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1.
A computational model for analysing the dry rolling/sliding wear behaviour of polymer gears made of POM
Aljaž Ignatijev, Matej Borovinšek, Srečko Glodež, 2024, original scientific article

Abstract: This study presents a computational model to determine the wear behaviour of polymer gears. Using PrePoMax finite element numerical calculation software, a proposed computational model was built to predict dry rolling/sliding wear behaviour based on Archard’s wear model. This allows the calculation of the wear depth in each loading cycle with constant mesh updating using the finite element method. The developed computational model has been evaluated on a spur gear pair, where the pinion made of POM was meshed with a support gear made of steel. The computational results obtained were compared with the analytical results according to the VDI 2736 guidelines. Based on this comparison, it was concluded that the proposed computational model could be used to simulate the wear behaviour of contacting mechanical elements like gears, bearings, etc. The main advantage of the model, if compared to the standardised procedure according to the VDI 2736 guidelines, is the geometry updating after a chosen number of loading cycles, which enables a more accurate prediction of wear behaviour under rolling/sliding loading conditions.
Keywords: polymer gears, rolling/sliding contact, wear, computational modelling
Published in DKUM: 12.04.2024; Views: 9; Downloads: 0
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2.
Sinergije in izzivi sodelovanja med družinskimi podjetji in startupi na praktičnem primeru
Eneja Zupanič, 2023, undergraduate thesis

Abstract: Diplomska naloga je namenjena pojasnilom, kako si lahko družinska in start-up podjetja medsebojno koristijo s sodelovanjem, da bi povečali svoje inovativne sposobnosti. Družinska podjetja igrajo ključno vlogo v današnjem gopodarstvu. Vendar pa je v trenutnem dinamičnem gospodarskem okolju družinsko podjetje pred izzivom, kako ohraniti svoj konkurenčni položaj. Na drugi strani imajo start-up podjetja pogosto obetavne inovativne ideje z velikim tržnim potencialom. Zato se od obeh strani pričakuje, da si med seboj pomagata. Najprej smo opredelili družinska podjetja in njihov pomen za gospodarstvo, kjer smo predstavili značilnosti družinskega podjetja in prednosti ter slabosti družinskih podjetij. Opredelili smo tudi vpliv družinskih podjetij na gospodarstvo v Sloveniji. V nadaljevanju smo proučili start-up podjetja in njihov pomen za gospodarstvo. Ob tem smo predstavili značilnosti start-up podjetij in opredelili njihove prednosti ter slabosti. Opredelili smo tudi vpliv start-upov na gospodarstvo v Sloveniji. Temo smo si izbrali, saj smo želeli ugotoviti, ali si družinska in start-up podjetja med seboj res lahko pomagajo in koristijo drug drugemu
Keywords: družinska podjetja, start-up podjetja, zagon, sodelovanje, zavezništva med podjetji, inovacije, socialno-čustveno bogastvo.
Published in DKUM: 11.04.2024; Views: 21; Downloads: 3
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3.
Priložnosti sodelovanja družinskih podjetij in startup podjetij na praktičnem primeru
Karin Žižek, 2024, undergraduate thesis

