Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure
Initial defects, for example, those occurring during the production of a rotor blade, encourage early damages such as rain erosion at the leading edge of wind turbine rotor blades. To investigate the potential that initial defects have for early damage, long-pulse thermography as a non-destructive a...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-10-01
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| Series: | Applied Sciences |
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| Online Access: | https://www.mdpi.com/2076-3417/11/20/9545 |
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| author | Friederike Jensen Marina Terlau Michael Sorg Andreas Fischer |
| author_facet | Friederike Jensen Marina Terlau Michael Sorg Andreas Fischer |
| author_sort | Friederike Jensen |
| collection | DOAJ |
| description | Initial defects, for example, those occurring during the production of a rotor blade, encourage early damages such as rain erosion at the leading edge of wind turbine rotor blades. To investigate the potential that initial defects have for early damage, long-pulse thermography as a non-destructive and contactless measurement technique is applied to a strongly curved and coated test specimen for the first time. This specimen is similar in structural size and design to a rotor blade leading edge and introduced with sub-surface defects whose diameters range between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>3.5</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> at depths between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.5</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2.5</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> below the surface. On the curved and coated test specimen, sub-surface defects with a depth-to-diameter ratio of up to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.04</mn></mrow></semantics></math></inline-formula> are successfully detected. In particular, defects are also detectable when being observed from a non-perpendicular viewing angle, where the intensity of the defects decreases with increasing viewing angle due to the strong surface curvature. In conclusion, long-pulse thermography is suitable for the detection of sub-surface defects on coated and curved components and is therefore a promising technique for the on-site application during inspection of rotor blade leading edges. |
| first_indexed | 2024-03-10T06:45:20Z |
| format | Article |
| id | doaj.art-67bf0e941c8840f594ff52f5a43d5837 |
| institution | Directory Open Access Journal |
| issn | 2076-3417 |
| language | English |
| last_indexed | 2024-03-10T06:45:20Z |
| publishDate | 2021-10-01 |
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| series | Applied Sciences |
| spelling | doaj.art-67bf0e941c8840f594ff52f5a43d58372023-11-22T17:20:21ZengMDPI AGApplied Sciences2076-34172021-10-011120954510.3390/app11209545Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-StructureFriederike Jensen0Marina Terlau1Michael Sorg2Andreas Fischer3Institute for Metrology, Automation and Quality Science, University of Bremen, 28329 Bremen, GermanyInstitute for Metrology, Automation and Quality Science, University of Bremen, 28329 Bremen, GermanyInstitute for Metrology, Automation and Quality Science, University of Bremen, 28329 Bremen, GermanyInstitute for Metrology, Automation and Quality Science, University of Bremen, 28329 Bremen, GermanyInitial defects, for example, those occurring during the production of a rotor blade, encourage early damages such as rain erosion at the leading edge of wind turbine rotor blades. To investigate the potential that initial defects have for early damage, long-pulse thermography as a non-destructive and contactless measurement technique is applied to a strongly curved and coated test specimen for the first time. This specimen is similar in structural size and design to a rotor blade leading edge and introduced with sub-surface defects whose diameters range between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>3.5</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> at depths between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.5</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>2.5</mn><mspace width="0.166667em"></mspace><mi>mm</mi></mrow></semantics></math></inline-formula> below the surface. On the curved and coated test specimen, sub-surface defects with a depth-to-diameter ratio of up to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.04</mn></mrow></semantics></math></inline-formula> are successfully detected. In particular, defects are also detectable when being observed from a non-perpendicular viewing angle, where the intensity of the defects decreases with increasing viewing angle due to the strong surface curvature. In conclusion, long-pulse thermography is suitable for the detection of sub-surface defects on coated and curved components and is therefore a promising technique for the on-site application during inspection of rotor blade leading edges.https://www.mdpi.com/2076-3417/11/20/9545active thermographysub-surface defectsdefect visualizationautomatic defect detectionleading edgewind turbine rotor blade |
| spellingShingle | Friederike Jensen Marina Terlau Michael Sorg Andreas Fischer Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure Applied Sciences active thermography sub-surface defects defect visualization automatic defect detection leading edge wind turbine rotor blade |
| title | Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure |
| title_full | Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure |
| title_fullStr | Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure |
| title_full_unstemmed | Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure |
| title_short | Active Thermography for the Detection of Sub-Surface Defects on a Curved and Coated GFRP-Structure |
| title_sort | active thermography for the detection of sub surface defects on a curved and coated gfrp structure |
| topic | active thermography sub-surface defects defect visualization automatic defect detection leading edge wind turbine rotor blade |
| url | https://www.mdpi.com/2076-3417/11/20/9545 |
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