National Repository of Grey Literature 34 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Detecting plasticity in al thin films by means of bulge test
Holzer, Jakub ; Pikálek, Tomáš ; Buchta, Zdeněk ; Lazar, Josef ; Tinoco, H.A. ; Chlupová, Alice ; Náhlík, Luboš ; Sobota, Jaroslav ; Fořt, Tomáš ; Kruml, Tomáš
The Bulge test proved to be a useful tool for measuring elastic properties of thin films and\nfree standing membranes, particularly Young’s modulus and residual stress. The basic principle\nof bulge test is application of differential pressure on one side of the a membrane, measurement of\nthe shape of bulged surface as a function of pressure, in this case via laser interferometer, and\nevaluation of a pressure-deflection relationship. In this study, bilayer membrane consisting of a\nsilicon nitride supporting layer and an aluminium layer deposited by means of magnetron\nsputtering is subjected to the bulge test. The results clearly show signs of a non-linear behavior\nthat is caused by plastic deformation in the aluminium layer. Finite element analysis is being\ndeveloped to describe this behavior because analytical model using deflection of central point and\npressure relation falls apart in case of non-linearity.
Reflectivity of a mirror in XUV spectral region (46.9 nm).
Schmidt, Jiří ; Koláček, Karel ; Štraus, Jaroslav ; Frolov, Oleksandr ; Prukner, Václav ; Melich, Radek ; Psota, Pavel ; Sobota, Jaroslav ; Fořt, Tomáš
A focusing mirror as an optical element is used in our applications that require light collection (e.g. for laser ablation studies). A knowledge of the mirror reflectivity is important for determination of focused laser pulse energy, or for determination of local fluencies near the laser focus. The reflectivity of our spherical focusing mirror with(/without) multi-layer coating was measured. Reflection coefficients of this mirror in a long period of time are also reported. Further, the incidence-angle dependence of the XUV reflectivity of flat mirrors is presented as well.
SMV-2017-28: Examination of local microstructural changes caused by dynamic indentation of the nanolaminate coatings
Sobota, Jaroslav
Method of analysis of the coated materials under dynamic impact load was performed using impact tester developed at the Institute of Scientific Instrumentation in Brno. Dynamical impact testing leads to identification of deformation and fatigue mechanisms of nanostructured and nanolaminated coatings. The impact force-imprint depth dependencies were interpreted with respect to the coating microstructure and computed simulation of indentation.
Interferometrical system for bulge test thin film characterization
Pikálek, Tomáš ; Holzer, Jakub ; Tinoco, H.A. ; Buchta, Zdeněk ; Lazar, Josef ; Chlupová, Alice ; Náhlík, Luboš ; Sobota, Jaroslav ; Fořt, Tomáš ; Kruml, Tomáš
Behavior of thin film materials undergoing stress and deformation differs from bulk materials. A common method for the mechanical characterization of thin films is nanoindentation based on indenting a small tip into the material. A different approach is a bulge test technique. In this method, a differential pressure is applied on a free-standing membrane and the mechanical properties (Young’s modulus and residual stress) are calculated from the shape of the bulged membrane. In our experiments, we developed an interferometrical system for the membrane shape measurement during the bulge test.
Impact resistence on nanocomposite Mo-B-C- and W-B-C coatings deposited using magnetron sputtering technique
Fořt, Tomáš ; Grossman, Jan ; Daniel, Josef ; Sobota, Jaroslav ; Dupák, Libor ; Buršíková, V. ; Zábranský, L. ; Souček, L. ; Mirzaei, S. ; Alishahi, M. ; Vašina, P. ; Buršík, Jiří
Recently, based on attractive mechanical properties of boride and carbide based X2BC ternary compounds (X = Mo, W and Ta) they became subjects of both theoretical calculations and experimental work. In the case of stoichiometric composition, X2BC with X = Mo, W and Ta are very promising candidates for protection of cutting and forming tools due to their unusually stiffness and moderate ductility.\nIn this work we focus on nanostructured Mo-B-C and W-B-C layers grown by magnetron sputtering on high speed steel (HSS) substrates. Mechanical properties of the layers were characterized by nanoindentation experiments in both static and dynamic loading regimes. Elastic modulus, indentation hardness and fracture resistance were evaluated and discussed. The fracture resistance of both Mo-B-C and W-B-C coatings was compared using both indentation and dynamic impact tests.\n
SMV-2016-22: Investigation of the local microstructure changes of nanolaminate coatings caused by dynamical indentation
Sobota, Jaroslav
The aim of the contracted research was to study the mechanical properties of the coatings deposited on high speed steel substrate. The classification of the coatings was performed using an impact tester our own construction in a dynamic mode and enabled us to predict the behavior of the coating.\n\n
Characterisation of Nanostructure Deposited by PVD and CVD Technology
Fořt, Tomáš ; Boušek, Jaroslav (referee) ; RNDr.Vilma Buršíková, Ph.D. (referee) ; Sobota, Jaroslav (advisor)
The thesis deals with mechanical properties of thin hard wear-resistant coatings. The work presents a method of dynamic testing of thin hard coatings on a newly constructed prototype of impact wear tester. It provides a comparison with standard methods of layer testing and presents new experimental results of dynamic impact wear test of the coatings. Finally, the thesis covers preparation techniques of thin film systems deposited on various substrates and their characterization using optical and electron microscopy.
Automation and control of multilayers deposition by IBS/IBAD
Pavera, Michal ; Sobota, Jaroslav (referee) ; Urbánek, Michal (advisor)
This diploma thesis deals with the automation of the deposition process by ion beam sputtering and ion beam assisted deposition. This work contains drawings of mechanical adjustments of the deposition chamber designed to control shutter and rotation of the target using stepper motors. There are presented ways to control stepper motors and troubleshoot their exact settings. Another task is to design a system for computer control of the deposition process. There are discussed ways to control the ion sources, pressure meter, flow meter and thickness meter, and their connection to a PC via RS-232 and analog-digital converters. It is also designed control program in LabVIEW, which allow automated multilayer deposition. Last part of the thesis deals with testing automatic deposition and results are commented.
SMV-2015-33: Investigation of the local microstructure changes caused by dynamical indentation of the coatings
Sobota, Jaroslav
The aim of the contracted research was to study the mechanical properties of the coatings deposited on high speed steel substrate. The classification of the coatings was performed using an impact tester our own construction in a dynamic mode and enabled us to predict the limit load causing the coating destruction.
Study of fracture toughness and wear resistance of thin MoBC coating under dynamic conditions
Buršíková, V. ; Grossman, Jan ; Fořt, Tomáš ; Souček, P. ; Zábranský, L. ; Buršík, Jiří ; Vašina, P. ; Dupák, Libor ; Sobota, Jaroslav
The aim of the present work was to study the mechanical properties of thin amorphous MoBC coatings and MoBC coatings consisting of nanocrystalline Mo2BC embedded in amorphous MoBC matrix. The hardness of the amorphous MoBC coatings (20 GPa) is comparable with the common amorphous diamond-like carbon coatings, however their elastic modulus as well as fracture toughness and ductility are significantly higher. Magnetron sputtering of three targets, B4C, C and Mo, for MoBC was used for coatings preparation. The aim of this work was to study the mechanical and tribological properties of MoBC coatings deposited on high speed steel substrate. The classification of MoBC coatings was performed using an impact tester in a dynamic mode and enabled us to predict the limit load causing the coating destruction.

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