Research On Non-destructive Testing Method Of Induction-activated Thermography

Corrosion and crack is the major injury types of vehicle. The detection of hidden corrosion andfatigue crack of metal strcture with complex surface, is a challenge to Non-destructive testingtechniques. With the development of science and technology of modern aviation and aircraft lifegreatly extended, threat on the aircraft safe operation of corrosion and cracks is also more prominent.Meanwhile, the application of a large number of new materials such as composite materials is a toughchallenge with which the non-destructive testing of the new century aviation industry must be faced.Induction-Activated Thermography is a new method with great value to solve the above problems. Itcombines the technology of eddy current with infrared thermography, using the infrared camera tocapture the temperature caused by electromagnetic field.The method of Induction-Activated Thermography in the article is studied from aspects ofsimulation and experimental analysis. The Finite Element Analysis software-COMSOL Multiphysicsis used for building calculating models and analyzing the process of electro-thermal interaction. Thedifferent models with edge crack, sub-surface crack and different angle shape crack are built, whichgive the temperature distribution of different defects formed by eddy current. We summarize themorphology of different defects by analyzing the heat distribution on the surface of the test piece. Theinfluences of different material, induced frequency, induced coil and lift off to the thermogram areanalyzed through simulation models. The Induction-Activated Thermography system is built, whichcontains an infrared camera, induced coil, excitation source and a PC. The different coils are designedaccording to the detected object. Using Induction-Activated Thermography testing method,experimental study is completed on different samples with defects, such as alloy steel test-piece withedge crack, rail with cracks, metal components with special-shaped cracks, and carbon fibercomposite piece with delaminations. The results show, Induction-Activated Thermography methodcan be applied to detect defects in metals and carbon fiber composite successfully, and it solves someexisting detection problems.