This study presents an experimental investigation on the combined effect of mechanical loads and corrosion using the designed polytetrafluoroethylene tube-packaged fiber Bragg grating (FBG) sensors, as to implement long-gauge FBG (LFBG) sensors in corrosion detection practices for structural health monitoring. A simplified LFBG-based sensing model was proposed for strain measurement in terms of the Bragg wavelength change. Correspondingly, a systematic corrosion assessment strategy was developed to estimate corrosion severity and average corrosion rate. Upon this, the experimental study was performed on epoxy-coated steel specimens embedded with LFBG sensors, where the loading, corrosion, and combined loading–corrosion tests were used to explore the effect of mechanical loads on corrosion behavior. Test results revealed that the specimens subjected to combined conditions exhibited more severe corrosion damage. The maximum mass loss was observed to be 1.82 and 2.43 in percentage under individual corrosion and combined loading–corrosion conditions, respectively. Also, the pit depth under combined conditions was found to develop rapidly in the early stage. The pit depth severity ratio was around 0.2–0.8 during the 67 days of exposure, indicating an evident impact of loading on corrosion severity. Furthermore, the maximum average corrosion rate under combined conditions was found to be 5.66 times that under individual corrosion conditions.
This content will become publicly available on June 13, 2024
Investigating combined effects between dynamic mechanical loads and corrosion on epoxy coated steel using distributed fiber optic sensors
Each year, the global cost that is accounted to corrosion was estimated at $2.5 trillion. Corrosion not only imposes an economic burden, when corroded structures are under various loading conditions, it may also lead to structurally brittle failure, posing a potential threat to structural reliability and service safety. Although considerable studies investigated the combined effect of external loads and structural steel corrosion, many of the current findings on synergetic interaction between stress and corrosion are contrary. In this study, the combined effects of dynamic mechanical loads and corrosion on epoxy coated steel are investigated using the distributed fiber optic sensors based on optical frequency domain reflectometry. Experimental studies were performed using the serpentine-arranged distributed fiber optic strain sensors embedded inside the epoxy with three different scenarios including the impact loading-only, corrosion-only, and combined impact loading-corrosion tests. Test results demonstrated that the distributed fiber optic sensors can locate and detect the corrosion processing paths by measuring the induced strain changes. The combined impact loading-corrosion condition showed significantly accelerated corrosion progression caused by mechanical loads, indicating the significant interaction between dynamic mechanical loading and corrosion on epoxy coated steel.
more »
« less
- NSF-PAR ID:
- 10424945
- Editor(s):
- Sanders, Glen A.; Lieberman, Robert A.; Udd Scheel, Ingrid
- Date Published:
- Journal Name:
- Proc. SPIE 12532, Optical Waveguide and Laser Sensors II
- Volume:
- 125320A
- Page Range / eLocation ID:
- 9
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
-
Fiber Bragg grating (FBG) sensors have been applied to assess strains, stresses, loads, corrosion, and temperature for structural health monitoring (SHM) of steel infrastructure, such as buildings, bridges, and pipelines. Since a single FBG sensor measures a particular parameter at a local spot, it is challenging to detect different types of anomalies and interactions of anomalies. This paper presents an approach to assess interactive anomalies caused by mechanical loading and corrosion on epoxy coated steel substrates using FBG sensors in real time. Experiments were performed by comparing the monitored center wavelength changes in the conditions with loading only, corrosion only, and simultaneous loading and corrosion. The theoretical and experimental results indicated that there were significant interactive influences between loading and corrosion for steel substrates. Loading accelerated the progress of corrosion for the epoxy coated steel substrate, especially when delamination in the epoxy coating was noticed. Through the real-time monitoring from the FBG sensors, the interactions between the anomalies induced by the loading and corrosion can be quantitatively evaluated through the corrosion depth and the loading contact length. These fundamental understandings of the interactions of different anomalies on steel structures can provide valuable information to engineers for better management of steel structures.more » « less
-
null (Ed.)Structural health monitoring (SHM) activities are essential for achieving a realistic characterisation of bridge structural performance levels throughout the service life. These activities can help detect structural damage before the potential occurrence of component- or system-level structural failures. In addition to their application at discrete times, SHM systems can also be installed to provide long-term accurate and reliable data continuously throughout the entire service life of a bridge. Owing to their superior accuracy and long-term durability compared to traditional strain gages, fiber optic sensors are ideal in extracting accurate real-time strain and temperature data of bridge components. This paper presents a statistical damage detection and localisation approach to evaluate the performance of prestressed concrete bridge girders using fiber Bragg grating sensors. The presented approach employs Artificial Neural Networks to establish a relationship between the strain profiles recorded at different sensor locations across the investigated girder. The approach is capable of detecting and localising the presence of damage at the sensor location without requiring detailed loading information; accordingly, it can be suitable for long-term monitoring activities under normal traffic loads. Experimental laboratory data obtained from the structural testing of a large-scale prestressed concrete bridge girder is used to illustrate the approach.more » « less
-
Steel, which has high tension and compression strength, is a widely used civil engineering material in constructing building, bridge, pipelines, and other structures. However, steel has a well-known weakness, which is suspected to corrosion. Steel corrosion would significantly impact the reliability and safety of steel structures. Accurately locating and assessing the corrosion of steel structures would contribute to timely maintenance and thus, extend the service life of the steel structures. Although advances have been made to use nondestructive evaluation (NDE) technologies to locate and assess corrosion on steel structures, due to the lack of labor and budget for frequent NDE assessment on steel structures, remote and real-time approaches to locate and assess corrosion are still in great needs. Fiber optic sensors, especially, fiber Bragg gating (FBG) sensors, with unique advantages of real-time sensing, compactness, immune to EMI and moisture, capability of quasi-distributed sensing, and long life cycle, will be a perfect candidate for long-term corrosion assessment. However, due to the fact that FBG is a localized sensor, it is very challenging to locate corrosion using FBG sensors. In this study, algorithms are developed to locate corrosion on steel structures using FBG sensors. Detail sensing principle, localization algorithm development and calibration are introduced in this paper together with experimental validation testing. Upon validation, the developed corrosion localization algorithm could give some guidance to locate corrosion using in-situ FBG sensors on steel structures across nation and would possibly reduce the corrosion induced tragedies.more » « less
-
more » « less
Abstract Conventional strain gauges are not designed for accurate measurement over the large range of deformations possible in compliant textiles. The thin, lightweight, and flexible nature of textiles also makes it challenging to attach strain gauges in a way that does not affect the mechanical properties. In this manuscript, soft, highly extensible fibers that propagate light (i.e., stretchable lightguides) are stitched as a strain gauge to map the deformation of a nylon parachute textile under tension. When under load, these fiber optic strain gauges propagate less light, and this strain‐induced light modulation is used to accurately (absolute error≈2.93%; Std. Dev.: 3.02%) measure strain in the <30% range before these textiles fail. This system has directionality; strain in parallel to the sensor results in little light attenuation while perpendicular loading shows high sensitivity (Gauge factor⊥≈24.8 and Gauge factor||≈0.05 at the first 1% strain). Structural and optical simulations are coupled to demonstrate that load transfer on the fiber optic by the stitchwork is the dominating cause of signal modulation. To further validate the hypotheses, digital image correlation was used under dynamic loading conditions to show that these sensors do not significantly affect the mechanical properties.
