National Repository of Grey Literature 7 records found  Search took 0.01 seconds. 
Estimation of mechanical parameters of thin films using finite element analysis
Tinoco Navaro, Hector Andres ; Holzer, Jakub ; Pikálek, Tomáš ; Buchta, Zdeněk ; Lazar, Josef ; Chlupová, Alice ; Kruml, Tomáš ; Hutař, Pavel
This study shows a methodology to estimate mechanical parameters of thin films by means of a bulge\ntest and a numerical approach. The methodology is based on the combination of finite element analysis with a\nclassical analytical method. Finite element modelling was conducted for monolayer (Si3N4) membranes of 2x2mm\nwith the aim to approximate both the load-deflection curves experimentally measured and the classical loaddeflection\nanalytical model. Error functions were constructed and minimized to delimit a coupled solution space\nbetween Young’s modulus and Poison’s ratio. In a traditional bulge test analysis only one of the elastic properties\ncan be determined due to that there is not unique solution in the estimations of these parameters. However, both\nelastic parameters were determined through the proposed numerical procedure which compares the deformed\nsurfaces for a specific set of optimal elastic parameters computed. Results shows that the estimated elastic\nproperties agree with corresponding values determined by other methods in the literature
Measurement of mechanical properties of thin films using the bulge test technique
Holzer, Jakub ; Cieslar, Miroslav (referee) ; Kruml, Tomáš (advisor)
Main objective of this diploma thesis is to finish a construction of the Bulge test apparatus for measurement of thin films, perform first tests on commercially available Si3N4 membranes and bilayer membrane with aluminium. First part of the thesis is focused mainly on literature review of current knowledge regarding this topic and other methods of thin films testing. Experimental part deals with construction of apparatus, methodology of data evaluation and results of the measurement. The thin films of interest are fabricated as amorphous silicon nitride or bilayer of mentioned nitride and either aluminium, titanium or Ta-B-C layer. The apparatus has been built in house in collaboration with Institute of Scientific Instruments of CAS. Both reliability and repeatability of this method has been tested on over 160 measurements of commercially available membrane. The results of measurements are compared with literature and nanoindentation test. More detailed data analysis is currently under development with colleagues at Institute of Physics of Materials. It has been proven beyond doubt that Bulge test method and constructed apparatus are suitable for the measurement of several mechanical properties of thin films.
Development of the bulge test equipment for measuring mechanical properties of thin films
Holzer, Jakub ; Pikálek, Tomáš ; Buchta, Zdeněk ; Lazar, Josef ; Tinoco, H.A. ; Chlupová, Alice ; Kruml, Tomáš
The bulge test apparatus designed for the measurement of mechanical material properties of thin films was constructed and tested. The principle of the test is to apply pressure on a free-standing membrane, to measure the membrane shape and to analyse the results. Commercially available silicon nitride (Si3N4) thin films were used for the testing. It is shown that interferometric set-up designed and assembled for the apparatus enables precise determination of 3D shape of the whole membrane, which allows more precise determination of materials parameters compared to measurement of the height of the center of the membrane only. Fit of an analytical formula gives values of Young modulus and residual stress with very good agreement with the literature data. Moreover, FEM model of the bulged membrane was developed. The main aim of the effort is to enable measurement of plastic properties of a thin film of interest, that will be deposited on the Si3N4 membrane with known properties and bulge test will be performed on the bilayer specimen. Subsequently, the material properties of the thin film will be obtained using FEM analysis.
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.
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.
Correlation of standard mechanical test results and small punch test results
Holzer, Jakub ; Němec, Karel (referee) ; Válka, Libor (advisor)
The Bachelor’s thesis is aimed to sum up relations of mechanical properties of metallic materials obtained by standard mechanical tests with material properties obtained by small punch test. Methods and procedures used to evaluate material properties are evaluated and influence of external circumstances is analysed. Most important difficulties, that limit correlation of standard mechanical tests results and small punch test results, are also stated. Thesis contains an experimental validation of few selected correlation formulas.
Design of micro stereo system
Holzer, Jakub ; Křenek, Ladislav (referee) ; Sládek, Josef (advisor)
This bachelor’s thesis deals with an analyse and design of the audio microsystem belonging to middle or upper class With an emphasis on its utility, intuitive control, ergonomic solution and inovative approach to the design.

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