Nondestructive residual stress depth profile analysis at the inner surface of small boreholes using energy-dispersive diffraction under laboratory conditions

Abstract

Energy-dispersive diffraction under both laboratory and synchrotron conditions was applied to study the hoop stress in the near-surface region of the inner wall of boreholes with a small diameter of 2 mm. By use of different X-ray beam cross sections for the sin2ψ measurements, it is demonstrated that the borehole-to-beam-diameter ratio must be considered in the evaluation. A beam cross section which is comparable to the borehole diameter reduces the slope of the d hkl φψ–sin2ψ distributions and thus invalidates the result of stress analysis. A quantitative relationship is applied, which allows the results obtained under the above conditions to be scaled so that they reflect the actual residual stress state at the measurement position. Owing to the small diffraction angles, energy-dispersive diffraction proves to be the only suitable experimental technique that allows a nondestructive and depth-resolved analysis of the hoop stress component at the inner surface of boreholes with a large length-to-diameter ratio.

A novel approach for nondestructive depth-resolved analysis of residual stress and grain interaction in the near-surface zone applied to an austenitic stainless steel sample subjected to mechanical polishing

“…Bremsstrahlung can be used due to an important breakthrough achieved recently in development of laboratory diffraction by the application of Metal Jet X-ray tubes, in which the anode consists of liquid metals (e.g. 80 % of gallium and 20 % of indium) [81,82]. Due to the wide energy spectrum (up to 72 keV used in [82]) and very high intensity of the produced X-rays this equipment is nowadays suitable for many methods which were previously used only with synchrotron radiation, including the Laplace space methods [82].…”

“…80 % of gallium and 20 % of indium) [81,82]. Due to the wide energy spectrum (up to 72 keV used in [82]) and very high intensity of the produced X-rays this equipment is nowadays suitable for many methods which were previously used only with synchrotron radiation, including the Laplace space methods [82]. It is worth noting, that there are alternative ways of development methodologies presented in this work.…”

Energy-dispersive X-ray stress analysis under geometric constraints: exploiting the material's inherent anisotropy

“…On the other hand, there is a high demand for such measurements, especially from industry, since failure-critical residual stresses are often expected at positions featuring strong concave curvatures, such as the tooth base of gears, sharp bends in formed components or the inner wall of boreholes. For this last case, we have recently presented an evaluation concept based on energy-dispersive (ED) diffraction (Genzel et al, 2021) which takes into account the influence of the strongly curved surface but still allows the use of the sin 2 method (Macherauch & Mu ¨ller, 1961) due to the very small diffraction angles. However, for measurement points in notches and other positions with a very small opening angle, the sin 2 -based measurement and evaluation strategies are no longer applicable.…”