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47 results on '"Vrána, Miroslav"'

5. Residual Stress Distribution Analysis in Advanced Materials by Neutron Diffraction: The Case of Spherical Storage Tank Butt Weld

Author

Hervoches Charles, Vrána Miroslav, Mikula Pavol, Mráz Ľuboš, Baksa Peter, and Baláž Milan

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

The two-axis diffractometer SPN-100 at the Center of Accelerators and Nuclear Analytical Methods (CANAM) in Řež, is a neutron diffraction instrument dedicated to residual stress analyses in polycrystalline materials, it has recently been equipped with a new two-dimensional position sensitive detector (2D-PSD) and a six-axis robotic arm for sample positioning. Recent results of strain/stress distribution measurements with the upgraded tools are presented. The measured materials are made of C-Mn unalloyed steel used for spherical storage tank. Welding-induced residual stresses have direct influence on ductility and toughness of both weld metal and heat affected zone of the weld area, which affect the service life time of structures. Normal, transversal and longitudinal components of the stresses obtained in the vicinity of the butt weld from a spherical storage tank were measured by neutron diffraction at CANAM.

Published
2019
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21. Neutron Diffraction Studies of Residual Stress Distribution in the Vicinity of the Single Pass Fillet Steel Welds

Author

Mráz, Lubos, Karlsson, Leif, Vrána, Miroslav, Mráz, Lubos, Karlsson, Leif, and Vrána, Miroslav

Abstract

In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds, which were carried out at different welding conditions, namely, with different filler materials are presented.

Published
2015
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23. Residual stress distribution measurement by neutron diffraction of the single pass fillet steel welds

Author

Mráz, Lubos, Karlsson, Leif, Vrána, Miroslav, Mikula, Pavol, Mráz, Lubos, Karlsson, Leif, Vrána, Miroslav, and Mikula, Pavol

Abstract

In this contribution the results of residual strain/stress measurements performed on several single pass fillet steel welds which were carried out at different welding conditions, namely, with different filler materials are presented.

Published
2014

44. Analytical model for neutron diffraction peak shifts due to the surface effect.

Author

Šaroun, Jan, Kornmeier, Joana Rebelo, Hofmann, Michael, Mikula, Pavol, and Vrána, Miroslav

Subjects
NEUTRON diffraction, SURFACE chemistry, RESIDUAL stresses, GAGES, MONOCHROMATORS, COLLIMATORS
Abstract

Residual strains measured by neutron diffraction near sample boundaries can be biased by the surface effect as a result of incomplete filling of the instrumental gauge volume. This effect is manifested as anomalous shifts of diffraction lines, which can be falsely interpreted as a lattice strain unless appropriate data corrections are made. A new analytical model for the surface effect has been developed, which covers a broad variety of instrumental arrangements, including flat mosaic and bent perfect crystal monochromators, narrow slits, and Soller and radial collimators. This model permits the spurious peak shifts to be predicted quantitatively, and also allows the optimum configuration parameters, such as curvature of a focusing monochromator, which lead to suppression of the surface effect, to be calculated. The model has been thoroughly validated by comparisons with Monte Carlo simulations and experiments on a stress-free calibration sample. Predictions of the model proved to be very accurate, often within the interval of experimental errors, which makes it suitable for use in data analysis. [ABSTRACT FROM AUTHOR]

Published
2013
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45. Neutron Diffraction and Acoustic Emission Study of Mg-Al-Sr Alloy Reinforced with Short Saffil® Fibers Deformed in Compression

Author

Farkas, Gergely, Máthis, Kristián, Lukáš, Petr, Pilch, Jan, Vrána, Miroslav, Janeček, Miloš, and Trojanová, Zuzanka

Abstract

Neutron diffraction method has been applied in the ex-situ investigation of the residual stresses in Mg-5wt.%Al-1 wt.%Sr (AJ51) magnesium alloy reinforced with short Saffil® fibers deformed in compression at room temperature. The residual stresses were measured in the axial and radial directions with respect to the load direction. It is shown that in the initial state the tensile stress is present in the matrix phase. The in-situ acoustic emission measurements were performed with the aim to reveal the main deformation mechanisms operating in the particular stages of the plastic deformation. Ex-situ neutron diffractions experiments showed that the tensile axial residual stress in the matrix increases with increasing plastic deformation while the radial residual stress decreases. In situ acoustic emission measurements indicate that the main deformation mechanisms are twinning and glide of bigger dislocation ensembles in the early stages of the compressive deformation while the fibers breakage was observed in the vicinity of the maximum stress.

Published
2014
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