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 met hod for an improvement of the accuracy by more than an order of magnitude. Using this technique, we were able to determine quantitatively a load stres s 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 Cre taceous sandstone from the Elbezone. (C) 2000 Elsevier Science Ltd. All rig hts reserved.