1. Time dependent load capacity of the press fitVinko Močilnik, Nenad Gubeljak, Jožef Predan, 2025, izvirni znanstveni članek Opis: This study investigates the loading capacity of a press fit using experimental, numerical and theoretical methods. Tests on specimens with different interferences showed that the loading capacity increases over time as long as the plasticity remains at the micro level. At larger interferences, the plasticity extends to the macro level, which in the long term means a reduction in the loading capacity of the press fit due to creep. Numerical simulations using finite element modelling showed the influence of surface roughness and time-dependent effect on contact pressure and friction. Models in text books do not take in account plasticity and creep of the material in press fit. The phenomenon can lead to a weakening of the press fit over time. The results highlight the importance of optimizing the interference and surface preparation to improve the loading capacity and joint performance. The article presents an approach for calculating the press fit taking in to account the Bowden Tabor friction model and the visco-plasticity of the material used.
Ključne besede: FEM analysis, interface oversize, hub, shafts, loading creep, press fit, roughness
Objavljeno v DKUM: 08.07.2025; Ogledov: 0; Prenosov: 15
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2. Numerical study of racking resistance of timber-made double-skin façade elementsErika Kozem Šilih, Miroslav Premrov, 2022, izvirni znanstveni članek Opis: The use of a double-skin façade (DSF) is a quite new approach in the building renovation process, complementing conventional renovation strategies. A double-skin façade is an envelope wall construction that consists of two transparent surfaces separated by a cavity and can essentially improve the thermal and acoustic resistance of the building envelope. The main double-skin wall components are usually composed of a hardened external single glazing pane and a double or triple thermal insulating internal glass pane, which are connected to the frame structure. Recently, many studies have analysed the thermal and acoustic performance of DSF elements, but almost none in terms of structural behaviour, especially in terms of determining the racking resistance of such wall elements. Moreover, with a view to reduce the global warming potential, an eco-friendly timber frame instead of a commonly used steel, aluminium or plastic frame is studied in this analysis. However, structurally combining timber and glass to develop an appropriate load-bearing structural element is a very complex process involving a combination of two materials with different material properties, where the type of bonding can be selected as a crucial parameter affecting the racking resistance range. Since the costs of experiments performed on such full-scale DSF elements are very high and such experiments are time-consuming, it is crucial to develop special mathematical models for analysing the influence of the most important parameters. Therefore, the main goal of this paper is to develop the finite element mathematical model of the studied DSF structural elements with a highly ecological solution by using a timber frame. In the second step, the developed model is further implemented in the numerical analysis of racking stiffness and followed by a comprehensive parametric numerical study on different parameters influencing the horizontal load-bearing capacity of such DSF timber elements. The obtained results indicate that the new approach of the developed load-bearing prefabricated timber DSF elements can essentially improve racking resistance and stiffness compared with the widely studied timber-glass single-skin wall elements and can thus be fully recommended especially in the structural renovation process of old buildings.
Ključne besede: timber, glass, double-skin façades, racking resistance, mathematical modelling, numerical analysis, Finite Elements Methods (FEM)
Objavljeno v DKUM: 11.03.2025; Ogledov: 0; Prenosov: 7
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3. The influence of the ratio of circumference to cross-sectional area of tensile bars on the fatigue life of additive manufactured AISI 316L steelLuka Ferlič, Filip Jerenec, Mario Šercer, Igor Drstvenšek, Nenad Gubeljak, 2024, izvirni znanstveni članek Opis: The static and dynamic loading capacities of components depend on the stress level to which the material is exposed. The fatigue behavior of materials manufactured using additive technology is accompanied by a pronounced scatter between the number of cycles at the same stress level, which is significantly greater than the scatter from a material with the same chemical composition, e.g., AISI 316L, but produced by rolling or forging. An important reason lies in the fact that fatigue cracks are initiated almost always below the material surface of the loaded specimen. Thus, in the article, assuming that a crack will always initiate below the surface, we analyzed the fatigue behavior of specimens with the same bearing cross section but with a different number of bearing rods. With a larger number of rods, the circumference around the supporting part of the rods was 1.73 times larger. Thus, experimental fatigue of specimens with different sizes showed that the dynamic loading capacity of components with a smaller number of bars is significantly greater and can be monitored by individual stress levels. Although there are no significant differences in loading capacity under static and low-cycle loading of materials manufactured with additive technologies, in high-cycle fatigue it has been shown that the ratio between the circumference and the loading cross section of tensile-loaded rods plays an important role in the lifetime. This finding is important for setting a strategy for manufacturing components with additive technologies. It shows that a better dynamic loading capacity can be obtained with a larger loading cross section.
Ključne besede: AISI 316L stainless steel, additive manufacturing, FEM, high-cycle fatigue, fractography analysis
Objavljeno v DKUM: 25.11.2024; Ogledov: 0; Prenosov: 20
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4. Influence of rotor structure on cogging torque in a surface-mounted PM-generatorMarian Greconici, Gheorghe Madescu, Daniela Milosevici, Marius Biriescu, Martian Mot, 2019, strokovni članek Opis: This paper deals with the analysis of the cogging torque in a surface-mounted permanent magnet generator in order to determine some techniques to minimize or eliminate the cogging torque. The simulation with finite element method (FEM) was carryout. A four-pole surface-mounted PM generator is investigated in the paper using FEM. The paper analyses the possibilities to reduce this type of torque by producing some asymmetry in the rotor structure. Two types of asymmetry were analysed: the PM pole arc with different widths, and the shifting of the PM. The numerical results obtained in the asymmetrical cases with symmetrical ones were compared and discussed. Finally, some conclusions are highlighted regarding the simulated results.
Ključne besede: cogging torque, electrical machines, FEM analysis, surface-mounted PM generator
Objavljeno v DKUM: 05.12.2023; Ogledov: 401; Prenosov: 276
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