|
|
Computational analysis of auxetic structures application potential in impact absorbers
Dohnal, Jakub ; Skalka, Petr (referee) ; Ševeček, Oldřich (advisor)
Master thesis deals with the analysis of the application potential of auxetic materials in the field of shock absorption (absorption of impact energy). Due to their cellular structure and specific geometry, these materials are characterized by a negative Poisson’s ratio, which means that they are able to reduce their transverse dimension under compressive stress in the longitudinal direction. The aim of this work is to use this interesting property for the absorption of kinetic energy. After the introduction, devoted to the theoretical basis and research in the field of auxetic structures, a numerical FEM model is described in detail. The task of the model is to study the mechanical response of auxetic and conventional cellular structure to an impact loading. An explicit solver in the commercial software LS-DYNA is used to numerically simulate fast processes. The results of the analyses are used to compare auxetic and conventional structures and quantify the differences in their ability to dampen the kinetic energy of the impact effectively and gently. It also serves to demonstrate the influence of individual geometric or material parameters on impact attenuation. At the end of the work, numerical simulations are confronted with available experiments in order to verify the informative value of computational models and to point out the application potential of auxetic structures in the discussion. There are also partial recommendations for their design so that they best serve the intended purpose.
|
|
|
Optimization of the safety shoe
Scholz, David ; Hrůza, Václav (referee) ; Sláma, David (advisor)
This thesis deals with designing shape modifications of a toecap used in Honeywell brand safety shoes. The thesis shows algorithm of compression test and impact test FEA in ANSYS software. The toecap was divided into areas according to von-Misses stress. Several modifications were made in all areas separately, according to design of experiments. Best of the modifications were combined together and two best combinations selected. The goals were verified by experimental testing of manufactured toecaps. The results were even a little bit better than simulations.
|
|
|
Evaluation of dynamic damage of composite structure
Štefanovič, Peter ; Jetela, Václav (referee) ; Klement, Josef (advisor)
The first part of the diploma thesis with name „Evaluation of dynamic damage of composite structure“ focuses on designing device for impact experiments and suitable laminate samples made from prepregs. The conditions and problems of impact tests are also demonstrated here. The second part of the thesis deals with non-destructive control of damaged specimens based on thermography. This is mainly the extent of defects in the impaired area and the evaluation of results using the pulse infrared thermography method. Finally, the relative deviation in the crack size comparison between the visual method and thermographic are compared. Consequently, the residual strength of the damaged samples against undamaged specimens are compared using bending tests.
|
|
|
Charpy tests of load measuring pins from ČSN 19 312 material
Šperl, Martin ; Gajdoš, Lubomír ; Bejdl, Jan
Charpy tests of load measuring pins from ČSN 19312 steel were carried out at the temperature 20 °C, 0 °C, -20 °C, and\n-40 °C with the aim to verify that Charpy notch toughness of the pins keeps its average magnitude even at -40 °C. The results showed that the steel did not exhibit a typical S-type transit curve in the temperature range 20 °C ÷ -40 °C due to which the Charpy notch toughness at -40 °C practically did not differ from that at higher temperatures.
|
|
|
Computational analysis of auxetic structures application potential in impact absorbers
Dohnal, Jakub ; Skalka, Petr (referee) ; Ševeček, Oldřich (advisor)
Master thesis deals with the analysis of the application potential of auxetic materials in the field of shock absorption (absorption of impact energy). Due to their cellular structure and specific geometry, these materials are characterized by a negative Poisson’s ratio, which means that they are able to reduce their transverse dimension under compressive stress in the longitudinal direction. The aim of this work is to use this interesting property for the absorption of kinetic energy. After the introduction, devoted to the theoretical basis and research in the field of auxetic structures, a numerical FEM model is described in detail. The task of the model is to study the mechanical response of auxetic and conventional cellular structure to an impact loading. An explicit solver in the commercial software LS-DYNA is used to numerically simulate fast processes. The results of the analyses are used to compare auxetic and conventional structures and quantify the differences in their ability to dampen the kinetic energy of the impact effectively and gently. It also serves to demonstrate the influence of individual geometric or material parameters on impact attenuation. At the end of the work, numerical simulations are confronted with available experiments in order to verify the informative value of computational models and to point out the application potential of auxetic structures in the discussion. There are also partial recommendations for their design so that they best serve the intended purpose.
