Engineering Criteria and Analysis Methodology for the Appraisal of Potential Fracture Resistant Primary Aircraft Structure

摘要

Design criteria and analysis procedures are presented such that a design system can be implemented to minimize the occurrence of major structural failures due to the presence of undetected damage. The design criteria define a flaw growth durability requirement and crack growth structural integrity requirements for three classes of inspectability of the structure; noninspectable, NDI in-service inspectable, and walk-around inspectable. Currently available crack growth and residual strength methods of analysis are presented which can be used to predict the remaining life and strength of damaged structure. To illustrate the use of the criteria and methods of analysis, a design study was conducted of the lower wing surface of a fighter/attack aircraft. The results of this study indicate that the structure could meet the design criteria with little or no weight penalty using 7075-T76 aluminum and annealed Ti-6Al-4V, and provided adequate inspection techniques and inspection frequencies are applied throughout the life of the aircraft. (Author)