of Automotive Brakes
3.3 Thermal Design Measures
3.3.4 Rotor Design Considerations
An important consideration in designing brake rotors is the expected thermal expansion and associated deformation of the entire rotor geometry. Minimizing thermal stresses results in increased thermal endurance strength and rotor life.
Thermal stress in the lateral or thickness direction of the rotor is mostly affected and controlled by material properties. Stress in the circumferential direction is a function of the deformation of the entire rotor, including hub.
Minimum circumferential stresses are obtained when the actual brake rotor ring is bolted to the hat section. In this design the ring can expand via the bolts without forcing its geometry change onto the hat or hub. The design is relatively expensive and not used for normal passenger cars.
For conventional ventilated rotors it is advantageous to make the rotor plates of different thickness. The outboard plate should be thicker than the inboard facing plate. This design reduces the cone-shape deformation or opening of the hub and rotor structure as well as minimizes surface cracking sensitivity.
If ventilation holes are used, they must be located such that cooling air can circulate from the inboard side of the brake underneath the vehicle through the brake. In this regard, wheel rim, hub design, and hub covers (if any) must be optimized for maximum brake cooling.
Thermal rotor stresses are minimized when stress raisers are eliminated as much as possible. For example, the number of cooling vanes of a ventilated rotor should always be arranged symmetrically with respect to the attachment bolts.
µL mp =λWaφi( / ) /R r App < 65N cm/ 2(95psi drum) ( )
eective drum or rotor radius, cm (in.) R = effective tire raadius, cm (in.)
u = effective width of brake drum swept areea, cm (in.) W = vehicle weight, N (lb)
= lining or pad
μL ffriction coefficient
Chapter 3 References
3.1 Thuresson, Daniel, “Thermo-mechanical Analysis of Friction Brakes,”
SAE Paper No. 2000-01-2775, SAE International, Warrendale, PA, 2000.
3.2 Arpaci, Vedat S., Conduction Heat Transfer, Addison-Wesley Publishing Company, 1966.
3.3 Limpert, R., “Temperature and Stress Analysis of Solid-Rotor Disc Brakes,”
Ph.D. Dissertation, University of Michigan, 1972.
3.4 Carlslaw, H. S. and J. C. Jaeger, Conduction of Heat in Solids, Oxford Science Publications, 2000.
3.5 Hasselgruber, H., Temperature Calculations for Friction Clutches, Friedrich Vieweg & Sohn Verlag, Braunschweig, 1956.
3.6 Limpert, R., “Cooling Analysis of Disc Brake Rotors,” SAE Paper No.
751014, SAE International, Warrendale, PA, 1975.
3.7 Emery, A.F., “Measured and Predicted Temperatures of Automotive Brakes under Heavy or Continuous Braking,” SAE Paper No. 2003-01-2712, SAE International, Warrendale, PA, 2003.
3.8 Wang, Xuanfeng, “Experimental Research on Heavy-Duty Tractor Heat Performance of Brake,” SAE Paper No. 2009-01-3039, SAE International, Warrendale, PA, 2009.
3.9 Zhang, Jian J., “A High Aerodynamic Performance Brake Rotor Design Method for Improved Brake Cooling,” SAE Paper No. 973016, SAE International, Warrendale, PA, 1997.
3.10 Daudi, Anwar R., “Hayes High Airflow Design Rotor for Improved Cooling and Coning,” SAE Paper No. 982248, SAE International, Warrendale, PA, 1998.
3.11 Daudi, Anwar R., “72 Curved Fins and Air Director Idea Increases Airflow Through Brake Rotors,” SAE Paper No. 1999-01-0140, SAE International, Warrendale, PA, 1999.
3.12 Daudi, Anwar R., “72 Curved Fin Rotor Design Reduces Maximum Rotor Temperature,” SAE Paper No. 1999-01-3395, SAE International, Warrendale, PA, 1999.