|
|
|
Influence of composition and fabric of volcanic rocks on their technological properties
Krutilová, Kateřina
Because of a very variable geological composition of the Czech Republic, there is a various scale of all genetic types of rocks that are used for the production of crushed stone. The most often used group of rocks are effusive magmatic rocks, which represent about 34 % of crushed stone marketed (Starý et al. 2010). These rocks are used for all kinds of construction purposes including roads. The experimental material of crushed stone used in this thesis was sampled from 40 active quarries in the Czech Republic. The studied volcanic rocks originated from Neoproterozoic and Paleozoic complexes of Barrandien, Carboniferous and Permian of Krkonose Piedmont Basin, Carboniferous and Permian of Intrasudetic basin, area of ordovician Železné Hory, from the main volcanic center of Bohemian Massif in the north-west Bohemia (České středohoří Mts. and Doupov Mts.), Neovolcanic area of Czech Cretaceous basin and area of Neovolcanic East and West Sudeten. Petrographic study was carried out in a form of standard petrographic analysis of thin sections and chemical analysis, which helped inclusion of rocks to a classified systems. The whole suite of volcanic rocks was separated to five petrographic-technologic subgroups defined as: (1) rhyolites / porphyres, (2) phonolites, (3) basalts s.l., (4) spilites and (5)...
|
|
|
Optimization of the safety shoe
Scholz, David ; Hrůza, Václav (referee) ; Sláma, David (advisor)
This thesis deals with designing shape modifications of a toecap used in Honeywell brand safety shoes. The thesis shows algorithm of compression test and impact test FEA in ANSYS software. The toecap was divided into areas according to von-Misses stress. Several modifications were made in all areas separately, according to design of experiments. Best of the modifications were combined together and two best combinations selected. The goals were verified by experimental testing of manufactured toecaps. The results were even a little bit better than simulations.
|
|
|
Evaluation of dynamic damage of composite structure
Štefanovič, Peter ; Jetela, Václav (referee) ; Klement, Josef (advisor)
The first part of the diploma thesis with name „Evaluation of dynamic damage of composite structure“ focuses on designing device for impact experiments and suitable laminate samples made from prepregs. The conditions and problems of impact tests are also demonstrated here. The second part of the thesis deals with non-destructive control of damaged specimens based on thermography. This is mainly the extent of defects in the impaired area and the evaluation of results using the pulse infrared thermography method. Finally, the relative deviation in the crack size comparison between the visual method and thermographic are compared. Consequently, the residual strength of the damaged samples against undamaged specimens are compared using bending tests.
|
|
|
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
|
|
|
Influence of composition and fabric of volcanic rocks on their technological properties
Krutilová, Kateřina
Because of a very variable geological composition of the Czech Republic, there is a various scale of all genetic types of rocks that are used for the production of crushed stone. The most often used group of rocks are effusive magmatic rocks, which represent about 34 % of crushed stone marketed (Starý et al. 2010). These rocks are used for all kinds of construction purposes including roads. The experimental material of crushed stone used in this thesis was sampled from 40 active quarries in the Czech Republic. The studied volcanic rocks originated from Neoproterozoic and Paleozoic complexes of Barrandien, Carboniferous and Permian of Krkonose Piedmont Basin, Carboniferous and Permian of Intrasudetic basin, area of ordovician Železné Hory, from the main volcanic center of Bohemian Massif in the north-west Bohemia (České středohoří Mts. and Doupov Mts.), Neovolcanic area of Czech Cretaceous basin and area of Neovolcanic East and West Sudeten. Petrographic study was carried out in a form of standard petrographic analysis of thin sections and chemical analysis, which helped inclusion of rocks to a classified systems. The whole suite of volcanic rocks was separated to five petrographic-technologic subgroups defined as: (1) rhyolites / porphyres, (2) phonolites, (3) basalts s.l., (4) spilites and (5)...
|
guest ::
