Stress measurements by means of neutron diffraction

The method of neutron diffraction for measuring the residual stress state in the interior of crystalline materials, is studied. This method is based upon the precise determination of the distance between crystalline lattice planes. Besides the presentation of the mathematical tools necessary, an overview is given of the experimental set-up required. The solution of alignment problems and the use of the set-up for actual measurements comprise an important part of the work described. The results obtained by means of neutron diffraction are compared to those obtained by using two other stress determination methods. In the first place this is the well established experimental technique of x-ray diffraction and secondly a theoretical technique, based on finite element calculations. The results of the measurements presented have been limited to ultra low carbon steel. However, by measurements at a ceramic material it was shown that the technique can be used at any crystalline material. As far as the steel type specimens are concerned, measurements have been carried out on several quenched cylinders and on a cold rolled plate. Both types of samples possess residual stresses that are characteristic for their production process. Base on the results, an evaluation is made of the requirements for instrumentation that performs stress measurements by means of neutron diffraction with an optimum result in the shortest possible measurement time. (author). 63 refs.; 46 figs.; 11 tabs