3.13 Barigozzi, Giovanna and Antonio Perdichizzi, “Aero-Thermal
Characteristics of an Automotive CCM Vented Brake Disc,” SAE Paper No.
2005-01-3930, SAE International, Warrendale, PA, 2005.
3.14 Mishra, Rakesh, David Bryant, and John D. Fieldhouse, “Analysis of Air Flow and Heat Dissipation from High Performance GT Car Front Brake Disc,”
SAE Paper No. 2008-01-0820, SAE International, Warrendale, PA, 2008.
3.15 Nutwell, Brian and Thomas N. Ramsay, “Modeling the Cooling Characteristics of a Disc Brake on an Inertia Dynamometer, Using Combined Fluid Flow and Thermal Simulation,” SAE Paper No. 2009-01-0861, SAE International, Warrendale, PA, 2009.
3.16 Limpert, R., Engineering Design Handbook, Analysis and Design of
Automotive Brake Systems, US Army Material Development and Readiness Command, DARCOM-P-706-358, 1976.
3.17 Kreith, F., Principles of Heat Transfer, International Textbook Company, 1965.
3.18 Pyung Hwang, Wu Xuan Wu, and Jeon YoungBae, “Repeated Brake Temperature Analysis of Ventilated Brake Disc on Downhill Road,” SAE Paper No. 2008-01-2571, SAE International, Warrendale, PA, 2008.
3.19 Parmigiani, John P. and Timothy C. Ovaert, “The Transient Temperature Distribution in a Heavy-Brake System During Fatigue Crack Testing,” SAE Paper No. 2000-01-0441, SAE International, Warrendale, PA, 2000.
3.20 Liang Li, Song Jian, and Qi Xuele, “Study on Vehicle Braking Transient Thermal Based on Fast Finite Element Method Simulation,” SAE Paper No.
2005-01-3945, SAE International, Warrendale, PA, 2005.
3.21 Apte, Amol A. and H. Ravi, “FE Prediction Thermal Performance and Stresses in a Disc Brake System,” SAE Paper No. 2006-01-3558, SAE International, Warrendale, PA, 2006.
3.22 Hertel, Jim E., et al., “Finite Difference Heat Transfer Model of a Steel-clad Aluminum Brake Rotor,” SAE Paper No. 2005-01-3943, SAE International, Warrendale, PA, 2005.
3.23 Schuetz, Thomas Christian, “Cooling Analysis of a Passenger Car Disc Brake,” SAE Paper No. 2009-01-3049, SAE International, Warrendale, PA, 2009.
3.24 Mi-Ro Kim, et al., “Numerical Investigation of Thermal Behaviour in Brake Assembly Driving the ALPINE Braking Mode,” SAE Paper No. 2007-01-1021, SAE International, Warrendale, PA, 2007.
3.25 Lozia, Zbigniew and Andrej Wolff, “Thermal State of Automotive Brakes After Braking on the Road and on the Roll-Stand,” SAE Paper No. 971040, SAE International, Warrendale, PA, 1997.
3.26 Jerhamre, Anders and C. Bergstrom, “Numerical Study of Brake Disc Cooling Accounting for Both Aerodynamic Drag Force and Cooling Efficiency,” SAE Paper No. 2001-01-0948, SAE International, Warrendale, PA, 2001.
3.27 Damodaran, Vijay, Radhika Cherukuru, and Ajith M. Jayssundera, CFD-Based Lumped Parameter Method to Predict the Thermal Performance of Brake Rotors in Vehicle,” SAE Paper No. 2003-01-0601, SAE
International, Warrendale, PA, 2003.
3.28 Eppler, Steffen, Thomas Klenk, and Jochen Wiedermann, “Thermal Simulation Within the Brake System Design Process,” SAE Paper No.
2002-01-2587, SAE International, Warrendale, PA, 2002.
3.29 Limpert, R., “An Investigation of Thermal Conditions Leading to Surface Rupture of Cast Iron Rotors,” SAE Paper No. 720447, SAE International, Warrendale, PA, 1972.