Papers by Author: Cristy Leonor Azanza Ricardo

Abstract: Tool steel (X155CrVMo121KU in the following UK15) samples were analyzed to determine the in-depth residual stress profile and to study modifications in the microstructure, induced by a shot-peening treatment. The influence of different tempering temperatures was studied. Residual stress and dislocation density profiles were measured using standard laboratory X-ray diffraction (XRD) residual stress analysis with progressive chemical layer removal. Dislocation density profiles where obtained using a Whole Powder Pattern Modeling (WPPM) procedure.

Abstract: Aluminum alloy (Al-7075-T6) samples were analyzed to determine the in-depth residual stress profile induced by a shot-peening treatment. The influence of coverage degree and Almen intensity on the surface residual stress and on the sub-surface residual stress gradient was investigated. Residual stress profiles were obtained using three different techniques: (i) standard laboratory X-ray diffraction (XRD) residual stress analysis with progressive chemical layer-removal; (ii) XRD residual stress analysis with synchrotron radiation using different X-ray energies, thus changing the penetration depths, and (iii) Blind Hole Drilling (BHD). A comprehensive comparison of the results given by the used techniques is shown.

Abstract: The main instrumental characteristics of MCX, the new beamline at the Italian synchrotron Elettra in Trieste, are presented. Design and geometrical set-up are well suited to the X-ray diffraction stress and texture analysis of thin films and surfaces, and are such to guarantee a full control of the main instrumental errors. Besides exploiting the typical features of synchrotron radiation, like high brilliance, tuneable beam energy and optimal beam geometry, MCX can also host tools for in-situ studies, like X-ray diffraction during four point bending. A few examples of current applications are shown.

Abstract: The residual stress profile in a shot-peened Al alloy component was studied by a recently proposed method based on the known procedure of progressive thinning and X-ray Diffraction measurements. The effect the cyclic stress on the fatigue life was studied in detail, showing the correlation between nominal load and residual stress relaxation. Besides showing the expected decrease of compressive stress with the load and number of cycles, the present work highlights the importance of changes in the through-the-thickness residual stress distribution.

Abstract: A new software was developed for the X-ray stress analysis of textured materials, especially useful in the case of thin films and coating. Literature data for a sputtered Cu thin film were used as a test case. Good agreement with the published results was found considering a grain interaction mechanism based on the combination of four models (Ruess/Voigt/Vook-Witt/inverse Vook-Witt). A similar value for the in-plane residual stress was obtained by the Eshelby-Kröner model, by optimizing the grain aspect-ratio. Main features and numerical/graphic output are briefly discussed.

Abstract: A new algorithm is proposed to determine the through-thickness residual stress gradient by X-ray Diffraction measurements on progressively thinned components. The procedure is based on a chemical or electrochemical attack of the component surface, which is then measured at each thinning stage. The simple algorithm provided for by a specific norm has been revised to take into account the X-ray absorption effects and the conditions of mechanical equilibrium of the component. The new procedure is illustrated for a typical case of study concerning a shot-peened metal component.