Reference-free infrared thermography detection with subsurface heating for deep cavity in adhesive of hidden frame glass curtain wall

Abstract

Since the current infrared thermography (IRT) is not effective in detecting deep and invisible cavity in silicone structural adhesive of hidden frame glass curtain wall (HFGCW), a reference-free infrared thermography with subsurface heating for deep cavity is proposed. A near-infrared linear laser with high energy density and high transmission is chosen as the subsurface heating source to directly heat the silicone structural adhesive through the glass. Temporal sequence reconstruction and imaging enhancement based on reference-free calibration are proposed to reduce thermal unevenness and thermal noise, and ensure comparable results of damage detection under different environments. The effects of traditional surface heating and subsurface heating are compared and analyzed through numerical simulations. And an evaluated feature, maximal temperature difference feature (MTDF), derived from temperature difference is used to quantitatively analyze the thermal effect caused by different cavities. The subsurface heating simulation results showed that the highest temperature difference between area with cavity and non-defect area is 88% higher than that of traditional surface heating. The experiments revealed that the deep cavities of different lengths, located at 7 mm, 9 mm, and 11 mm below the glass surface, can be successfully detected using subsurface heating and reference-free calibration. A quadratic linear model was proposed to reflect the relationship between depths and lengths of cavities. In conclusion, the proposed method can protect the hidden frame glass curtain wall from deep and invisible cavities that can reduce its adhesion and strength.

Data-powered NDE for smart structure manufacturing and maintenance

“…The paper by Hong et al [9] introduced a no-reference infrared thermal imaging technique to detect the deep cavity in the adhesive of the concealed frame glass curtain wall. This technique introduces no-reference infrared thermal imaging to detect deep cavities in the adhesive of the hidden frame glass curtain wall.…”