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MODELING ULTRASONIC STRUCTURAL NOISE
BASED ON THE MICROSTRUCTURAL PROPERTIES
OF METALS IN THE CONTEXT OF NON
DESTRUCTIVE EVALUATION
NDCM 2013
V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
APPLICATION CASES
FOCUS ON COMPLEX NUCLEAR COMPONENTS
20 mm 1 mm
O.D.
I.D.
Thickness of large bands: 5 to 8 mm
Pressurizer
Steam generatorPump
Reactor
Nuclear power plant Cast Stainless Steel (CASS) components
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
APPLICATION CASES
FOCUS ON COMPLEX AERONAUTIC COMPONENTS
Superalloys turbine blades
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
NON DESTRUCTIVE TESTING OF COMPLEX MATERIALS
Homogeneousmedium
Scatteringmedium
t
x
Structural noise and attenuation
These phenomena can cause significant loss in ultrasonic non destructive evaluation of highly scattering materials.
A part of the energy is scattered in all direction by the microstructure
STRUCTURAL NOISE
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
EXAMPLE: UT NOISE IN TITANIUM ALLOY BILLETS
Focused transducerFocal length F = 406.2 mmDiameter = 25.4 mmCenter frequency f0 = 10 MHz
70 mm
ImmersionNormal incidence
The waterpath was chosen such thatthe beam was focused in the half depthof the block
LONGITUDINAL WAVES IN TI ALLOY
Measurement setup
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
348 350 352 354 356 358 360 362 364-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
) and
sta
ndar
d de
viat
ion
348 350 352 354 356 358 360 362 364-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
) and
sta
ndar
d de
viat
ion
348 350 352 354 356 358 360 362 364-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
) and
sta
ndar
d de
viat
ion
Z205 Face R1
Z205 Face R2
Z205 Face Z1
»Envelopes of the signal are measured for each probe position
»Envelopes are averaged over probe positions
»Expressed in dBs compared to the amplitude of the echo of a reference FBH echo
Cscan
1- Cscan 2- Bscan
3- Mean noise level
UT NOISE IN TITANIUM ALLOY BILLETS
LONGITUDINAL WAVES IN TI ALLOY
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
UT NOISE IN TITANIUM ALLOY BILLETS
348 350 352 354 356 358 360 362 364-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
) and
sta
ndar
d de
viat
ion
348 350 352 354 356 358 360 362 364-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
) and
sta
ndar
d de
viat
ion
348 350 352 354 356 358 360 362 364-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
) and
sta
ndar
d de
viat
ion
Z205 Face R1
Z205 Face R2
Z205 Face Z1
Time (µs)
348 350 352 354 356 358 360 362 364-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
) an
d st
anda
rd d
evia
tion
Z205 Face Z1 Face Z1
Time (µs)
Z1
R1
R2
R1
R2
Z1
Z1
R1
R2
R1
R2
Z1
Face Z1
Face R1 Face R1Macrograph Micrograph
Ti alloy
70 mm
Biphasic structure with equiaxed macrograins
Biphasic structure with elongated macrograins
Biphasic structure with elongated macrograins
Z205 Face R1
Noise level anisotropy depends strongly on the metallurgical structure
LONGITUDINAL WAVES IN TI ALLOY
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
ORIGIN OF THE PHENOMENON
In case of a monophasic medium, scattering is due to acoustic impedance fluctuations of grains
• Mono-phasic medium, random, homogeneous and isotropic (statistically)
• Single scattering (Born approximation)• Plane wave(far field)
rCCrC ijklijklijkl
0
ijklijkl CC 0with
r
rkiB
r
rkiAru
s
t
m
s
l
m
s
m
exp,
exp,,
Spatial correlation function:Shape and size of grainsElastic constants variation
skkisWsdCCrr
kksiOrlj
ssil
sl
expˆˆ4
33333
,22
26
2iA
2iB
skisWsdCCk
ilLL
2exp4
3333322
8
In case of LL and θ = 180°
STRUCTURAL NOISE SIMULATION
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
In case of biphasic medium, scattering is due to acoustic impedance fluctuations of grains and contrast between phases
- Random crystallographic orientation of macrograins- Crystallographic orientation relationships between phases: each variant occurs with equal probability- Individual crystallites are too small to make a significant contribution to the grain noise
gCCfCCk CCMMlLL
333333333333333322
8
4
skisWsWsdg CM 2exp
skisWsdf M 2exp
In case of LL and θ = 180°
Averaged over all macrograins orientation
Averaged over all colonies orientation
ORIGIN OF THE PHENOMENON
STRUCTURAL NOISE SIMULATION
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
Higher scattering coefficients are obtained for transverse waves than for longitudinalwaves. In both cases, the backscattering coefficient for two phases case has a frequency dependencysimilar to the macrograin coefficient for low frequencies and to the colonies coefficient for the higher frequencies.
