Residual stress measurement techniques

Residual Stress
Measurement
Techniques
Presented By
Gulamhushen A. Sipai
160280708016

Introduction to the Residual stress[1]
Residual stresses can be defined as those stresses that
remain in a material or body after manufacture and
processing in the absence of external forces or thermal
gradients
RS can be defined as either macro or micro stresses
Macro stress = Type I
Micro stress = Type II & Type III
Origins of residual stresses :
• Mechanical
• Thermal
• Chemical

Need For RS Measurement
The static loading performance of brittle materials can be improved
markedly by the intelligent use of residual stress.
Common examples include
• thermally toughened glass
• pre-stressed concrete
• sword.
• Gun [2,14]

Measurement Techniques[1]
small Hole , strain , strain gauge, stress
X-RAY , BRAGG’S LAW , DIFFRACTION , PEAKS
HIGH PENETRATION & SPATIAL RESOLUTION
VERY LARGE PENETRATION DEPTH
LAYER REMOVED , CURVATURE
MAGNETO ELASTIC EFFECT
SPEED , US WAVES
LIGHT
HOLE DRILLING
X-RAY DIFFRACTION
SYNCHROTRON
NEUTRON DIFFRACTION
CURVATURE & LAYER REMOVAL
MAGNETIC METHOD
ULTRASONIC METHOD
RAMAN METHOD

Hole Drilling method[1]
Contact or
Non contact
Destructive ? Lab based or
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
contact semi-
destructive
both Easily available Fast/Med ASTM E-
837
Low Low/Med
Material Type Composites Crystalline or
Amorphous ?
Coated ? Surface preparation
Metal/ceramics
/plastics
yes Either yes Important
Resolution Penetration Stress type Stress state
50-100μm depth increment 0.4D
D= dia of strain gauge circle
Macro
micro
Uniaxial
Biaxial

Three different rosette types: [3]
Specimen Preparation:
• Cementing , cleaning , degreasing
• Abrading or grinding that could appreciably alter the surface stresses must
be avoided.
[3]

Drilling:
The center of the drilled hole shall
coincide with the center of the strain
gage circle to within either ±0.004 D or ±
0.001in. (±0.025mm), it is recommended
that an optical device be used for
centering the tool holder
Alignment—Tool guide aligned with the
center of gage circle
Hole Milling—After removing the alignment
microscope, the drilling tool is introduced
Drilling Techniques:
• Abrasive jet machining
• Drilling at very high speed( 400 – 1000 rpm )
• End mills, carbide drills, and modified end mills
[3]

Alignment & Drilling setup :
[4]

Computation of Stresses:
For Thin Specimen:
where
[3]

Computation of Stresses:
For Thick Specimen:
where
[3]

Contact or
Non contact
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
Non-contact no both Generally
available
Fast/Med No Med Med
Amorphous ?
Metal/ceramics yes Crystalline yes Important
20μm depth 1mm laterally 5μm-Ti , 50μm-Al ,
1mm-layer removal
Macro
micro
Uniaxial
Biaxial
X-ray Diffraction Method[1]

Diffraction = Reflection + Interference
Interference is Constructive or Destructive
2dsinƟ = n λ
If the Miller indices of the plane is (hkl) and the system is
cubic then d is related to a by
The typical interatomic spacing in a crystal is of the
order of Å , the wavelength of X-ray is of the same
order . This makes crystals to act as diffraction grating
for X-radiation
[5]

Diffraction pattern consists of a set of peaks with certain
height (intensity) and spaced at certain intervals (X-ray
diffraction pattern of a BCC material graph : intensity VS
2theta )
A beam of X-rays directed at a crystal interacts with the
electrons of the atoms in the crystal , undergoes
diffraction and gives rise to intensity distribution in the
diffracted output, which is characteristic of the crystal
structure. The output is known as diffraction pattern.
Video
X-ray diffraction has a spatial resolution of 1-2 mm down
to tens of μm and a penetration depth of around 10 -30
μ, depending on the material and source
[5]

Limitations of XRD:
• Geometry of Component
• Size of Component
• surface roughness of Component
[1]

Synchrotron[1]
Contact or
Non contact
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
non contact non-
destructive
lab based
method
specialist fast no Government
facility
Amorphous ?
Metal/ceramics yes Crystalline yes Important
20μm lateral to incident
beam.
>500μm
100 mm for Al
Macro
micro
Uniaxial
Biaxial
Triaxial

