Hot-rod thermography for defect detection

Abstract

The quality of critical parts, such as aircraft components, is of extreme importance. Since cracks are the initiators of failure, crack detection by non-destructive testing (NDT) has become a necessity. Structural failure is always accompanied by the formation of cracks. Hence, the life of a structure can be extended by the early detection of cracks and appropriate corrective action to prevent structural failure. Among the various NDT techniques available for the detection of these defects, thermography is relatively new. Infrared (IR) thermography has the advantage of being able to inspect large areas in a smaller amount of time. In IR thermography, the thermal contrast on the test specimen is captured by an IR camera in the form of thermograms (transient temperature images), which are further processed to determine the defects and flaws in the specimen. Active thermography requires an external source of energy to induce a temperature gradient between the defective and non-defective areas in the specimen under inspection. This active approach is necessary in many cases where the specimen to be inspected is usually in equilibrium with the surroundings and may not exhibit thermal contrast. The commonly-used excitation sources are optical (flash, laser) and electromagnetic (induction) and produce a spot, line or area source of heating.