Stephen NeidigkDennis Roach, Randy Duvall, Tom Rice
Sandia National Labs August 14th, 2013
2013 Wind Plant Reliability Work ShopEvolution and Technology Transfer of Advanced Inspection
Methods for Wind Turbine Blades
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security
Administration under contract DE-AC04-94AL85000
Wind Blade NDI Test Specimen Library
WINDIE Experiments and Inspection Results
BSDS 9 Meter Fatigue Test Blade Inspections
Presentation Overview
On Blade Factory Testing
Development and Testing of Automated and Semi-Automated Phased Array Inspections
How NDI Relates to Reliability
UT Inspection Methods
Objectives
• Produce optimum deployment of automated or semi-automated NDI to detect undesirable flaws in blades (time, cost, sensitivity)
• Transfer technology to industry through hardware and technology evaluation, inspector training, and procedure development
Create the ability for manufacturers to determine the quality of their product before it leaves the factory
DevelopEvaluateValidateTransfer
Potential nondestructive inspection methods for the detection of flaws in composite wind turbine blades
NDI in the Wind Industry
• Different blade manufacturers use different inspection techniques, procedures and detection requirements.• Different blade designs• Varying manufacturing practices• Varying materials
Post manufacturing in the plant In the field (up tower)
Not necessarily the same hardware
Spar Caps & Shear Web Box Spar & Shear Webs
Different composite materials and designs, but looking for similar manufacturing defects:• Laminate porosity• Interply disbonds• Adhesive voids and disbonds• Contaminates and foreign objects• In-plane and out-of-plane waves
Early detection of manufacturing flaws enhances blade reliability
NDI in the Wind Industry
Thick Spar Structure
Thick Adhesive Bond Lines
Balsa or Foam Cores
1 2 3
Spar Cap
Spar cap back wall
Adhesive back wall
Slight Shift
3
2
1
Large Increase in Amplitude
Large Decrease in Amplitude
Example Bond Line Inspection (A-Scan)
Example Inspection (2 Dimensional C-Scan)
X-Y Position EncoderA-Scan
C-Scan
High Amplitude
Low Amplitude
Gate
Phased Array verses Single Element Transducer
Single Element Transducer
A-Scan
C-Scan
Phased Array with Liner Encoder
B-Scan
A-Scan
16 Elements
Sandia Labs Wind Turbine BladeTest Specimen Library
Additional large samples are housed at the Wind & AirworthinessAssurance NDI Validation Center (WAANC) hangar
Added carbon sample set
NDI Feedback Specimens 1, 2 & 4 –Shear Web & Foam Core Specimens
Laminate with Waviness and Dry Regions
Foam Core with Disbonds and Delaminations
Shear Web/Spar with Disbonds and Delaminations
Different Flaw Types Engineered into NDI Feedback Specimens (Examples)
Glass Beads Grease Pillow InsertMold ReleaseMaterials inserted into multiple layers
Voids in bond joint Glass beads
In bond joint
Dry fabric areasWaviness produced by pre-cured
resin rods and stacked plies
Pull tabs inbond joint
Single ply of dry fabric
Fabrication of Carbon Feedback Specimens and NDI Reference Standards at TPI
Flaws were placed at varying depths and locations using a template
Line of various flaws at same depth
Spar caps prior to bonding of shear web
Blade assemblies developed for bond line inspection
Different Flaw Types Engineered into Carbon NDI Feedback Specimens (Examples)
Dry Areas –Removed Resin
Pillow Insert Grease Contamination
Pre-Preg Backing
Carbon Fuzz Ball
Fiberglass FOD
Adhesive Void
Glass Microballoons in Bond Line
Pull Tab Disbonds
Completed Carbon Feedback Specimens & NDI Ref Stds
The set of specimens will be used to:
• Develop and test NDI technology• Train inspectors and familiarize them with
carbon material• Calibrate and set up NDI equipment• Ultrasonic flaw signal characterization• Inspection procedure development
Carbon Pre Preg Spar Inspection Challenges
A-scan 40 mm. thick Fiberglass
Gain – 55.2 dBBack Wall
Increase gain to achieve 80% FSH
Noise
A-scan 40 mm thick Carbon Pre-Preg
Gain – 55.2 dB
200x magnification
A-scan 40 mm Carbon Pre-PregWorking with material manufacturers to ensure inspectability of their product
Gain – 65.5 dB
Carbon Wind Blade Specimen Characterization
C-scan produced by Omniscan Unit 1.5L16(1.5 MHZ) 40mm Water Box REF-BLK-C2-TPI
75%75%75%CSPIFBH
75%GREASE
