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This page has not been updated since 2015, are there are many more comparisons now in the literature.

Summary

  • Overall, the contour method results agree well with the majority of the independent validations.
    • For non-weld specimens, agreement is almost always very good.
  • Most uncertainties in papers are for 1 standard deviation (sd). Statistically, independent measurements should agree to within one sd error bars at ~ only 68% of the points. The remainder should disagree randomly.
  • There are some results where contour seems to have a systematic error, some when the other method has an error, and some are not possible to tell.
    • Contour systematic errors are discussed below the table.
    • The more textured the material, or the higher the intergranular stress (micro stress or type II), or when there are chemistry changes, the less likely for contour and diffraction to agree. This hints at a diffraction issue. Welds usually fall in this category.
  • The results on the NeT specimen and the VPPA weld show the scatter in multiple neutron or synchrotron results - important to keep in mind when comparing with a single measurement.
  • See recent Hill and Olson paper on repeatability of the contour method.
  • There are some contour errors in this table that are caused by poor practice of the practitioner.

The table below attempts to show all significant experimental validations (verifications) of the contour method. Comparisons at different points (e.g., surface vs. bulk) or only a few points are not included. If there are additional validations that should be included or any of these details or characterizations are misleading, please email Mike Prime.

Article (reverse chronological)

Specimen and Materials Comparison Results and comments
Achintha, M., and Balan, B. A., 2015, "An experimentally validated contour method/eigenstrains hybrid model to incorporate residual stresses in glass structural designs," The J of Strain Analysis for Engg. Design. Published online before print September 2, 2015, doi: 10.1177/0309324715601914 i 10 mm thick float glass Polariscope In spite of very low stresses, the agreement was good.
Toparli, M. B., and Fitzpatrick, M. E., 2015, "Development and Application of the Contour Method to Determine the Residual Stresses in Thin Laser-Peened Aluminium Alloy Plates," Experimental Mechanics, published online. The Open U./Coventry U. 2 mm thick 2024 Al, laser peened. X-ray diffraction and incremental hole drilling. In a challenging near-surface measurement, the agreement with validating measurements is OK.
Toparli, M. B., Fitzpatrick, M., and Gungor, S., 2015, "Determination of Multiple Near-Surface Residual Stress Components in Laser Peened Aluminum Alloy via the Contour Method," Met. and Mat. Trans. A, 46(9), pp. 4268-427. The Open U./Coventry U. 28 mm thick 7050 Al, laser peened. X-ray diffraction and incremental hole drilling. This is validation for measuring multiple components using superposition and x-ray diffraction. The agreement (Figure 8) with the validation measurements on the most similar sample is very good.

Xie, P,et al., 2015, "Evaluation of Residual Stresses Relaxation by Post Weld Heat Treatment Using Contour Method and X-ray Diffraction Method," Experimental Mechanics, 55(7), pp. 1329-133. Tsinghua U., China

