Effects of finish turning on an austenitic weld investigated using diffraction methods

Arc welding generally introduces undesired local residual stress states on engineering components hindering high-quality performance in service. Common procedures to reduce the tensile residual stresses are post-heat treatments or mechanical surface treatments like hammering or shot-peening. Assessments of residual stress profiles of post-weld treatments underneath the weld surface are essential, especially in high safety exigency systems like pressure vessels or piping at power plants. In this study, neutron diffraction is used to determine the stress profile after finish milling of an austenitic steel weld in order to verify a chained finite element simulation predicting the final residual stress fields including milling and welding contributions. Non-destructive measurements with spatial resolutions of less than 0.2 mm within the first 1 mm from the surface were mandatory to confirm the finite element simulations of the coarse-grained austenitic material. In the data analysis procedure, the obtained near-surface data have been corrected for spurious strain effects whenever the gauge volume was partially immersed in the sample. Moreover, constraining the surface data to values obtained by x-ray diffraction and data deconvolution within the gauge volume enabled access of the steep residual stress profile within the first 1 mm

Focusing double bent crystal diffractometer in combination with PSD for SANS experiments

A new concept of medium resolution SANS measurements in a double bent crystal arrangement using fully asymmetric analyzer geometry was suggested earlier. This setup enables a positional analysis of the scattering curve and thus, to collect the whole spectrum simultaneously by a linear position sensitive detector (PSD). It is shown, on the basis of both calculations and Monte Carlo simulations, that the neutron beam can be focused at the PSD, which practically leads to the gain in angular resolution. These theoretical predictions are proved experimentally

General formula for determination of cross section from measured SANS intensities

A detailed derivation of the formula connecting measured SANS intensity with the smeared cross-section (raw-data treatment) is presented. The derivation is carried out considering also a possible high probability of the coherent small-angle scattering. The information content of the so-called transmission measurement is analyzed. The individual effects which contribute to the primary-beam attenuation as well as the different modes of the transmission measurement are described. Multiple scattering contribution to the excess of the forward scattering of the water calibration standard is discussed.</jats:p