0 1 2 3 4 5-50
-40
-30
-20
-10
0
Frequency (MHz)
(1
80
°)LL
(d
B)
DuplexMacrograinsColonies
0 1 2 3 4 5-50
-40
-30
-20
-10
0
Frequency (MHz)
(1
80
°)T
T (
dB
)
DuplexMacrograinsColonies
It confirms that it is necessary to take into account both scales of the material structurein order to be able to properly model the scattering at all frequencies.
BACKSCATTERING COEFFICIENT
STRUCTURAL NOISE SIMULATION
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
For both L and T waves, the attenuation coefficient for the two-phases structure is somewhereinbetween the attenuation for macrograins and that for colonies.
For the case of L waves, it is very close to the attenuation due to colonies, but this is not a general behavior, as it is strongly dependent on the material properties .
1 2 3 4 50
0.5
1
1.5
Frequency (MHz)
L (d
B/m
m)
DuplexMacrograinsColonies
1 2 3 4 50
0.5
1
1.5
Frequency (MHz)
T (
dB
/mm
)
DuplexMacrograinsColonies
L T
ATTENUATION COEFFICIENT
STRUCTURAL NOISE SIMULATION
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
SUMMARY OF THE COMPUTATION METHOD
Properties of the microstructure
Properties of the probe and the part
Input parameters
Determination of a sufficient number of
scatterers
Scattering coefficient
Computation of the emission and the
reception by the probe
Distribution of scatterers
Simulated B-Scan
Tim
e
Position
STRUCTURAL NOISE SIMULATION
Objective: To predict the influence of the metallic alloys microstructure on the inspection performances
(see presentation LUT-10 Session D5 – Laser ultrasound – Thursday at 5:40 PM)
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
348 350 352 354 356 358 360 362 364-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
Time(µs)
Mea
n no
ise
leve
l (dB
)
Experimental resultCIVA result
Face Z1- Biphasic structure- Equiaxed Macrograin = 100 µm-Colony = 2 µm -Elastic constants (bibliography)
348 350 352 354 356 358 360 362
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Time (µs)
Mea
n no
ise
leve
l (dB
)
Experimental resultCIVA result
Face R1- Biphasic structure- Ellipsoidal macrograin = 100 µmwith L/l = 5.5-Colony = 25 µm-Elastic constants (bibliography)
Very good agreement between experimental and CIVA results
COMPARISONS BETWEEN EXPERIMENTAL AND NUMERICAL RESULTS
LONGITUDINAL WAVES IN TI ALLOY
Face R1
Face Z1
TI ALLOY
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
Structural noise
Echo defect(notche)
Echo Defect(end of block)
Structural noise
Echo defect(notche) Echo
Defect(end of block)
ExperienceSimulation
Time (µs)
LONGITUDINAL WAVES IN STEEL ALLOY
Input data in CIVA software
Elastic constants of biphasic medium
Percentage of colony 85 %
Macrograin size 4 mm
Colony size 1 mm
Macrograin shape Equiaxe
Colony shape Equiaxe (?)
COMPARISONS BETWEEN EXPERIMENTAL AND NUMERICAL RESULTS
STEEL ALLOY
SHEAR WAVES IN SMALL GRAIN AUSTENITIC STEEL
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
Simulated B-ScanMeasured B-Scan
Tim
e
Tim
e
Position Position
12 14 16 18 20 22 24 26 28 30
-36
-34
-32
-30
-28
-26
-24
-22
-20
-18
Time (s)
Env
elop
e/R
efer
ence
(dB
)Shear 45° 2.25MHz
Measurement
Computation
Constructive interferences near the
backwall of the part are correctly simulated
• Comparison of noise levels by plotting the average envelope as a function of time
• Evolution of the noise correctly simulated, but underestimation by 5 dBs
Inspection with shear wave at 45° at 2.25MHz on a sample of austenitic steel
with ≈120μm grains
SHEAR WAVES IN STEEL ALLOY
CONCLUSION
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
• Structural noise can be simulated using a random distribution of scatterers with properties that are related to properties of the microstructure
• Correct prediction of the evolution of the noise level in several cases (Titanium and steel alloys)
• Limitations of the method:• Multiple scattering not taken into account• Underestimation of the noise for austenitic steel inspected with shear waves
PERSPECTIVES
• Simulation of multiple scattering (presentation concerning the work of T. Bedetti)• Amelioration of the accuracy of the simulation:
• Possible explanation for the underestimation for austenitic steel with shear waves: inaccuracy of the Born approximation due to the important variations of elastic properties in this material with shear waves
• Development of a more accurate scattering model in the SIMPOSIUM European project with IZFP (S. Hirsekorn)
• Experimental Determination of elastic properties in collaboration with LAUM (Session D5 at 5:40 PM)
2013 International Congress on Ultrasonics | V. Dorval, L. Ducousso-Ganjehi, S. Chatillon, F. Jenson
Thank you for your attention