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Residual stresses of laser-welded pressure vessel steel determined by X-ray and neutron diffraction
Trojan, K. ; Vlk, A. ; Čapek, J. ; Hervoches, Charles ; Ganev, N.
To gain insight into the quality of the laser weld, information about the residual stress state across the weld is very useful. In this contribution, the residual stress profiles for lowalloy carbon steel plates of P355NL1 grade, which were laser welded from both sides, are presented. To separate the effects of the production of plates from the welding process, the samples were annealed for stress relieving. Using X-ray and neutron diffraction, the surface and bulk RS profiles were obtained. From the obtained data, first, the difference in the character of the longitudinal (parallel to the weld axis) and the transversal component of the RS tensor can be seen. The longitudinal component has a tensile character with a maximum value approximately 500 MPa. Values and character of the transversal component vary strongly with depth and distance from the weld axis.
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Evaluation of thin discontinuities in planar conducting materials using the diffraction of electromagnetic field
Savin, A. ; Nový, F. ; Fintová, Stanislava ; Steigmann, R.
The current stage of nondestructive evaluation techniques imposes the development of new electromagnetic (EM) methods that are based on high spatial resolution and increased sensitivity. In order to achieve high performance, the work frequencies must be either radifrequencies or microwaves. At these frequencies, at the dielectric/conductor interface, plasmon polaritons can appear, propagating between conductive regions as evanescent waves. In order to use the evanescent wave that can appear even if the slits width is much smaller that the wavwelength of incident EM wave, a sensor with metamaterial (MM) is used. The study of the EM field diffraction against the edge of long thin discontinuity placed under the inspected surface of a conductive plate has been performed using the geometrical optics principles. This type of sensor having the reception coils shielded by a conductive screen with a circular aperture placed in the front of reception coil of emission reception sensor has been developed and 'transported' information for obtaining of magnified image of the conductive structures inspected. This work presents a sensor, using MM conical Swiss roll type that allows the propagation of evanescent waves and the electromagnetic images are magnified. The test method can be successfully applied in a variety of applications of maxim importance such as defect/damage detection in materials used in automotive and aviation technologies. Applying this testing method, spatial resolution can be improved.
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