Residual Stresses VII, ICRS7

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Authors: Bob B. He, Ke Wei Xu, Fei Wang, Ping Huang
Abstract: This paper introduces the recent progress in two-dimensional X-ray diffraction as well as its applications in microstructure and residual stress analysis. Based on the matrix transformation between diffraction space, detector space and sample space, the unit vector of the diffraction vector can be expressed in the sample space corresponding to all the geometric parameters and Bragg conditions. The same transformation matrix can be used for texture and stress analysis. The fundamental equations for both stress measurement and texture measurement are developed with the matrix transformation defined for the two-dimensional diffraction. Stress measurement using twodimensional detector is based on a direct relationship between the stress tensor and the diffraction cone distortion. The two-dimensional detector collects texture data and background values simultaneously for multiple poles and multiple directions.
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Authors: U. Welzel, Sylvain Fréour, A. Kumar, Eric J. Mittemeijer
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Authors: Makoto Hayashi, Shinobu Okido
Abstract: In the X-ray diffraction method, the diffraction intensity, the half-value width, the residual stress and the amount of residual austenitic phase can be measured. By using these parameters, the quality, the mechanical properties and the fatigue strength of materials, the remaining life of fatigue and creep can be evaluated. While the X-ray study has been widely performed for the various kinds of industrial fields in the laboratory, the applications to the actual structure and components have not so many. However, the small size X-ray residual stress analyzer, the position sensitive detector and the micro area diffraction apparatus have been developed for these twenty years. Thus the X-ray diffraction methods have been variously applied to the industrial fields. The X-ray diffraction methods were used to be applied for the large scale structures and machine parts, but recently applied to the semi-conductor fields. On the other hand, the neutron diffraction method has been introduced to measure the residual stresses in the internals of components because of its deep penetration depth. Based on the experiences of X-ray diffraction method, the various kinds of techniques have been proposed. In this paper, the applications of X-ray and neutron diffraction method to the reliability evaluations of structural components and the electronic devices are described.
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Authors: Ersan Üstündag, Robert C. Rogan, Mark R. Daymond, Nobumichi Tamura, L. Margulies, Henning Friis Poulsen
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Authors: Axel Steuwer, D.J. Hughes, Zhe Fei Chen, B. Malard, N. Ratel, M. Turski, P.J. Webster
Abstract: FaME38 is a new facility at the ILL/ESRF in Grenoble with the aim of improving the accessibility and effectiveness of neutron and synchrotron strain measurements. In addition to providing basic materials engineering facilities, it enables users from both commercial and academic backgrounds to prepare and to evaluate experiments on-site. The real success and impact of a strain scanning experiment depends on the quality of the collected data and its practical use. FaME38 provides a knowledge base and tools which can increase the efficiency of the measurement. These tools include a VAMAS standard sample base-plate, a materials support laboratory and enhanced visualisation software. The VAMAS base-plate allows pre-configuration of the sample position and set-up, as well as so-called “hot-swapping” of samples with minimum time required for re-configuration of the instrument. The visualisation tools feature web-based simulation and, in particular, 3D visualisation of both the experimental environment as well as the data. The use of the support facility can significantly reduce the set-up time, thus increasing the time available for measurement. The visualisation naturally enhances the understanding of the data and ties in with existing engineering code such as CAD/FEA software. We demonstrate how the use of additional technology can improve the effectiveness and impact of strain mapping experiments at neutron and synchrotron facilities by disseminating the workflow of a typical experiment undertaken in the FaME38 framework. This approach is aimed at paving the way toward technology-oriented application of synchrotron and neutron strain scanning.
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Authors: Yoshihisa Sakaida, Yozo Sawaki, Keisuke Tanaka, Yoshiaki Akiniwa
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Authors: P. Matos, Pedro Miguel Guimarães Pires Moreira, J.C.P. Pina, A. Morão Dias, Paulo Manuel Salgado Tavares de Castro
Abstract: Cold working introduces a compressive stress field around rivet holes, reducing the tendency for fatigue cracks to initiate and grow under cyclic mechanical loading. As it is well known, for the accurate assessment of fatigue lifetimes a detailed knowledge of the residual stress profile is required. Powerful experimental and numerical tools are nowadays available for that purpose. In the present work both types of tools, X-ray diffraction and 3D Finite Element Analysis (FEA), were used in order to evaluate the residual stress profile. A comparison of experimental and numerical data is presented and discussed.
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Authors: Clemens Franz, Gerhard Besserdich, Volker Schulze, Hermann Müller, Detlef Löhe
Abstract: The field of heat treatment of steels offers a large variety of applications for the use of simulation tools. It always includes the development of residual stresses and distortions. The geometry of the part, the composition of the material, the heat treatment process as well as the initial state of the part interact with each other in complex ways and have an influence on the distortion of the part. Using simulation the temporal development of temperature, phases, stresses and distortions while quenching as well as the residual stress distribution and distortion after quenching can be calculated. Transformation plasticity has been proved to be very important for heat treatment simulation. Three steels with identical contents of alloying elements but different carbon contents of 0.2, 0.5 and 0.8 wt. % were analysed. The influence of transformation plasticity during the martensitic transformation on the distortions and residual stresses after quenching of cylinders made out of the three steels was analyzed in simulations and compared to experimental results.
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Authors: Dimitrios Elias Katsareas, Anastasius Youtsos
Abstract: Dissimilar metal welds are commonly found in the primary piping of pressurized water nuclear reactor power plants. The safety assessment practice for such welds requires residual stresses to be taken into consideration. In the present paper the finite element method is utilized for the simulation of the welding process and prediction of the residual stress field in a dissimilar metal weld pipe joint. Although it is common practice to develop in-house finite element codes for weld simulation, the ANSYS commercial finite element code is selected. This is mainly due to the fact that industry focuses on commercial software, since residual stress analysis procedures based on them can be readily transferred to industrial applications. A simplified 2-D axi-symmetric model, in which residual stresses are produced due to the thermo-mechanical properties mismatch during cooling of the weld, is compared with a detailed model in which the complete multi-pass welding procedure is simulated. The latter incorporates the “birth & death of elements” technique, temperature dependant material properties and kinematic hardening material behavior. The aim of this comparison is to establish the degree of model detail and complexity, necessary to obtain satisfactory results and consequently to define a golden rule between computational cost and practically accurate predictions. Identifying the specific simulation parameters and variables, that have the highest impact on the accuracy of the computed results, is also important. It is concluded that, a bead-by-bead or lump-by-lump detailed simulation is necessary in order to obtain reasonably accurate residual stresses that cannot be predicted by a simplified model. A general conclusion is that the proposed method, being simple in implementation and cost effective concerning model complexity and analysis time, is a potential weld residual stress prediction tool.
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