Eddy Current Thermography Testing on Lack of Fusion (LOF) Defect of Carbon Steel Welded Sample

Abstract

Eddy current thermography (ECT) employs the combination of conventional and advanced nondestructive testing (NDT) technique. This technology is capable to detect defect in subsurface of carbon steel welded sample of dimension 200 × 150 × 20 mm. The optimum joule heating process via eddy current distribution is 300A with the heat diffusion around 50–500 kHz (which is relatively high-frequency electromagnetic wave). Along with the emerging development of eddy current thermography, the infrared camera permits its radiation range to visualize the real-time image of the defect via the application of the thermoimager TIM software. The quantitative information about the defect will be acquired by the camera which is sensitive to the transient signal of heat through material under inspection. The analysis due to the geometrical shape, position, and length of lack of fusion (LOF) defect can be made through maximum amplitude temperature analysis. The investigation performs the temperature linescan graph of temperature amplitude via Matlab. The result obtained from ECT is compared to the error bar analysis in line with radiography technique. The studies demonstrate the effectiveness and reliability of the technique for the quantification analysis of lack of fusion (LOF) defect of welded sample.