Post on 15-Jan-2016
8th Jun. 2003 SEM X International Congress
X-Ray Microdiffraction on Diamond-shaped NiTi for Biomedical Applications
Apurva Mehta
SSRL/ SLAC, Stanford University
Valentina Imbeni
8th Jun. 2004 SEM X International Congress
Apurva MehtaNew Boss
8th Jun. 2004 SEM X International Congress
Apurva MehtaCollaborators
Valentina Imbeni – SRI
Brad Boyce – Sandia Labs
Nobumichi Tamura – LBL
Xiao-Yan Gong, Alan Pelton, & Tom Duerig –
NDC
Rob Ritchie’s Group (Scott Robertson, Monica
Barney) – LBL/ UC Berkeley
8th Jun. 2004 SEM X International Congress
Apurva Mehta
Motivation:Macroscopic --- Microscopic
Understanding of Deformation and Failure of NiTi components at Local Level under Multiaxial Loading.
Validation of Design Models. Towards Improved Models that
include: Austenite to Martensitic Phase Transition Mechanics Beyond Continuum Mechanics.
In vivo loadingIn vivo loadingfracturesfractures
8th Jun. 2004 SEM X International Congress
Apurva Mehta
MotivationE.g., understanding Fatigue Tests
Location of Fracture
Increase of Fatigue Life Above 1.5% Strain !!
0.0
0.2
0.4
0.6
0.8
1.0
-4 -3 -2 -1 0 1 2 3 4
Mean Strain (%)
Hal
f Alt
ern
atin
g S
trai
n (
%)
BrokenRun Out
A. Pelton et. al. - NDC
8th Jun. 2004 SEM X International Congress
Apurva MehtaTalk Outline
What did we do? Methodology
What did we find? Diamond in Compression Diamond in Compression Cycling Diamond in Tension
Five “New” Insights
8th Jun. 2004 SEM X International Congress
Apurva Mehta
MethodologyLoad Cell
FEA Simulations
X-ray Beam
Tension
•Nitinol Tube 4.67mm OD with 0.38mm wall
•Laser machined
•Fully Annealed – Grains ~ 20-100 microns
compression
8th Jun. 2004 SEM X International Congress
Apurva Mehta
Bend MagnetSource(250x40m)
1:1 Toroidalmirror
1:1 imageat slits
Elevation view
Plan view
4 CrystalSi(111)Monochromator
CCDcamera
Sampleon scanningXY stage
Horizontal focusing K-B mirror Vertical focusing K-B mirror
MethodologyX-ray Microdiffraction
Beam size on sample: 0.8x0.8 m2
Photon energy range: 5-14 keV
Schematic layout of the X-ray Microdiffraction
Beamline (7.3.3.) at the ALS
8th Jun. 2004 SEM X International Congress
Apurva Mehta
MethodologyX-ray Microdiffraction-1 micron spot
NiTi Diffraction Patterns
10 m Grain Map
Elastic Strain
Plastic Strain
• Ni & Ti Fluorescence
• Austenite Diff. Pattern
8th Jun. 2004 SEM X International Congress
Apurva Mehta
300
03
0
003
3'
3'
3'
332313
232212
131211
332313
232212
131211
ij
DeviatioricDeviatioric DilationalDilational
kkkb o )(lkkc o )(hkka o )(
From energy scan(Variably Monochromated X-rays)
From Laue Patterns deviations(broad bandpass (White) X-rays)
Strain Tensor
Strain TensorsIn crystal reference
frame
xx xy xz
xy yy yz
xz yz zz
+
Crystal OrientationFrom Laue Patterns
In Sample reference frame
8th Jun. 2004 SEM X International Congress
Apurva MehtaDisplacement Strain
8th Jun. 2003 SEM X International Congress
Findings
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 0 mm : F = 0 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5% 0.0 mm
xx
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
X (microns)
Y (
mic
rons
)
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%0.0 mm
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
X (microns)Y
(m
icro
ns)
xx yy
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 0.5 mm : F = -0.393 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
01.5%
-1.5%
Y (
mic
rons
)X (microns)
Compression 0.5 mm
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
Y (
mic
ron
s)
X (microns)
1.5%
-1.5%
Compression 0.5 mm
xx
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
xx yy
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 1.0 mm : F = -0.747 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
Y (
mic
rons
)
X (microns)
-1.5%
1.5%Compression 1.0 mm
xx
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
xx yy
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
rons
)X (microns)
Compression 1.0 mm
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 1.5 mm : F = -1.080 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
01.5%
-1.5%
X (microns)Y
(m
icro
ns)
Compression 1.5 mm
yy
-15.00
-14.00
-13.00
-12.00
-11.00
-10.00
-9.000
-8.000
-7.000
-6.000
-5.000
-4.000
-3.000
-2.000
-1.000
0
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.00
11.00
12.00
13.00
14.00
15.00
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
rons
)
X (microns)
Compression 1.5 mm
xx
-15.00
-14.00
-13.00
-12.00
-11.00
-10.00
-9.000
-8.000
-7.000
-6.000
-5.000
-4.000
-3.000
-2.000
-1.000
0
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.00
11.00
12.00
13.00
14.00
15.00
xx yy
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 2.5 mm : F = -1.465 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
0 1.5%
-1.5%
Y (
mic
rons
)X (microns)
Compression 2.5 mm
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
0 50 100 150 200 250 300 350 400500
400
300
200
100
0 1.5%
-1.5%
Y (
mic
rons
)
X (microns)
Compression 2.5 mm
xx
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
xx yy
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 3.7 mm : F = -1.543 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
rons
)X (microns)
Compression 3.7 mm
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
rons
)
X (microns)
Compression 3.7 mm
xx
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
xx yy
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 3.7 mm : F = -1.543 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
rons
)
X (microns)
Compression 3.7 mm
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
Phase Map
yy
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
Y (
mic
ron
s)
X (microns)
Compression 3.7 mm
Austenite
Martensite
8th Jun. 2004 SEM X International Congress
Apurva MehtaInsight #1
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
ron
s)
X (microns)
