TY - CONF A1 - Chaudhuri, Somsubhro A1 - Junker, Birgit T1 - Infrared thermography as an inspection tool for wind turbine rotor blades N2 - With the rapid expansion of wind turbine construction, rotor blades have increasingly been identified as a primary cause of turbine downtime and failure. This has led to a growing demand for inspection technologies through which energy production losses can be minimised—particularly in comparison to conventional methods such as rope-access inspections—and through which sub-surface blade conditions can be assessed to detect damage or failure in advance. Infrared thermography has been considered as a promising non-contact, full-field inspection method that can be applied to rotor blades in both operational and idle states. In this presentation, delivered at BladesEurope 2025, the physical mechanisms that give rise to thermal contrast during thermographic inspection were explained, as this contrast enables the detection and visualisation of structural features. Results obtained from a collaborative project between BAM and Statkraft Norway were presented, followed by the validation of a finite element simulation through experiments conducted in a climate chamber.” T2 - BladesEurope Forum 2025 CY - Edinburgh, Scotland DA - 29.04.2025 KW - Thermography KW - Wind energy KW - Inspection KW - Windenergie anlage rotorblätte KW - Damage detection PY - 2025 AN - OPUS4-63060 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Elahi, Seyed Ahmad A1 - Mehri Sofiani, F. A1 - Chaudhuri, Somsubhro A1 - Balbin, J.A. A1 - Larossa, N.O. A1 - De Waele, Wim T1 - A numerical study on fatigue strength degradation due to pitting corrosion of S355 structural steel in a marine environment N2 - This study investigates the influence of pitting corrosion on the fatigue strength of S355 steel, commonly used in offshore wind support structures. A short crack microstructural model is employed to estimate the degraded fatigue strength, effectively capturing the physics of the problem with minimal input parameters. Material characterization tests provide the key mechanical properties of S355 steel. A parametric analysis is used to examine the effects of pit shape, size, and aspect ratio. A generic relationship is identified between degraded fatigue strength and pit size for various pit aspect ratios. A sensitivity analysis reveals that the pit aspect ratio significantly influences fatigue strength, with sharper pits leading to greater reductions. The threshold stress intensity factor has a moderate effect, while in-air fatigue strength and grain size have minimal impacts. A case study is performed to evaluate the fatigue strength degradation of S355 steel exposed to the North Sea environment. Findings indicate that the most severe degradation occurs in the initial years of exposure, with the degradation rate declining over time. The results align well with experimental data, offering a robust framework for assessing structural integrity in a marine environment. KW - Fatigue strength KW - Corrosion fatigue KW - Pitting corrosion KW - Short crack KW - Micromechanical model KW - S355 structural steel PY - 2025 DO - https://doi.org/10.1016/j.engfailanal.2025.109669 SN - 1873-1961 VL - 177 SP - 1 EP - 21 PB - Elsevier Ltd. AN - OPUS4-63062 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chaudhuri, Somsubhro T1 - Infrared thermography as an inspection tool for wind turbine rotor blades N2 - This presentation explores the use of infrared thermography as an inspection tool for wind turbine rotor blades. It highlights the implementation of ground-based thermographic techniques, demonstrates what can be achieved through such inspections, and presents a case study conducted in partnership with Statkraft. Particular attention is given to the discussion of thermal contrast and how it can be obtained for effective defect detection. To assess the potential and limitations of thermography, results from controlled climate chamber experiments and complementary simulations are also presented. T2 - IQPC Wind Week 2025 CY - Bremen, Germany DA - 26.08.2025 KW - Thermography KW - Thermografie KW - Wind turbine rotor blades KW - Windenergie anlage rotorblätte KW - Damage detection PY - 2025 AN - OPUS4-64056 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chaudhuri, Somsubhro T1 - WTB-IRT: Modelling and Measurement of Thermal Contrast in wind turbine rotor blades (WTBs) N2 - To understand the results that can be obtained with thermography of operational wind turbine blades, a climate chamber based experiment was performed. The results of these experiments were additionally modelled using COMSOL Multiphysics. The results have been presented at the conference. T2 - Advanced Infrared Technology and Applications (AITA) 2025 CY - Kobe, Japan DA - 15.09.2025 KW - Thermography KW - Thermografie KW - Wind turbine rotor blades KW - Windenergie Anlage Rotorblätter KW - FEA PY - 2025 AN - OPUS4-64222 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chaudhuri, Somsubhro A1 - Purayil, Sruthi Krishna Kunji A1 - Kruse, Julius A1 - Madia, Mauro A1 - Nielsen, Sören T1 - Thermography-Assisted Mechanical Testing of Cold-Spray (AM) Repair N2 - Cold Spray Additive Manufacturing (CSAM) is a solid-state process that is being increasingly used for structural repairs in aerospace and energy sectors. It enables the deposition of dense material at low temperatures by accelerating metal particles to supersonic velocities, thereby reducing thermal distortion. However, the structural integrity of CSAM repairs—particularly at the interface between the deposited layer and the substrate—remains a critical concern. Various post-treatments and characterization methods have been explored to optimize performance. While X-ray Computed Tomography (XCT) is effective for sub-surface inspection, it cannot be applied in situ during mechanical testing. Digital Image Correlation (DIC), a surface-based method, also lacks sub-surface sensitivity. To address this, Infrared Thermography (IRT) was employed alongside DIC during the tensile and fatigue testing of aluminum CSAM-repaired specimens. A cooled IRT camera operating at 200 FPS captured thermal data, with lock-in processing subsequently applied in post-processing. IRT successfully detected early interfacial damage and enabled the tracking of crack propagation, which was later confirmed through fracture surface analysis. This extended abstract presents findings from fatigue tests using IRT. T2 - 18th International Workshop on Advanced Infrared Technology and Applications (AITA 2025) CY - Kobe, Japan DA - 15.09.2025 KW - Thermography KW - Thermografie KW - Thermal stress analysis KW - Cold spray KW - Damage detection PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-642299 DO - https://doi.org/10.3390/proceedings2025129018 VL - 129 IS - 1 SP - 1 EP - 5 PB - MDPI CY - Basel AN - OPUS4-64229 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chaudhuri, Somsubhro A1 - Krankenhagen, Rainer A1 - Lapšanská, Ivana A1 - Stamm, Michael T1 - WTB-IRT: Modelling and Measurement of Thermal Contrast in Wind Turbine Rotor Blades (WTBs) N2 - The rapid growth of wind energy infrastructure over the past two to three decades has led to an urgent need for advanced non-destructive testing (NDT) methods—both for newly installed wind turbine blades (WTBs) and for ageing components nearing the end of their service life. Among emerging techniques, passive infrared thermography (IRT) offers a promising solution by enabling contactless, time-efficient inspection based on naturally occurring thermal variations. The effectiveness of passive IRT depends on the presence of sufficient thermal contrast to distinguish surface features, subsurface structures, and defects. To better understand the possibility of obtaining such contrast in composite structures such as WTBs, a controlled study was carried out on a blade section exposed to programmed temperature transients in a climate chamber. Infrared measurements were recorded, and the thermal behaviour of the specimen was simulated using finite element models (FEM) in COMSOL Multiphysics 6.3. Although direct validation is limited by measurement uncertainties and transient effects, the comparison provides insight into the capabilities and limitations of FEM in replicating real-world thermal behaviour. This paper focuses specifically on the challenges related to the modelling approach. T2 - 18th International Workshop on Advanced Infrared Technology and Applications (AITA 2025) CY - Kobe, Japan DA - 15.09.2025 KW - Thermography KW - Wind energy KW - Wind turbine rotor blades KW - Windenergie Anlage Rotorblätter KW - FEA PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-642308 DO - https://doi.org/10.3390/proceedings2025129015 VL - 129 IS - 1 SP - 1 EP - 5 PB - MDPI CY - Basel AN - OPUS4-64230 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chaudhuri, Somsubhro T1 - Thermography-Assisted Mechanical Testing of Cold-Spray (AM) Repair N2 - Cold Spray Additive Manufacturing (CSAM) is a solid-state process that is being increasingly used for structural repairs in aerospace and energy sectors. It enables the deposition of dense material at low temperatures by accelerating metal particles to supersonic velocities, thereby reducing thermal distortion. However, the structural integrity of CSAM repairs—particularly at the interface between the deposited layer and the substrate—remains a critical concern. Various post-treatments and characterization methods have been explored