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Los Alamos National Laboratory The Slitting Method for Residual Stress Measurement:  : Compare
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Comparison with other residual stress measurement methods

figure showing depth ranges of methods

Depth Ranges:

The figure at right shows the depth ranges of various methods compared with (1) the depth of residual stresses produces by common manufacturing processes and (2) the depth ranges where residual stresses would likely contribute to failure mechanisms.

Crack compliance spans a very nice range of depths.


Plusses and minuses of various techniques:

Neutron Diffraction

This is the only method that can measure variation with depth nondestructively, however ...
  • It has limited resolution since it averages residual stress over a volume. For example, in our ring test the stresses of interest occurred in the first 1 mm of depth - which is difficult for neutrons to resolve.
  • You need to bring your part to a neutron source, i.e., a reactor or a spallation source.
  • Microstructural changes can make measurements difficult. Welds are especially tough.

X-ray Diffraction

  • This is nondestructive for measuring surface residual stresses.
  • If you want to measure stress variation with depth you have to etch away layers, which is very time consuming.
  • It won't work on non-crystalline materials (neither will neutrons) and is sensitive to grain size and texturing.

Hole Drilling

  • Lack of sensitivity - the strains for a given residual stress distribution are much lower than for compliance.
  • You can only measure stresses to a limited depth whereas crack compliance can measure through-thickness.

Crack Compliance (Slitting)

  • All the methods above measure both residual stress components in the surface plane, compliance only measures the component normal to the face of the cut.
  • If you are cutting into a tensile residual stress field, it is possible for the crack to propagate. It doesn't happen often but it has happened.

Contour

  • The contour method measures a full 2D stress map over the cross-section of a part. Slitting (Crack Compliance) is only 1D
  • However, it is less sensitive than slitting, so not as good for very low magnitude stresses.

Deep Hole Drilling

  • Measures all the way through very thick parts
  • Measures all three stress components in the plane. Slitting and contour only measure the component normal to the cut plane.