3D Backscatter and Advanced DR Rebecca Rudolph1, Clifford Bueno2, William Ross2, Forrest Hopkins2, Aaron Couture2, Gautam Parthasarathy2 1.GE Inspection Technologies, 50 Industrial Park Road, Lewistown, PA 2. GE Global Research, One Research Circle, Niskayuna, NY Presentation to the In-Space Non-Destructive Inspection Technology Workshop Feb 29 - Mar 1, 2012 Gilruth Center Alamo Ballroom, Johnson Space Center, Houston, TX

2 3/6/2012

Approaches to Space and Airframe inspection for Pitting, Corrosion, Cracking

Technique Single sided Wide coverage

Detection through

structures

Detection capability

Handheld backscatter

Yes No, must be raster-

scanned

Yes, with collimation or

motion

Good – mm sized pits

Radiography No Yes, with reasonable

spatial resolution

Yes, potentially reduced

sensitivity

Excellent, sub-mm

If two sided approach is amenable, radiography and micro-focus radiography can be used through walls, insulation and storage bins to interrogate skins with

good success.

Backscatter Imaging

4 3/6/2012

Penn State1 Handheld X-ray for CUI

• Weighs <14 lbs, 6-in diameter, 8-in long, radiation safe, shielded, <1 Curie Hg-203, < 1mR/hr

• Crawler approach to map out regions, in a step and sample mode

• Backscatter quantitatively determines remaining wall thickness to within 2% of total wall thickness for walls under 0.25-in, 5% of total wall thickness for walls over 0.25-in, and is single sided

1"An Erosion-Corrosion Monitor Using Gamma Ray Backscatter" (with E. Klevans, E. S. Kenney, R. L. Baxter, K. A. Burkert, B. Petrovic, B. Wilks and W. J. Groszko), Proceedings of the EPRI 5th Piping and Bolting Inspection Conference (San Antonio, 1999)

Plate Hole ResolutionOne Inch Hole, 4-Inch Insulation, Empty

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.5 1 1.5 2

Traverse Direction (inches)

Thic

knes

s (in

ches

)

Hole 1 (25%)

Hole 2 (50%)

Hole 3 (75%)

Hole 4 (100%)

Poly. (Hole 1 (25%))

Poly. (Hole 2 (50%))

Poly. (Hole 3 (75%))

Poly. (Hole 4 (100%))

5 3/6/2012

Penn State1 Handheld X-ray for CUI Calibration Tests of backscatter unit

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5

Cou

nts/

S

Distance

No: 8B collimator response curve(central masked, 3" focus design) Feb/04/1999

Validation of collimation focal point

• Removing insulation is costly and time consuming

• Calibration curves needed to account for variation in sampling, i.e. temperature and orientation change in device, non-uniform thickness in insulation

• Actual thickness must be calculated according to application specific calibration curve

1"An Erosion-Corrosion Monitor Using Gamma Ray Backscatter" (with E. Klevans, E. S. Kenney, R. L. Baxter, K. A. Burkert, B. Petrovic, B. Wilks and W. J. Groszko), Proceedings of the EPRI 5th Piping and Bolting Inspection Conference (San Antonio, 1999)

y = 6116.2x3 - 12027x2 + 8357.4x + 908.56

500

1000

1500

2000

2500

3000

3500

0 0.0625 0.125 0.1875 0.25 0.3125 0.375 0.4375 0.5 0.5625 0.625

CO

UNTS

(PE

R SE

C)

THICKNESS (INCHES)

Calibration Curve

MEASURED

Poly. (MEASURED)

Calibration of response vs. metal thickness

6 3/6/2012

Commercialization of Penn State Design

• Professor Klevans and Penn State are seeking commercialization options for this technology, and have offered unrestricted rights and hardware to facilitate this.

• System modernization and upgrades are certainly needed for improved usability that GE would undertake. Gage R&R and/or Probability of Detection capability studies would also be needed.

