GB/T 3098.12-1996

This standard specifies a test method for verifying the mechanical performance of nuts under a cone-shaped proof load, simulating the stress conditions when a nut is tightened against a non-parallel or tapered bearing surface. It is applied in the quality control and certification of fasteners used in mechanical assemblies, particularly in automotive, aerospace, and heavy machinery industries where joint integrity under angular loading is critical. The test ensures nuts can withstand specified axial forces without failure or permanent deformation when installed on conical washers or angled flanges.