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Practical study on the thermographic detectability of internal defects using temporally structured laser heating

  • Modern laser systems have proven to be highly versatile heat sources for active thermographic testing. Compared to more traditional light sources, e.g. flash or halogen lamps, their output power can be easily modulated at high rates, allowing a wide variety of complex excitations to be realized. Although their total optical output power can be theoretically scaled to arbitrary values, the maximum output power is practically limited by many factors: the maximum power that the sample under test can absorb without altering the lighted surface itself, the trade-off between irradiance and inspected area, the cost of the laser system, etc. Furthermore, when working with spatial modulator systems, the output power must be limited to avoid damaging such devices. Nevertheless, to guarantee a sufficient amount of heating even for highly thermally conductive materials and/or deeply buried defects, the heating times can be extended, e.g., either by using step heating, long pulse thermography, orModern laser systems have proven to be highly versatile heat sources for active thermographic testing. Compared to more traditional light sources, e.g. flash or halogen lamps, their output power can be easily modulated at high rates, allowing a wide variety of complex excitations to be realized. Although their total optical output power can be theoretically scaled to arbitrary values, the maximum output power is practically limited by many factors: the maximum power that the sample under test can absorb without altering the lighted surface itself, the trade-off between irradiance and inspected area, the cost of the laser system, etc. Furthermore, when working with spatial modulator systems, the output power must be limited to avoid damaging such devices. Nevertheless, to guarantee a sufficient amount of heating even for highly thermally conductive materials and/or deeply buried defects, the heating times can be extended, e.g., either by using step heating, long pulse thermography, or by lock-in thermography with a continuously modulated heating. However, for all these approaches, the ranging capabilities of the thermographic defect detection are reduced due to the limited frequency content of the excitation. To tackle this problem, i.e. to increase the excitation energy while preserving its frequency content, new approaches have been developed in the last two decades, among them the use of coded excitations in combination with pulse-compression, and the use of multiple lock-in analysis or a frequency modulated excitation signal. The challenges of such temporally structured heating techniques are manifold, for example, the DC component inherent in optical heating must be taken into account. In general, a wider frequency bandwidth or greater variability of the frequency components also means greater complexity for signal generation and data processing. In this paper, temporally structured excitation schemes with different degrees of complexity are compared on a high-power laser system.zeige mehrzeige weniger

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Metadaten
Autor*innen:Julien LecompagnonORCiD, M. RicciORCiD, S. LauretiORCiD, Mathias ZieglerORCiD
Persönliche Herausgeber*innen:X. Maldague
Dokumenttyp:Beitrag zu einem Tagungsband
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):The 2024 International Conference on Quantitative InfraRed Thermography
Jahr der Erstveröffentlichung:2024
Organisationseinheit der BAM:8 Zerstörungsfreie Prüfung
8 Zerstörungsfreie Prüfung / 8.3 Thermografische Verfahren
Veröffentlichende Institution:Bundesanstalt für Materialforschung und -prüfung (BAM)
Verlag:QIRT Council
Erste Seite:1
Letzte Seite:9
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurbau
Freie Schlagwörter:Coded excitation; Defect identification; Laser; NDT; Thermography
Themenfelder/Aktivitätsfelder der BAM:Infrastruktur
Infrastruktur / Leichtbau
Veranstaltung:17th International Conference on Quantitative InfraRed Thermography 2024
Veranstaltungsort:Zagreb, Croatia
Beginndatum der Veranstaltung:01.07.2024
Enddatum der Veranstaltung:05.07.2024
DOI:10.21611/qirt-2024-077
URN:urn:nbn:de:kobv:b43-653790
ISSN:2371-4085
Verfügbarkeit des Dokuments:Datei für die Öffentlichkeit verfügbar ("Open Access")
Lizenz (Deutsch):License LogoCreative Commons - CC BY - Namensnennung 4.0 International
Datum der Freischaltung:21.01.2026
Referierte Publikation:Nein
Schriftenreihen ohne Nummerierung:Wissenschaftliche Artikel der BAM
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