Analysis of effects of diffraction and interference on detection by microwave thermography

Keo, Sam Ang; Yune, Chan-Young; Dragan, Razvan Gabriel; Defer, Didier; Breabăn, Florin

doi:10.1007/s13349-019-00329-8

Cited by 5 publications

(10 citation statements)

References 5 publications

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“…The geometrical relation between ∆ i , θ t , and the concrete cover (e) can be illustrated in Figure 3. As shown in Figure 3a, which was discussed in the previous study [35], the concrete in the areas of inference (superposition of the waves) of the refracted waves is hotter than in the other areas. The same study also showed that the steel bars in the detected wall play a role as an obstacle to the transmitted waves, which makes some fractions of the waves totally reflected to the concrete surface.…”

Section: Methodsmentioning

confidence: 57%

“…The same way of measurement is used to obtain the shift values for the other cases of incident wave angles. It is worth noticing that the shifts (Δi) are generated by the effect of the refraction of the waves after reaching the steel bars inside the detected RC wall, which was interpreted in the previous study [35]. From step five to step seven, which is the last step, a combination of a physical law and a mathematical analysis method is needed.…”

Section: Methodsmentioning

confidence: 92%

“…As a result of the study, the effects of incident waves on the thermograms in both detection approaches (reflection and transmission) have also been clarified. On the thermograms in the reflection approach, concrete parts in the reflected areas are hotter than other areas, whereas the fractions in the areas of wave superposition (interference) are hotter than other areas in the transmission approach [35].…”

Section: Introductionmentioning

confidence: 98%

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Detection of Concrete Cover of Reinforcements in Reinforced Concrete Wall by Microwave Thermography with Transmission Approach

et al. 2022

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Concrete cover has an important role in reinforced concrete (RC) structures because it protects reinforcement bars from the bad effects of weather, fire, and bad environmental conditions that cause the corrosion of the reinforcements. Although it is an essential parameter to be considered for structural health monitoring (SHM), its detection by infrared thermography, especially in the heating phase, has not been accessed yet. The detailed analysis and discussions of physical phenomena, known as diffraction and interference, affecting the thermograms during the detection of the steel bars by microwave thermography have given an essential key for resolving this issue. The present paper proposes an innovative methodology with microwave thermography for determining the concrete cover thickness of one-layer reinforcements (12 mm in diameter and regularly placed at 10 cm) in an RC wall (1 m × 1m × 6.5 cm). By using the transmission approach with five angles of microwave antenna direction (0°, 15°, 30°, 45°, and 60°) and the Snell–Descartes law and linear law, the proposed methodology leads us to deduce the approximate value of the concrete cover thickness (37.74 mm), which is close to the real value (38 mm), as well as the spacing of the steel bars and dielectric constant of the concrete. The detection of the concrete cover thickness is another new remarkable achievement of infrared thermography methods.

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Section: Methodsmentioning

confidence: 57%

Section: Methodsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 98%

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Detection of Concrete Cover of Reinforcements in Reinforced Concrete Wall by Microwave Thermography with Transmission Approach

et al. 2022

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“…Studies in the literature have utilized microwave heating to expedite the process of concrete curing, disinfect cement, and facilitate the drilling or melting of concrete [28][29][30][31][32][33][34][35][36][37]. Microwaves have the potential to provide the necessary energy for infrared thermography, as indicated by several studies [20,[38][39][40][41][42][43][44]. The primary advantage of microwave heating lies in its volumetric nature.…”

Section: Introductionmentioning

confidence: 99%

“…An additional advantageous aspect of this approach is its non-invasive characteristic, which is particularly valuable in situations when direct entry to the object under investigation is not possible and assessment from a distance is required. In the microwave infrared thermography (MIRT) method, the heating ratio of this alternative energy source is influenced by both thermal and electrical properties, specifically the dielectric constant [38,45]. In the case of conductive materials such as CFRP, microwave heating is limited by a shallower depth of penetration.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Carbon Fiber Reinforced Polymer Concrete Reinforcement Ageing Using Microwave Infrared Thermography Method

Szymanik,

Keo,

Brachelet

et al. 2024

Applied Sciences

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This study presents the utilization of the microwave infrared thermography (MIRT) technique to identify and analyze the defects in the carbon-fiber-reinforced polymer (CFRP) composite reinforcement of concrete specimens. At first, a set of numerical models was created, comprising the broadband pyramidal horn antenna and the analyzed specimen. The utilization of the system operating at a power of 1000 W in a continuous mode, operating at frequency of 2.45 GHz, was analyzed. The specimen under examination comprised a compact concrete slab that was covered with an adhesive layer and, thereafter, topped with a layer of CFRP. An air gap represented a defect at the interface between the concrete and the CFRP within the adhesive layer. In the modeling stage, the study investigated three separate scenarios—a sample with no defects, a sample with a defect located at the center, and a sample with a numerous additional random defects located at the rim of the CFRP matte—to analyze the effect of the natural reinforcement degradation in this area. The next phase of the study involved conducting experiments to confirm the results obtained from numerical modeling. In the experiments, the concrete sample aged for 10 years with the defect in the center and naturally developed defects at the CFRP rim was used. The study employed numerical modeling to explore the phenomenon of microwave heating in complex structures. The aim was to assess the chosen antenna design and identify the most effective experimental setup. These conclusions were subsequently confirmed through experimentation. The observations made during the heating process were particularly remarkable since they deviated from earlier studies that solely conducted measurements of the sample post-heating phase. The findings demonstrate that MIRT has the capacity to be employed as a technique for detecting flaws in concrete structures reinforced with CFRP.

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In situ near-field microwave characterization and quantitative evaluation of phase change inclusion in honeycomb composites

Wang

Zhou

Liu

et al. 2021

NDT & E International

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Analysis of effects of diffraction and interference on detection by microwave thermography

Cited by 5 publications

References 5 publications

Detection of Concrete Cover of Reinforcements in Reinforced Concrete Wall by Microwave Thermography with Transmission Approach

Detection of Concrete Cover of Reinforcements in Reinforced Concrete Wall by Microwave Thermography with Transmission Approach

Investigation of Carbon Fiber Reinforced Polymer Concrete Reinforcement Ageing Using Microwave Infrared Thermography Method

In situ near-field microwave characterization and quantitative evaluation of phase change inclusion in honeycomb composites

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