High-precision neutron-diffraction measurements for the determination of low-level residual stresses in a sandstone

Strain analysis by means of neutron diffraction usually has an accuracy of about 10−4, which is far too inaccurate in view of the very low level of residual strains to be expected in most geological samples. We report a method for an improvement of the accuracy by more than an order of magnitude. Using this technique, we were able to determine quantitatively a load stress as low as 1 MPa applied to a sandstone sample. The same technique allowed us to show that there are residual stresses in the order of 1 MPa in a Cretaceous sandstone from the Elbezone.