AN INTEGRATED METHODOLOGY FOR ASSESSING WIDESPREAD FATIGUE DAMAGE IN COMMERCIAL AIRCRAFT

摘要

A methodology to predict the point of widespread fatigue damage has been developed. The three major components of this methodology are crack initiation, crack growth and linkup, and residual strength. The crack initiation methodology approach uses experimentally generated equivalent initial flaw size (EIFS) data and an analytical closure model to determine initial flaw sizes and distribution for multiple-site cracking. The crack tip opening angle (CTOA) and the T~* integral, a modified J-integral, are used to determine crack growth and linkup. Elastic-plastic finite element analysis is used in conjunction with CTOA or T~* to determine the residual strength in the presence of multiple-site damage (MSD). These methodologies are being verified through a comprehensive test program being conducted by The Boeing Company.