1

Integrity Service Excellence

NDE, Materials State

Awareness, and

Reliability Within the

US Air Force

22 June 2016

Ryan Mooers

Associate Materials Research Engineer

Materials State Awareness Branch (RXCA)

Structural Materials Division

Materials and Manufacturing Directorate

Air Force Research Laboratory

2

Disclaimer

• The views expressed in this presentation are

those of the author and do not reflect the

official policy or position of the United States

Air Force, Department of Defense, or the

United States Government

3

Outline

• Introduction

– Vision/ Motivation

– Who, What, How, and Where’s

• Current Branch Efforts

– In-House Research

– Contracted Efforts

• POD and Reliability

– Connection with ASIP

– Doing a POD study

Photo Courtesy of Dr. Eric Lindgren

4

USAF NDE Vision

Digitally-enabled Reliable

Nondestructive Quantitative

Materials / Damage Characterization

Regardless of Scale

5

Motivation / Objectives

Improve NDE Capability / Reliability / Efficiency to

• Provide decision quality information to

determine asset integrity (Safety FIRST!)

Maintain user confidence in asset safety

• Minimize disassembly and related maintenance

induced damage (save time and money)

Minimize false calls

• Optimize materials design and production

For Our Airmen

6

Where We Came From

• Initially for Quality Control

– 1919 Materials Section mission included “make

routine inspection tests for Procurement Section”*

– Initial applications in radiography and magnetic

particle inspections

• Evolved to include parts in use

• US Air Force established in 1947

• Formalized NDT Section in 1952

• NDE Branch stood up in 1974

• Materials State Awareness Branch:

– Result of Reorganization in 2012Lt. H.H. Arnold,

Military Aviator Number 1, 1911

General of the Air

Force

*Slipstream, 1919 McCook Field Newsletter

“The next Air Force is going to be built around

scientists – around mechanically minded fellows.”

Gen H.H. Arnold

7

Where We Fit & What We Do

Air Force

Research Laboratory

RXSAAdvanced

Engineering,

Rapid Response

RXCAResearch,

Development,

Transition

AF

Life Cycle

Management Center

AF

Sustainment

Center

AFSC NDI Program ManagerComplex NDI Managers

Depot/Field/SPO Support

AF NDI Office

Maintain NDI operational

infrastructure

NDI Executive

Working Group

8

How We Do It

Augmented Materials Design, Processing, and Performance

Efficient and Effective ASIP/PSIP/MX Actions

Model-driven Quantitative Representation of Material/Damage State with Statistical Metrics

3D Representation and Validation

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.20

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

crack length (in)

PO

D

MAPOD

exp.

Signal Analysis and Uncertainty Quantification

NDE Damage / Materials

Characterization

9

Current Branch Activities

Photo Courtesy of Dr. Eric Lindgren

10

In House Research Efforts

Modeling and Simulation

• Eddy Current

– Complex/ Commercial

Probes

– Angular/ Dimension

Variation

– True Impedance

Comparison

• Ultrasound

– Realistic microstructure

– Anisotropy

– Characterization based

on received signal

11

In-House Research Efforts

Composites

• Impact Damage

Characterization

– Area and depth

5 MHz Beam Model

shear longitudinal

10 MHz Beam Model

shear longitudinal

12

In-House Research

Material Characterization

• Micro texture Regions

– Produce false indication

– Potential to affect

material properties

• Single Crystal Elastic

Constant Measurement

– Crystal plasticity models

– Need accurate values

• CMC Degradation

– FTIR Inspection

– Chemical changes due

to heating

SiC fiber

BN

matrix

SiO2

Oxygen

70 μm

13

Contractual Efforts

Structures

• Advanced Scanning

Systems

– Increased accuracy,

reliability, effectiveness

• Magneto Resistive

Sensing

– Low frequency, multi-

layer inspection

• Remote Access NDE

– Hard to reach areas

– Minimize disassembly

14

Contractual Efforts

Propulsion

• Sonic IR for Turbine

Blades

– Whole field inspection

– Reduction operator time

– Reduced false call and

hazardous waste

– Transitioning to Tinker

AFB

– Next step: Disks

• Crack sizing in disk

– Model assisted inversion

routine

scan,x (mils)

index,y

(m

ils)

