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Grey cast iron alloys for brake drum and brake disc applications are being developed with niobium additions and a range of equivalent carbon for commercial, passenger vehicle, and performance applications. The benefit of niobium in cast iron is based on the contribution of strength by matrix refinement for a given carbon equivalence that may permit the direct improvement of wear improvement or allow for an increase in carbon equivalence for a given strength. Proper carbon equivalency and pearlite stabilization contribute to an improved pearlite structure with an optimized distribution of graphite. These structures, when refined with niobium, demonstrate increased service life and reduced wear relative to their niobium-free equivalents as measured by lab dynamometer testing and by on-vehicle testing in passenger bus fleets.

The objective of this paper is to highlight the design, analysis, testing, and application engineering performed to develop a lightweight brake drum made of aluminum metal matrix composite (MMC). Current cast iron brake drums are “design-limited” in the sense that new designs do not significantly change performance and they offer minimal weights savings. This paper will begin with the design of the drum with respect to SAE requirements, and then show how the drum was optimized using finite element analysis (FEA). FEA was used to predict maximum drum temperatures and stress levels reached during various braking events. There were a number of design iterations that led to the current design that has been extensively tested on the dynamometer and on a vehicle. In addition to test performance, the casting and infiltration challenges led to significant design changes.