National Research Council of Canada. NRC Institute for Aerospace Research
Text, Book Chapter
This chapter presents preliminary results on the development of an analytical framework for evaluating the effects of prior exfoliation corrosion on the residual strength and remaining life of wing skins. A number of pristine and corroded specimens are cut from naturally exfoliated wing panels fabricated from 7075-T6511 alloys, and an ultrasonic nondestructive inspection (NDI) is carried out on the exfoliated specimens. The maximum depth and three-dimensional (3D) profile of the exfoliation damage are determined from the NDI data analysis. These specimens are tested using static tension and compression loading and the strain distributions on the specimens are measured using strain gauges, and photoelastic coating techniques. An analytical model is developed based on a "soft inclusion" technique, which is used to simulate the exfoliation damage. Using the PATRAN Command Language, automatic geometry and finite element (FE) model generation techniques are developed to create the "soft inclusion" for any shape and depth of exfoliation including the detailed 3D profile determined by NDI data analysis. The 3D FE model is first verified with the pristine specimen test results. FE analyses are then carried out on the exfoliated specimens and compared with the tests results. The good agreements between the modeling and testing results indicate that the analytical models are capable of evaluating the effects of exfoliation on the residual strength.
Environment-Induced Cracking of Materials: Prediction, Industrial Developments and Evaluation2 (2008): 375–385.