Integration of microwave and thermographic NDT methods for corrosion detection

Abstract

Abstract. Infrastructure health monitoring is an important issue in the transportation industry. For the case of cementbased structures in particular, detection of corrosion on reinforcing steel bars (rebar) is an ongoing problem for aging infrastructure. There have been a number of techniques that have shown promise in this area including microwave nondestructive testing (NDT) and thermography. Thermography is quite advantageous as it is an established method, and can be utilized for large inspection areas with intuitive results. Typical heat sources include induction heating and flash lamps, but these are not without drawbacks. Microwave nondestructive testing has also been successful at detecting corroded rebar, but at the cost of lengthy scan times. This paper presents an investigation into the potential of utilizing aspects of microwave NDT and thermography to create a hybrid NDT method, herein referred to as Active Microwave Thermography (AMT). AMT takes advantage of the electromagnetically lossy nature of corrosion byproducts and uses microwave energy to induce heat in the corrosion. Subsequently, the resultant heat profile is captured using an infrared camera. This paper presents initial simulations and measurements that highlight the potential of AMT to detect corroded rebar.

Estimation of Damage Thickness in Fiber-Reinforced Composites using Pulsed Thermography

“…Through establishing a NFIR model, the influence of , and ℎ on will be evaluated initially. An inverse model, written as ℎ = ( , , ), (6) can then be inferred to reconstruct ℎ based on , and .…”

“…Majority of NDT research focus on measuring the location and sizes of defects or damages, but limited studies on characterisation of their thickness. Microwave thermography has been used to study the effect of corrosion layer thickness on reinforcing steel bars [6], [7], but has not been applied on composites. Wang et al proposed a microwave equiphase frequency truncation method to detect and evaluate the thickness of kissing defects in GFRP laminate [8].…”

Application of Thermal Image Data to Detect Rebar Corrosion in Concrete Structures

“…Defect detection methods that employ infrared cameras are useful non-destructive testing methods to detect defects in concrete structures [18][19][20][21][22][23][24]. These methods are non-contact, stable, prompt, remote detection, and continuous testing methods [25][26][27]. However, the measurement results from these methods would vary depending upon several factors that affect thermography.…”

Application of Active Microwave Thermography to delamination detection

“…For example, utilizing microwave energy as a source of heat allows localized heating at a location of interest, as well as faster inspection rates as compared to traditional raster scanning techniques (e.g., microwave or ultrasound imaging, etc.). AMT is a relatively new hybrid method, and preliminary work has shown this method to have potential as a structural health monitoring tool [13]. As such, this work investigates a new application of AMT as a structural health monitoring tool for evaluation of rehabilitated cement-based (e.g., concrete) structures.…”

“…Thermography has also been successfully applied for structural health monitoring, but typically requires the use of a powerful heat lamp (which carries the risk of subsequent heat damage). As such, to build upon the success and legacy of thermography and potentially improve the method as an NDT tool, hybrid thermography techniques have been developed including laser [8], eddy current [9], induction [10], microwave [11]- [13], etc. These hybrid methods utilize other means for the generation of heat and subsequently measure the surface temperature profile of the SUT with a thermal camera (similar to traditional thermography).…”