Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Dennis Roach, Tom Rice, Josh PaquetteWind Blade Reliability Center

Sandia National Labs

Optimizing Quality Assurance Inspections to Improve the Probability of

Damage Detection in Wind Turbine Blades

Blade Reliability Collaborative – NDI Objectives

• Develop, evaluate and validate the array of potential nondestructive inspection methods for the detection of flaws in composite wind turbine blades

• Plan and implement a national capability – including a physical presence and methodology - to comprehensively evaluate blade inspection techniques

• 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 & to enhance the

in-service inspection of blades for wind farm operators

Optimized InspectionsTraining

Inspectors,Equipment, &

NDI Techniques

Procedures

NDI Calibration &Reference Standards

BladeMaintenance

Programs

Blade Reliability Collaborative -Program Thrusts to Improve Wind NDI

Enhance factory reliability, facilitate repairs before acritical is reached, minimize turbine downtime & increase blade lifetime

Create the ability for manufacturers to determine the quality of their product before it leaves the factory & to

enhance the in-service inspection of wind blades

VoidsVoids

Inspection Areas and Flaw Types of Interest

Flaws include: Ply Waves Delaminations, Adhesive Voids, Joint Disbonds, Snowflaking and Porosity

Ultrasonic Transducer

Captured Water Column

Scanning Shoe for Offset of UT Wave

Plastic Membrane

Weeper Body

Water Inlet(pumped in from reservoir)

Water Couplant Pool

Inspection Surface

Excess Water Flow(recovered into reservoir)

To Data Acquisition System

MAUS P-E UT with Focused Probe (1 MHz/2”) and Adjustable Water Path

New “Immersion” Probe Holder

Allows for Adjustable Water Path

Flat Bottom HolesPillow Inserts

Pull TabsREF-STD-6-202-250-SNL-1

1.01"

0.34"

1.35"

0.68"

0.67"

1.35"

0.34"

1.01"1.35"

USED VECTORPLY ELT 5500 24 PLIES OF MATERIAL (UNIAXIAL FIBER)

2.000"1.000"

2.000"

.40" (10mm) BONDLINE

INSPECTION SIDE

PERCENTAGE OF FULLTHICKNESS AT BONDLINE(.100" SKIN AND .400" BONDTHICKNESS)

25% (OF FULL THICKNESS)

50% (OF FULL THICKNESS)

75% (OF FULL THICKNESS)FLAT BOTTOM HOLE (FBH)

PILLOW INSERT

EXAMPLES OF VARIOUS FLAW DEPTHS IN SPAR CAP SECTION

INSPECTION SURFACE

NDI REFERENCE STANDARD 2 FABRICATION DRAWING SPAR CAP AND SHEAR WEB BLADE SCHEMATIC

(DISBONDS IN ADHESIVE)PULL TABS

(DELAMS) (DELAMS) (BASED ON 24 PLIES OF UNIAXIAL MAT'L) (DISBONDS IN ADHESIVE)

25%(.125" MR)

50%(.25" MR)

1.00" DIA

2.00" DIA

SHEAR WEB

ADHESIVE

FLAT BOTTOM HOLES

1.00" (25mm) FOAM CORE

INTERFACE 2

INTERFACE 1

INTERFACE 1

25%(B/W PLIES 18 & 19)

75%(B/W PLIES 6 & 7)

75%(.375" MR)

4 PLY PILLOW INSERTSFLAT BOTTOM HOLES

25% (B/W PLIES18 & 19)

50% (B/W PLIES12 & 13)

75% (B/W PLIES6 & 7)25% (.34" MR)50% (.68" MR)75% (1.01" MR)

2.00" DIA

.50" DIA

1.00" DIA 1.50" DIA

1.50" DIA 1.00" DIA

.50" DIA2.00" DIA

2.00" DIA

.50" DIA

1.00" DIA 1.50" DIA

1.50" DIA 1.00" DIA

.50" DIA

2.00" DIA

2.00" DIA

1.50" DIA

1.00" DIA

.50" DIA

.50" DIA

1.00" DIA

1.50" DIA

2.00" DIA

18.00"

