Investigation of Textured Sensing Skin for Monitoring Fatigue Cracks on Fillet Welds

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Liu, Han
Li, Jian
Bennett, Caroline
Collins, William N.
Downey, Austin
Ziehl, Paul
Jo, Hongki
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Civil, Construction and Environmental EngineeringElectrical and Computer EngineeringCenter for Nondestructive Evaluation
Load-induced fatigue cracking in welds is a critical safety concern for steel transportation infrastructure, and the automation of their detection using commercial sensing technologies remains challenging due to the randomness in crack initiation and propagation. The authors have previously proposed a corrugated soft elastomeric capacitor (cSEC), which is a flexible and ultra-compliant thin-film strain gauge that transduces strain into a measurable change in capacitance. The cSEC technology has been successfully demonstrated for measuring bending strain as well as angular rotation in a folded configuration. This study builds on prior discoveries to characterize the sensor's capability at monitoring fatigue cracks in corner welds, for which the sensor needs to be installed in a folded configuration. A crack monitoring algorithm is developed to fuse the cSEC data into actionable information. Experimental work is conducted on an orthogonal welded connection, mimicking a plate-to-web joint in steel bridges, with cSECs folded over the fillet welds. The sensor's electromechanical behavior is characterized, and results confirm that the cSEC is capable of fatigue crack detection and quantification. In particular, results show that the cSEC can detect a minimum crack length of 0.48 mm and that its overall sensing performance, including signal linearity, resolution, and accuracy, is adequate under no damage, yet decreases with increasing crack size, likely attributable to the simplification of the electromechanical model and higher noise produced by the loading equipment under smaller applied displacement.
This is the Accepted Manuscript version of an article accepted for publication in Measurement Science and Technology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it.  The Version of Record is available online at DOI: 10.1088/1361-6501/ac6935. Copyright 2022 IOP Publishing Ltd. CC BY-NC-ND 3.0. Posted with permission.