AFWAL-TR-83-3027, USAF DURABILITY DESIGN HANDBOOK: GUIDELINES FOR THE ANALYSIS AND DESIGN OF DURABLE AIRCRAFT STRUCTURES (JAN 1984)

AFWAL-TR-83-3027, USAF DURABILITY DESIGN HANDBOOK: GUIDELINES FOR THE ANALYSIS AND DESIGN OF DURABLE AIRCRAFT STRUCTURES (JAN 1984)., This is the first edition of the Durability Design Handbook. Objectives of the handbook are: (1) summarize and interpret the essential U.S. Air Force Durability Design requirements for metallic airframes, (2) provide durability analysis criteria for economic life and durability critical parts, (3) provide state-of-the-art durability analysis concepts and methods for quantifying the extent of damage for a population of details (e.g., fastener holes, Afillets, cutouts, lugs, etc.) as a function of time, (4) provide guidelines and design data for implementing the durability methodology and for assisting contractor and USAF personnel in complying with the intent of the durability specifications for metallic airframes. This document, loosely called a "Handbook", provides guidelines, concepts, analytical tools and the framework for incorporating future durability methodology advancements and design data. The durability analysis methodology, based on'a probabilistic fracture mechanics approach, accounts for initial fatigue quality, fatigue crack growth accumulation in a population of structural details, load spectra and structural properties. A statistical distribution of equivalent initial flaw sizes is used to represent the initial fatigue quality of structural details (e.g., fastener holes, fillets, cutouts, lugs, etc.). The equivalent initial flaw size distribution is grown forward, using the applicable design conditions, to a selected service time using a deterministic crack growth relationship, Procedures are described and illustrated. The durability analysis methodology has been demonstrated for quantifying the extent of damage due to relatively small cracks in clearance-fit fastener holes (e.g.,0.10"). Further research is needed to extend the methodology to larger crack sizes and to verify the methodology for other details, such as, fillets, cutouts and lugs. The effects of fretting, faying surface sealant, fastener clamp-up, environment, interference-fit fasteners, etc., on the initial fatigue quality need to be investigated. An evaluation is made of the accuracy of the durability analysis by correlating analytical predictions with test data for a fighter full-scale test article and complex splice specimens subjected to a bomber load spectrum.