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Multiple Stress Components by Superposition

 
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Principle
   - make cut
   - measure surface
   - calculate stress
Validations
Applications
   - bent beam
   - weld plate
   - quenched steel
   - impacted plate
   - alum. forging
   - friction stir weld
   - Ti FSW
   - Railroad rails
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Residual Stress
Conferences
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download pdf Pagliaro, P. at al., 2011, "Measuring Inaccessible Residual Stresses Using Multiple Methods and Superposition," Experimental Mechanics, 51 (7):1123-1134.

Superposition

Standard contour method:

The contour method is usually used to measure only σx on the cut plane (x = 0), as shown on the left side of this figure.

equation

Superposition method for multiple stress components:

But you can measures other stress components, like σz, on the cut surface after the cut. That measurement is σzB. Superposition will let you calculate the original stress:

equation

Where you already have σzC from the FEM calculation of σx

 

indented disk

Validation specimen:

  • 60 mm diameter, 10 thick disk of Aluminum 2024-T351
  • Indented in central 10 mm to induce residual stress
  • Measured with neutron diffraction before cutting

 

x-ray measurements

Experiment:

  • Disk cut in half using wire EDM
    • With usual contour method, this measures hoop stress
  • Surface contours measured using laser scanner
  • EDM-affected layer on cut surfaces by electropolishing
  • One one cut surface (section plane in picture above), radial stresses measured using hole drilling
  • On other cut surface, radial stresses measured using x-ray diffraction (photo left)

Reconstruct radial stresses by superposition: equation

Once on each half of part:

xrayHole drilling

And the final results agree with independent neutron measurements!

Final results

 

 

 

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contact: Mike Prime at prime@lanl.gov | Copyright & Disclaimer
U.S. patent 6,470,756 | Last Modified:August 18, 2013

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