Residual Stress Measurement

Stress-Space Ltd specialises in determining surface and volumetric maps of residual stress in engineered structures using the measurement technologies listed below: 

adaptive X-ray neutron diffraction contour method residual stress measurement adaptive X-ray neutron diffraction contour method residual stress measurement adaptive X-ray neutron diffraction contour method residual stress measurement adaptive X-ray neutron diffraction contour method residual stress measurement

The Contour Method

contour method residual stress measurement

Merits

  • Uses standard workshop equipment

  • Inexpensive

  • Cross-section map of direct stress

  • Resolves 2 mm length-scale stresses

  • Multiple stress components with multiple cuts and multiple methods

  • Can leverage other methods

  • Insensitive to microstructure

Limitations

  • Destructive

  • Electrical conducting materials

  • Max cut area depends on size of wire EDM machine (typically 0.6 m x 1.0 m)

  • Direct stress normal to cut face

  • Quality of wire EDM cut surface

  • Errors from elastic bulging, plasticity and data analysis

Surface Hole Drilling

 

Merits

  • ASTM E837 Standard

  • Portable for field use

  • Low cost and quick

  • In-plane stresses near to surface

  • Depth profiling up to 2 mm

  • Optical techniques available

Limitations

  • Local damage

  • Flat and smooth surfaces

  • Locations remote from geometric features

  • Plasticity errors for stresses > 60% yield

  • Needs skilled practitioner

X-ray Diffraction

x-ray diffraction residual stress pattern

Merits

  • International Standard

  • Portable for field use

  • Low cost and quick

  • No damage

  • In-plane stresses at surface

  • Depth profiling up to 1 mm

Limitations

  • Crystalline materials

  • Small grains for good sampling

  • Best for isotropic microstructure

  • Local surface curvature error

  • High surface roughness error

  • Needs skilled practitioner

Neutron Diffraction

neutron diffraction residual stress measurement

Merits

  • International Standard

  • Non-destructive

  • Can measure full stress tensor

  • Volumetric mapping

  • 35 mm steel, 100 mm Aluminium

Limitations

  • Crystalline materials

  • Expensive - needs neutron source

  • Needs zero stress reference

  • Needs skilled practitioner

Synchrotron Diffraction

Merits

  • Non-destructive

  • In-plane stresses

  • Volumetric mapping

  • Fast acquisition

  • 35 mm steel in transmission

Limitations

  • Crystalline materials

  • Expensive - needs synchrotron source

  • Needs zero stress reference

  • Data intensive

  • Needs skilled practitioner

Hybrid Methods

Limitations

  • Uncertainties can propagate

  • Needs skilled practitioner

Merits

  • Powerful combinations of methods
    (e.g. Contour + XRD)

  • More stress tensor data

  • More volumetric coverage

  • Confidence from cross-comparison of results

The Slitting Method

Merits

  • Laboratory method

  • Applicable to many materials

  • 1-D line profile of direct stress through the thickness of prismatic shaped specimens

  • Good length-scale resolution of stresses

Limitations

  • Destructive

  • Gives average stress across width

  • Plasticity error when stresses are high

  • Sensitive to data analysis