to optimize performance. While X-ray Computed Tomography (XCT) is effective for sub-surface inspection, it cannot be applied in situ during mechanical testing. Digital Image Correlation (DIC), a surface-based method, also lacks sub-surface sensitivity. To address this, Infrared Thermography (IRT) was employed alongside DIC during the tensile and fatigue testing of aluminum CSAM-repaired specimens. A cooled IRT camera operating at 200 FPS captured thermal data, with lock-in processing subsequently applied in post-processing. IRT successfully detected early interfacial damage and enabled the tracking of crack propagation, which was later confirmed through fracture surface analysis. T2 - Advanced Infrared Technology and Applications (AITA) 2025 CY - Kobe, Japan DA - 15.09.2025 KW - Thermography KW - Thermografie KW - Thermal stress analysis KW - Cold spray KW - Damage detection PY - 2025 AN - OPUS4-64227 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chaudhuri, Somsubhro T1 - EvalTherm: Evaluation of passive thermography for the inspection of operational wind turbine rotor blades N2 - Wind turbine rotor blades (WTBs) have undergone numerous developments related to their design, manufacturing, and material selection. The drive for cost efficiency has resulted in increasingly longer WTBs over the past two decades [1]. Despite advancements in wind turbine technology, WTB inspection methods have seen little change over the years. While drones are increasingly used, inspections still rely primarily on visual assessments. However, critical structural damage - often originating from manufacturing defects - typically begins within the composite blade structure. With the increase in wind turbine blade (WTB) sizes, now exceeding lengths of 120 meters, passive infrared thermography (IRT) has been explored as an alternative inspection method when thermal or optical excitation is impractical [2]. Despite its advantages, employing IRT in wind industry presents significant challenges due to inherent uncertainties related to material properties, environmental conditions, and calibration factors [3]. The effects of these conditions can be analysed through finite element (FE) modelling, albeit with certain limitations [4, 5]. This work is part of the multi-partner project “EvalTherm,” which aims to evaluate passive IRT as a non-destructive inspection tool for WTBs in operation (schematic of the project is shown in Figure 1:). One parameter that can be used to investigate its effectiveness is thermal contrast, which allows two distinct features to be distinguished in thermal data. Selected results from the project “EvalTherm” are discussed and shown in the presentation. They are primarily categorised into inspections done under controlled conditions: i.e. in laboratory (with active excitation in the form of irradiation) and a climate chamber (with a temperature transient introduced with airflow). Results from these trials help understand the combined effect that are observed in outside measurements, with exposure to the sun and diurnal temperature changes. The presentation will include results obtained from field inspections on operational WTBs. T2 - Wind Energy Science Conference (WESC) 2025 CY - Nantes, France DA - 24.06.2025 KW - Thermography KW - Wind energy KW - Wind turbine rotor blades KW - Windenergie Anlage Rotorblätter KW - Damage detection PY - 2025 AN - OPUS4-63558 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Chaudhuri, Somsubhro T1 - Infrarot-Thermografie zur Überwachung von mittels Kaltgasspritzen (Cold- Spray) reparierten Bauteilen unter zyklischer Belastung N2 - Das Kaltgasspritzen ist ein vielversprechendes Verfahren für die Reparatur von metallischen Komponenten , insbesondere sicherheitsrelevante Bauteile in der Luft- und Raumfahrt. Durch die Abscheidung von Partikeln mit hoher Geschwindigkeit ohne Schmelzen entsteht eine mechanisch verbundene Grenzfläche zwischen dem Substrat und der Beschichtung. Die Überwachung der Integrität dieser Grenzfläche unter Ermüdungsbelastung stellt jedoch nach wie vor eine Herausforderung dar, da die Grenzfläche nicht sichtbar ist. Die Röntgencomputertomographie (XCT) wird bereits häufig zur Charakterisierung von Defekten in Kaltgasspritzbeschichtungen und Grenzflächenbereichen eingesetzt. XCT bietet zwar hochauflösende Einblicke in interne Strukturen, ihre Anwendung bei mechanischen Prüfungen ist jedoch aufgrund praktischer Einschränkungen bei der In-situ-Implementierung begrenzt. In dieser Studie wurde die Infrarot-Thermografie (IRT) eingesetzt, um die Schadensentwicklung in kaltgespritzten Al6061-Proben während Zug- und Ermüdungsbelastung zu überwachen. Eine gekühlte Infrarotkamera mit hoher Bildfrequenz wurde synchron mit den mechanischen Prüfungen