Insights into Engineering

1
Insights into Engineering

• Prof. Philip. J. Withers

Unit for Stress Damage Characterisation,Manches
ter Materials Science Centre UMIST/University of
Manchester, UK
2
The Engineering Dimension

• Scientists often concerned with specimens
• Engineers concerned with components under
• Real Timescales
• Actual temperatures
• Full scale components
• Difficult environments
• Complex loading histories

3

• Diffraction an atomic strain gauge -Recording
  elastic strains

4
Obtaining Strain Maps
Scan object very precisely through the gauge
volume to build up a 3D map of the strain
5
Why use synchrotron X-rays?
high energy high flux micron resolution fast data
acquisition excellent depth penetration
Synchrotrons offer
6
Typical layout (at the ESRF)
7
Neither peak shift (strain) nor measurement
location is correct near a surface!

• Partial filling of sampling gauge gives a peak
  shift - need to correct peak shift
• Translator records centre of gauge which is
  rarely the centre of gravity of diffracting
  region
• need to correct gauge position

8
Correcting for Position
9
Apparent surface strains
Surface strains can be corrected for
mathematically or .
10
Surface strains can largely be removed using an
analyser crystal
11
Set up at the European Synchrotron

• 900 images/rotation
• Parallel beam geometry
• 0.7, 2 or 5mm resolution
• 30keV X-rays

12
Lab X-ray tomography

• best possible resolution 5-10?m, up to 225 keV
  X-rays
• Samples 3 to 100mm
• Cone beam
• 360 images
• Filtered back-projection algorithm used to
  reconstruct entire volume

13
Imaging arrangement of lab system
14
CASE STUDIESNear surface stresses

• Shot peening

15
(No Transcript)
16
Shift
Width
17
CASE STUDIES Better Process Models

• Welded Aircraft

Towards Low Stress Low Distortion TIG Welding
for Aerospace
18
FE Modelling Requires

• Material thermal property data required
• Thermal conductivity variation with temperature.
• Specific heat variation with temperature.
• Thermal expansion change with temperature.
• Real industry data needed to model heat
  generation based on the four heat sources
• Torque to rotate the tool.
• Horizontal force to slide the tool.
• Vertical force to plunge the tool into the
  material.
• Needs thermocouple experiments to compare with FE
  to ensure reliable heat generation model

19
FE Validation

• Longitudinal strain in TIG weld

Weldline
20
FE Validation
Synchrotron

• Transverse strain in TIG weld

Model
Weldline
21
Predictions
High resolution mapping
Synchrotron Measurements

• Mapped area 20x40 mm

22
CASE STUDIES High resolution strain mapping

• Composite Micromechanics

23
Measuring Interface StrengthFibre Fragmentation
Sample Geometry
24
Full fibre fragmentation
Reduction in fibre strength after first fracture
means post mortem assessment would overestimate
the interface strength
25
Tomography of single fibre sample
26
Interfacial Shear Stress
27
Residual Strains
FE Model
Loaded
Final Residual
28
Interface displacements
29
Fatigue Cracking

• 0.4mm fatigue crack grown in bending and then 1mm
  square cross section tomographic inspection
  sample cut out.
• Sample viewed at Kmin and Kmax in tension

Crack
30
Kmin Kmax
31
Strain Measurement Scan Details

• slit size height 0.1mm
• slit size width 0.2mm
• receiving slits 2x2mm2
• counting time for SiC(108) 1min
• counting time for Ti(102) 10s
• x step size 0.38mm
• z step size 0.15mm

measurement pattern
32
Longitudinal strain SiC(108)
0
1
2
3
0
1
2
3
2
0
0
0
1
5
0
0
0
5
2
5
2
0
3
3
0
3
3
0
-
1
0
0
0
0
5
0
0
0
0
0
2
0
5
2
-
-
0
-
0
5
2
0
-
1
5
0
0
-
2
-
0
0
0
0
5
0
0
5
0
5
5
7
0
0
1
1
2
-
0
0
1
0
5
2
2
2
2
m
0
m
0
0
1
0
5
0
0
0
m
m
2
0
0
0
2
0
-
5
0
0
0
0
/
1
0
/
-
0
0
2
5
5
0
5
0
-
5
1
z
z
2
-
0
2
-
0
0
0
0
0
0
0
0
-
1
0
0
0
0
0
5
5
2
0
0
0
0
-
0
0
0
1
2
-
0
1
1
0
1
1
0
0
0
0
0
0
5
1
-
0
-
1
5
0
0
0
0
-
0
.
0
0
0
2
0
5
-
5
0
0
-
2
2
5
5
-
1
7
-
-
2
0
0
0
2
-
-
2
5
0
0
0
0
0
0
0
1
2
3
0
1
2
3
-
3
0
0
0
x
/
m
m
x
/
m
m
microstrain
SiC unloaded
SiC loaded (1.22kN)
33
Longitudinal strain Ti(102)
Ti unloaded
Ti loaded (1.22kN)
microstrain
Ti-6Al-4V/SCS-6
34
loaded-unloaded
x
/
m
m
SiC
Ti
microstrain
Ti-6Al-4V/SCS-6
35
Getting started.Facility for Engineering
Materials

• Directed by Peter Webster
• Co-located between ESRF (synchrotron X-rays) and
  ILL (neutrons)
• UK funded to for all European users
• Aims to provide assistance for new engineering
  users
• Webster_at_ill.fr

36
Summary

• High penetration excellent spatial time
  resolution
• It can help to follow
• Real Timescales
• Actual temperatures
• Some Full scale components
• Difficult environments
• Complex loading histories