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Autor

  • Ziegler, Mathias (72)
  • Myrach, Philipp (17)
  • Maierhofer, Christiane (12)
  • Thiel, Erik (12)
  • Kreutzbruck, Marc (7)
  • Hempel, M. (5)
  • Röllig, Mathias (5)
  • Tomm, J.W. (5)
  • Elsaesser, T. (4)
  • Jonietz, Florian (4)
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Erscheinungsjahr

  • 2019 (5)
  • 2018 (12)
  • 2017 (9)
  • 2016 (7)
  • 2015 (7)
  • 2014 (7)
  • 2013 (6)
  • 2012 (8)
  • 2011 (8)
  • 2010 (3)
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Dokumenttyp

  • Vortrag (26)
  • Beitrag zu einem Tagungsband (23)
  • Zeitschriftenartikel (19)
  • Posterpräsentation (4)

Sprache

  • Deutsch (37)
  • Englisch (35)

Referierte Publikation

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  • ja (23)

Schlagworte

  • Thermography (25)
  • Thermografie (11)
  • Active thermography (8)
  • Laser (8)
  • Laser Thermography (7)
  • NDT (7)
  • Zerstörungsfreie Prüfung (7)
  • Laser thermography (6)
  • Lock-in Thermography (5)
  • Non-destructive testing (5)
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Organisationseinheit der BAM

  • 8 Zerstörungsfreie Prüfung (53)
  • 8.7 Thermografische Verfahren (44)
  • 8.4 Akustische und elektromagnetische Verfahren (13)
  • 9 Komponentensicherheit (4)
  • 9.3 Schweißtechnische Fertigungsverfahren (4)
  • 8.5 Mikro-ZfP (2)

