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Proceedings Paper

Weld line degradation assessment using chaotic attractor property analysis
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Paper Abstract

This paper describes results from an investigation into weld line unzipping. The experiments use a series of steel plates (762 x 408 x 3.17 mm) instrumented with five fiber Bragg grating strain gauges. We rely on tuned chaotic excitation using a Lorenz oscillator to maintain a low dimension system suitable for chaotic attractor property analysis. Weld unzipping is simulated by leaving gaps in a weld line which start at one edge of the plate and extend for 34 or 74 mm (8 or 18% of the plate width). Two speeds of the Lorenz oscillator are used for excitation. These correspond to positive Lyapunov exponents of 5 and 10 and provide insight into our ability to control the dimensionality of the system. Strain data from the sensors are cast into attractors and analyzed for changes using a feature called nonlinear prediction error. The nonlinear prediction error results demonstrate that the LE=5 excitation barely excites any structure dynamics while the LE=10 excitation clearly excites the first LE of the structure. At the 95% confidence limit with LE=10 excitation three of the five sensors can distinguish all three damage cases with the other two sensors able to separate damaged from undamaged. At the 95% confidence limit with LE= 5, only one sensor was able to distinguish damaged from undamaged and no sensors could distinguish the two damage cases.

Paper Details

Date Published: 1 August 2003
PDF: 6 pages
Proc. SPIE 5047, Smart Nondestructive Evaluation and Health Monitoring of Structural and Biological Systems II, (1 August 2003); doi: 10.1117/12.483982
Show Author Affiliations
Mark E. Seaver, Naval Research Lab. (United States)
Jonathan M. Nichols, Naval Research Lab. (United States)
Stephen T. Trickey, Naval Research Lab. (United States)
Michael D. Todd, Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 5047:
Smart Nondestructive Evaluation and Health Monitoring of Structural and Biological Systems II
Tribikram Kundu, Editor(s)

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