Optical fiber sensors for direct corrosion monitoring and detection
Abstract
The proposed approach to optical detection of corrosion has no analogs in current state-of-the-art corrosion sensing research. Fiber optic sensor solution, in which the entire sensor is composed of fused silica covered with protective polymer layers can provide excellent compatibility with majority of highly corrosive environments. Currently, several fiber optic solutions have been proposed. However, these solutions rely on indirect detection of corrosion through strain/stress measurements or degradation of sacrificial sensing layers similar in structure to the observed material. This leads to late or incorrect detection, requires mechanical excitation, and often can be used only in certain predetermined mechanical configurations. Signal processing techniques associated with these optical sensing principles are often complex and unreliable. According to ONR Code 33 PO Ignacio Perez, unacceptably poor performance of indirect optical corrosion detection techniques renders them unusable for Navy applications.The proposed investigation approaches detection of corrosion directly through sensing surface changes and degradation. This ensures sensor~s robustness and offers possibility to install sensors in harsh operating environments using protective polymer layer cover. Direct detection of the corrosion process through sensing of corrosion induced microscopic surface displacements in monitored metal surfaces represents the core conception of this research proposal. These displacements are proposed to be detected by properly designed microbend fiber optic sensors. Development of such sensors involves: - design of specialty fiber that produces optical throughput, which is highly sensitive to micron-scale displacements perpendicular to the longitudinal fiber axis - development of all-optical detection scheme that produces tailored optical response to surface changes due to corrosion while taking into account physical conditions arising from fiber adhesion to monitoring surface- extensive experimentation involving proposed fiber optic sensor detection of various types of corrosion during range of time spans.A complimentary approach is proposed for very confined places and detection of localized corrosion effects, such as for example crevice corrosion. It is based on Fabry-Perot interferometer that monitors minute changes in surface height between two chosen reference points. This allows for nanometer resolution of changes in the observed surfaces. The third proposed direct detection approach relies on thermo-optic effect caused by corrosion. Metal oxides, which are products of corrosion process different thermal conductivities than base metal thus detection of heat conduction provides information about a metal surface conditions. In the proposed scheme corrosion sensor is designed using absorbing fibers heated remotely by laser sources. The focus of the efforts in all three proposed approaches is fundamental research of suitable optical system design including studying physics of optical fiber and tailoring optical signal response to environmental physical conditions. From ONR Code 33 PO Ignacio Perez:~Even though the approach appears to be straightforward, it is nevertheless different to other approaches that I have funded in the past, therefore original.~PI and facilitiesThe PI is an internationally recognized expert with over 20 years of experience in specialty fiber and fiber sensors, he has a strong understanding of the state-of-the-art in this field and his fiber sensors are unique according to NRL subject matter experts. The lab facilities are well suited to conduct the proposed research.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2019
- Source ID
- N629091912082
Entities
People
- Denis Đonlagić
Organizations
- Office of Naval Research
- United States Navy
- University of Maribor