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Manoucher Doroshtnasir - One of the best experts on this subject based on the ideXlab platform.
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thermographic inspection of a wind turbine rotor Blade Segment utilizing natural conditions as excitation source part i solar excitation for detecting deep structures in gfrp
Infrared Physics & Technology, 2016Co-Authors: Tamara Worzewski, Rainer Krankenhagen, Manoucher Doroshtnasir, Mathias Rollig, Christiane Maierhofer, Henrik SteinfurthAbstract:Abstract This study evaluates whether subsurface features in rotor Blades, mainly made of Glass Fibre Reinforced Plastics (GFRP), can generally be detected with “solar thermography”. First, the suitability of the sun is tested for acting as a heat source for applying active thermography on a 30 mm thick GFRP test specimen. Second, a defective rotor Blade Segment is inspected outdoors under ideal natural conditions using the sun as excitation source. Additionally, numerical FEM-simulations are performed and the comparability between experiment and simulation is evaluated for outdoor measurements.
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thermographic inspection of wind turbine rotor Blade Segment utilizing natural conditions as excitation source part ii the effect of climatic conditions on thermographic inspections a long term outdoor experiment
Infrared Physics & Technology, 2016Co-Authors: Tamara Worzewski, Rainer Krankenhagen, Manoucher DoroshtnasirAbstract:Abstract The present study continues the work described in part I of this paper in evaluating a long-term-experiment, where a rotor Blade Segment of a wind turbine is exposed to the elements and thereby monitored with passive thermography. First, it is investigated whether subsurface features in rotor Blades – mainly made of GFRP – can generally be detected with thermography from greater distances under favorable conditions. The suitability of the sun for acting as a heat source in applying active thermography has been tested in the previous study. In this study, the climatic influence on thermographic measurement is evaluated. It is demonstrated that there are favorable and unfavorable circumstances for imaging thermal contrasts which reflect inner structures and other subsurface features like potential defects. It turns out that solar radiation serves as a very effective heat source, but not at all times of day. Other environmental influences such as diurnal temperature variations also create temperature contrasts that permit conclusions on subsurface features. Particular scenarios are reconstructed with FEM-simulations in order to gain deeper insight into the driving mechanisms that produce the observed thermal contrasts. These investigations may help planning useful outdoor operations for inspecting rotor Blades with thermography.
Alexandros Antoniou - One of the best experts on this subject based on the ideXlab platform.
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benefits of subcomponent over full scale Blade testing elaborated on a trailing edge bond line design validation
Wind Energy Science Discussions, 2017Co-Authors: Malo Rosemeier, Gregor Basters, Alexandros AntoniouAbstract:Abstract. Wind turbine rotor Blades are designed and certified according to the current IEC ( 2012 ) (International Electrotechnical Commission) and DNV GL AS ( 2015 ) (Det Norske Veritas Germanischer Lloyd Aksjeselskap) standards, which include the final full-scale experiment. The experiment is used to validate the assumptions made in the design models. In this work the drawbacks of traditional static and fatigue full-scale testing are elaborated, i.e., the replication of realistic loading and structural response. Subcomponent testing is proposed as a potential method to mitigate some of the drawbacks. Compared to the actual loading that a rotor Blade is subjected to under field conditions, the full-scale test loading is subjected to the following simplifications and constraints: first, the full-scale fatigue test is conducted as a cyclic test, wherein the load time series obtained from aeroservoelastic simulations are simplified to a damage-equivalent load range. Second, the load directions are typically applied solely in two directions, often pure lead–lag and flapwise directions which are not necessarily the most critical load directions for a particular Blade Segment. Third, parts of the Blade are overloaded by up to 20 % to achieve the target load along the whole span. Fourth, parts of the Blade are not tested due to load introduction via load frames. Finally, another downside of a state-of-the-art, uni-axial, resonant, full-scale testing method is that dynamic testing at the eigenfrequencies of today's Blades with respect to the first flapwise mode between 0.4 and 1.0 Hz results in long test times. Testing usually takes several months. In contrast, the subcomponent fatigue testing time can be substantially shorter than the full-scale Blade test since (a) the load can be introduced with higher frequencies which are not constrained by the Blade's eigenfrequency, and (b) the stress ratio between the minimum and the maximum stress exposure to which the structure is subjected can be increased to more realistic values. Furthermore, subcomponent testing could increase the structural reliability by focusing on the critical areas and replicating the design loads more accurately in the most critical directions. In this work, the comparison of the two testing methods is elaborated by way of example on a trailing-edge bond line design.
Antoniou Alexandros - One of the best experts on this subject based on the ideXlab platform.