75%PB
75%PT
75%BOND
25%BOND INT 1INT 2
PTPTFBHFBH
Gate 1: Spar Cap and Adhesive Shear Web Gate 2: Adhesive Shear Web
CH1
CH5
CH3 CH6
CH8
CH9
CH10
CH11
CH4 CH7CH2
CH12
CH13
9 Meter Fatigue Test Blade Inspections
Flaw Location/Type Identifier
9 Meter Blade Inspections (pre-fatigue)
Note: Significant noise in signals (visible porosity)
Flaw signals showing through noise
Balsa Wood
Shear Web Area
Balsa Wood
Inspections Included:
MAUS V Pulse Echo UTPulse Echo A-Scan Capture (over 500)
OmniScan Phased ArrayPulsed Thermography
Vibro Thermography (Resodyne)Millimeter Wave Inspection Tool (POC)
Laser Shearography (LTI)RotoArray Phased Array (GE)
WINDIE & 9 Meter Blade Inspections–Recent Inspections
Physical Optics Corporation – Millimeter Wave Inspection Device
Pillow Insert Detected in BSDS Blade
WINDIE & 9 Meter Blade Inspections –Recent Inspections
Olympus - Phased Array Ultrasonics
Full length scan capability
Curvature Inspection Challenge
GE RotoArray –1 MHz Rolling Phased Array
WINDIE & 9 Meter Blade Inspections –Recent Inspections
Ultrasonic C-Scan of 2.25 inch thick feedback specimen
Ultrasonic B-Scan of fiberglass 9 meter blade
Spar Cap Back Wall
Adhesive/Spar Cap Back Wall
As deployed on Omniscan vs. GE Phasor
Fatigue Test Blade Prior to Failure Inspections
Inspections templates used to relocate the exact point where the initial measurements were taken.
Out of plane wave at 3750 mm on the HP side induced:• Large delamination the width of the
spar cap• Cracks perpendicular to the spar in
the matrix
24G-HP-OPW-SC-3750-18-A
A BD
C
24G – C Pre
24G – D Pre
24G – C Post
24D – D Post
Signal Shift and Amplitude Decrease
Signal Shift and Amplitude Decrease
75% (ON PLIES 9-11)
50% (ONPLIES 19-21)
25% (ONPLIES 29-31)
INTERFACE 1AA
B B
2.00" DIA
1.00" DIA
50% (ONPLIES 19-21)
25% (ONPLIES 29-31)
75% (ON PLIES 9-11)
2.00" DIA
1.00" DIA
1.65" DIA
1.15" DIA
1.00" DIA
2.50" DIA 2.50" DIA
1.00" DIA
2.50" DIA
1.00" DIA
2.00" DIA 2.00" DIA
2.50" DIA
1.00" DIA 1.00" DIA
2.00" DIA 2.00" DIA
2.00" DIA
2.00" DIA
2.50" DIA
1.00" DIA
2.50" DIA
INTERFACE 2
Probe Frequency & Type Analysis500 KHZ vs. 1 MHz Contact vs Focused
Spar Cap = 2.14” thAdhesive Bond Line = 2.65” th.
Balancing Clarity with
Depth of Penetration
500 KHz Contact 1 MHz Contact
1 MHz Focused Probe
Gate Setting AnalysisMAUS V 500 KHZ Contact Test C-Scan Results
Defects at the shear web flange and adhesive layer may, or may not, be detected depending on gate settings and part thickness.
Adhesive Back Wall
Laminate and Adhesive Back Wall
Probe Housing Development for Factory Deployment
Sandia has focused on two water box deployment options:• Adjusts to slight curvature surfaces• Maximizes signal strength• Accommodates necessary standoffs for signal clarity• Easily saves scanned images for reference using the
unidirectional Mouse encoder• Either sealed or pierced bladder construction
4 Ply Pillow Inserts
FBH
FHB’s Pillow Inserts
On-Blade Testing in Manufacturing Facility
36 Meter Station
Scanning Direction
Higher Amplitude
Scan Area
Spar Cap Back WallAdhesive Back Wall
On-Blade Testing in Manufacturing Facility
16 Meter Station on Fiberglass Spar Cap Blade
Spar Cap Cross Section Schematic Showing the Spar Cap, Adhesive
Bond Line and Shear Webs
Scanning Direction
Vertical Strip C-Scan Image Showing Adhesive Void in
Upper Bond Line
Adhesive Void Between Spar
Cap and Shear Web
Sealed water box and 1.5L16 Phased Array probe was used to detect missing adhesive in bond lines
Wind Blade NDI Program Results at Sandia
NDI Test Specimen Library including:• Full-scale test specimens• Fiberglass and carbon specimens with engineered defects ranging in
thickness up to 2.5 inches• Feedback specimen and reference standard development• Statistically valid, blind probability of detection experiment
Developing enhanced NDI methods for wind blades• Improved signal to noise and image resolution (improved flaw detection)• Factory deployment
Evaluation of various NDI technologies on standardized specimen set (WINDIE – worked with 22 different NDI developers)• Assessment of multiple methods to comprise NDI tool box
Early detection of manufacturing flaws enhances blade reliability
Stephen NeidigkSandia National Labs(505)[email protected]
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