T D40 20 x 10.matb

-50 0 50

-80

-60

-40

-20

0

20

40

60

80 -60

-40

-20

0

20

40

60

scan,x (mils)

index,y

(m

ils)

T D40 20 x 10.matb

-50 0 50

-80

-60

-40

-20

0

20

40

60

80 -400

-300

-200

-100

0

100

200

300

400

scan,x (mils)

index,y

(m

ils)

VIC-3D: 20x10x1.2 mil

-50 0 50

-80

-60

-40

-20

0

20

40

60

80-50

0

50

scan,x (mils)

index,y

(m

ils)

VIC-3D: 20x10x1.2 mil

-50 0 50

-80

-60

-40

-20

0

20

40

60

80-400

-300

-200

-100

0

100

200

300

400

Simulation

Experimental.

Vhoriz Vvert

x

y

Model-assisted

analysis of EC

impedance plane

EC Probe

15

Longer Term Initiatives

• ASK (Advance Sustainment Knowledge) NDE

– Capture / exploit all NDE related data

• Assure inspections performed and performed as intended

• Increase effectiveness/efficiency of inspection processes

• Integrate into characterization efforts

• Damage State Awareness (DSA)

– Quantify size of damage detected

• Significant leveraging of modeling and simulation

• Data driven and Bayesian inversion routines

• Data Registration

– Register inspection data to specific location

• Use for potential inversion

• Tie to location and into Digital Thread/ Digital Twin

16

Life Management,

POD and Reliability

Photo Courtesy of Dr. Eric Lindgren

17

Link to USAF Integrity Programs

Structures

Aircraft Structural Integrity Program (ASIP)

• Established in 1958 after five destroyed

B-47 aircraft in March – April 1958*– Four losses attributed to fatigue

• Uses probabilistic approach to establish

aircraft service life capability: “Safe-Life”

*ASC-TR-2010-5002, Threats to Aircraft Structural Safety, Incl. a Compendium of Selected Structural Accidents/Incidents, March 2010.

• Loss of F-111 (Dec, 1969)* and F-5 (April,

1970)* far short of qualified “Safe-Life”– Designs intolerant of manufacturing and/or

service-induced defects

• Leads to Damage Tolerance Approach– Tolerate defects for some inspection-free period

of service usage

– Formally integrated into ASIP in 1975

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Link to USAF Integrity Programs

Propulsion

Propulsion Structural Integrity Program (PSIP)

• Introduced in 1978 as Engine Structural

Integrity Program (ENSIP)

• ENSIP MIL-STD 1783, published 1984

– Becomes MIL-HDBK-1783 in 1997, now Rev B

• PSIP MIL-STD 3024, published 2008

– Applicable to gas turbine engines

– Essentially a safe life approach

… but crack growth criteria also enforced

– Components retired with remaining serviceable life

• Damage Tolerance Methods to extend service

life are being pursued

*http://www.f-16.net/f-16-news-article3930.html. **http://www.geaviation.com/military/engines/f110/

P&W F-100*

GE F-110**

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Overview of ASIP

Aircraft Structural Integrity Program (ASIP)

• Governed by MIL-STD-1530C

• Establishes required safety metrics for structures

• Fracture mechanics enables predictive management

of fatigue– Periodic inspection before crack reaches critical size

USAF is meeting required safety metrics for structures,

but at a high cost

• Composites are approaching DTA capability– Predictive damage evolution is maturing towards realization

• Corrosion managed by time-based assessments– Prediction of corrosion evolution not available

– Primary hurdle is predicting breakdown of coatings and/or

inhibitors in primers/sealants

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NDE in ASIP: Representative

DTA Risk Assessment

Initial Crack

Size

Distribution

Max Stress

per Flight

Crack

Growth

CurveStress

Intensity

Factor

Fracture

Toughness

Single Flight

Probability of

Failure

Probability of

Failure

between

Inspections

Cumulative

Expected

Failures

Integration/

Calculation

Repair

Crack Size

Distribution

Inspection

Capability

(POD)

