Quantification of Fastener- Hole Quality

TLDR: The Equivalent Initial Quality Method, a method of quantifying the quality of fastener holes, was used to assess the manufacturing quality of the F-4C/D/E(S) and A-7D aircraft.

Abstract: This paper describes a method, the Equivalent Initial Quality Method, of quantifying the quality of fastener holes. This quantification is accomplished by representing the imperfections that are either inherent in a material or introduced during the manufacturing of a structural component with a fatigue crack of a particular size and shape. This initial quality representation can be used in a crack-propagation analysis to determine the life of the structural component. For example, the Equivalent Initial Quality Method can be used in design by providing the assumptions necessary to satisfy the USAF airplane damage tolerance design requirements (MIL-A-83444) and the USAF airplane durability design requirements (MIL-A-8866B). The method was used to assess the manufacturing quality of the F-4C/D/E(S) and A-7D aircraft. The more recent A-7D quality assessment is discussed in detail and the equivalent initial quality results for the F-4C/D and A-7D aircraft are presented. The potential applications (e.g., determination of required inspection intervals and maintenance and modification schedules, use in design, assessment of quality of manufacturing procedures, etc.), as well as the possible limitations (e.g., sensitivity of method to stress level, material, etc.), of the Equivalent Initial Quality Method are discussed.