Presently, synchrotron diffraction is only available at
central facilities, in much the same way as with neutron
diffraction. Two such facilities are
• the European Synchrotron Research Facility in
Grenoble,
• the SRS in Daresbury.
• Synchrotron = Circular particle accelerator
• In synchrotron charged particles are accelerated to very high speeds, the radiation is referred to as
synchrotron radiation
• This radiated energy is very high and using this high intense radiation we get the very useful structure
information of crystals and atoms up to very high penetration depth .
• Advantages of synchrotron radiation is high penetration depth and intense narrow beam.
• Measurement is very quicker than conventional x-ray diffraction
[1]

NEUTRON DIFFRACTION[1]
Contact or
Non contact
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
non contact non-
destructive
lab based
method
specialist Med/
Slow
no Government
facility
High
Amorphous ?
Metal/ceramics yes Crystalline no Not critical
500μm 100 mm for Al
25 mm for Fe
4 mm for Ti
Macro
micro
Uniaxial
Biaxial
Triaxial

Why we use neutron diffraction rather than X-ray Diffraction?
The principle used in neutron diffraction is similar to that of the well-known
X-ray Diffraction technique.
In neutron diffraction the internal 'lattice' stress present in a material is
obtained from the measured elastic 'lattice' strain it produces in the
crystallites of which it is composed. The strain is determined using Bragg's
law of diffraction,
2dsinƟ = n λ
measurement can be made with continuous monochromatic or pulsed
polychromatic beam of neutrons. If spacing of planes change than the
strain in the direction of scattering vector Q is given by
[6]

Stress measurement
When the principal directions coincide with the
coordinate directions normal, transverse and axial and
the material is isotropic with a Young’s modulus E and
Poisson’s ration, the principal stresses are obtained from
Q=2∏/d.
[7]

CURVATURE & LAYER REMOVAL[1]
Contact or
Non contact
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
contact destructive Lab based generally
available
Med No Low Low/Med
Amorphous ?
All yes N/A yes Not critical
Depends on material and
measurement method
On surface Macro Uniaxial
Biaxial

The principle of layer removal method depends on the balance of internal stresses and moments when residual
stresses are gradually removed from the material by thin layers using chemical or electro chemical machining.
Set Up for the Layer Removal Method Using Strain Gages
[8]

Deflections can be also measured directly instead of using strain gages to handle any possible problems
regarding strain gage usage
Set Up for the Deflection Method Using Displacement Sensors.
[8]

MAGNETIC METHOD[1]
Contact or
Non contact
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
Non-contact Non-
destructive
Both generally
available
rapid No Med Low
Amorphous ?
Ferromagnetic
materials
No Crystalline no Not critical
1mm 20-300μm
(Barkhausen)
Macro Uniaxial
Biaxial

Magnetostriction & Magnetoelastic effect
Magnetic domain align with crystalline direction
Reduction in magneto elastic energy
Calibration of magnetic parameters
Advantages : rapid , portable , biaxial stresses
Limitation : limited material
[1]

• AWG 31 wire wound around U core to generate 1T Flux
density.
• Signal given to the coil is generated by waveform generator
and amplified by bipolar supply.
• The generated MBN signal is received by magnetic read head.
• The read head probe was mounted permanently inside the
ferrite U-core magnet.
• This read head is coupled with abrupt flux changes within the
sample.
• The signal from the read head is amplified by a preamplifier
with a gain of 500, then sent through a bandpass filter (3-200
kHz)
• Finally, the signal was interfaced with a personal computer
that had a resident digital oscilloscope board
(Computerscope). The MBN records were stored for
subsequent retrieval and analysis.
[9]

ULTRASONIC METHOD[1]
Contact or
Non contact
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
contact Non-
destructive
Both generally
available
rapid No Med Med
Amorphous ?
Metal
ceramics
yes Crystalline yes Not critical
5 mm >100 mm
Along specimen
Macro Uniaxial
Biaxial

This method utilize the Acoustoelastic effect
Changes in the speed of ultrasonic waves in a material
are directly affected by the magnitude and direction of
stresses present in the component.
1. The main measurement unit with built-in
microprocessor
2. A set of two gauges for measurement of the velocities
of ultrasonic waves thorough the investigated
material
3. Ultrasonic transducer holder
4. Portable oscilloscope (optional) for visualization of
the ultrasonic signals
5. Laptop computer (optional) with an advanced
database and an Expert System for analysis of the
influence of residual stresses on the fatigue life of
welded elements
[10,11,12]

