National Repository of Grey Literature 2 records found  Search took 0.01 seconds. 
Computational modelling of the nanoindentation with Berkovich indenter
Fiala, Lukáš ; Fuis, Vladimír (referee) ; Kovář, Jaroslav (advisor)
This diploma thesis deals with computational modelling of the nanoindentation of tungsten with Berkovich indenter. In the beginning of thesis, research about nanoindentation test and Oliver-Pharr analysis is performed. The next part of thesis deals with deformation-stress analysis of the nanoindentation test with the linear-elastic model of material of tungsten and with comparison of results obtained with a diamond indenter and with an ideal rigid indenter. In the following model, plastic deformation is already considered. On the computational model with elasto-plastic model of material a sensitivity analysis of the influence of specimen and indenter dimensions and the influence of the penetration on results determined using the Oliver-Pharr analysis is performed. Furthermore, the applicability of the correction factors which were founded in the literature is assessed on this model and their exact value is determined. The last part of the work deals with the analysis of the influence of blunting of the indenter on results of the nanoindentation test and the comparison of different approaches for determining the projection of the contact surface.
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

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