Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Long Pulse Thermography for Nondestructive Inspection of Aeronautical Materials
Submission Author:
José Faria , SP , Brazil
Co-Authors:
José Faria, Alfredo Faria
Presenter: José Faria
doi://10.26678/ABCM.COBEM2021.COB2021-0995
Abstract
Infrared Thermography (IRT) is a contactless, rapid Nondestructive Testing (NDT) technique that has received considerable attention over the last years, mainly due to its simplicity and suitability for large-scale inspection of complex structures. IRT can be classified as passive or active, depending on the available control of the thermal radiation source. In passive mode, the object under analysis is naturally at a temperature higher or lower than the environment, creating a measurable thermal contrast on its surface. On the other hand, in active mode, the object is thermally excited by an external source and its thermal response is analyzed. Stimulation sources include optical radiation, ultrasonic wave propagation, eddy current and others. Among the different active thermography techniques, Long Pulse Thermography (LPT) with optical excitation is a cost-effective and promising technique, especially for the inspection of large composite structures. The objective of the present research is to evaluate the performance of the technique combined with computer vision algorithms on both composites and metallic materials. The evaluated LPT system is comprised of an uncooled microbolometer imager with resolution of 640x480 pixels and 2kW halogen lamps. A data set of thermograms from specimens with simulated flaws were collected and used to train a pixel classification model, based on random forests, for automatic image segmentation into defective and sound areas. The model was then evaluated on curved and flat specimens manufactured out of Carbon Fiber Reinforced Polymer (CFRP) and aeronautical grade aluminum. Results revealed that the technique can be successfully applied to both materials; however, considerably better performance was achieved on the CFRP samples. Additionally, the proposed pixel classification model achieved a higher degree of accuracy when compared to other automatic segmentation strategies, with accurate identification of defective areas and good defect size estimation.
Keywords
nondestructive testing, Infrared thermography, image processing, Aeronautical Structures