Abstract: Družinska podjetja imajo ključno vlogo v evropskem gospodarstvu, vendar se soočajo z izzivi v hitro spreminjajočem se okolju. Globalizacija in digitalizacija postavljata družinska podjetja pred številne izzive, saj se morajo spretno odzivati na vse večjo kompleksnost in hiter razvoj trgov. Sodelovanje s startup podjetji se vse bolj prepoznava kot potencialna rešitev za soočanje s temi izzivi. Sodelovanje z novoustanovljenimi podjetji je za korporacije zelo obetavno, ostaja pa nejasno, kako izvedljiva je odločitev za ta pristop za družinska podjetja zaradi njihovih posebnih lastnosti, kot so nenaklonjenost tveganju, nepripravljenost za vlaganje v inovacijske namene, dolgoročna usmeritev in nepripravljenost za sodelovanje. Kljub različnim lastnostim družinskih podjetij pa družinska podjetja vedno bolj prepoznavajo pomembnost sodelovanja z novimi podjetji za inovacije. Prihodnost družinskih podjetij je mogoče okrepiti s sodelovanjem s startup podjetji, kar obeta inovativne rešitve za obe strani. To potrjuje tudi analiza praktičnega primera, ki je pokazala, da sodelovanje prinaša koristi tako družinskim podjetjem kot startupom. Na podlagi teh ugotovitev predlagamo razširitev takšnih partnerstev, ki bi lahko povečala raznolikost idej in konkurenčnosti ter spodbudila dinamičen razvoj v panogah, kjer podjetja delujejo, s čimer bi izboljšali storitve za uporabnike. Diplomsko delo je sestavljeno iz dveh delov, in sicer iz teoretičnega in praktičnega dela. V prvem oziroma teoretičnem delu smo predstavili temeljne pojme sodelovanja podjetij, kot so oblike sodelovanja, inovacije kot rezultat sodelovanja, dejavnike uspeha za sodelovanje in tveganja, ki se lahko pojavijo pri sodelovanju; podrobneje je predstavljen vpliv sodelovanja na družinska in startup podjetja. V drugem oziroma praktičnem delu pa smo na osnovi zapisane teorije predstavili praktičen primer vplivanja oziroma priložnosti sodelovanja družinskega podjetja s startup podjetji.
Keywords: družinsko podjetje, startup, sodelovanje, inovacije
Published in DKUM: 11.04.2024; Views: 21; Downloads: 2
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Study of ▫$Ni/Y_2O_3/polylactic$▫ acid composite
Tilen Švarc, Matej Zadravec, Žiga Jelen, Peter Majerič, Blaž Kamenik, Rebeka Rudolf, 2023, original scientific article

Abstract: This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3% strain at the break, when compared to the base PLA. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in injection moulding applications and warrant further exploration of their properties and new applications in various fields.
Keywords: ultrasound spray pyrolysis, Ni/Y2O3, lyophilization, PLA, extrusion, injection moulding
Published in DKUM: 05.04.2024; Views: 48; Downloads: 1
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7.
Obnašanje giroidnih materialov z dodanimi avksetičnimi vzorci
Blaž Vičman, 2024, undergraduate thesis

Abstract: Cilj diplomske naloge je bil preučiti vpliv spreminjanja parametrov avksetičnih vzorcev na vrednost Poissonovega razmerja giroidnih materialov pod obremenitvijo. S pomočjo geometrijskih modelov ter računalniških simulacij smo pokazali, da avksetični vzorci vplivajo na Poissonovo razmerje giroidnih materialov. Vpliv je odvisen od materialnih lastnosti avksetičnih vzorcev, razmerja med velikostjo avksetične in giroidne celice ter od položaja avksetičnega vzorca na modelu. Ugotovili smo tudi, da je za vpliv na Poissonovo razmerje dovolj uporabiti samo del avksetičnega vzorca.
Keywords: giroidni materiali, avksetične strukture, Poissonovo razmerje, metoda končnih elementov
Published in DKUM: 04.04.2024; Views: 36; Downloads: 11
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Design of an Efficient Fan Steering Strategy for Efficient Cooling of Engine Peripheral Components during Vehicle Thermal Soak : magistrsko delo
Tjaša Pečnik, 2024, master's thesis

