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Local Nondestructive
Evaluation and Materials
Characterization
Glenn A. Washer, Ph.D., P.E.
University of Missouri – Columbia
[email protected]
Agenda
•
•
•
•
•
Introduction in NDE
NDE timelines
NDE for defect detection
Materials Characterization
Conclude
Nondestructive Evaluation
• Technologies to determine the condition of
a material without altering that condition
What are NDE Methods?
• NDE methods use waves to transmit data on
material condition
• Acoustic and electromagnetic waves carry the
legacy of their environment
• NDE methods measure common wave properties
to infer the condition of the material – frequency,
amplitude, time of flight
– Example: visual inspection
– Reflection of light
Why NDE?
• Safety – detect deterioration at sub-critical levels
– Fatigue cracks in steel bridges
• Maintenance – detect deterioration during embryonic stages
to:
– Identify repair needs
– Reduce the cost of repairs
• Management
– Provide quantitative knowledge
on inventory condition
– Focus funding on most
critical needs
• Quality Control
– Materials characterization
Classifying NDE Technologies
•
Local defect detection
– Single point binary detection (threshold) + analysis
– UT, ET, MT, etc
•
Full-Field defect detection and imaging
– Spatial representation of common wave properties (ex. Amp. )
– Binary detection (threshold) + quantitative spatial measurements + analysis
– Infrared thermography, imaging (dt), interferometric optical methods
•
Global Techniques
– Health Monitoring
• Stress, strain, dynamic characteristics
• Corrosion, distributed local NDE technologies within a system
•
Materials Characterization
– Quality control
– Gross Materials Degradation
• UT pulse velocity in concrete
Timelines and NDE
• Most traditional NDE technologies are historical
– Record events that have previously occurred
– Defects are detected once they have grown to detectable levels
– Inspection intervals can be optimized for these techniques such
that known defect growth rates combined with known POD rates
form a reliable and safe system
• There are a few exceptions
– Acoustic Emission systems
– “Real time” is a benefit and a deficiency
• Cannot measure damage that already exists, and generally is not
intended to detect manifestations of that damage
Timelines and NDE
• Pre-construction
– Material characterization, defect detection
• Weld flaws, voids in pre-cast concrete
• Characterizing earth properties
• Construction
– Quality control, installation stresses
• Ex. Anchor bolt stresses, erection stresses
• Post-construction
– GPR for pavement thickness, rebar depth etc.
• Service Life
– Detect deterioration and defect growth
• Deconstruction
– Quantify material conditions/properties following service life
• Corrosion rates, chloride intrusion etc.
Example
• Acoustic detection of subsurface features
September 2000
• Imaging of acoustic
backscatter (density
changes)
• Fixed point in time
• Detection and analysis
– single fetus
November, 2000
Jack and Beau
Pin Inspection
Ref: FHWA NDE Center
Bridge Pin Evaluation
C-Scan Image
100
80
60
40
20
0
0
1
2
3
4
5
Crack
Surface
6
7
8
9
10
Pin Barrel
Crack
Surface
S106
S108
Phased Array Ultrasonics
Pin Radiography
Computed Tomography
099
Acoustic Wave Spectrum
A/E
Audible
Impact - echo
Ultrasonic
Structural vibrations
1
Hz
101
102
103
KHz
104
105
106 107
MHz
PHz THz MHz
IR
GHz
radar
MHz
KHz
Materials Characterization
• Waves carry the legacy of the environment in
which they propagate
– Electromagnetic waves and acoustic waves
• Many physical properties are linear over certain
ranges, for example steel modulus of elasticity
– Scale
– Magnitude
• NDE technologies can measure physical
properties when other variables can be controlled
– Quality control, production control, and
global/localized materials degradation
Equation of Motion for a Anisotropic Linear - Elastic Solid
2uk
cijkl
ui
x
x
i
j
Orthortropic Case
c11
v11
c
v12 66
c55
v13
v11
Isotropic Case
v22 c22
v21
v23 c44
2
v12 v13
vij = wave velocity
= density
, = Lamé Constants
c66
c
v31 55
v32 c44
v33
c33
E
3 2
2
= Poisson’e ratio
u = Displacement
RPC Structure
3D reconstruction
(steel fibers)
UT vs. Static Modulus
By Curing Method
Correlation coef. 0.94
9000
STATIC MOD. (ksi)
8500
8000
Steam cured
Delayed Steam
Tempered Steam
Air Cured
7500
7000
1:1
6500
6000
6000
6500
7000
7500
8000
8500
UT Modulus (ksi)
Ref. Washer, Fuchs, Graybeal & Rezai, QNDE 2003
9000
Acoustoelastic Equation of Motion
V11
2 4( 2 ) 2( 2m) (1 2l )
0
dV11 V110 K11d
V12 V13
4 (n 2) m(1 2 )
0
dV12 V120 K12 d
Concept
Strand
Transmitter
Receiver pair
t
Threshold A
AMPLITUDE
P/S Beam
Threshold B
Threshold
4e-5
8e-5
1e-4
TIME (secs)
2e-4
2e-4
dV/Vo
Strands
0.0005
0
-0.0005
-0.001
-0.0015
-0.002
-0.0025
-0.003
-0.0035
S2
S3
1
1.2
1.4
STRESS (GPa)
Ref. Washer, Green & Pond, RNDE 2001
1.6
Future Opportunities
Managing the aging infrastructure into the future will require the
development of increasing sophisticated condition assessment
tools
• NDE Technologies
– Detect defects and material
degradation
– Physical properties of
engineering materials
• Variability and scale of civil
structures presents a significant
challenge
• Local NDE techniques can be
distributed as part of health
monitoring systems
– Development of systematic
approaches and sensor
technologies is required
Acknowledgements
• FHWA NDE Center
Thank you – Questions?