were investigated for a combination of prior braking conditions and moisture adsorption influencing in-stop friction and noise during low-speed stops, and in-stop-friction during moderate-speed stops. Prior braking conditions and moisture adsorption strongly influence subsequent in-stop friction behavior and noise at room temperature. The low-speed in-stop friction behavior looks totally different from that of moderate-speed stops. The low-speed in-stop friction increasingly oscillates with increasing moisture adsorption and goes down towards the end of a stop, which is accompanied by increasing low-frequency noise.</div><div class="htmlview paragraph">The moisture content needs to be quantified/specified to obtain repeatable/reproducible brake test results as the moisture is an unintended and uncontrolled ingredient of a friction material. As the disc surface roughness increases due to prior braking conditions, the friction coefficient of low-speed stops is found to decrease. The changing friction coefficient is explained by the nature of the friction film and its interactions with moisture.</div></div>

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Effect of Moisture Adsorption on Low-Speed and Moderate-Speed Braking: Effect on In-Stop Friction Coefficient and Low Frequency Noise

Sriwiboon,

Koetniyom,

Rhee

et al. 2023

SAE Technical Paper Series

View full text Add to dashboard Cite

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Brake Pad Moisture Adsorption and Its Effect on Brake Pad Compression Strain/Modulus and Friction Coefficient: Effect of Pad Cure Temperatures

Rhee,

Rathee,

Singh

et al. 2023

SAE Technical Paper Series

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<div class="section abstract"><div class="htmlview paragraph">The moisture adsorption kinetics of copper-free brake pads was studied to confirm an earlier finding that the adsorption weight gain follows a logarithmic relationship with respect to the square root of humidity exposure time and the relationship is linear in the beginning. When the pad cure temperature was raised from 120 to 180 and 240 °C, the adsorption rate increased. The 180 °C cure produced the highest pad modulus. With increasing moisture adsorption, the pad compression modulus increased just like the pad dynamic modulus, meaning decreasing compression/compressibility while the ISO ‘compressibility’ determined after 3 compressions under 160 bars increased in contradiction. It is concluded that the ISO ‘compressibility’ is a destructive hardness measurement like the Gogan or Rockwell hardness: the key difference is the indenter covers the entire surface of the pad. The true compressibility must be determined as an inverse function of bulk modulus. It is recommended that the pad compression modulus should be measured under low pressures like 10 bars for the purpose of determining the initial quality of virgin pads if the current ‘compressibility’ machines are to be used. Compression tangent modulus and dynamic modulus measurements produce the same results, meaning that one could replace the other. Pad cure temperature affects friction coefficient and moisture adsorption influences friction coefficient in opposite direction for moderate-speed snubs of 80 km/h vs. low-speed stops of 5 km/h.</div></div>

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Kinetics of Moisture Adsorption and Its Impact on Brake Pad Compression Modulus and Compressibility: Static Modulus of Compression vs. Dynamic Modulus of Compression vs. Hardness vs. Friction Coefficient

Cited by 2 publications

References 20 publications

Effect of Moisture Adsorption on Low-Speed and Moderate-Speed Braking: Effect on In-Stop Friction Coefficient and Low Frequency Noise

Effect of Moisture Adsorption on Low-Speed and Moderate-Speed Braking: Effect on In-Stop Friction Coefficient and Low Frequency Noise

Brake Pad Moisture Adsorption and Its Effect on Brake Pad Compression Strain/Modulus and Friction Coefficient: Effect of Pad Cure Temperatures

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