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Flash Temperature in Clutches
ISSN: 0148-7191, e-ISSN: 2688-3627
Published October 24, 2005 by SAE International in United States
Annotation ability available
Sliding contact between friction surfaces occurs in numerous torque transfer elements: torque converter clutches, shifting clutches, launch or starting clutches, limited slip differential clutches, and in the meshing of gear teeth under load. The total temperature in a friction interface is the sum of the equilibrium temperature with no sliding and a transient temperature rise, the flash temperature, caused by the work done while sliding. In a wet shifting clutch the equilibrium temperature is typically the bulk oil temperature and the flash temperature is the temperature rise during clutch engagement. The flash temperature is an important factor in the performance and durability of a clutch since it affects such things as the reactivity of the sliding surfaces and lubricant constituents (e.g., oxidation) and thermal stress in the components. Knowing how high the flash temperature becomes is valuable for the formulation of ATF, gear oil, engine oil and other lubricants.
This paper presents two models for approximating flash temperature in clutch interfaces for: (1) a large thermal mass with a good conduction path to an equilibrium temperature boundary, and (2) a small thermal mass without a good conduction path to a constant temperature boundary. The explicit expressions given for flash temperature in terms of material and friction properties are useful for applications such as estimating thermal effects on the lubricant and changes in the friction properties and clutch torque. Friction heating expressions for different slipping conditions are given and are used in the models to predict surface flash temperatures for specific cases: (a) plate #1 (front steel plate) in SAE #2 rig tests such as the MERCON® V and DEXRON® III H friction tests, (b) plate #3 (interior steel plate) in SAE #2 tests, and (c) the steel plate in an LVFA test.
CitationCameron, T., McCombs, T., Tersigni, S., and Jao, T., "Flash Temperature in Clutches," SAE Technical Paper 2005-01-3890, 2005, https://doi.org/10.4271/2005-01-3890.
- Carslaw, H. S., Jaeger, J. C., Conduction of Heat in Solids, © 1959 Oxford University Press, p. 50. (Different nomenclature is used, e.g., temperature is ν).
- Carslaw, H. S., Jaeger, J. C., Conduction of Heat in Solids, © 1959 Oxford University Press, p. 75.
- See  for the usage of erfc() here. For detailed discussion see http://mathworld.wolfram.com/Erfc.html.
- ASM Handbook, Vol. 18, Friction Lubrication and Wear Technology, p. 40 (equation (8)).
- Carslaw, H. S., Jaeger, J. C., ASM Handbook, Vol. 18, Friction Lubrication and Wear Technology, p. 112 (equation (8)).
- Adapted from MERCON® V Specification, 1 July 2004, p. 8, Test Procedure 3.12, Clutch Friction Durability.
- JASO M 348-95, “Test method for friction property of automatic transmission fluids,” JSAE.
- Chrisope, D. R., Stinnett, D. W., Hartley, R. J., “Friction Retention and Thermal Decomposition of Fluid Additives in Wet Clutch System,” 1992 TAE Tribology Colloquium, Esslingen, Germany, reports measured temperatures as high as 364 °C. The authors note: “we consider this [to be] a lower limit for the interface temperature, since the temperature will drop as the heat diffuses from the surface to the center of the cooler reaction plate where the thermocouple is located.”
- Moon, W-S, and Yang, S-W, “Effect of Base Oils Characteristics on ATF Performance,” Proceedings of the 2001 International Symposium on the Tribology of Vehicle Transmissions, February 7-9, 2001, Toyota, Japan, pp. 55-60. [Note: The “Net Friction Area” reported in Table 4 of this reference appears to be wrong. Dividing by the number of friction interfaces does not yield the correct area for each plate even after accounting for possible grooves.]
- Deur, J., Petric, J., Asgari, J., Hrovat, D., “Modeling of a Wet Clutch Engagement Including a Thorough Experimental Validation,” SAE 2005-01-0877.
- Xiang, X., Kremer, J. M., “A Simplified Close Form Approach For Slipping Clutch Thermal Model,” SAE 2001-01-1148.
- Thuresson, D., “Thermomechanical Analysis of Friction Brakes,” SAE 2000-01-2775.
- Velardocchia, M., Amisano, F., Flora, R., “A Linear Thermal Model for an Automotive Clutch,” SAE 2000-01-0834.
- Yang, Y., Lam, R. C., Fujii, T., “Prediction of Torque Response During the Engagement of Wet Friction Clutch,” SAE 981097.
- Yang, Y., Lam, R. C., Chen, Y. F., Yabe, H., “Modeling of Heat Transfer and Fluid Hydrodynamics for a Multidisc Wet Clutch,” SAE 950898.
- Han, Z.-P., Song, W.-Y., Dai, B.-R., “Measuring Surface Temperature Distributions on Clutch Discs,” SAE 922094.
- Dundore, M. W., Schneider, R. C., “Clutch Energy - A Criteria of Thermal Failure,” SAE 680582.