microbolometer thermoelastic evaluation (mite) evolution ... · 1 microbolometer thermoelastic...
TRANSCRIPT
1
Microbolometer Thermoelastic Evaluation (MiTE) – Evolution of a Cracking ASI
Management Tool
Nik Rajic & Chris Brooks
Airframe Diagnostic Systems
Aircraft Health & Sustainment Branch
© 2016 Australian Defence Science and Technology Group
2
UNCLASSIFIED – cleared for public release
Outline
ASI dividends from MiTE
– Evolution of a transformative capability for ASI management
The next installment
– A new experimental capability for automated crack detection and crack-growth monitoring.
3
UNCLASSIFIED – cleared for public release
Separating FEM Fiction from FEM Fact
Finite Element Modelling (FEM) underpins airframe certification/lifing but has a patchy record on predicting failure in FSFT’s, e.g. F-35 – Prediction based on assumptions, assertions and approximations.
Validation relies on strain gauge (SG) readings – SGs provide limited measurements, and
– never in high stress gradient locations where fatigue normally initiates.
Full-field stress imaging is the answer (can resolve stress-gradients) but – Digital image correlation (DIC) not sensitive enough
– Electronic speckle pattern interferometry not robust enough
– Photoelasticity impractical
– Thermoelastic stress analysis (TSA)
Measuring temperature gets you stress
Temperature variations are small – 3 mK/MPa.
For 30 years conventional wisdom said only cooled photon infrared detectors were up to the job.
Expensive and bulky – major deterrents
)( 321 KT
4
UNCLASSIFIED – cleared for public release
Evolution of a Transformative Capability
1982 2005 1993
1995
Commercial
release of
SPATE begins
the modern TSA
era (Ometron,
U.K.)
DSTG unveils
FAST - the first
TSA system to use
a staring-array
detector.
Commercial release
of a staring-array
based system called
DeltaTherm (Stress
Photonics Inc., USA)
DSTG develops
MiTE, the first
thermal detector
based TSA system.
ASI use of TSA
accelerates.
Photon detector era (TSA technology bulky and expensive …. primarily an R&D
instrument)
Thermal detector era (TSA transformed into a low cost, miniature, and robust engineering tool
….. stress imaging everywhere all the time!)
5
UNCLASSIFIED – cleared for public release
Evolution of a Transformative Capability
1982 2005
1993 1995
Commercial
release of
SPATE begins
the modern TSA
era (Ometron,
U.K.)
DSTG unveils
FAST - the first
TSA system to use
a staring-array
detector.
Commercial release
of a staring-array
based system called
DeltaTherm (Stress
Photonics Inc., USA)
DSTG develops
MiTE, the first
thermal detector
based TSA system.
ASI use of TSA
accelerates.
Photon detector era (TSA technology bulky and expensive …. primarily an R&D
instrument)
2008
In situ TSA
pioneered on
F/A-18 centre
barrel FSFT
Thermal detector era (TSA transformed into a low cost, miniature, and robust engineering tool
….. stress imaging everywhere all the time!)
6
UNCLASSIFIED – cleared for public release
Evolution of a Transformative Capability
1982 2005
1993 1995
Commercial
release of
SPATE begins
the modern TSA
era (Ometron,
U.K.)
DSTG unveils
FAST - the first
TSA system to use
a staring-array
detector.
Commercial release
of a staring-array
based system called
DeltaTherm (Stress
Photonics Inc., USA)
DSTG develops
MiTE, the first
thermal detector
based TSA system.
ASI use of TSA
accelerates.
Photon detector era (TSA technology bulky and expensive …. primarily an R&D
instrument)
2008
In situ TSA
pioneered on
F/A-18 centre
barrel FSFT
Largest ever in
situ full-field
stress survey
of an airframe,
F-35A (AJ1)
2015
MiTE
demonstrated
on F-35C &
then F-35B
FSFTs
2014
Thermal detector era (TSA transformed into a low cost, miniature, and robust engineering tool
….. stress imaging everywhere all the time!)
7
UNCLASSIFIED – cleared for public release
Evolution of a Transformative Capability
1982 2005
1993 1995
Commercial
release of
SPATE begins
the modern TSA
era (Ometron,
U.K.)
DSTG unveils
FAST - the first
TSA system to use
a staring-array
detector.
Commercial release
of a staring-array
based system called
DeltaTherm (Stress
Photonics Inc., USA)
DSTG develops
MiTE, the first
thermal detector
based TSA system.
ASI use of TSA
accelerates.
Photon detector era (TSA technology bulky and expensive …. primarily an R&D
instrument)
2008
In situ TSA
pioneered on
F/A-18 centre
barrel FSFT
Largest ever in
situ full-field
stress survey
of an airframe,
F-35A (AJ1)
2015
MiTE
demonstrated
on F-35C &
then F-35B
FSFTs
2015 2014
HOWSAT - first
TSA scan of a
full-scale aircraft
composite
structure
Thermal detector era (TSA transformed into a low cost, miniature, and robust engineering tool
….. stress imaging everywhere all the time!)
