Prospects for Titanium-Based Materials as Truck Disc Brake Rotors

Technical Report · Mon May 14 04:00:00 EDT 2007

DOI:https://doi.org/10.2172/1081592· OSTI ID:1081592

Blau, Peter Julian ^[1]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Strategies to improve the energy efficiency of cars and trucks can take many forms, like reducing parasitic frictional losses in the engine and drive-train, reducing rolling resistance of the tires, and designing the shape of vehicles for lower aerodynamic drag. With these strategies to reduce drag comes the penalty of making the vehicles harder to stop. Therefore, several research projects were begun under Department of Energy sponsorship to evaluate lightweight materials for new energy-efficient brakes. There was no pre-conceived notion as to what kinds of materials these would be, and research included ceramic composites, graphite materials, aluminum-based composites, and titanium-based composites. Cast iron was used as a benchmark in these studies since most current ground vehicle brake materials are cast iron or steel. Structural materials used in brakes have to fulfill a combination of functions. They must be dependable, durable, corrosion resistant, structurally-sound, and economically viable. Two general types of brake designs are currently used on heavy trucks: (a) drum brakes in which curved contact surfaces (‘shoes’) are forced outward against the inner diameter of a circular drum, and (b) disc brakes in which flat pads are clamped against a circular rotor that is attached to the wheel hub. Disc brakes are commonplace on automobiles and on some types of buses and trucks. The rotor/pad design of disc brakes tends to exhibit better resistance to fade (the decrease in friction when the brake temperature rises too high) than do drum/shoe type brakes. The European trucking industry has widely adopted disc brakes, and the U.S. trucking industry is likely to witness an increasing use of disc brakes in the face of new government-mandated, 20-30% reductions in stopping distances. Caliper clamping forces in commercial air disc brake systems for trucks can exceed 300 kN and the brake assembly might be called on to dissipate as much as 900 kW (1200 h.p.) during a single stop. Most disc brake rotors in use today are made from gray cast iron, typically containing about 3.5% carbon and various additives. Compositional modifications and heat treatments are also optimized to avoid thermal cracking and rotor distortion. In contrast to the rotors, brake pads are complex composite materials. They typically contain a phenolic resin binder with additions of mineral fibers, fillers, friction-modifying compounds, abrasives, and metallic particles to modify heat flow characteristics. Numerous compositions of friction materials have been developed, largely by empirical testing, and as a result, they vary greatly.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1081592
• Report Number(s): ORNL/TM--2007/111; VT1007000; CEVT910
• Country of Publication: United States
• Language: English