E-beam welded Ti-6Al-4V. X-ray diffraction Very good agreement for near-surface stresses, which is tough to measure with contour.
Kaiser, R. et al., 2015, "Experimental characterization and modelling of triaxial residual stresses in straightened railway rails," J Strain Analysis for Engineering Design, 50(3), pp. 190-198. Montanuniversitaet Leoben, Austria Railroad rails approximately 150 mm X 172 mm. Steel grade R260 (ferritic) Neutron diffraction using 211 and 110 reflections. Very good agreement with neutron, agreeing with uncertainties at about 83% of locations. Neutron error bars are large because of low penetration.
Ahmad, B., and Fitzpatrick, M. E., 2015, "Effect of Ultrasonic Peening and Accelerated Corrosion Exposure on the Residual Stress Distribution in Welded Marine Steel," Met. & Mat. Trans. A, 46(3), 1214-1226. The Open University. 25 mm thick plates of ferritic steel, measured near welded-on attachment. Neutron diffraction and X-ray. Fair to very good agreement with neutron. X-ray only done on the one specimen that was not measured optimally for surface stress, so agreement poor.
Woo, W. et al., 2014, "Through-thickness distributions of residual stresses in an 80 mm thick weld using neutron diffraction and contour method," J. of Materials Science, 50(2) pp. 784-793. KAER, South Korea. 80 mm thick butt welded plates of high-strength, low carbon steel. Neutron diffraction using two-peak combined methodology. Good. Within uncertainty bars at ~ 75% of measurement points, but outside at other 25%, including peak stress location. This was a very thick specimen for neutrons.
Araujo de Oliveira, J., Fitzpatrick, M. E., and Kowal, J., 2014, "Residual stress measurements on a metal matrix composite using the contour method with brittle fracture," Advanced Materials Research, 996, 349-354. The Open University. 14 mm thick Al 2124 -SiC particle reinforced metal matrix composite. Neutron diffraction using single peaks in both matrix and reinforcement, averaged to give macrostresses. Fair to good agreement with the traditional contour method, poor agreement for the fracture surface method, possible because of gross plasticity in the fracture.
Zhang, Z., et al., 2014, "Machining distortion minimization for the manufacturing of aeronautical structure." Int. J. of Advanced Manufacturing Tech., 73, 1765-1773. Nanjing University. 30 mm thick Aluminum ally 7050 plate Layer removal Very good agreement, but the layer removal resolution is relatively poor.
Kerr, M., Prime, M. B., Swenson, H., Buechler, M. A., Steinzig, M., Clausen, B., and Sisneros, T., 2013, "Residual Stress Characterization in a Dissimilar Metal Weld Nuclear Reactor Piping System Mock Up," Journal of Pressure Vessel Technology, 135(4), pp. 041205-041205. 7 pass GTA weld using filler metal in 12.5 mm thick 304L stainless steel plate. Neutron diffraction Poor to good agreement in various regions. Agreement is worst with neutron points overlapping the weld metal/base metal interface, where d0 is suspect.
Naveed, N., Hosseinzadeh, F., & Kowal, J., 2013, " Residual Stress Measurement in a Stainless Steel Clad Ferritic Plate Using the Contour Method," ASME 2013 Pressure Vessels and Piping Conference. The Open University. 50 mm thick SA508 steel with a 10 mm thick weld overlay of 308L stainless. Neutron diffraction Good agreement over most of the depth profile, a few points were noticeably different.
Hosseinzadeh, F., Bouchard, P. J., 2013, "Residual Stress Measurement of a Hipped Bonded Valve Seat Using the Contour Method," ASME 2013 Pressure Vessels and Piping Conference. Paper No. PVP2013-97922. The Open University. 95 mm diameter, 100 mm long HIP'd valve seat, complicated geometry. Incremental hole drilling. Good to very good agreement. The comparison was with near-surface stresses. They made extra effort to get a very good cut.
Elmesalamy, A., J. A. Francis, and L. Li, 2014, "A comparison of residual stresses in multi pass narrow gap laser welds and gas-tungsten arc welds in AISI 316L stainless steel." Int. J. of Pressure Vessels and Piping 113, 49-59. U. Manchester. 28 Narrow Gap Laser Welded 10 mm thick plate of 316L stainless steel. X-ray diffraction Good to very good agreement. This was an attempt to measure near-surface stresses, which is tough. The contour results should have fairly big error bars on them.