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Benefits of sub-component over full-scale Blade testing elaborated on a trailing edge bond line design validation
2017Co-Authors: Rosemeier Malo, Basters Gregor, Antoniou AlexandrosAbstract:Wind turbine rotor Blades are designed and certified according to the current IEC and DNV GL standards, which include the final full-scale experiment. The experiment is used to validate the assumptions made in the design models. The drawbacks of traditional full-scale testing are elaborated, i. e. the replication of realistic loading and structural response plus its observation during testing. Sub-component testing is proposed as potential method to sufficiently solve the drawbacks. Compared to the actual loading that a rotor Blade is subjected to in the field, however, the full-scale test loading underlies the following simplifications and constrains: (1) The full-scale fatigue test is conducted as dynamic test, where the load time series obtained from aero- servo-elastic simulations are simplified to a damage equivalent load range. (2) The load directions are typically applied solely in two directions, often pure lead-lag and flap-wise directions which are not necessarily the most critical load directions for a particular Blade Segment. (3) Parts of the Blade are overloaded by up to 20 % to achieve the target load along the whole span. Another downside of the full-scale testing method is that dynamic testing at natural frequencies between 0.4 and 1.0 Hz results in long test times. Testing takes usually several months. Sub-component testing may replicate real design loading conditions more accurately than full-scale Blade testing, while allowing more flexible loading conditions. Furthermore, different span-wise Blade Segments can be tested with different load directions, representing the critical load for that particular Segment. Since fatigue sub-component testing is conducted as actuator driven the testing frequency is not constrained to the specimen’s natural frequency. This allows faster testing compared to the full-scale test. In this work the comparison of both testing methods is exemplary elaborated on a trailing edge bond line design
Tamara Worzewski - One of the best experts on this subject based on the ideXlab platform.
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thermographic inspection of a wind turbine rotor Blade Segment utilizing natural conditions as excitation source part i solar excitation for detecting deep structures in gfrp
Infrared Physics & Technology, 2016Co-Authors: Tamara Worzewski, Rainer Krankenhagen, Manoucher Doroshtnasir, Mathias Rollig, Christiane Maierhofer, Henrik SteinfurthAbstract:Abstract This study evaluates whether subsurface features in rotor Blades, mainly made of Glass Fibre Reinforced Plastics (GFRP), can generally be detected with “solar thermography”. First, the suitability of the sun is tested for acting as a heat source for applying active thermography on a 30 mm thick GFRP test specimen. Second, a defective rotor Blade Segment is inspected outdoors under ideal natural conditions using the sun as excitation source. Additionally, numerical FEM-simulations are performed and the comparability between experiment and simulation is evaluated for outdoor measurements.
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thermographic inspection of wind turbine rotor Blade Segment utilizing natural conditions as excitation source part ii the effect of climatic conditions on thermographic inspections a long term outdoor experiment
Infrared Physics & Technology, 2016Co-Authors: Tamara Worzewski, Rainer Krankenhagen, Manoucher DoroshtnasirAbstract:Abstract The present study continues the work described in part I of this paper in evaluating a long-term-experiment, where a rotor Blade Segment of a wind turbine is exposed to the elements and thereby monitored with passive thermography. First, it is investigated whether subsurface features in rotor Blades – mainly made of GFRP – can generally be detected with thermography from greater distances under favorable conditions. The suitability of the sun for acting as a heat source in applying active thermography has been tested in the previous study. In this study, the climatic influence on thermographic measurement is evaluated. It is demonstrated that there are favorable and unfavorable circumstances for imaging thermal contrasts which reflect inner structures and other subsurface features like potential defects. It turns out that solar radiation serves as a very effective heat source, but not at all times of day. Other environmental influences such as diurnal temperature variations also create temperature contrasts that permit conclusions on subsurface features. Particular scenarios are reconstructed with FEM-simulations in order to gain deeper insight into the driving mechanisms that produce the observed thermal contrasts. These investigations may help planning useful outdoor operations for inspecting rotor Blades with thermography.
Henrik Steinfurth - One of the best experts on this subject based on the ideXlab platform.
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thermographic inspection of a wind turbine rotor Blade Segment utilizing natural conditions as excitation source part i solar excitation for detecting deep structures in gfrp
Infrared Physics & Technology, 2016Co-Authors: Tamara Worzewski, Rainer Krankenhagen, Manoucher Doroshtnasir, Mathias Rollig, Christiane Maierhofer, Henrik SteinfurthAbstract:Abstract This study evaluates whether subsurface features in rotor Blades, mainly made of Glass Fibre Reinforced Plastics (GFRP), can generally be detected with “solar thermography”. First, the suitability of the sun is tested for acting as a heat source for applying active thermography on a 30 mm thick GFRP test specimen. Second, a defective rotor Blade Segment is inspected outdoors under ideal natural conditions using the sun as excitation source. Additionally, numerical FEM-simulations are performed and the comparability between experiment and simulation is evaluated for outdoor measurements.