Contour Method, Neutron Diffraction and X-Ray Diffraction

CONTOUR METHOD The contour method enables residual stress measurements in most conductive materials of virtually any geometry and performs well with a range of part thicknesses from 2 up to 600 mm, while other sample dimensions can be even larger. Such versatility enables the identification of the weakest links in solid structures, the optimisation of material processing routes as well as conducting more accurate lifting and structural integrity assessment.

NEUTRON DIFFRACTION Residual stress measurement with neutron diffraction can provides a 3-D map of the full residual stress tensor with a good resolution, in many cases, non-destructively. To perform this technique, we have access to central nuclear facilities, such as the STFC Rutherford Appleton Laboratory. With neutron diffraction, any poly-crystalline material can be measured, but it works best in solids with small grains and with minimal texture.

X-RAY DIFFRACTION Residual stress measurement by x-ray diffraction (XRD) allows a multitude of points to be non-destructively measured on a solid surface. The method is particularly suitable for determining the near-surface in-plane residual stress state. In general, the measurement depth is in the order of a few micrometres. Depth profiles can be determined by removing thin layers of material from the surface and measuring the stresses at different depths. Where deeper measurements are required, the technique can also be combined with the contour method. Incremental Centre Hole Drilling With incremental centre hole drilling (ICHD), a depth profile of the residual stresses can be determined by incrementally and carefully drilling a small hole on the surface of interest and monitoring the relaxation strains. The method is particularly suitable for determining the near-surface in-plane residual stress state. It can be combined with the contour method to determine residual stresses deep within solid structures. The technique works for any machinable material with virtually any geometry, as long as it is at least 0.5 mm thick. Synchrotron Diffraction With synchrotron diffraction, a 3-D map of the full residual stress tensor can be measured with a very high resolution (down to 50 ┬Ám), in many cases, non-destructively. To perform this technique, we have access to central nuclear facilities, such as the STFC Rutherford Appleton Laboratory. With synchrotron diffraction, any poly-crystalline material can be measured, but it works best in solids with very fine grains and with minimal texture. The structure of interest should be at least 0.1 mm in all directions and weigh no more than 1 tonne.

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