Identification of technological defects of bonded joints for the automotive industry needs using active thermography

W artykule skupiono się na termograficznej metodzie detekcji wad ścieżek kleju. Przeprowadzone zostały rozważania teoretyczne oraz doświadczalne (z zastosowaniem termografii aktywnej metodą impulsową) związane z przepływem ciepła w obszarach gdzie występuje ciągła warstwa kleju oraz tam gdzie występuje defekt. W rezultacie dokonano kalibracji parametrów pomiaru i potwierdzono założenia teoretyczne dla prostej próbki testowej posiadającej wyraźną nieciągłość.A bonded joint is one of the most popular types of joints in the production process of modern cars [1, 2]. The main reason for that is its uncommonly good ownerships i.e. durability, visual and economical properties [2]. To keep this features, it is necessary to provide continuity of all joints. However, there commonly occur the defects like delamination, poor cure, cracks, porosity, voids, “kissing” bonds and discontinuity of application in the industry environment (Fig. 1). There are many NDT methods (non-destructive tests) to disallow appearing these defects in the final product. In this paper, the active thermography method of NDT is described (Fig. 2). Pulse thermography as well as the simplest active thermography method, whose main idea is shown in Fig. 3, are well-known. There were made many theoretical consideration about various configurations of layers, which could occur in bonded joints (Figs. 4 and 5, Tab. 1). To verify these considerations, there was constructed a test stand (Fig. 7) and there was prepared a sample with a broken path of glue shown in Fig. 8. The results of the experimental research confirmed that earlier calculations of differences in the velocity between sectors with and without defects (Fig. 9) were right. On the other hand, a couple of the results obtained for various heating times (Fig. 10) was helpful to choose the best time of thermal influence duration