Damage Tolerance Evaluation of the Anti-Camout Rib (ACR) Torq-Set Recess Fasteners

摘要

This report describes the latest effort in the continuation of the Air Force's technical evaluation of aerospace fastener recesses. Earlier work has investigated the prototype Anti-Camout Rib (ACR) recess design, i.e., one rib on each removal wall of the recess and the driver bit. This test program, at the request of the Secretary of Defense, evaluated the production configuration with multiple horizontal ribs on each removal wall of the driver bit and one vertical rib on each removal face of the fastener recess. This effort was confined predominantly to the damage tolerance testing of the following recess/driver bit combinations: (a) standard Torq-Set recess and standard Torq-Set driver bit, (b) ACR Torq-Set recess and ACT Torq-Set driver bit, (c) ACR Torq-Set recess with standard Torq-Set driver bit and (d) standard Torq-Set recess with ACR Torq-Set driver bit. Limited tests of the Torx recess fastener modified with 5 deg taper on the side wall of the recess were also conducted. This test program was coordinated with and approved by the Army and Navy. Besides the testing of the recesses, this effort was expanded to determine the cost and service benefits of the Anti-Camout Rib on the Torq-Set recess.