Soft Elastomeric Capacitor for Angular Rotation Sensing in Steel Components

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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.

Section: Electromechanical Modelmentioning

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Section: Crack Monitoring Algorithmmentioning

confidence: 99%

Section: Crack Monitoring Algorithmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Investigation of textured sensing skin for monitoring fatigue cracks on fillet welds

Liu¹,

Laflamme²,

Li³

et al. 2022

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Roadmap on measurement technologies for next generation structural health monitoring systems

Laflamme

Ubertini

Matteo

et al. 2023

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Structural Health Monitoring (SHM) is the automation of the condition assessment process of an engineered system. When applied to geometrically large components or structures, such as those found in civil and aerospace infrastructure and systems, a critical challenge is in designing the sensing solution that could yield actionable information. This is a difficult task to conduct cost-effectively, because of the large surfaces under consideration and the localized nature of typical defects and damages. There has been significant research efforts in empowering conventional measurement technologies for applications to SHM in order to improve performance of the condition assessment process. Yet, the field implementation of these SHM solutions is still in its infancy, attributable to various economic and technical challenges. The objective of this Roadmap publication is to discuss modern measurement technologies that were developed for SHM purposes, along with their associated challenges and opportunities, and to provide a path to research and development efforts that could yield impactful field applications.

Validation of large area capacitive sensors for impact damage assessment

Vereen,

Downey,

Sockalingam

et al. 2023

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Impacts in fiber-reinforced polymer matrix composites can severely inhibit theirfunctionality and prematurely lead to the composite’s failure. This research focuses ondetermining the efficacy of a novel capacitive sensor, the Soft Elastomeric Capacitor or SEC,to monitor the magnitude of out-of-plane deformations in composites. This work forwards thedevelopment of a sensing skin that can be used as an in situ monitoring tool for composites.The capacitive sensor can be made to arbitrary sizes and geometries. The sensor comprisesan elastomer composite that measures strains experienced by the material it is bonded to. Thestructure of the sensor, fabricated to function as a parallel plate capacitor, responds to impactsby transducing strains into a measurable change in capacitance. The SEC is deployed onrandomly oriented fiberglass-reinforced plates with a polyester resin matrix in this work. Thematerial is impacted at various energy levels until the monitored composite material reachesits yielding point. The behavior of the sensor in impact detection applications below the proofresilience shows little to no change in the capacitance of the sensor. As the impacts surpassthis yielding point, the sensor responds linearly with induced change in the area, validating thesensor’s behavior model in out-of-plane deformation. The sensor demonstrates the efficacyof the proposed large-area sensor as a damage quantification tool in the structural healthmonitoring of composites.