Accession Number : ADP010187

Title :   Failure Analysis of Modular Lift Link, Lug Mounting, Self-Locking Nuts

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Grendahl, Scott

PDF Url : ADP010187

Report Date : APR 1996

Pagination or Media Count : 13

Abstract : The U.S. Army Research Laboratory-Materials Directorate (USARL-MD) conducted a failure analysis of two self-locking nuts from an army attack helicopter, at the request of the U.S. Army Aviation and Troop Command (ATCOM). Light optical and scanning electron microscopy were utilized to characterize the fracture halves of the broken nuts. The self-locking nuts are governed by Specification MS21042, Nut, Self- Locking, 450 deg F, Reduced Hexagon, Reduced Height, Ring Base, Non-Corrosion Resistant Steel. During phase maintenance on the lift beam in the pylon area, maintenance crews noticed the bolts securing the lift link support lug were not properly seated. Further inspection showed that the left side self-locking nuts were cracked and/or missing. The right side nuts were also cracked.

Descriptors :   *SYMPOSIA, *FAILURE(MECHANICS), *LOCKING FASTENER DEVICES, *NUTS(FASTENINGS), MAINTENANCE, ATTACK HELICOPTERS, SCANNING ELECTRON MICROSCOPES, HYDROGEN EMBRITTLEMENT, STRESS CORROSION, CHEMICAL ANALYSIS, METALLOGRAPHY.

Subject Categories : Attack and Fighter Aircraft
      Properties of Metals and Alloys
      Machinery and Tools

Distribution Statement : APPROVED FOR PUBLIC RELEASE