Compression 3.7 mm
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
Finite Elem. Analysis Microdiffraction
3.7 mm compression
Qualitative agreement with FEA
But – Granular and Speckled
X. –Y. Gong et al.
8th Jun. 2004 SEM X International Congress
Apurva MehtaInsight #2
Local Strain Never exceeds 1.5 %
NiTi Superelastic because the Aust. And Mart. Elastic region separated by a large region of Transformation Strain
Mar
tens
ite
Aust
enit
e
Molar vol ~ strain 1.5%
Aust + Mart2 phase region
Transformation strain @
const. Stress
8th Jun. 2004 SEM X International Congress
Apurva MehtaInsight #3
Strain relief on transformation
Strain reversal
140 145 150 155 160
150
140
130
120
110
100
yy
X (microns)
Y (
mic
rons
)
Aust
enit
eMolar vol ~ strain
1.5%
Nucleation energy
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 2.5 mm unload : F = -1.037 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
X (microns)
Y (
mic
rons
)
xx
Compression 2.5 mm on unload
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
rons
)X (microns)
Compression 2.5 mm on unload
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
xx yy
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
8th Jun. 2004 SEM X International Congress
Apurva Mehta
CompressionD = 0.0 mm unload : F = +0.282 N
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
-1.5%
1.5%
Y (
mic
rons
)X (microns)
Compression 0.0 mm on unload
yy
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
Y (
mic
rons
)
X (microns)
-1.5%
1.5%Compression 0.0 mm on unload
xx
-15.00-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
xx yy
-4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
For
ce (
N)
Displacement (mm)
8th Jun. 2004 SEM X International Congress
Apurva MehtaLoad Cycling @3.7 mm
0 50 100 150 200 250 300 350 400500
400
300
200
100
0
Y (
mic
rons
)
X (microns)
Compression 3.7 mm
0 50 100 150
100
0
Martensite map
X (microns)
Y (
mic
rons
)
0 50 100 150
160
140
120
100
80
60
40
20
0
yy
X (microns)
Y (
mic
rons
)
0 20 40 60 80 100 120 140 160 180
160
140
120
100
80
60
40
20
0
Martensite map
X (microns)
Y (
mic
rons
)
0 20 40 60 80 100 120 140 160 180
140
120
100
80
60
40
20
0
yy
X (microns)
Y (
mic
rons
)
0 20 40 60 80 100 120 140 160 180
140
120
100
80
60
40
20
0
Martensite map
X (microns)
Y (
mic
ron
s)
0 20 40 60 80 100 120 140 160 180
140
120
100
80
60
40
20
0 yy
X (microns)
Y (
mic
rons
)
-5 -4 -3 -2 -1 0
-1.5
-1.0
-0.5
0.0
0.5
Force
(N)
Displacement (mm) Zero Cycles0 – 3.7 mm
One Cycles3.7- 0- 3.7 mm
Eleven Cycles4.9 – 2.5 - 3.7 mm
8th Jun. 2004 SEM X International Congress
Apurva MehtaInsight #4
On cycling Martensitic region grows.
Growth Pattern unpredictable from FEA
Strain relief as Martensite grows
Explanation for increased Fatigue Life for macroscopic strains > 1.5 %
8th Jun. 2004 SEM X International Congress
Apurva Mehta
Tension : yy
-200 -100 0 100 200 300-150
-100
-50
0
50
100
150
200
250
300
350
400
Tension 3.0 mm
yy
-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
X (microns)
Y (
mic
rons
)
-200 -150 -100 -50 0 50 100 150 200 250 300
-100
0
100
200
300
400
Tension 2.0 mm
yy
-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
X (microns)Y
(m
icro
ns)
-200 -100 0 100 200 300
-100
0
100
200
300
400
Tension 0.3 mm
yy
-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
X (microns)
Y (
mic
ron
s)
-200 -100 0 100 200 300
-100
0
100
200
300
400
Tension 6.0 mm
yy
-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
X (microns)
Y (
mic
rons
)
-200 -100 0 100 200 300
-100
0
100
200
300
400
Tension 5.0 mm
yy
-14.00-13.00-12.00-11.00-10.00-9.000-8.000-7.000-6.000-5.000-4.000-3.000-2.000-1.00001.0002.0003.0004.0005.0006.0007.0008.0009.00010.0011.0012.0013.0014.0015.00
X (microns)
Y (
mic
rons
)
8th Jun. 2004 SEM X International Congress
Apurva MehtaInsight #5
Transformation front and hence stress “hotspot” changes direction, and traverses down the stem of the diamond.
Failure occurs when the “hotspot” encounters a defect or weakness in the material. Location of failure maybe different from FEA prediction.
8th Jun. 2004 SEM X International Congress
Apurva MehtaSummary
Insights: Strain map granular, martensite evolution speckled. In the superelstic region max stress doesn’t exceed
stress corresponding to 1.5% Austenite strain. Strain relief and strain reversal at the transformation
front. On load cycling, the martensite region grows. Overall
stress drops. Transformation and max stress front changes directions.
Further Questions: What is the crystallographic relationship between the
Martenite and the Austenite phase? What happens around a crack tip?
8th Jun. 2004 SEM X International Congress
Apurva Mehta
Crystallographic Relationships
8th Jun. 2003 SEM X International Congress
Thanks !