8
UNCLASSIFIED – cleared for public release
Evolution of a Transformative Capability
2015
Miniaturised
autonomous stress
imaging cores –
proof of concept
established – world
first
1982 2005 1993
1995
Commercial
release of
SPATE begins
the modern TSA
era (Ometron,
U.K.)
DSTG unveils
FAST - the first
TSA system to use
a staring-array
detector.
Commercial release
of a staring-array
based system called
DeltaTherm (Stress
Photonics Inc., USA)
DSTG develops
MiTE, the first
thermal detector
based TSA system.
ASI use of TSA
accelerates.
Photon detector era (TSA technology bulky and expensive …. primarily an R&D
instrument)
2008
In situ TSA
pioneered on
F/A-18 centre
barrel FSFT
Largest ever in
situ full-field
stress survey
of an airframe,
F-35A (AJ1)
2015
MiTE
demonstrated
on F-35C &
then F-35B
FSFTs
2015 2014
HOWSAT - first
TSA scan of a
full-scale aircraft
composite
structure
Thermal detector era (TSA transformed into a low cost, miniature, and robust engineering tool
….. stress imaging everywhere all the time!)
9
UNCLASSIFIED – cleared for public release
Looking Ahead
2005
Thermal detector era (TSA transformed into a low cost, miniature, and robust engineering tool
….. stress imaging everywhere all the time!)
2015
Miniaturised
autonomous stress
imaging cores –
proof of concept
established
Future FSFT
programs will
probably look
something like
this
DSTG develops
MiTE, the first
thermal detector
based TSA system.
ASI use of TSA
accelerates.
Historical record of stress state. Continuous real-time trend analysis - detection
of load path variations, crack growth tracking etc.
201?
miniMiTE stress imaging
core (wireless comms.)
miniMiTE network accessible via tablet or smart phone
10
UNCLASSIFIED – cleared for public release
Crack Detection & Crack Growth Monitoring
Automated crack
detection and
crack growth
monitoring
2005
Thermal detector era (TSA transformed into a low cost, miniature, and robust engineering tool
….. stress imaging everywhere all the time!)
2015
Miniaturised
autonomous stress
imaging cores –
proof of concept
established
DSTG develops
MiTE, the first
thermal detector
based TSA system.
ASI use of TSA
accelerates.
2016
𝜎𝑏 = 𝜎1 + 𝜎2 =2𝐾𝐼
2𝜋𝑟cos
𝜃
2−
2𝐾𝐼𝐼
2𝜋𝑟sin
𝜃
2
11
UNCLASSIFIED – cleared for public release
CGM - State of the Art
Current Crack Growth Monitoring Technologies
• Travelling Microscope
• Needs polished surface
• Hard to automate
• Compliance method
• Readily automated
• Calibration required – standard specimens
• Infers crack length, does not measure
• Average crack length not crack tip position
• PD methods
• As for Compliance
12
UNCLASSIFIED – cleared for public release
𝜎𝑏 = 𝜎1 + 𝜎2 =2𝐾𝐼
2𝜋𝑟cos
𝜃
2−
2𝐾𝐼𝐼
2𝜋𝑟sin
𝜃
2
1. Thermoelastic response is a function of the effective stress intensity factor
2. Signal peak is at the crack tip
CGM using Thermoelastic Response Measurements
Can (i) locate a crack tip and (ii) determine effective stress intensity factors
13
UNCLASSIFIED – cleared for public release
A Fully Automated System
microbolometer
vertical
stage
horizontal
stage
edge-notched
coupon
microscope load signal Infrared data
Correlate data
Detect Crack Tip
Move Stages Image Crack
Tip
14
UNCLASSIFIED – cleared for public release
Comparison to Visual Tracking
10mm
5mm
10mm
5mm
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.080
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
TSA (m)
Vis
ua
l (m
)
15
UNCLASSIFIED – cleared for public release
Crack Growth Rate
10-8
10-7
10-6
10-5
10-4
10-3
da
/dN
(m
/cycle
)
Visual TSA
ΔK (MPa m)10
110
2
10-9
10-8
10-7
10-6
10-5
10-4
10-3
da
/dN
(m
/cycle
)
Visual TSA
ΔK (MPa m)10
110
2
10-9
10-8
10-7
10-6
10-5
10-4
10-3
da
/dN
(m
/cycle
)
Visual TSA
ΔK (MPa m)10
110
2
16
UNCLASSIFIED – cleared for public release
Advantages
Full automation
No polishing
No calibration
No geometry limits
Can be applied to real structure
Profiling of the crack front – i.e. tunneling
Effective stress intensity factor
17
UNCLASSIFIED – cleared for public release
Questions?
MiTE Freeware available at: http://www.dsto.defence.gov.au/opportunity/mite