21

NDE in ASIP: Representative

DTA Risk Assessment

Initial Crack

Size

Distribution

Max Stress

per Flight

Crack

Growth

CurveStress

Intensity

Factor

Fracture

Toughness

Single Flight

Probability of

Failure

Probability of

Failure

between

Inspections

Cumulative

Expected

Failures

Integration/

Calculation

Repair

Crack Size

Distribution

Inspection

Capability

(POD)

NDE/SHM POD:

a primary input

into risk

assessment

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DTA Crack Growth

Crack Size, 𝑙

Flight

Hours

Initial Flaw Size

Estimate

Critical Length

Time to Critical

Length𝐼1 𝐼2

23

DTA Crack Growth Cont.

Crack Size, 𝑙

Flight

Hours

𝐼1

We didn’t find

anything

We get to use new

initial crack length

based on NDE

capability

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DTA Crack Growth Cont.

Crack Size, 𝑙

Flight

Hours

𝐼1

We get to use new

initial crack length

based on NDE

capability

We didn’t find

anything

How Do We

Determine our

NDE Capability

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Probability of Detection

• Probability that, for a

crack of certain length:

– The signal will be at a

detectable level during a

given inspection

scenario &…

– The inspector will call

out a flaw

• Sources of uncertainty:

– Probe characteristics

– Operator

– Calibration procedure

– Electrical noise in

systems

– Crack features

– And many more…

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Major Parts to a POD Study

• Capture variability in parameter space

– Some are known to be unimportant others are too

difficult to vary over

• Develop a test matrix to capture data from all

variations

– Determine min and max values of parameters or guess

at distributions (Full or Sparse)

– Document why other parameters weren’t considered

• Gather Experimental Data

– Many inspection opportunities – representative parts

– With and without flaws

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Building a POD Curve

0 2 4 6 8 100

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Flaw Size, 𝑎(mm)

Sig

nal S

trength

, 𝑎

(V)

𝑎 = 𝛽0 + 𝛽1𝑎 + 𝜀

𝜀~𝑁[0, 𝜎2]

28

0 2 4 6 8 100

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Flaw Size, 𝑎(mm)

Sig

nal S

trength

, 𝑎

(V)

0

2

4

6

8

10

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0

2

4

6

8

10

0

0.0

5

0.1

0.1

5

0.2

0.2

5

0.3

0.3

5

02

46

81

00

0.0

5

0.1

0.1

5

0.2

0.2

5

0.3

0.3

5

Fla

w S

ize, 𝑎

(mm

)

Signal Strength, 𝑎 (V)

Building a POD Curve

• Flip the

graph on

its side

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Building a POD Curve

• Set threshold

value

• Fix value of a

• Identify region of

response curve

above threshold

• Integrate this area

for all values of aF

law

Siz

e, 𝑎

(mm

)

Signal Strength, 𝑎 (V)

𝑎𝑡ℎ

Fixed 𝑎 value

30

POD Curve

• This is where we

get the NDE limit

– Which Point

• Input to DTA

– Curve or just a few

points

• Largest flaw we

will miss

0 1 2 3 4 5

x 10-3

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Pro

bab

ilit

y o

f D

etect

ion,

PO

D(a

)

Flaw Size, a

𝑎90 𝑎90/95

𝑎20

31

NDE in ASIP: Representative

DTA Risk Assessment

Initial Crack

Size

Distribution

Max Stress

per Flight

Crack

Growth

CurveStress

Intensity

Factor

Fracture

Toughness

Single Flight

Probability of

Failure

Probability of

Failure

between

Inspections

Cumulative

Expected

Failures

Integration/

Calculation

Repair

Crack Size

Distribution

Inspection

Capability

(POD)

32

Thank you! Questions?

Photo Courtesy of Dr. Eric Lindgren