Lock-In Thermography NDT Technique
The principle of lock-in thermography is based on the application of a periodic input energy wave (i.e. thermal emitter, ultrasound, microwave, eddy current, flash or xenon lamp, halogen lamp, or laser) to the surface of the object being examined and analyzing the resulting local temperatures on the surface of the object.
When the input energy wave penetrates the object’s surface, is it absorbed and phase shifted. When the input wave reaches areas within the object where the thermophysical properties are not homogeneous in relation to the surrounding material, (i.e. at delaminations or inclusions), the input wave is partially reflected.
The reflected portion of the wave interferes with the incoming input wave at the surface of the object, causing an interference pattern in the local surface temperature, which oscillates at the same frequency as the thermal wave.
The internal structure of the object being examined can then be derived by evaluating the phase shift of the local surface temperatures in relation to the input energy wave. The ability to derive internal thermophysical inconsistencies within the object, however, requires that the input energy source be used at an optimal frequency, which depends on both the thermophysical characteristics of the object as well as its thickness.
The principle measurement setup is shown here.
MoviTHERM Lock-In Thermography NDT Solution
MoviTHERM Lockin Thermography Non-Destructive Test System. This system is a Lockin Thermography System used for defect detection in materials, such as composites, metals and non-metals. Lockin Thermography allows the detection of some very weak signals even below the noise floor of the camera in the micro-Kelvin range. This ability makes this method the perfect candidate for locating tough to find material defects.
In this video we explain the application of the Lock-In Thermography method using a FLIR camera and an irNDT system.
Find out more about the MoviTHERM irNDT Infrared Non-Destructive Testing Solutions
About MoviTHERM
MoviTHERM – Advanced Thermography Solutions was founded in 1999. The company offers solutions for plastic welding, package sealing, and non-destructive testing. In addition, MoviTHERM provides IoT Cloud monitoring solutions for thermal imaging applications for early fire detection, machine condition monitoring, and other applications. MoviTHERM is a Teledyne FLIR Premium Partner and master distributor for FLIR Thermal Cameras for automation and science applications.