Abstract: The aim of this Master's thesis was to find a mathematical correlation between various fan momentum fields for a fan which is used for cooling the underhood area of a car. The correlation had to link a known momentum field to all possible momentum fields related to fan rotation speed and car velocity. With this correlation, new alternative fan steering strategies can be used to cool the vehicle underhood area. An already functioning RBM (Rigid Body Motion) simulation was used as a base, since it already gave satisfying results in the past. With this simulation file, several tests were run to ensure that the results really converge nicely. In this way it was established that the results are accurate enough for further use. After obtaining the results, a set of 30 simulation files was calculated. The simulations were a combination of different fan rotation speeds and car velocities. After the set was done, the results were analysed using various computer software (Star-CCM+, MS Excel and Matlab). It was concluded that a polynomial approach for the momentum field was a suitable option but to add some additional complexity, surface equations were used. To obtain the equations, tables with different results were put into Matlab and the program did the rest. The result were two sets of three surface equations with x and y values. In both cases, x represented the rotation speed of the fan and y represented the car velocity in one case and the delta pressure between two evaluation surfaces in the other. After that it was time to implement the newly acquired surface equations in a Star-CCM+ simulation file. The old simulation file was again used as a base, but new field functions were put in with the help of which the UDMS (User Defined Momentum Source) is being changed. Both types of surface equations were tested and calculated. In the end, it was decided to go with the one where the delta pressure on two evaluation surfaces is being used as the y value. One surface was placed in front of the fan and the other after the fan. The final step was to test different fan steering strategies. The usual cooling procedure consists of a phase where the fan cools for a specific amount of time with a defined rotation speed and then turns off. Temperatures on critical points around the engine and in the underhood area of the car are being looked at as a result. The first strategy was to run the fan at the same speed as usual, but gradually slow it down in uniform steps so that the shut down time remains the same. With this approach, the highest temperature values were actually lower than usual, but certain temperature probes became warmer as the fan speed decreased. Nevertheless, the temperatures at the end were very similar. The second tested strategy was inspired by the idea of potentially saving some battery energy if we could somehow manage to cool the underhood area quicker. In this case, the fan ran for a short time at a high rotation speed and after that at a slightly lower speed. Then it was turned off for a few minutes and subsequently switched back on. The maximum temperature in this scenario reached even higher values. The reason for this was that the fan blew warm air toward certain measurement points, causing them to heat up further. The temperatures at the end of the simulation were similar to those in the previous two cases. In conclusion, it is indeed possible to steer a fan momentum field with the help of field functions and equations which describe the relationship between different fan rotation speeds and car velocities.
Keywords: fan, momentum, RBM, CFD, thermal soak
Published in DKUM: 02.04.2024; Views: 48; Downloads: 0
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10.
Microstructure, mechanical properties and fatigue behaviour of a new high-strength aluminium alloy AA 6086
Franc Zupanič, Jernej Klemenc, Matej Steinacher, Srečko Glodež, 2023, original scientific article

Abstract: This study presents the comprehensive experimental investigation of the microstructure, mechanical and fatigue properties of a new high-strength aluminium alloy AA 6086, which was developed from a commercial aluminium alloy AA 6082. The new alloy possesses a higher content of Si, and, it also contains Cu and Zr. The alloy was characterised in the as-cast condition after homogenisation, extrusion, and T6 heat treatment. Light microscopy, scanning and transmission electron microscopy with energy dispersive spectrometry were used to analyse the microstructure and the fractography of broken specimens. The quasi-static and fatigue tests were performed on the MTS Landmark 100 kN servo-hydraulic test machine, controlled with a mechanical extensometer with a 25 mm gauge length. The quasi-static strength of the analysed aluminium alloy AA 6086 was found to be significantly higher if compared to some other AA 6xxx alloys, while the ductility was kept almost the same. The experimental results of the comprehensive fatigue tests in a Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) regime showed a good fatigue resistance, and represent a good basis for engineering design applications of the newly developed aluminium alloy AA 6086.
Keywords: aluminijeve zlitine, karakterizacija materiala, utrujanje, eksperimentalno testiranje, statistično ovrednotenje, Aluminium Alloy AA 6086, material characterisation, fatigue behaviour, experimental testing, statistical evaluation
Published in DKUM: 02.04.2024; Views: 27; Downloads: 4
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