Studies on the infrared thermography technique for quantitative nondestructive evaluation of surface crack and delamination of multilayer structures

Abstract

In this paper, some researches on the laser infrared thermography (LIT) and the eddy current infrared thermography (ECIT) for quantitative nondestructive testing and evaluation of surface cracks and delamination of multilayer structures are introduced. At first, a laser array spots thermography (LAST) method for inspection of surface cracks in metallic structures is presented. LAST related measurement and image processing methods for inspection and quantitative evaluation of crack profiles are introduced in detail. Second, LIT technique and numerical analysis methods for detection and sizing of interface delamination of multilayer structures are introduced aiming at application to the in-vessel structures of Tokamak fusion reactors, such as the first wall panels of blanket modules. At last, some studies on the quantitative nondestructive evaluation of delamination of thermal barrier coating system of gas turbine blades with ECIT are given. The numerical methods for forward analysis of heat generation and transfer process of infrared thermography, and for inverse analysis of defect size with infrared thermography signals are emphasized in this paper, in addition with experimental validations of both the numerical methods and the new inspection techniques.