1974-02-01

Evaluating Copper Alloy Brake Discs by Thermal Modeling 740560

Past work has shown that brake discs constructed of a copper alloy containing 1% chromium can significantly reduce temperatures at the sliding interface. The purpose of this investigation was to demonstrate this fact further, and specifically to determine how copper discs should be configured to provide desired temperature response with a minimum amount of material.
To accomplish this objective, an analytical thermal model was developed of a disc design for heavy trucks. The model employed the finite difference approach, in which the disc was subdivided into a number of small volumes. The model specifically simulated disc temperature response during 50 mph fade tests performed on a dynamometer. The thermal model was correlated with test data to verify and improve its accuracy, and then utilized to evaluate the effects of material and geometry changes.
Results show that mass concentration in the disc faces yields lower temperatures at the friction interface, particularly during the first several stops. In fact, thickness of the vanes and hub might be reduced to conserve copper, as long as stress levels are adequate. Even after a large number of successive stops, temperature cycling would be less extreme with thicker faces. A chromium copper disc with a cast iron hub is one possibility for minimizing copper requirements.
The study has demonstrated that thermal modeling is a valid and potentially valuable tool in the design optimization of brake discs. Indeed, the analytical approach, combining both thermal and stress analyses, along with prototype testing, may prove the most effective method for future design development of disc brakes.

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