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Examination of Spot Welded Joints with Active Thermography (2016)
Jonietz, Florian ; Myrach, Philipp ; Suwala, H. ; Ziegler, Mathias
The method described here allows to determine the size of the thermal contact between two metal sheets joined by spot welding. This size is a measure for the size of the weld nugget, i.e. the zone melted during the welding process, and thus the quality of the welded joint. The method applies active thermography in transmission or reflection setup. Especially the reflection setup offers an attractive possibility for non-destructive testing when components can be accessed from one side only. The spot weld region is optically heated by laser or flash light radiation. The weld nugget provides the mechanical joint, but also constitutes a thermal bridge between the two welded sheets. The latter will be exploited in this method. The better thermal contact at the weld Nugget contrasts with the surrounding material, where the heat transfer between the two sheets is comparatively low. A major advantage of the described method is the applicability on sheets without any surface treatment. This is achieved by a proper normalization of the data, allowing for a correction of the varying surface emissivity.
Vergleich konventioneller und neuer Oberflächenprüfverfahren für ferromagnetische Werkstoffe (2015)
Casperson, Ralf ; Heideklang, René ; Myrach, Philipp ; Onel, Yener ; Pelkner, Matthias ; Pohl, Rainer ; Stegemann, Robert ; Ziegler, Mathias ; Kreutzbruck, Marc
Sicherheitsrelevante und zyklisch hoch belastete Bauteile erfordern zur Vermeidung von kostenintensiven Ausfällen besonders stabile Prozessparameter. Bereits sehr kleine Randzonenfehler können unter zyklischer Bauteilbelastung zu Risswachstum und letztendlich zum Bauteilversagen führen. Die frühzeitige Erkennung von Randzonenfehler in Hochleistungsbauteilen wie z.B. Zahnräder, Ritzelwellen und Kurbelwellen erfordert daher eine leistungsfähige zerstörungsfreie Oberflächenrissprüfung, die es ermöglicht in den hochbeanspruchten Funktionsflächen auch Härterisse, Schleifrisse oder Zundereinschlüsse zu detektieren. Hierzu sind in den letzten Jahren einige neue, innovative Oberflächenprüfverfahren wie die laserangeregte Thermografie und die Streuflussprüfung mit hochauflösenden GMR-Sensoren oder magnetooptischen Verfahren entwickelt worden. Zusätzlich zur hohen Empfindlichkeit zeichnen sich diese innovativen Verfahren durch einen schnellen und teils auch berührungslosen Einsatz aus. Da die noch relativ neu-en Verfahren naturgemäß noch nicht normativ verankert sind, wurden auch bereits erste Validierungen durchgeführt. Um die Leistungsfähigkeit der Verfahren eingehend zu untersuchen, erfolgten Testreihen an verschiedenen Testkörpern in Bezug auf Ortsauflösung, Empfindlichkeit, Automatisierung und Bewertung der Messsig-nale. Neben den neuen Verfahren und ihren ersten Schritten hin zur Validierung kamen als Referenz auch die „klassischen“ Verfahren der Magnetpulver- und Wirbelstromprüfung zum Einsatz, deren Leistungsfähigkeit durch angepasste Sondenentwicklung auch für sehr kleine Oberflächendefekte nochmals unter Beweis gestellt wurde. Zusätzlich wurde an einigen Testkörpern eine hochauflösende CT durchgeführt. Die Ergebnisse dieses Vergleiches werden vorgestellt und Möglichkeiten sowie Grenzen der einzelnen Verfahren herausgearbeitet.
Thermographic Crack Detection in Hot Steel Surfaces (2016)
Unnikrishnakurup, Sreedhar ; Myrach, Philipp ; Polomski, Benjamin ; Le Claire, Elisabeth ; Vengara, N. ; Balasubramaniam, Krishnan ; Ziegler, Mathias
The detection and characterization of surface cracks in steel specimens prior to damage is a technologically and economically highly significant task and is of utmost importance when it comes to safety-relevant structures. In steel production where steel billets at high temperatures have to be inspected while moving a number of well-established NDT methods cannot be applied. Laser thermography however is a promising candidate to serve as a fast, non-contact and remote tool in this case. We present a study that shows that the crack detection capabilities of laser thermography can be extended also to specimens at high temperature. A combination of inductive and laser heating allows to systematically study the contrast formation as well as the optimization of the important measurement parameters. The experiments are accompanied by FEM simulations that provide a better insight of the physical correlations and support the experimental developments. The aim of these studies is to develop a system with high inspection speed and detection performance to be in-line operated under the hostile environment of steel production lines.
In-line laser thermography for crack detection at elevated temperature: A Numerical modeling study (2016)
Puthiyaveettil, N. ; Krishna, S. ; Kidangan, R. ; Unnikrishnakurup, Sreedhar ; Krishnamurthy, C. V. ; Ziegler, Mathias ; Myrach, Philipp ; Balasubramaniam, Krishnan
The detection and characterization of cracks prior to damage is a technologically and economically highly significant task and is of very importance when it comes to safety-relevant structures. The evaluation of a components life is closely related to the presence of cracks in it. Laser thermography has already high capability for the detection of surface cracks and for the characterization of the geometry of artificial surface flaws in metallic samples. Crack detection in metallic samples at high temperature is highly significant in present manufacturing scenario. During the casting process of billets, surface cracks form, due to the suboptimal cooling rates. These cracks reduce value of the billet and must be removed using machining process after cooling. This secondary process increases cost of manufacturing. In this work we developed a heat transfer model for laser thermography to study the thermal contrast variation with increase in surface temperature using finite element method (FEM). Here we are mainly concentrating the capability of the scanning laser thermography in crack detection which are in elevated temperature and numerical modeling study of thermal contrast variation of crack with respect increase in metal surface temperature. This study is important to prove the capability of laser thermography for crack detection in elevated temperature. Since we are using High power CW Laser to local heating of the metal surface which can give relatively high thermal contrast even at elevated temperature compare to other heating source. Here we are modeled and simulated 2D laser scanning across a surface breaking crack and developed an algorithm to produce the vicinity of crack. The algorithm we developed applied for various surface temperature data. And validated the credibility of the algorithm with experimental data.
