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Residual Stress Analysis by

Diffraction using

High-Energy Synchrotron Radiation

By ,

Aniket Suresh Waghchaure.Michigan Tech University,Houghton.


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What is Residual Stress? Definition :

Residual Stresses are that remain after the original cause ofthe stresses (external forces heat gradient) has been

removed.Residual stresses occur for a variety of reasons, including

inelastic deformations and heat treatment.

Heat from welding may cause localized expansion, which istaken up during welding by either the molten metal or the

placement of parts being welded.When the finished weldment cools, some areas cool and

contract more than others, leaving residual stresses.


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Types of Residual StressesI] Macroscopic stresses

Long- range in nature, spreads over several grains of the

material.

II] Intergranular stresses

Vary over the grain scale.

III] Atomic Scale stresses

Stresses due to coherency at interfaces anddislocation stress fields


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Different types of residual stresses.

Figure 1 [1]


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Residual stress measurement techniques

Residual stressesDestructive MethodsNon Destructive Methods

Hole DrillingMethod

CurvatureMethod

X rayDiffraction

Neutronor

Synchrotondiffraction

Ultrasonics Magneticwaves


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Experimental setup at the high Energy beam line ID 15A at the ESRV,Grenoble,France. [2]

Fig 2.0

Basic Principle Of High Energy Synchrotron Diffraction


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Gauge volume and Scanning of the sample

Figure 3 [2] Figure 4 [2]


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Gauge volume is given by the intersection of the incoming and the diffracted beam

Formulae's:

d hkl =

Where, dhkl -lattice spacing with hkl denoting Millers indexes,

-Bragg angle ,h -Plancks constant,

c -velocity of light.

=

and are the diffraction elastic constants (DEC).


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Gage Volume Dependence

Figure 5[2] Figure 6 [2]


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Applications:I] Composites (C/SiC-composite):

Residual stresses arise due to the shrinkage of the matrix material and due tothe mismatch of the coefficient of thermal expansion (CTE) of the fibers andthe matrix

The aim of the HESD analysis was to determine the residual stresses paralleland perpendicular to the fibers within a layer in the bulk of the sample

The penetration depth and the resolution required for experiment cannot beachieved using X-ray or neutron diffraction but can be by employing HESD

Figure 7Residual stresses parallel and perpendicular tothe C fibers in the Sic matrix of a C/Sic-composite. [2]


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Results:

a) It was observed by W. reimers,that in the perpendicular direction to the

fiber axis, the thermal mismatch is lower and thus the matrix residual

stresses become zero in this direction.

b) The average residual stress (Gage volume A) for the two combinations of

reflections (6H 110 and 3C 220 resp. 6H 116 and 3C 311) was found to be -

30 +/- 40 MPa, while in gage volume B the residual stress in the SiC matrix

parallel to the fibers was observed to be 230 +/- 80 MPa.


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II] Thermal Barrier Coating :

The residual stresses of a duplex thermal barrier coating system consisting of aplasma sprayed, NiCoCrAlY bond layer with a thickness of 0.15 mm, both

deposited on a super alloy in 718 substrate with a thickness of 2 mm (Fig. 9.0), were

determined by HESD

Figure 9 Figure 10


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Recent research done by Pedro Fernandez that hydrostatic M-RS (microscopic

residual stress)has following objectives

The investigation of the influence of alloy strength on the matrix RS evolutionwith deformation.

The evaluation of the reinforcing particles effect (15 vol.% of Al2O3) on the RSevolution.

The assessment of the influence of the loading mode (compressive versus tensile)on the plastic

Recent Research


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Strength difference between W2A15A composite and W2A00A alloy is result of

Strength Differential Effect(SDE)

Figure 11 [3]Compressive behavior in T6 condition of

2014Al (W2A00A) and 6061Al

(W6A00A)alloys and corresponding

composites.


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Future ScopeFuture research may be concentrated upon residual

stress analysis and texture analysis of componentwhich is loaded under thermal and mechanicalloading .

Dynamic residual stress analysis of thermally loadedcomponents.


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SUMMARYHigh-energy synchrotron radiation has been introduced as a

new method which is extensively being used to determine the

residual stresses in composites , thermal barrier coating to

analyze the residual stresses.

High depth of penetration and high resolution are some

advantages of HESD which made it possible to use in variety

of applications.


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1 .Withers.Bhadeshia, 2001, Overview of Residual Stress Part 1-Measuremnt

Techniques,MST/4640A Vol 17

2. A. Pyzalla ,2000, Methods and Feasibility of Residual Stress Analysis by High-Energy

Synchrotron Radiation in Transmission

3. M.E. Fitzpatrick et al,2007, Analysis of Residual Stress by diffraction using Neutron and

Synchrotron Radiation. 4. Hutchings, et al,Introduction to the Characterization of Residual Stress by Neutron Diffraction

5. W. Reimers,18 (1999) , Journal of materials science letters 581-583, The use of high-energy

synchrotron diffraction for residual stress Analyses

6. G. Brusch et al, Proceedings of the ICRS 5, Linkrping, Sweden, 1997, pp. 557-562.

7. R. Ostertag et al, in Advanced Structural Inorganic Composites,P. Vincenzini, ed. (Elsevier Science

Publishers, London,New York, 1991), pp. 469-477. 8.W. Reimers et al, Evaluation of Residual Stresses in the Bulk of Materials

by High Energy Synchrotron Diffraction

9. Y. M. Chiang et al, Physical Ceramics-Principles for Ceramic

Science and Engineering (John Wiley & Sons, New York, 1997), pp. 26-33.

10. G. Arlt et al. Soc. Am. 37:384 (1965).

References


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Thank You

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