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Brake drum failure due to cracking is a significant concern in the design of automotive brake systems. A dynamometer simulation of typical highway driving conditions indicated that for a gray cast iron drum to be resistant to large crack formation under typical driving conditions it should have a high graphite content. Drums with a relatively thin wall may also be more resistant to large crack formation however additional testing is required. Graphite flake length and drum hardness were not found to have an effect large crack formation. Defining the characteristics of drums resistant to large crack formation and failure can lead to safer, more efficient drum designs.

Lubricant effectiveness is critical to the overall operational success of engine systems and components, particularly when boundary lubricated conditions occur in the contacting regions. In this investigation, several material and base oil/additive combinations were studied under low-speed boundary lubricated conditions in the ball-on-flat configuration, under predominantly bulk elastic Hertzian contact stresses. The purpose of the tests was to investigate the thermal behavior of base oil/additive mixtures through controlled heat input and performance monitoring as indicated by measured friction coefficient. In doing so, the sliding friction coefficients were sensitive to the lubricant mixture and evolving boundary film generated at the interface, minimizing contributions from plastic deformation and asperity flash temperature generation. The steels used were AISI 304 stainless, 1095 high-carbon, and 52100. The base oils used were mineral oil and poly-alpha-olefin (PAO) synthetic oil.