Experimental Characterization of an Active Infrared Thermography Heat Source

Abstract

Accurate knowledge of the heat flux characteristics provided by optical heat sources of long heating time nondestructive infrared thermography techniques is essential to determine the adequate application of such techniques; however, detailed characterizations are scarce. Therefore, a thermal and statistical characterization of a halogen lamp was developed. A highly repeatable experimental procedure was used to characterize the heat flux generated at an ideal inspection sample top surface. The characteristics studied were: lamp distance, bulb color, lamp orientation, heat quality, and heating time. The heat flux was determined by using the readings of temperature and heat flux from the sample back, and a finite differences lumped capacitance thermal model. Detailed studies using three sensors determined that the heat flux was nonuniform (13% maximum variation). Therefore, a full quantitative characterization of the lamp was developed by using the average of such sensor readings, determining that: this halogen lamp can provide consistent top heat fluxes (although not uniformly distributed) adequate for nondestructive testing infrared thermography, the lamp distance and bulb color affected the amount of heat provided as well as the heat flux uniformity, and lamp orientation did not affect the mean top heat fluxes. This research approach can be used to determine an approximation of the lamp time-averaged heat fluxes for any material with similar top surface optical characteristics. Moreover, the technical data provided are useful to determine the adequacy of heating time, lamp distance, lamp orientation, and bulb color for long heating time nondestructive testing infrared thermography.