Table 3.

Comparison of advantages and disadvantages of various infrared thermography testing methods.

Method	Advantage	Disadvantage
Infrared Pulsed Thermography Testing	The heating mode is simple, fast detection speed and high efficiency	Not suitable for the detection of complex structural components, only for the detection of flat components. In addition, the uniformity of the heat source is very high and the detection depth is limited
Infrared Lock-in Thermography Testing	Large area for one-time detection; provide certain depth information; continuous thermal excitation modulation requires only a small amount of thermal load. Strong ability to suppress noise	For a specific defect depth, a specific frequency is required for detection, with low efficiency; the phenomenon of blind frequency, which is easy to be missed
Infrared Ultrasonic Thermography Testing	Strong penetration and high detection depth; high detection sensitivity and safe operation	Not easy to check the workpiece with complex shape, and the surface finish of the tested object is required to be high; couplant should be filled in the test piece
Infrared Laser Thermography Testing	High power density; high detection accuracy	The method of laser point heat source is limited by the small area of single detection and the longtime of detection process; the laser line scanning method requires higher signal sensitivity; the high-power laser may cause surface damage
Grating Infrared Thermal Wave Scanning Testing	Simultaneous detection of horizontal and vertical cracks; localizable detection; low requirement for sampling frequency of thermal imager	Lack of experimental verification; the existing heat sources are not satisfactory