Braga, D. F. O. et. al, 2013, "Assessment of residual stress of welded structural steel plates with or without post weld rolling using the contour method and neutron diffraction," J. of Materials Processing Technology, 213(12), pp. 2323-2328. Universidade de Porto. MIG weld bead on plate on 6mm thick 5355JR steel Neutron diffraction at SALSA using {2 1 1} peak. Very good agreement for rolled weld with 1300 MPa compressive stress. Only fair agreement for untreated weld with +400 MPa stress.
Toparli, M. B., Fitzpatrick, M. E., and Gungor, S., 2013, "Improvement of the Contour Method for Measurement of Near-Surface Residual Stresses from Laser Peening," Experimental Mechanics, 53(9), pp. 1705-1718. The Open University. 28 and 30 mm thick samples of 7050 Al, laser peened on 3 edges X-ray diffraction and incremental hole drilling. Fair to very good agreement in different regions. This was an attempt to measure near-surface stresses, which is tough. The contour results should have fairly big error bars on them, which would make the agreement good.
Rolph, J., et al., 2012, "Residual Stress Evolution during Manufacture of Aerospace Forgings," Superalloys 2012, John Wiley & Sons, Inc., pp. 881-891. U. Manchester. Varying thickness (50 mm max), 89 mm diameter forgings of nickel superalloy RR1000 Neutron diffraction. Very good agreement
Rolph, J. et al., 2013, "The effect of d0 reference value on a neutron diffraction study of residual stress in a γ/γ′nickel-base superalloy," J.of Strain Analysis for Engineering Design, 48(4), pp. 219-228. U. Manchester. 25 mm thick, 76 mm diameter disks of two-phase nickel superalloy RR1000. Neutron diffraction. Very good agreement with both scans on specimen 2. Good agreement with one scan on specimen 1. Other scan has 20% difference between neutron and contour.
Woo, W., et al., 2013, "Through-thickness distributions of residual stresses in two extreme heat-input thick welds: A neutron diffraction, contour method and deep hole drilling study," Acta Materialia, 61(10), pp. 3564 - 3574. KAERI Korea and Bristol U. 70 mm thick welds in ferritc steel. Deep hole drilling and neutron diffraction. Fair agreement. General trends are the same. Magnitudes are off sometimes. Neutron and DHD are closer to each other than to contour, but all measurements disagree to some extent.
Zabeen, S., Preuss, M., and Withers, P., 2013, "Residual stresses caused by head-on and 45° foreign object damage for a laser shock peened Ti-6Al-4V alloy aerofoil," Materials Science and Engineering: A, 10, pp. 518–527. U. Manchester. Airfoil shapes of Ti-6Al-4V Synchrotron diffraction Good agreement at one measurement location (as laser-peened) and very good at the other (near foreign object damage).
Kundu, A., Bouchard, P., Kumar, S., Venkata, K., Francis, J., Paradowska, A., Dey, G., and Truman, C., 2013, "Residual stresses in P91 steel electron beam welds," Science and Technology of Welding & Joining, 18(1), pp. 70-75. The Open University. E-beam welded plates of PP91 ferritic-martensitic steels. Neutron diffraction Only fair agreement. Differences of about 100 MPa. Contour may have not resolved the peaks, but also lots of variation and scatter in neutron d0 measurements.
Traore, Y., Paddea, S., Bouchard, P., and Gharghouri, M., 2012, "Measurement of the Residual Stress Tensor in a Compact Tension Weld Specimen," Experimental Mechanics. The Open University. E-beam welded compact tension specimen of austenitic stainless steel. Neutron diffraction and slitting. Very good agreement. A slight shift in the contour results could be a bulge error since the part was only clamped on one side during the cut.
Hosseinzadeh, F., Toparli, M. B., Bouchard, P. J., 2012, "Slitting and Contour Method Residual Stress Measurements in an Edge Welded Beam," J. of Pressure Vessel Technology, 134(1), pp. 011402-011406. The Open University. Edge welded beam of 316H stainless steel. Specimen only clamped on one side during EDM cut - likely to increase errors. Neutron diffraction, synchrotron diffraction, and slitting. Very good agreement with synchrotron (noisy) and slitting. Fair to good agreement with neutron.
Savaria, V., Hoseini, M., Bridier, F., Bocher, P., and Arkinson, P., 2011, "On the measurement of residual stress in induction hardened parts," Materials Science Forum, 681, pp. 431-436. Case hardened disks of 4340 steel. X-ray diffraction with layer removal. Compared only for about 2 mm of depth and mostly poor agreement. They used a zinc coated EDM wire, which some have found to be a problem.
Moat, R. J., Pinkerton, A. J., Li, L., Withers, P. J., and Preuss, M., 2011, "Residual stresses in laser direct metal deposited Waspaloy," Materials Science and Engineering, A528(6), pp. 2288-2298. U. Manchester, School of Materials. Laser-deposited Waspaloy (nickel-based superalloy) Neutron diffraction - single peak {3 1 1}. d0 determined by assuming 0 stress in thin direction. Very good agreement (within error bars). Such is often the case in specimens other than welds.
download preprint Brown DW, Holden TM, Clausen B, Prime MB, Sisneros TA, Swenson H, Vaja J, 2011, "Critical Comparison of Two Independent Measurements of Residual Stress in an Electron-Beam Welded Uranium Cylinder: Neutron Diffraction and the Contour Method," Acta Materialia 59 (3):864-873. doi:10.1016/j.actamat.2010.09.022. Circumferentially (girth) welded cylinder of depleted uranium (Orthorhombic crystal structure) Neutron diffraction - time of flight and Rietveld refinement. Fair to poor agreement quantitatively although good qualitatively. However, the neutron measurements were averaged over the circumference, so not directly comparable. Also, see the discussion in the paper: these measurements were very challenging for both methods, so several possible error sources.
download pdf Pagliaro, P., Prime, M. B., Robinson, J. S., Clausen, B., Swenson, H., Steinzig, M., and Zuccarello, B., 2010, "Measuring Inaccessible Residual Stresses Using Multiple Methods and Superposition," Experimental Mechanics, doi:10.1007/s11340-010-9424-5. (LA-UR-10-02450) Plastically indented disks of 2024-T351 aluminum alloy. Neutron diffraction - time of flight and Rietveld refinement. Good agreement (within error bars) over most of the profile for traditional contour measurement, see Figure 9. Also quite good agreement for Surface Superposition Contour Method to get multiple stress components, see Figure 12
Thibault D, Bocher P, Thomas M, Gharghouri M, Côté M, "Residual stress characterization in low transformation temperature 13%Cr-4%Ni stainless steel weld by neutron diffraction and the contour method," Materials Science and Engineering: A, 527(23):6205-6210, 2010. Institut de recherche d'Hydro-Québec (IREQ), Québec, Canada. Plate of martensitic steel welded with 410NiMo filler, also martensitic. Neutron diffraction. Good agreement over much of the measurements. Poor agreement in the Heat-Affected Zone. Authors' explanation is that the HAZ has retained austenite but stresses were only measured in the martensitic phase. Contour measures total stress, which is an average.
download preprint Pagliaro, P., Prime, M. B., Swenson, H., and Zuccarello, B., "Measuring Multiple Residual-Stress Components Using the Contour Method and Multiple Cuts," Experimental Mechanics, 50(2), pp. 187-194, 2010. (LA-UR-09-01120) Plastically indented disks of 316L stainless steel. Same specimen as next paper below. Neutron diffraction - time of flight and Rietveld refinement. One additional results to paper below. Very good agreement (within error bars) to validate multiple cuts procedure.
download preprint Pagliaro, P., Prime, M. B., Clausen, B., Lovato, M. L., and Zuccarello, B., "Known Residual Stress Specimens Using Opposed Indentation," J. of Engineering Materials and Technology, 131, 031002, 2009. Plastically indented disks of 316L stainless steel. Neutron diffraction - time of flight and Rietveld refinement. Very good agreement (within error bars) over most of the profile. See Figure 15. Some disagreement from r = 10 to 20 mm.
Frankel, P.; Preuss, M.; Steuwer, A.; Withers, P.J.; Bray, S., "Comparison of residual stresses in Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo linear friction welds," Materials Science and Technology, 25(5), 640-650, 2009. Multiple institutions. Linear friction welded Ti-6Al-4V, one as welded and two different heat treatments. Synchrotron diffraction with d0 measurements by laboratory x-ray. Contour peak stresses are significantly lower then synchrotron results. Could be contour issues. Weld region has severe microstructural gradients and is a two-phase alloy, making diffraction challenging. See Johnson thesis for earlier reporting of similar (same?) measurements showing better agreement.