eingesetzt, und die Daten wurden mit Lock-in-Thermografieverfahren verarbeitet, um Phasen- und Amplitudensignale zu extrahieren, die mit thermoelastischen und dissipativen Effekten in Zusammenhang stehen. Die IRT ermöglichte die Erkennung thermischer Anomalien an der Grenzfläche zwischen Beschichtung und Substrat, die mit der Rissbildung und -ausbreitung korrelierten. Parallel dazu wurde die digitale Bildkorrelation (DIC) angewendet, um Oberflächenverformungsfelder abzubilden. Der Vergleich von DIC und IRT ermöglichte eine multimodale Betrachtung der Schadensmechanismen. Die fraktografische Analyse bestätigte, dass die mit IRT identifizierten Bereiche gut mit der Rissentstehung an der Grenzfläche übereinstimmen. Diese Ergebnisse bestätigen den Wert der Infrarot-Thermografie als zerstörungsfreies Verfahren zur In-situ-Überwachung der strukturellen Integrität bei Kaltgasspritzreparaturen. Sie ergänzt XCT und DIC, indem sie eine kontinuierliche Verfolgung der Schadensentwicklung unter realistischen Belastungsbedingungen ermöglicht. T2 - Thermo25: Infrarot-Thermografie im Dialog zwischen Forschung und Praxis CY - Garching bei München, Germany DA - 12.11.2025 KW - Thermografie KW - Lock-In KW - Kaltgasspritzen KW - Grenzflächenintegrität PY - 2025 AN - OPUS4-64709 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krankenhagen, Rainer A1 - Chaudhuri, Somsubhro A1 - Pittner, Andreas A1 - Winterkorn, Rene A1 - de Finis, Rosa A1 - Palumbo, Davide A1 - Galietti, Umberto T1 - Thermographic investigation of the anisotropic behaviour of additively manufactured AISI316 steel using DED-Arc N2 - Additive manufacturing is one of the most promising techniques for industrial production and maintenance, but the specifics of the layered structure must be considered. The Direct Energy Deposition-Arc process enables relatively high deposition rates, which is favourable for larger components. For this study, specimens with different orientations were prepared from one AISI316 steel block – parallel and orthogonal to the deposition plane. Quasistatic tensile loading tests were carried out, monitored by an infrared camera. The obtained surface temperature maps revealed structural differences between both orientations. The consideration of surface temperature transients yields more details about the behaviour of the material under tensile loading than the conventional stress-strain-curve. These preliminary investigations were supplemented by thermographic fatigue trials. Although the anisotropy was also observed during fatigue loading the fatigue behaviour in general was the same, at least for both inspected specimens. The presented results demonstrate the abilities and the potential of thermographic techniques for tensile tests. T2 - 17th Quantitative Infrared Thermography Conference CY - Bologna, Italy DA - 07.07.2025 KW - Thermoelastic effect KW - Wire-arc-additive manufacturing KW - thermal stress analysis KW - fatigue testing PY - 2026 DO - https://doi.org/10.21611/qirt-2024-029 SP - 1 EP - 8 AN - OPUS4-65372 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kunji Purayil, Sruthi Krishna A1 - Röllig, Mathias A1 - Hirsch, Philipp Daniel A1 - Chaudhuri, Somsubhro A1 - Lecompagnon, Julien A1 - Strobach, L. A1 - Ziegler, Mathias T1 - PCA-enhanced Computational Thermography for the Non-destructive Investigation of the Historic Bücker Bü 181 Aircraft N2 - Infrared thermography is a widely recognized non-destructive testing (NDT) method used in material research and defect detection across various industrial applications. Moreover, thermography plays a crucial role in preserving cultural heritage, including historical paintings and buildings. This study focuses on the application of thermography in inspecting the historic Bücker Bü 181 aircraft, which was used in Germany during World War II. Over time, the original appearance of aircraft has often been altered as part of preservation efforts, either before or during their time in museums, leading to deviations from their historically original state. Additionally, the operational history of such objects is frequently undocumented or entirely lost, making it difficult to understand the presence of artifacts and historically significant data. These factors present major challenges in cultural heritage preservation, and destructive methods cannot be used to investigate such invaluable objects. Therefore, thermography is implemented as a non-destructive and contactless examination method. Active flash thermography combined with phase analysis is a powerful tool for evaluating multilayer systems. In this study, multiple layers of old paint on the object posed a challenge in assessing defect conditions and retrieving other critical information beneath the surface coatings. Nevertheless, pulse