~1.35" (34mm) UNIAXIAL (SPANWISE)

30.00"

__(+45, +45)2 PLIES OF DOUBLE BIAS (DB)

2 PLIES OF DOUBLE BIAS (DB)

11-30-10

MR = MATERIAL REMAINING

PLY NO. 1 OF SPAR CAP

2 PLIES OF DOUBLE BIAS (DB)

(+45, +45)_ _

__(+45, +45)

(NOTE: IF USING TEFLON BASED RELEASE FABRIC WHEN CURING MAIN SPAR, BE SURE TO LIGHTLY SAND SURFACE AREA WHERE SHEAR WEB BONDWILL TAKE PLACE) 0.60"-1.00"

2.500"

(BASED ON 24 PLIES OF UNIAXIAL MAT'L)NOTE: PULL TABS (.007" THK) WILL EXTEND OUT FROM SPECIMENEDGE DURING CURE PROCESS, BE SURE TO USE SPECIALCARE NOT TO PUNCTURE VACUUM BAG (COVER SHARPEDGES WITH BREATHER FABRIC) . PULL TABS REMOVED AFTER CURE PROCESS.

1 of 2NOTES:1. SPECIMEN CURED USING 14 IN. HG. VACUUM PRESSURE AND VACUUM LEFT ON OVER NIGHT.2. POST CURE SPECIMEN AT 70 C FOR 10 HOURS.

3. FINAL FLAT BOTTOM HOLE DEPTH MAY CHANGE DEPENDING ON FINAL PART THICKNESS.

1.875"

2.750"

2.750"

2.750"

2.750"

2.750"

(41)

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(46)

(52)(51)(50)(49)(48)(47)

(53) (54) (55) (56) (57) (58)

(64)

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(65) (66) (67) (68)

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Tapered Adhesive Wedge Fiberglass Inspection Surface

Adhesive Bond Line

Out of Spec Thickness

Develop and assess methods to inspect bond line thickness

Phased Array UT Results

Good Bond Line Thickness

Anomalies in Bond Line

Adhesive Thickness Measurements with Phased Array UT

Phased Array UT – Display and Deployment

Olympus 1.5Mhz, 42 element probe

Sonatest RapidScan 2

GE Phased Array UT RotoArray

On-Blade Phased Array UT Inspections

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

Sealed water box and 1.5L16 Phased Array probe was used to detect missing adhesive in bond lines

Vertical Strip C-Scan Image Showing Adhesive Void in

Upper Bond Line

Adhesive Void Between Spar

Cap and Shear Web

Purpose• Generate industry-wide performance curves to quantify:

Ø how well current inspection techniques are able to reliably find flaws in wind turbine blades (industry baseline)

Ø the degree of improvements possible through integrating more advanced NDI techniques and procedures.

An Experiment to Assess Flaw Detection Performance in Wind Turbine Blades (POD)

Expected Results - evaluate performance attributes1) accuracy & sensitivity (hits, misses, false calls, sizing)2) versatility, portability, complexity, inspection time (human factors)3) produce guideline documents to improve inspections4) introduce advanced NDI to industry

Wind Blade NDI Probability of Detection Experiment

- Blind experiment: type, location and size of flaws are not know by inspector- Statistically relevant flaw distribution – Probability of Detection (POD)- Used to analytically determine the performance of NDI techniques – hits,

misses, false-calls, flaw sizing, human factors, procedures

Experimental Design Parameters• Representative design and manufacturing• Various parts of blade such as spar cap,

bonded joints, leading and trailing edge• Statistically valid POD (number, size of flaws

and inspection area)• Random flaw location• Maximum of two days to perform experiment• Deployment

Fabrication Considerations• Realistic, random flaw locations• Portable sample set• Range of thickness• Material types (fiberglass and adhesives)