Influence of the acquisition parameters on the performance of laser-thermography for crack detection in metallic components (2014)
Myrach, Philipp ; Ziegler, Mathias ; Maierhofer, Christiane ; Kreutzbruck, Marc
We present a systematic study on the performance of laser-thermography for the detection of surface cracks in metallic components. Scanning a metallic surface with laser causes local heating that is mapped simultaneously by an IR-camera and allows identifying cracks with sub-µm openings. The detectability, however, depends on a number of acquisition parameters (e.g. scanning speed, laser power, IR-camera resolution) that typically relate on each other. Most importantly, the detection-sensitivity of surface breaking cracks is given by a particular combination for the acquisition parameter values. As a result, this sensitivity is adaptable within wide ranges allowing the detection of cracks with openings ranging from 200 to 0.1 µm at testing speeds of 100 to 0.05 cm²/s. By examining artificial as well as fatigue cracks, we demonstrate that the method can be even applied to shiny surfaces with no need of pretreatments, which makes it an entirely contactless, remote and automatable NDT technique. A comparison with magnetic particle testing shows that laser-thermography has the potential to become a strong competitor to conventional surface inspection methods in the future.
Laser projected photothermal thermography for characterizing hidden defects (2016)
Thiel, Erik ; Kreutzbruck, M. ; Ziegler, Mathias
For the last 20 years active thermography has developed into a standard method in non-destructive material testing. It has become possible to detect defects such as cracks, voids, or even material inhomogeneities. Until now, it is still difficult to quantify subsurface or hidden defects in size due to the diffusive nature of heat flow within a solid. Facing this issue, lockin thermography and other photothermal techniques have been established. They are based on exciting a sample periodically (e.g. with a halogen lamp), causing a controlled periodical heat flow and thereby representing strongly damped thermal waves. These techniques make use of interference and reflection of thermal waves which allow enhancing depth resolution. So far, only the temporal component of the light source was modified to achieve a defined vertical heat flow – In contrast, we propose a novel technique in which we are able to control both: time and space. This technique enables us to exploit the possibilities of coherent thermal wave shaping. We achieve that by combining a spatial light modulator (SLM) with a high power laser. This approach allows us to launch a set of individually controlled and fully coherent high energy thermal waves into the sample volume. That means, we intentionally use wave propagation throughout the sample’s material in both - vertical and lateral direction. As one possible application, we use a thermal waves’ interference effect of two phase shifted wave patterns to detect the position of hidden defects. The wave patterns are positioned with a certain distance and a 180° phase shift to each other creating an amplitude depletion zone right in the middle of the two patterns. When a defect is brought unsymmetrically into the depletion zone, the lateral heat flow is disturbed. If the sample is now moved through the depletion zone, a defect can be easily characterized. Exciting periodically while controlling simultaneously phase and amplitude enables us to have a defined thermal wave propagation throughout the sample which means thermal waves can be controlled almost like acoustical or optical waves. This offers the opportunity to transfer known technologies from wave shaping techniques to thermography methods.
Localization of subsurface defects in uncoated aluminum with structured heating using high-power VCSEL laser arrays (2019)
Thiel, Erik ; Ziegler, Mathias ; Studemund, Taarna
We report on photothermal detection of subsurface defects by coherent superposition of thermal wave fields. This is made possible by structured heating using high-power VCSEL laser arrays whose individual emitter groups can be arbitrarily controlled. In order to locate the defects, we have developed a scanning method based on the continuous wavelet transformation with complex Morlet wavelet using the destructive interference effect of thermal waves. This approach can also be used for thermally very fast and highly reflective materials such as uncoated aluminum. We show that subsurface defects at an aspect ratio of defect width to defect depth down to 1/3 are still detectable in this material.
Thermography using High-Power Laser Arrays (2019)
Ziegler, Mathias
Due to their high irradiance and wide modulation bandwidth, high-power lasers open up a wide field of application. For example, the classical methods of pulse and lock-in thermography can be realized in high quality. In addition, structured heating is also possible by using arrays of such lasers. This makes it possible to implement new thermographic methods, such as interference-based detection of cracks or super resolution.
Prüfung von Punktschweißverbindungen mit Laser-Thermografie (2015)
Ziegler, Mathias
Laser-Thermografie für die schnelle Prüfung auf mikroskopische Risse in reflektierenden metallischen Oberflächen (2013)
Ziegler, Mathias
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