Damage Analysis in Mechanical Structures Using Vibrothermography

Abstract

This work aims to contribute to the development, understanding, and advancement of damage detection in composite materials using the technique of vibrothermography. This technique, classified as an active infrared thermography technique, uses vibrations to add energy to the system and thermal mapping of the material’s surface to identify temperature profiles or gradients that indicate the possibility of internal damage to the structure. In the search for innovation in numerical analysis applied to the subject, the formulation proposed to evaluate the viscoelastic response of the material was applied, making it possible to detect the damage induced at the interface between the Prepreg and Rohacell Hero 71®materials. The change in the temperature profile generated on the surface of the material after numerical analysis of the structure made it possible to detect points with greater temperature gradients, such as the crimping region, the force application region and the region where the damage was inserted. In addition to the initial numerical analysis carried out for sinusoidal excitation, experimental tests were carried out to evaluate the generation of internal heat in the structure during excitation. At this stage, the use of different frequencies (natural and unnatural) and different types of signals (composed of sine, triangular or square waves) proposed to investigate the presence of damage in the sandwich beam were evaluated, obtaining different responses for the combinations used. A higher rate of internal heat generation was observed for excitation using the square type signal and lower for triangular type excitation. The measurement of the accelerations at the reference points defined in the test plan, together with the analysis of the thermograms generated for the different combinations, made it possible to verify, for the damage region, greater heat exchange between the beam and the environment when excited at a frequency of 545.65 Hz. At 938.96 Hz, for the damaged region, the lower energy exchange between the beam and the environment and the greater generation of internal heat when compared to the same undamaged region led to a change in the temperature profile, indicating the possibility of damage.