Spar Caps & Shear Web Box Beam

Specimens designs applicable to various blade construction

Wind Blade Flaw Detection Experiment -Probability of Detection Experiment

Benefit to Participants• Training perspective, inspections on representative

blade structure• Inspector and production facility received feedback on

how they performed• POD Value, smallest flaw size detectable with 95%

confidence• Number of flaws detected & missed• Number of false calls, if any• Flaw sizing• Location and type of flaws missed

NRELUpWind

DOEClipper

LM Wind PowerGamesa

Molded FiberglassSNL

TPI CompositesGE – Global Research

VestasSandia

Review Committee

Ensure representative bladeconstruction and materials

POD Specimen Development and Characterization

Laminate Flaws Include:Pillow Inserts

Grease ContaminateWrinkles – Dry stacked plies

Dry AreasFlat Bottom Holes

Glass Microballoons

Bond Line Flaws Include:Pillow Inserts

Pull TabsFlat Bottom Holes

VoidsGlass Microballoons

Phased Array UT 40mm Water Box Scan

Implementation of Wind POD Experiment

• 11 POD specimens with spar cap and shear web geometry• Thickness ranges from 8 Plies (0.45” thick laminate, 0.85” thick with

adhesive bond line) to 32 Plies (1.80” thick laminate, 2.20” thick with adhesive bond line)

• All panels painted with wind turbine blade paint (match inspection surface)

Wind Blade Flaw Detection Experiment – Individual Inspector and Cumulative POD Comparison

All Panels - Spar Cap with Shear Web and Box Spar Construction Types

Conventional Single Element Pulse-Echo Ultrasonic Inspection Method

Wind Blade Flaw Detection Experiment – Various NDI Performance Attributes Evaluated

Spar Cap with Shear Web and

Box Spar Construction Types

Spar Cap with Shear Web

Construction Types

All Panels - Constant Thickness Flaws

All Panels - Complex Geometry Flaws

Wind Blade Flaw Detection Experiment –Improvements Produced by Use of Advanced NDI

C-scan images produced by single-

element ultrasonic scanner systems –

easier to interpret data

All Panels, All Flaw Types –Conventional NDI

POD 90/95 = 1.333

All Panels, All Flaw Types –Advanced NDI(example only)

POD 90/95 = 1.105

Results from Single-Element UT Scanner System

Wind Blade Flaw Detection Experiment –Optimizing Results with Proper Analysis

Non-optimal use of gate settings can allow damage to go undetected

Initial Results -flaw under bondline is

not imaged

Inspector BB – 2” Flaw “Miss” is changed to a “Hit”(additional data gates used to detect deeper flaws)

Second Analysis – data reviewed using additional gate settings; damage detected

• Need to develop array of inspection tools to comprehensively assess blade integrity

• Consider time, cost, & sensitivity issues (minimize production, maintenance and operation costs)

• Develop NDI solutions in concert with related studies: effects of defects, field surveys, analysis, certification, standards

• NDI investigation has produced promising results thus far & may lead to hybrid approach with multiple NDI tools (e.g. near surface and deep flaws)

• There are sensitive & rapid NDI options available for inspecting wind blades, both for manufacturing QA and in-service NDI

• Evolution in phased array UT methods & use of C-scan technology provides the greatest & easiest-to-achieve benefits

• Training, experience (apprenticeships) and optimized procedures are key factors in determining the overall performance of NDI for detecting flaws/damage in wind blades

• NDI can help ensure that wind blades meet their design life and possibly beyond

Wind Blade Flaw Detection Experiment –Steps to Improve Probability of Flaw Detection

If you are interested in participating in the Sandia Labs wind blade inspection activities:

Tom RicePhone: (505) 844-7738Email: tmrice@sandia.gov

Dennis RoachPhone: (505) 844-6078Email: dproach@sandia.gov

Ray ElyPhone: (505) 284-9050Email: grely@sandia.gov

Optimizing Quality Assurance Inspections to Improve the Probability of

Damage Detection in Wind Turbine Blades