NeT 2009 special issue of I.J. of Pressure Vessels and Piping. Multiple institutions.

also in Bouchard, PJ, 2008, "Code Characterisation of Weld Residual Stress Levels and the Problem of Innate Scatter," Int. J. of Pressure Vessels and Piping 85:152-165.

Bead-on-plate TIG weld on 316L stainless steel plate. 4 Neutron diffraction measurements at different labs. Also 1 deep hole drilling measurement. Good to very good agreement. One profile shows contour results right in the middle of scatter of neutron and deep hole results. Another profile shows contour results on low side of scatter. This comparison is especially informative because of scatter in multiple measurements.
DeWald, AT ; Hill, MR, Eigenstrain-based model for prediction of laser peening residual stresses in arbitrary three-dimensional bodies. Part 1: model description , Journal of Strain Analysis for Engineering Design, 44(1), 1-11, 2009. U. C. Davis. Laser peened blocks, 4 thicknesses 10-40 mm. 316L stainless steel. Slitting (crack compliance). In general quite good agreement. Not as good within 2 mm of the surface (surface stresses are difficult with contour.)

Download pdf (26 MB) Johnson, G, 2008, "Residual stress measurements using the contour method," Ph.D. Dissertation, University of Manchester, School of Materials.

(results not published elsewhere listed here)

Chapter 6: Hoop stress in inertia friction welded cylinders of Aermet 100 (ultra high strength steel) to SCMV (Super Chromium Molybdenum pressure Vessel Steel)

Chapter 7: Linear friction welded Ti-6Al-4V, one as welded and two different heat treatments.

Neutron diffraction.

 

 

Synchrotron diffraction.

After correcting for cutting artifacts, good agreement. See this publication on the issue of measuring hoop stresses in cylinders - a two cut process works better.

Very good agreement. Johnson developed a nice process for processing data with very high local gradients and smooth variations elsewhere. Best validation for such a situation.

Dennis, R. J., Bray, D.P., Leggatt, N.A., Turski, M. , 2008, "Assessment of the Influence of Plasticity and Constraint on Measured Residual Stresses Using the Contour Method." 2008 ASME Pressure Vessels and Piping Division Conference, Chicago, IL, USA, PVP2008-61490. Frazer-Nash Consultancy and U. Manchester. 3 pass groove weld. 316L Austenitic stainless steel. Results from Kartal et al. study. Neutron diffraction. Results on a region with poor agreement were simulated with FEM to explain errors as a result of plasticity. May actually also have a bulge effect.
M.E. Kartal, C.D.M. Liljedahl, S. Gungor, L. Edwards, M.E. Fitzpatrick, "Determination of the profile of the complete residual stress tensor in a VPPA weld using the multi-axial contour method," Acta Materialia, 56(16), 4417-4428, 2008. The Open University Variable-Polarity Plasma-Arc (VPPA) autogenous butt weld. 2024-T351 Aluminum plate Neutron diffraction. Mostly very good agreement for longitudinal stresses. 17 MPa rms disagreement! Some disagreement at one edge (bulge error?). Also good agreement for transverse stresses to verify DeWald/Hill multiaxial method, but those stresses are quite small.
Richter-Trummer, V., Tavares, S. M. O., Moreira, P. M. G. P. et al. "Residual stress measurement using the contour and the sectioning methods in a MIG weld: Effects on the stress intensity factor." Ciência & Tecnologia dos Materiais, 20(1-2), p.114-119, 2008. U. Porto Single MIG weld bead on a thin plate of 6082-T6 Aluminum. Sectioning. Very good agreement, 1-D stress profile only.
Withers, P.J.; Turski, M.; Edwards, L.; Bouchard, P.J.; Buttle, D.J., "Recent advances in residual stress measurement," Int. J. of Pressure Vessels and Piping, 85, 118-127, 2008. U. of Manchester et al.

