Optimization Method for evaluating Essential Factors of Plate Backside Thinning Defects using Lock-in Thermography

In this study, an optimization method for evaluating the essential factors of thinning defects on a plate backside, such as a containment linear plate, was investigated using a nondestructive testing method through lock-in thermography(LIT). A quantified mockup was developed, in which LIT under various heat conditions was applied, tools for defect analysis were developed using the four-point correlation method and MATLAB, and the full-time amplitude and phase value were calculated. In addition, the optimal conditions and evaluation times were determined, and detectability, resolution, defect sizing, and the error rate were analyzed using the signal-to-noise ratio and the full width at half maximum of phase. Based on the results, it was possible to suggest the optimal test conditions and evaluation time through LIT for thinning defects on the plate backside. Furthermore, the optimum essential factor for thinning defect sizing under the defect detection conditions was analyzed