SAE J379_200908

Hardness measurements are used as a quality control check of the consistency of formulation and processing of brake linings. Gogan hardness is nondestructive (the penetrator causes shallow surface deformation.). Gogan hardness method alone does not show anything about a lining’s ability to develop friction or to resist fade when used as a friction element in brakes. The hardness and the range of hardness are peculiar to each formulation, thickness, and contour; therefore, the acceptable values and ranges must be established for each formulation and part configuration by the manufacturer. There is considerable confusion about the various hardness methods used to measure friction materials. True penetration hardness is measured by Rockwell measurements. Gogan hardness measures compressibility more than conventional hardness. To cover Rockwell hardness, we have written a new proposed standard (SAE J2654.) Compressibility is best measured by a compressibility test machine (SAE J2468) A considerable number of older engineering specifications have been written using Gogan measurements. Many Gogan machines are in daily use worldwide and a large body of historical data exists for Gogan measurements. It was therefore felt that Gogan hardness should be retained as a separate standard. The Standard was renamed to be "Gogan Hardness of Friction Materials" to differentiate it from J2564. The purpose statements of the two hardness standards were modified to acknowledge each other. There were minor editorial changes in J379. The actual Gogan measurement technique in J379 is not significantly changed from the previous version.