Single bead on plate weld. 316H Stainless steel.

Neutron diffraction. Agreement was very good over half of the profile but differences as much as 100 MPa elsewhere. Could be a bulge error in contour results.
Download preprint W. Woo, H. Choo, M. B. Prime, Z. Feng, and B. Clausen, “Microstructure, texture and residual stress in a friction-stir-processed AZ31B magnesium alloy,” Acta Materialia, 56(8), 1701-1711, 2008. Friction stir weld (or friction stir processed) Magnesium AZ31B Neutron diffraction. Agreement was good, generally within uncertainty but not always. There were ambiguities in interpreting the neutron diffraction results due to texture.
A. Evans;  G. Johnson;  A. King; P. J. Withers, "Characterization of laser peening residual stresses in Al 7075 by synchrotron diffraction and the contour method," J. of Neutron Research, 15(2), 147 - 154, 2007. U. of Manchester. Also with more details in Johnson thesis (pdf). 2 Laser peened plates- 1 single location and 1 overlapping. 7075-T351 Aluminum. Synchrotron diffraction using a plane stress assumption. Agreement was good. Synchrotron stresses tended to be 50 MPa more compressive (could be d0), and shifted a little (could be bulge). Agreement was good all the way to surface because of careful work on contour.
H. Nasri, J. Lanteigne, and H. Champliaud, "Usage of the Contour Method in Measuring Residual Stress in Welding and Peen-Welding Applications," Proc. of the IASTED Asian Conference: Modelling and Simulation, Beijing, China, 2007, ISBN CD 978-0-88986-701-7, Paper 571-801. École de technologie supérieure (U. Québec) and Institut de recherche d’Hydro-Québec. A516 carbon steel plates welded in a V-groove and then one plate hammer peened. Hole drilling. About 5 points taken across the weld bead on the surface. Hole depth is not stated. Agreement is good. Contour does not measure surface stresses well, so one should not expect too much. Stresses were very high, so plasticity errors possible for hole drilling and contour.
Download preprint Prime, M. B., Gnäupel-Herold, T., Baumann, J. A., Lederich, R. J., Bowden, D. M., Sebring, R.J., "Residual Stress Measurements in a Thick, Dissimilar Aluminum Alloy Friction Stir Weld,” Acta Materialia, 54(15), 4013-4021, 2006. Friction stir weld butt joint in 25 mm thick plates of 2024-T351 and 7070-T7451 Aluminum. Neutron diffraction. Agreement is excellent in weld region especially considering the low stresses (< 40 MPa). 20 MPa difference in base material, which may have intergranular stresses.
download preprint Kartal, M ; Turski, M ; Johnson, G ; Fitzpatrick, ME ; Gungor, S ; Withers, PJ ; Edwards, L, "Residual stress measurements in single and multi-pass groove weld specimens using neutron diffraction and the contour method," Materials Science Forum, Vols. 524-525, pp. 671-676, 2006. The Open University and U. of Manchester. 1 and 3 pass groove weld. 316L Austenitic stainless steel. Neutron diffraction. Good general agreement, but not everywhere. Some of the disagreement is attributed to how the contour data was processed. See Dennis et al. for more results from this study with larger disagreement.
download from publisher Y. Zhang, S. Pratihar , M. E. Fitzpatrick and L. Edwards, ‘Residual stress mapping in welds using the contour method', Mater. Sci. Forum , 490, 294-299, 2005. The Open University. Bead-on-plate metal arc weld. 316L Austenitic stainless steel. Neutron diffraction at only 7 points. Trends are same, neutron results are higher by 50 MPa. Reference lattice parameter (d0) errors for neutron could be part of that. The authors also report some cutting difficulties which may have affected contour.
Zhang, Y.; Ganguly, S.; Edwards, L.; Fitzpatrick, M.E., "Cross-sectional mapping of residual stresses in a VPPA weld using the contour method," Acta Materialia, 52(17), pp. 5225-5232, October 2004. The Open University. Variable-polarity plasma-arc (VPPA) weld. 2024-T351 Aluminum. Synchrotron and neutron. Independent of each other. Agreement is good. Contour is mostly right in the middle of the scatter between neutron and synchrotron. All 3 methods agree/disagree about equally.
download preprint M. B. Prime, R. J. Sebring, J. M. Edwards, D. J. Hughes, P. J. Webster, "Laser Surface-Contouring and Spline Data-Smoothing for Residual Stress Measurement," Experimental Mechanics, 44(2), pp. 176-184, April 2004. TIG weld using filler metal. BS 4360 Grade 50D ferritic steel. Neutron diffraction (reactor using 211 reflection) Agrees quite well but not perfectly. Neutron and contour were done on different sections of long specimen. Unfortunately, neutron round robin results were only published for one strain component. It would be nice to see how much scatter there was.
Zhang, Y., Ganguly, S., Stelmukh, V., Fitzpatrick, M. E., and Edwards, L., "Validation of the Contour Method of Residual Stress Measurement in a MIG 2024 Weld by Neutron and Synchrotron X-Ray Diffraction," J. of Neutron Research, 11(4), pp. 181-185, 2003. The Open University.