• A number of O&G companies have expressed interest

• GE is considering building/upgrading this device, pending further market interest

7 3/6/2012

Higher Energy Backscatter Using an Energized X-ray Source - GE • ~2-3 mm spatial resolution • 0.5mm defect detection • 0.2mm dimensional measurement accuracy • Up to 450kVp x-ray source energies • Depths to ~1inch steel • Both analytic and Monte Carlo modeling

employed

8 3/6/2012

Front

Middle

Back: through ¼” steel attenuator

Scan of imbedded steel test plate (0.06” thick) X-Y scans @450kVp (2mA) 1x4 beamspot, 30 x 30 grid, 1mm steps, 3secs./step

Black regions represent holes in the plate

1/16” thick hole plate detected through 1/4” steel attenuator

1/16” thick hole plate behind foam, an additional ¼” steel

plate was added

Higher Energy Backscatter Using an Energized X-ray Source - GE

9 3/6/2012

Scanning Head Configuration

Corner scan

Open scan

(two detector panels)

Standard 420kVp tube head

Single cone-beam scatter

detector panel

Substantial shielding of tubehead to eliminate head

leakage (1-2” W/Pb)

10 3/6/2012

Technical approaches: detector geometry is the key Cone-beam detector (1) Entire detector receives scatter from a single localized scatter volume (2) Advantages include: simplicity/robustness/cost of detector and maximization of signal for a single volume (beneficial where sweet spot can be rapidly located through scout scans and geometry baseline database) (3) Disadvantage is that 3 axis (X-Y-Z) motion is required to produced a 3D raster scan

Multi-layer annular detector (1) Each layer of detector receives scatter from a single localized scatter volume (2) Advantages include fixed “in-depth” imaging and 2 axis motion to provide a 3D scan (3) Disadvantage is a much slower “directed” scan where imaging of a localized scatter volume is desired

X rays Pencil beam

X rays Pencil beam

Example of X-Y scan at plate depth

1mm resolution raster scan of hole phantom

Radiography on Airframes

13 3/6/2012

Manufactured crack plate placed on interior at lap

Insulation and sidewall returned for imaging

Detector off skin

Tube close to side wall

0.060”

0.220” Equivalent to 0.220” at crack

•Thickness measured by UT gage •Conditions: 55 kV, Magnification 2, SDD = 30-in.

Lap Joint Inspection on 737 Set-Up

0.44-in. 0.35-in.

Total Metal Thickness, 0.22-in.

Total Metal Thickness, ~ 0.4-in.

Crack

Similar crack length here

through greater thickness

Cropped view Geometric Magnification of 2, plus display magnification

Lap Joint Inspection on 737

15 3/6/2012

Mag 1 unsharpness

= 0.02”

Fine fatigue cracks detected

on airframes using geometric

magnification techniques with

DR panels

Can be used on other structures,

i.e., Space Vehicles to detect pitting, cracking

Mag 2 unsharpness

= 0.065”

Cracks visible

Cracks not visible

Geometric Magnification Helps DR Images Detect Cracks

16 3/6/2012

Radiography on Airframes company • Need geometric magnification techniques to bring the crack size above or closer

to pixel size

• Though unsharpness is technically worse, magnification effectively makes cracks larger

• If two sided approach is amenable, radiography and micro-focus radiography can be used through walls, insulation, storage bins to interrogate skins with good success.

17 3/6/2012

Rugged & Flexible Digital X-Ray

Flexible Scintillator

Flexible TFT Array

Flexible substrate

Multiplexing & readout

WirelessPortable Readout

Pipeline inspection

IED Detection

Image Sensor on Flexible Array Flexible DXR Concept

Manufacturing inspection

Battlefield Medical NDE Applications

• No glass panel • Can be

permanently installed

18 3/6/2012

Summary • Single-sided backscatter imaging, may show promise for

micro-meteorite damage detection. Size and density of pitting will likely affect results.

• DR has been shown to detect fatigue cracks through aircraft internal walls, and insulation using geometric magnification. Similar approach can be used on Space Vehicles for pitting.

• Backscatter and DR will provide rough estimate of depth of pitting/corrosion

• Non-breakable, flexible arrays under development: roll-up for storage, roll-out for use. Can be permanently mounted, inside or out – Can Cosmic rays be used for imaging??

Questions?

21 3/6/2012

Back-up

Line Scan, Middle @450kVp Beam Shape Dependence

0

40000

80000

120000

160000

0.00 10.00 20.00 30.00 40.00 50.00Location [mm]

Rel

ativ

e A

mp

litu

de

1x41x21x11x0.5

Examples of profiles from X-Y scans