thermography not only demonstrated its capability to identify defects and markings in multilayered coatings but also provided insights into the internal structure and subsections of the investigated aircraft. KW - Non-destructive Testing KW - Infrared Thermography KW - Defect Detection KW - Cultural Heritage KW - Multilayer Coatings PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-645709 DO - https://doi.org/10.58286/31934 SN - 2941-4989 VL - 3 IS - 2 SP - 1 EP - 10 PB - NDT.net AN - OPUS4-64570 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chaudhuri, Somsubhro A1 - Krankenhagen, Rainer A1 - Lapšanská, Ivana A1 - Stamm, Michael T1 - Modeling Temperature Responses of a Wind Turbine Blade Section Under Climate Chamber Conditions – Part 1: Challenges for FEM Simulations N2 - The rapid expansion of wind energy infrastructure over the past 20–30 years has led up to a situation where advanced non‐destructive testing (NDT) technologies are the need‐of‐the‐hour, not only for new wind turbine blades (WTBs) that are being installed, but also for older infrastructure which is reaching their designed lifetime. NDT technologies that improve both the quality as well as reduce the time required for the inspection are sought after, and one such example is passive infrared thermography (IRT). For passive IRT to provide significant information/insight into the integrity of the WTB, there needs to exist certain thermal contrast to both visualize and distinguish between features in WTB. These features could be surface features, subsurface structure or defects. The temperature variations due to air temperature fluctuations and the sun assist (passively) to obtain the necessary thermal contrast. To better understand the thermal response of composite structures such as WTBs, a validation study was conducted using a WTB section subjected to controlled temperature transients within a climate chamber, without external irradiation. Infrared measurements were recorded using a thermographic camera, and the same specimen was modeled using finite element methods (FEM) in COMSOL Multiphysics. While a direct validation of the simulation is limited due to transient and unmeasured variables in the experimental data, qualitative comparison provides valuable insight into the applicability of FEM for predicting thermal behavior in passive IRT scenarios. This article represents the first part of a two‐part study, focusing on the FEM modeling approach and associated challenges. The second part will address the experimental investigation in more detail, with an emphasis on thermal contrast behavior under varied transient conditions. KW - Finite element modeling KW - Non- destructive testing KW - Passive infrared thermography KW - Thermal contrast KW - Wind turbine blades PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655330 DO - https://doi.org/10.1002/we.70102 SN - 1095-4244 VL - 29 IS - 3 SP - 1 EP - 14 PB - Wiley AN - OPUS4-65533 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mehri Sofiani, F. A1 - Chaudhuri, Somsubhro A1 - Elahi, S. A. A1 - Wallaert, E. A1 - Depover, T. A1 - De Waele, W. T1 - Accelerated laboratory simulation of corrosion pit evolution in low-carbon steel using phase-field guided overpotential application N2 - This study is performed to replicate field data of pit geometry evolution in the laboratory by accelerating pit evolution through the application of relatively high overpotential on low-carbon steel. A phase-field model is used to reduce the number of trials and errors in the laboratory. The effect of overpotential on pitting corrosion is studied in low-carbon steel in the electrolyte representative of the North Sea. Based on the results obtained through the numerical model, potentiostatic polarisation tests are performed, and a comparison is made between such accelerated tests and steel coupons collected from the field. The results of this comparison suggest that the pitting corrosion acceleration mechanism effectively produces surface conditions closely resembling those of naturally pitted steel. Additionally, it enables the investigation of the electrochemical characteristics of a stable pit over long-term exposure, where direct probing is challenging. This framework strives to mitigate the excessive costs of time-consuming coupon experiments by correlating accelerated pitting corrosion in short periods of time with actual pitting corrosion observed over the long term. KW - Pitting corrosion KW - Corrosion acceleration KW - Potentiodynamic tests KW - Phase-field KW - S355 PY - 2025 DO - https://doi.org/10.1016/j.engfailanal.2025.110352 SN - 1350-6307 VL - 184 SP - 1 EP - 20 PB - Elsevier CY - Oxford AN - OPUS4-64805 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -