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Micro-lattice structures with variable strut diameter
Brulík, Karel ; Jaroš, Jan (referee) ; Červinek, Ondřej (advisor)
Due to their specific properties, micro-lattice structures have a great potential for use in energy absorption applications. It turns out that conventional micro-lattice structures with constant volume fraction can be designed for a known amount of absorbed energy. In real applications, however, we often do not know it in advance. Therefore, the use of functionally graded micro-lattice structures, which can be designed for a wider range of applied energies, appears to be more promising. The aim of this work is to compare micro-lattice structures with variable strut diameter made from 316L stainless steel by Selective Laser Melting technology in terms of energy absorption capability. For this purpose, two types of structures, F2BCC and F2BCC_45, were fabricated, both in configuration with constant, continuously variable and stepwise variable strut diameter. The structures were subsequently dynamically loaded using a drop-weight test, the results of which were described by the time history of deformation and forces. The greater amount of absorbed energy was measured for structures of type F2BCC_45, up to 73 % depending on the configuration of the structures. The results revealed that the variable strut diameter does not have a large effect on the amount of absorbed energy, but it significantly reduces the shock generated, up to 54 % depending on the type and configuration of the structure. This thesis provides a comprehensive view of the deformation and stress characteristics of both types of structures, and in particular a comparison of the effect of variable strut diameter.
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Comparison of micro-lattice structures for energy absorption
Koban, Tomáš ; Vrána, Radek (referee) ; Červinek, Ondřej (advisor)
Additively manufactured metal micro-structures have great potential in energy absorption applications. The recent research in this field led to a much better understanding of failure behaviour of these micro-structures. This thesis focuses on comparison of energy absorption ability of strut-based micro-lattice structures manufactured by selective laser melting depending on their topology and basic material. Energy absorption of three types of lattice structures (BCC, BCCZ, GBCC) made from stainless steel 316L and aluminium alloy AlSi10Mg was examined. Specific energy absorption was used to compare the two materials. The results show that micro-lattice structures made from stainless steel outperform the aluminium ones in energy absorption ability. The highest amount of absorbed energy was measured for BCCZ structure. This thesis describes the failure mechanism of micro-lattice structures and offers a complex evaluation of energy absorption for both materials.
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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.
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Impact loading of lattice structures produced by Selective Laser Melting technology from magnesium alloy WE43
Foltán, Tomáš ; Červinek, Ondřej (referee) ; Jaroš, Jan (advisor)
Strut-based lattice structures manufactured with magnesium alloy WE43, due to their high strength-to-weight ratio, seem like an ideal solution for biomedical and aerospace industries. Previous research has focused mainly on the behaviour of these structures under quasi-static stress conditions. Dynamic stressing of these structures has not been deeply researched. Therefore, this work deals with impact testing of strut-based lattice structures manufactured by SLM. Low-velocity impact tests were performed on a set of cell topologies with different strut diameters. Absorbed energy, stress-strain curve, and deformation mechanism of each sample were studied. Clear effect of cell topology on the amount of absorbed energy was observed, where structures of similar relative densities displayed considerably different values. Highest specific absorbed energy was achieved with the FCCZ cell. In comparison with other materials (e.g., steel) magnesium proved to be far less efficient. This was most probably caused by its brittle fracture failure mode. Conducted tests give insight into mechanical behaviour of magnesium alloy structures under dynamic compression and their ability to absorb energy. Collected data may prove useful for biomedical applications e.g., in designing bone implants.
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Micro-lattice structures with variable strut diameter
Brulík, Karel ; Jaroš, Jan (referee) ; Červinek, Ondřej (advisor)
Due to their specific properties, micro-lattice structures have a great potential for use in energy absorption applications. It turns out that conventional micro-lattice structures with constant volume fraction can be designed for a known amount of absorbed energy. In real applications, however, we often do not know it in advance. Therefore, the use of functionally graded micro-lattice structures, which can be designed for a wider range of applied energies, appears to be more promising. The aim of this work is to compare micro-lattice structures with variable strut diameter made from 316L stainless steel by Selective Laser Melting technology in terms of energy absorption capability. For this purpose, two types of structures, F2BCC and F2BCC_45, were fabricated, both in configuration with constant, continuously variable and stepwise variable strut diameter. The structures were subsequently dynamically loaded using a drop-weight test, the results of which were described by the time history of deformation and forces. The greater amount of absorbed energy was measured for structures of type F2BCC_45, up to 73 % depending on the configuration of the structures. The results revealed that the variable strut diameter does not have a large effect on the amount of absorbed energy, but it significantly reduces the shock generated, up to 54 % depending on the type and configuration of the structure. This thesis provides a comprehensive view of the deformation and stress characteristics of both types of structures, and in particular a comparison of the effect of variable strut diameter.
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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.
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Comparison of micro-lattice structures for energy absorption
Koban, Tomáš ; Vrána, Radek (referee) ; Červinek, Ondřej (advisor)
Additively manufactured metal micro-structures have great potential in energy absorption applications. The recent research in this field led to a much better understanding of failure behaviour of these micro-structures. This thesis focuses on comparison of energy absorption ability of strut-based micro-lattice structures manufactured by selective laser melting depending on their topology and basic material. Energy absorption of three types of lattice structures (BCC, BCCZ, GBCC) made from stainless steel 316L and aluminium alloy AlSi10Mg was examined. Specific energy absorption was used to compare the two materials. The results show that micro-lattice structures made from stainless steel outperform the aluminium ones in energy absorption ability. The highest amount of absorbed energy was measured for BCCZ structure. This thesis describes the failure mechanism of micro-lattice structures and offers a complex evaluation of energy absorption for both materials.
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Energy absorption of cellular foams in high strain rate compression test
Králík, V. ; Němeček, J. ; Jíra, A. ; Fíla, Tomáš ; Zlámal, P.
Aluminum foams are structural materials with excellent energy absorption capacity jointed with very low specific weight and high stiffness. Products of aluminum foams are used in a wide range of structural and functional applications (e.g. as a part of composite protection elements) due to its attractive properties. Full characterization of deformation behaviour under high-strain rate loading is required for designing these applications. The aim of this study is to compare stress-strain behaviour and energy absorption of the aluminium foam structure with conventional energy absorbing materials based on polystyrene and extruded polystyrene commonly used as protective elements. The compressive deformation behaviour of the materials was assessed under impact loading conditions using a drop tower experimental device.
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