Song, Gangbing2020-10-09August 2022020-08August 202Portions of this document appear in: Jiang, Jinwei, Siu Chun Michael Ho, Taylor Tippitt, Zheng Chen, and Gangbing Song. "Feasibility study of a touch-enabled active sensing approach to inspecting subsea bolted connections using piezoceramic transducers." Smart Materials and Structures (2020).https://hdl.handle.net/10657/7019Bolted flange connections are commonly utilized to link pressure vessels and pipeline systems. Although there exists a series of design codes and standards to specify the design of flange joints, multiple adverse factors, such as unexpected loads and excessively high pressures and temperatures, can directly cause leakage failures of the flange connections in service. Leakage failures, if undetected, may result in crippling economic losses and sometimes irreversible environmental damages, especially for offshore applications. Therefore, integrity monitoring and inspection of both onshore and offshore bolted flange connections is necessary. In this dissertation, a comprehensive integrity monitoring system is proposed and developed through the implementation of cutting-edge sensing technologies to thoroughly investigate the integrity of a bolted flange assembly under tensile loads, internal pressure loads and a combination of both. API 6A flanges (4-1/16”, Type 6B, 2000 psi) were selected to perform the proposed research. Fiber Bragg grating (FBG) -enabled bolts offer a direct measurement of the bolt strains in the flange assembly. The piezo-based active sensing method and the electromechanical impedance (EMI) method provide different approaches to monitor the characteristic variations in the metal-to-metal sealing condition. Upon seal failure, the acoustics generated by the sudden release of the escaping pressurized nitrogen gas were readily detected by the acoustic emission (AE) system. Meanwhile, the internal pressure of the flange assembly was simultaneously recorded as a reference for other measurements. Through the data analysis, this comprehensive integrity monitoring system provides useful insights of flange connection behaviors under different internal pressures and tensile loads and a preliminary understanding of a leakage failure envelope considering the bolt torques and tensile loads. Moreover, a touch-based sensing mechanism was also explored and further applied on a specifically designed robotic manipulator, which was incorporated with an undersea remotely operated vehicle (ROV) to comprise a remote inspection system for subsea bolted connections. Its undersea inspection performance was demonstrated through field testing in a local marine environment. Thus, the proposed comprehensive integrity monitoring system offers potential solutions for assuring the performance and integrity of onshore and offshore bolted flange joints in practical applications.application/pdfengThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).Bolted flange connectionsIntegrity monitoring systemsOnshore and offshore applicationsPiezo-based active sensingElectromechanical impedanceFiber Bragg grating (FBG) enabled strain monitoringAcoustic emission (AE) systemRemotely operated vehicle (ROV)Undersea bolt inspection2020-10-09Thesisborn digital