Residual stress measurement techniques

Residual stress measurement techniques

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  Residual Stress Measurement Techniques Presented By GulamhushenA. Sipai 160280708016
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  TABLEOFCONTENTS 1 2 3 4
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  Introduction to theResidual 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
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  Need For RSMeasurement 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]
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  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
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  Hole Drilling method[1] Contactor 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
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  [3 , 4] video
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  Three different rosettetypes: [3] Specimen Preparation: • Cementing , cleaning , degreasing • Abrading or grinding that could appreciably alter the surface stresses must be avoided. [3]
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  [3 ]
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  Drilling: The center ofthe 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]
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  Alignment & Drillingsetup : [4]
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  Computation of Stresses: ForThin Specimen: where [3]
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  Computation of Stresses: ForThick Specimen: where [3]
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  Contact or Non contact Destructive? Lab based or 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 Material Type Composites Crystalline or Amorphous ? Coated ? Surface preparation Metal/ceramics yes Crystalline yes Important Resolution Penetration Stress type Stress state 20μm depth 1mm laterally 5μm-Ti , 50μm-Al , 1mm-layer removal Macro micro Uniaxial Biaxial X-ray Diffraction Method[1]
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  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]
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  Diffraction pattern consistsof 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]
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  Limitations of XRD: •Geometry of Component • Size of Component • surface roughness of Component [1]
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  Synchrotron[1] Contact or Non contact Destructive? Lab based or 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 Material Type Composites Crystalline or Amorphous ? Coated ? Surface preparation Metal/ceramics yes Crystalline yes Important Resolution Penetration Stress type Stress state 20μm lateral to incident beam. >500μm 100 mm for Al Macro micro Uniaxial Biaxial Triaxial
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  Presently, synchrotron diffractionis 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]
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  NEUTRON DIFFRACTION[1] Contact or Noncontact Destructive ? Lab based or 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 Material Type Composites Crystalline or Amorphous ? Coated ? Surface preparation Metal/ceramics yes Crystalline no Not critical Resolution Penetration Stress type Stress state 500μm 100 mm for Al 25 mm for Fe 4 mm for Ti Macro micro Uniaxial Biaxial Triaxial
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  Why we useneutron 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]
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  Stress measurement When theprincipal 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]
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  CURVATURE & LAYERREMOVAL[1] Contact or Non contact Destructive ? Lab based or 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 Material Type Composites Crystalline or Amorphous ? Coated ? Surface preparation All yes N/A yes Not critical Resolution Penetration Stress type Stress state Depends on material and measurement method On surface Macro Uniaxial Biaxial
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  The principle oflayer 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]
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  Deflections can bealso 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]
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  MAGNETIC METHOD[1] Contact or Noncontact Destructive ? Lab based or 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 Material Type Composites Crystalline or Amorphous ? Coated ? Surface preparation Ferromagnetic materials No Crystalline no Not critical Resolution Penetration Stress type Stress state 1mm 20-300μm (Barkhausen) Macro Uniaxial Biaxial
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  Magnetostriction & Magnetoelasticeffect Magnetic domain align with crystalline direction Reduction in magneto elastic energy Calibration of magnetic parameters Advantages : rapid , portable , biaxial stresses Limitation : limited material [1]
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  • AWG 31wire 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]
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  ULTRASONIC METHOD[1] Contact or Noncontact Destructive ? Lab based or portable ? Availability of equipment Speed Standard available Cost of equipment Level of expertise require contact Non- destructive Both generally available rapid No Med Med Material Type Composites Crystalline or Amorphous ? Coated ? Surface preparation Metal ceramics yes Crystalline yes Not critical Resolution Penetration Stress type Stress state 5 mm >100 mm Along specimen Macro Uniaxial Biaxial
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  This method utilizethe 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]
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  • The supportingsoftware 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]
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  • An exampleof 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]
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  RAMAN METHOD[1] Contact or Noncontact Destructive ? Lab based or 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 Material Type Composites Crystalline or Amorphous ? Coated ? Surface preparation polymers ceramics yes either yes Not critical Resolution Penetration Stress type Stress state 0.5 μm Surface Macro Uniaxial Biaxial
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  Raman instrumentation fora) MRS and b) remote MRS [13]
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  • The Ramaneffect 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
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  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
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  Thank you