optical measurement systems applied to wind turbine...
TRANSCRIPT
Slide 1 | Blade Workshop | July 2010
Optical Measurement Systems applied to Wind Turbine Blades for the Detection and
Characterization of Defects
Slide 2 | Blade Workshop | July 2010
• Dantec is the world’s leading supplier of optical measurement systems for air flows, liquid flows, combustion diagnostics and materials testing
• US Owned Company (Nova Instruments) Headquartered in Copenhagen,Denmark
• Wind Industry Applications in Air Flows- Aerodynamic Optimization- Computational Fluid Dynamics (CFD) Validation- Modeling of turbines and civil engineering projects
• Wind Industry Applications for Materials Testing- Inspection of blades using Shearography- Digital Image Correlation for R&D, new material characterization, Computer Aided Engineering
(CAE) validation, fatigue tests, QA
Introduction to Dantec Dynamics
Slide 3 | Blade Workshop | July 2010
How is Dantec Dynamics Involved in the Wind Industry?
• Several key customers using our technology including Vestas and Siemens Windpower
• Perform blade inspections in manufacturing and in-field• Working with Rope Partner, a leading inspection services
provider to develop shearography for up-tower use
Slide 4 | Blade Workshop | July 2010
What Dantec Dynamics has observed in the US market:
- Emphasis was on fulfilling orders and not on producing quality products
- European Manufacturers have been more proactive regarding quality inspection of blades
- Manufacturers who embraced quality controls are seeing the business benefits with products that require less maintenance
- Many valuable lessons can be learned from the Aerospace Industrythat apply to manufacturing, quality control and ultimate responsibility
- Blade Manufacturing defects are starting to manifest themselves in the field as cycle times increase and the damage propagates
- Several high profile failures and large scale mitigation efforts- Warranty periods will increase due to competitive pressures- Owners and Operators are beginning to understand what is required to
protect their assets
Slide 5 | Blade Workshop | July 2010
What can be measured?
• Digital Image Correlation- Strain- Displacement- Shape
• Shearography- Sub-surface defectse.g wrinkles, delaminations, disbonds,
porosity, core displacements
Slide 6 | Blade Workshop | July 2010
Digital Image Correlation (DIC) for Quantifying Defects
• Used for testing new materials, and blade testing
• Small and Compact- easily mounted to blades, gantry systems or test stands
• Results show strain distributions and ‘hot-spots’
• Quantitative results used to determine criticality of defects (accept/reject)
Slide 8 | Blade Workshop | July 2010
Coupon with wrinkle
• Average Strain ~ 750με
• Max Strain ~ 2000 με
• Cracks will start in these areas
Slide 9 | Blade Workshop | July 2010
Tests on a full-size Blade
7500 data points (7500 strain gauges)
All strain gradients captured across wrinkles
Maximum strain 3 times higher!
Slide 11 | Blade Workshop | July 2010
How can DIC be used for QA?
• Measure strain distribution in critical areas of blade in production
• Measure strain on detected defects• System easily mounted on blade or gantry system
and moved to each measurement area• Real-time correlation can be used to monitor blades
under fatigue testing and detect damage growth• Blade can pass or fail based on maximum strain
criteria
Slide 12 | Blade Workshop | July 2010
Laser Shearography to find defects under the surface
• Technique to identify defects in almost any material• Slightest surface excitation leads to surface
deformations from the internal flaws• The shearography system can detect these very
small deformations• Full-field, non-contact and fast
Slide 14 | Blade Workshop | July 2010
Principle of Shearographic Measurement
= Differential displacement(between sheared points)
Camera
Shearelement
Laser
Deformation
Slide 15 | Blade Workshop | July 2010
Advantages of Shearography• Full-Field Results, not point or scanned
• Real-Time Results, instant judgment, no post processing
• Non-contact, no surface preparation or couplant
• Works with sandwich construction- foam or balsa core
• ‘Performance tests’ the material- only see weak areas
• High level of structural detail
• Proven to detect wrinkles, delaminations, disbonds, dry spots, porosity
Limitations: Material thickness, no depth information, stability
Slide 16 | Blade Workshop | July 2010
NDT Standards Shearography
• Incorporated in ASNT recommended practice 2006 (SNT TC-1-A) • Incorporated in European EN4179 and NAS410 (2008)• ASTM E2581 – 07 2007 Shearography Standard
• Training available to Level 1, 2 and 3
Slide 17 | Blade Workshop | July 2010
Shearography Applications-A giant step toward higher value inspection
• Production Inspection• Pre-installation inspection,
transportation damage• Condition monitoring• Damage assessment• Post Warranty Inspection
-> Commonly only visual inspections are made in-field
Slide 18 | Blade Workshop | July 2010
Systems for Lab, In-field or Production
• Customized solution for in-field
• 2 button operation up-tower
• Full Blade Inspection Systems in pipeline
• Automatic system covers 1m2 / 90s
• Focus on critical areas of blade only
Slide 20 | Blade Workshop | July 2010
Examples of Wrinkles/ Waving
Image 5: Typical results of wrinkles in a laminate
Slide 21 | Blade Workshop | July 2010
Lightning Damage Strong material with visible lay-up direction
Large deformation measured
Boundary of damaged material
Slide 22 | Blade Workshop | July 2010
Cracks/ Wrinkles
• Visible cracks in gelcoat
• Shearography started where cracks stopped
• Wrinkles continued for more than 12ft
Slide 23 | Blade Workshop | July 2010
Correlation of Techniques -Wrinkles in Skin
Shearography Result
“Qualitative”Digital Image Correlation Result
“Quantitative”
Accept/ Reject Criteria
Slide 24 | Blade Workshop | July 2010
Correlation of Techniques –Wrinkles in Spar Cap
Shearography Result Digital Image Correlation Result
Slide 25 | Blade Workshop | July 2010
For wind to remain competitive as an energy source and manufacturers to remain competitive, blade quality must improve
The earlier the baseline inspection is performed in the life of a blade:• The sooner serial remediation issues will be eliminated• The cheaper the fixes will be if problems are found
Blade Quality would be improved if inspections were made a prerequisite by the customer and/or finance industry
Shearography is migrating from the Aerospace and Marine Industries to the Wind Industry and is a vital component to a complete Quality Inspection both in production and in the field
Digital Image Correlation can be used to charaterize defects or critical areas of the blade with full-field strain measurements
Conclusion: