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

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.

EDDIDAT: a graphical user interface for the analysis of energy-dispersive diffraction data

EDDIDAT is a MATLAB-based graphical user interface for the convenient and versatile analysis of energy-dispersive diffraction data obtained at laboratory and synchrotron sources. The main focus of EDDIDAT up to now has been on the analysis of residual stresses, but it can also be used to prepare measurement data for subsequent phase analysis or analysis of preferred orientation. The program provides access to the depth-resolved analysis of residual stresses at different levels of approximation. Furthermore, the graphic representation of the results also serves for the consideration of microstructural and texture-related properties. The included material database allows for the quick analysis of the most common materials and is easily extendable. The plots and results produced with EDDIDAT can be exported to graphics and text files. EDDIDAT is designed to analyze diffraction data from various energy-dispersive X-ray sources. Hence it is possible to add new sources and implement the device-specific properties into EDDIDAT. The program is freely available to academic users.

Reassessment of evaluation methods for the analysis of near-surface residual stress fields using energy-dispersive diffraction

In this paper two evaluation methods for X-ray stress analysis by means of energy-dispersive diffraction are reassessed. Both are based on the sin2ψ measuring technique. Advantage is taken of the fact that the d ψ hkl –sin2ψ data obtained for the individual diffraction lines E hkl not only contain information about the depth and orientation dependence of the residual stresses, but also reflect the single-crystal elastic anisotropy of the material. With simulated examples, it is demonstrated that even steep residual stress gradients could be determined from sin2ψ measurements that are performed up to maximum tilt angles of about 45°, since the d ψ hkl –sin2ψ distributions remain almost linear within this ψ range. This leads to a significant reduction of the measuring effort and also makes more complex component geometries accessible for X-ray stress analysis. Applying the modified multi-wavelength plot method for data analysis, it turns out that a plot of the stress data obtained for each reflection hkl by linear regression versus the maximum information depth τψ=0 hkl results in a discrete depth distribution which coincides with the actual Laplace space stress depth profile σ(τ). The sensitivity of the residual stress depth profiles σ(τψ=0 hkl ) to the diffraction elastic constants ½S 2 hkl used in the sin2ψ analysis can be exploited to refine the grain-interaction model itself. With respect to the universal plot method the stress factors F ij which reflect the material's anisotropy on both the microscopic scale (single-crystal elastic anisotropy) and the macroscopic scale (anisotropy of the residual stress state) are used as driving forces to refine the strain-free lattice parameter a 0 during the evaluation procedure.

Visualizing the morphological and compositional evolution of the interface of InLi-anode|thio-LISION electrolyte in an all-solid-state Li–S cell by in operando synchrotron X-ray tomography and energy dispersive diffraction

The interfacial evolution in ASSLSB is reported.