MIG Butt weld (double V). 2024-T351 Aluminum

Synchrotron (measure 2 strains, assume uniaxial stress). Also some neutron results. Agreement is quite good. Trends and magnitudes are same, but synchrotron results have bigger amplitude variations. Contour data was possibly over-smoothed.
download preprint M. B. Prime, "Cross-Sectional Mapping of Residual Stresses by Measuring the Surface Contour After a Cut," Journal of Engineering Materials and Technology, 123, pp. 162-168, 2001.

Plastically bent beam. 21Cr-6Ni-9Mn austenitic stainless steel. (Nitronic 40).

Experimentally determined during bending from strains and loads. Agrees well. Contour peak stresses are slightly lower magnitude, but within uncertainty of "known" stresses.

There are some trends in the differences that are caused by contour systematic errors or other issues:

  • As stresses are released, stretching or compressing of the material right in from of the cut causes an error that can shift contour results a little (like a phase shift) and reduce stress magnitudes. Good restraint can usually keep this error below 5-10 %. Sometimes called a "bulge" error. Tends to accumulate some as cut gets deeper - so error depends on cut direction. Look for a future publication on this. See
    download preprint M. B. Prime and A. L. Kastengren, "The Contour Method Cutting Assumption: Error Minimization and Correction" Proceedings of the SEM Annual Conference & Exposition on Experimental and Applied Mechanics Indianapolis, Indiana USA, Society for Experimental Mechanics Inc., June 7 - 9, 2010, paper # 507 (LA-UR-10-1605)
    .

  • Plasticity at the cut tip can cause errors. Depends on stress magnitude and cyclic yield strength. Good restraint reduces this error. Hard to distinguish from the error in previous bullet.
  • Contour does not generally measure surface stresses well because of difficulty getting a perfect cut and good data right up to the edge of the surface. One must also use special care processing the data. Most careful study done by Alex Evans and Greg Johnson shows that you can get good results as close as 100 µm from surface with careful experiment and analysis.

 

 

 

 

 

 

 

 

 

 

 

 

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contact: Mike Prime at prime@lanl.gov | Copyright & Disclaimer
U.S. patent 6,470,756 | Last Modified: July 28, 2017

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