• The supporting software allows
controlling the measurement
process, storing the measured and
other data and calculating and
plotting the distribution of
residual stresses.
• Using the Expert System (ES) it is
possible to assess, the various
treatment’s influence on the
service life of welded elements
without having to perform time-
and labor-consuming fatigue tests.
[11]

• An example of using the Expert System for residual stress
analysis, the results of computation of the residual stress
effect on the fatigue life of a transverse loaded butt weld
(made in shop in flat position, toe angle ≤ 30°, NDT),
depending on the stress ratio R, are presented in Figure
Fatigue curves of transverse loaded butt weld:
1 - with high tensile residual stresses for all levels of R;
2, 3,4 and 5 - without residual stresses at R=-1, -0.5, 0
and 0.5
[11]

RAMAN METHOD[1]
Contact or
Non contact
portable ?
Availability of
equipment
Speed Standard
available
Cost of
equipment
Level of
expertise
require
Non-contact Non-
destructive
Both generally
available
Fast No Med Med
Amorphous ?
polymers
ceramics
yes either yes Not critical
0.5 μm Surface Macro Uniaxial
Biaxial

Raman instrumentation for a) MRS and b) remote MRS
[13]

• The Raman effect involves the interaction of light with matter.
• Incident laser light causes the vibration of bonds between atoms.
• Analysis of the scattered light, known as Raman spectrum, reveals
vital information about a sample's physical state and chemical
structure.
• Raman or fluorescence lines shift linearly with variations in
hydrostatic stress.
• This method has fine spatial resolution and by using optical
microscopy it is possible to select regions of interest just a few
microns in size.
• The method is essentially a surface strain measurement technique,
but with optically transparent materials such as epoxy and
sapphire it is even possible to obtain sub-surface measurement.
• Materials that give Raman spectra include silicon carbide and
alumina-zirconia ceramics and the method is particularly useful for
studying fiber composites
[1,13,14]
Vibrational energy states in a material and
behavior resulting in infrared and Raman
effects

1. Kandil, F. A., Lord, J. D., Fry, A. T., & Grant, P. V. (2001). A review of residual stress measurement methods. A Guide to Technique
Selection, NPL, Report MATC (A), 4.
2. https://en.wikipedia.org/wiki/Residual_stress
3. Standard, A. S. T. M. (1992). E837-99: Standard Test Method for Determining Residual Stresses by the Hole-Drilling Strain-Gage
Method.
4. Measurements, V. M. (2010). Measurement of residual stresses by the hole drilling strain gage method. Technical Note, TN-503
5. http://nptel.ac.in/courses/113108054/module1/lecture3.pdf
6. Webster, G. A., & Wimpory, R. C. (2001). Non-destructive measurement of residual stress by neutron diffraction. Journal of Materials
Processing Technology, 117(3), 395-399.
7. Park, M. J., Yang, H. N., Jang, D. Y., Kim, J. S., & Jin, T. E. (2004). Residual stress measurement on welded specimen by neutron
diffraction. Journal of Materials Processing Technology, 155, 1171-1177.
8. Ekmekçi, B., Ekmekçi, N., Tekkaya, A., & Erden, A. (2004). Residual stress measurement with layer removal method. Meas. Tech, 1, 3.
9. Gauthier, J., Krause, T. W., & Atherton, D. L. (1998). Measurement of residual stress in steel using the magnetic Barkhausen noise
technique. NDT & E International, 31(1), 23-31.
10. Kudryavtsev, Y., Kleiman, J., & Gustcha, O. (2000). Ultrasonic measurement of residual stresses in welded railway
bridge. ultrasound, 6, 8.
11. Kudryavtsev, Y., Kleiman, J., Gushcha, O., Smilenko, V., & Brodovy, V. (2004, June). Ultrasonic technique and device for residual stress
measurement. In X International Congress and Exposition on Experimental and Applied Mechanics. Costa Mesa, California USA (pp. 1-
7).
12. http://www.itlinc.com/stress_engineering_ultrasonic.html
13. Schadler, L. S., & Galiotis, C. (1995). Fundamentals and applications of micro Raman spectroscopy to strain measurements in fibre
reinforced composites. International materials reviews, 40(3), 116-134.
14. Withers, P. J., & Bhadeshia, H. K. D. H. (2001). Residual stress. Part 1–measurement techniques. Materials science and
Technology, 17(4), 355-365.
Reference

Residual stress measurement techniques

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