Papers by Keyword: Residual Stress Gradients

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Authors: T. Erbacher, Michael Ott, Tilmann Beck, Otmar Vöhringer
Abstract: Al2O3 ceramic plates of diameter 166 mm and thickness 5 mm were subjected to frictional loading regimes. The resultant residual stress effect in the material was analyzed using the sin2y and AP methods based on a modified measurement condition for the pole angle y and the azimuth angle F on a 4 cycle goniometer. Furthermore, the frictional loading of the Al2O3 plates lead to clear differences in the residual stress state near the surface. An underlying correlation was observed between the residual stress state of the Al2O3 material and its residual strength with this effect being ascribed to the magnitude of frictional load applied.
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Authors: Cristy Leonor Azanza Ricardo, Mirco D'Incau, Paolo Scardi
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.
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Authors: Klaus J. Martinschitz, C. Kirchlechner, R. Daniel, G. Maier, C. Mitterer, Jozef Keckes
Abstract: A temperature behaviour of residual stresses in shot-peened steel coated with 3m CrN is characterized using in-situ energy dispersive synchrotron X-ray diffraction performed in the temperature range of 25-800°C. The samples are thermally cycled and the development of volumeaveraged residual stresses in the coating and residual stress depth gradients in the steel is characterized. The results reveal complex changes of stresses in CrN and in the substrate. The annealing results in the removal of stress gradients in the steel which starts at the temperature of about 600°C. After cooling down, there are no stresses detected in the steel. The temperature dependence of stresses in CrN is very complex and indicates the presence of phenomena like an annealing of intrinsic stresses about the deposition temperature of 350°C, a formation and a closing of micro-cracks in the tensile region and finally a stress relaxation of approximately 500 MPa after the cooling down. The presented approach allows a complex characterization of thermo-mechanical processes in coating-substrate composites and opens the possibility to understand phenomena related to the thermal fatigue of coated tools.
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Authors: Manuela Klaus, Ingwer A. Denks, Christoph Genzel
Abstract: Thin hard coatings for wear protection usually do not consist of single layers but of stacks of alternating sublayers which have to meet different demands. With respect to X-ray residual stress analysis (XSA) such multilayer systems pose a series of challenges. In addition to those problems which generally arise in thin film diffraction like small layer thickness or strong texture, neighbouring sublayers with similar chemical composition may superimpose each other, or sublayers of identical structure and composition, which contribute to the same diffraction line, are separated by other sublayers. Starting from a formalism that yields the X-ray penetration depth τ in multilayer systems of arbitrary sublayer sequences, we show how a combination of measurements using ‘conventional’ photon sources available at any X-ray lab and synchrotron radiation allowing for wavelength tuning near the TiKβ absorption edge, can be used to evaluate the residual stress state in the top sublayer stack of a hard coating multilayer system deposited by chemical vapour deposition.
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