J. M. Papazian, E. L. Anagnostou, S. Engel, D. Fridline, J. Madsen, J. Payne, J. Nardiello, R. Silberstein, Northrop Grumman, Bethpage, NY; P. C. Hoffman, NAVAIR, Patuxent River, MD; A. Roerden, G. Werczynski, Navair, Patuxent River, MD
The Northrop Grumman/DARPA Structural Integrity Prognsosis System (SIPS) was applied to a full-scale fatigue test of a retired EA-6B outer wing panel. The test was conducted by NAVAIR at Patuxent River, MD. The panel had been retired from active service with a Fatigue Life Expended index of 185. Laboratory fatigue testing of the entire panel was performed to evaluate several sensor systems, SIPS fatigue models, and the SIPS reasoning and prediction system. Phased array ultrasonics was used as a non-destructive inspection system to evaluate the starting state, and pitch-catch ultrasonics, eddy current (MWM®-Array) and the electrochemical fatigue sensors were used to monitor fasteners on rib 1 during the test. A FASTRAN-based modeling system was used to predict the evolution of cracking. The SIPS reasoning system combined the model and sensor outputs to provide a probabilistic crack size prediction that was updated daily. After the test, the panel was disassembled and actual crack sizes in the bores of the fastener holes were measured using scanning electron microscopy and compared to the sensor readings. The entire system performed admirably, and much useful data was obtained.
*This work is partially sponsored by the Defense Advanced Research Projects Agency under contract HR0011-04-C-0003. Dr. Leo Christodoulou is the DARPA Program Manger
Summary: This paper describes a full-scale fatigue test of a retired outer wing panel from an EA-6B aircraft. The test involved an adaptive prognosis methdology whereby the expected evolution of cracking in fastener holes was predicted. These predictions were updated periodically in response to data from sensors placed on the panel. Sensors inculded eddy current (MWM-Array), ultrasonic and electrochemical techniques. Non-linear elastic-plastic finite element models were used to predict crack lengths. The results of post-test SEM characterization of cracking in the fastener holes were compared to the predictions.
