1. Fatigue behaviour of different chiral auxetic structures using a numerical approachBranko Nečemer, Patrik Lampret, Srečko Glodež, 2025, original scientific article Abstract: This study presents the computational analysis for determining the fatigue life of different chiral auxetic structures made of aluminium alloys 5083-H111. The influence of Poisson's ratio on the loading process was investigated to determine which structures exhibited the auxetic effect and how intense it was. Finally, the fatigue life calculation was performed using the strain life approach in the framework of the ANSYS software. The fatigue life determination was evaluated using the approach of amplitude strains, amplitude forces, and strain energy density per cycle. The computational results were described and presented according to predefined approaches, from which it was determined which chiral structure can withstand the highest number of loading cycles at the prescribed load, and which structure shows the most favourable combination of mechanical and physical properties.
Keywords: advanced metamaterials, chiral auxetic structures, fatigue behaviour, numerical simulations, aluminium alloys
Published in DKUM: 20.05.2025; Views: 0; Downloads: 5
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2. Maximizing the power output and net present value of organic rankine cycle: application to aluminium industryMonika Dokl, Rok Gomilšek, Lidija Čuček, Ben Abikoye, Zdravko Kravanja, 2022, original scientific article Abstract: This study presents an integrated design and optimization of an Organic Rankine Cycle (ORC) for the recovery of waste heat from aluminium production. Non-Linear Programming (NLP) models were developed, with the objectives of maximizing electricity production and the Net Present Value (NPV) of the system. The models account for optimizing the operating conditions and changes in thermodynamic features of the system. The developed models are applied to a case study of Slovenian aluminium company where the performance of three different working fluids (R245fa, R1234yf and R1234ze) are compared. The optimization is performed considering different temperatures and prices of produced hot water and electricity, minimum approach temperature (DTmin), concentration of CO2 in flue gas and temperature and flowrate of flue gas. Results show that the selected working fluids for the proposed waste heat-based ORC system have the potential to substitute up to about 830 kW of electricity in a sustainable and economic manner. Out of the three working fluids considered, R245fa showed up to 7.9% efficiency of the ORC cycle and was identified as the best performing working fluid considering both economic viability and the amount of electricity produced by the system, however the refrigerant inherently has higher GHG footprint.
Keywords: waste heat, waste heat utilization, aluminium industry, organic rankine cycle, power generation, optimization
Published in DKUM: 10.04.2025; Views: 0; Downloads: 1
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3. Microstructure and indentation properties of single-roll and twin-roll casting of a quasicrystal-forming Al-Mn-Cu-Be alloyFranc Zupanič, Matjaž Macerl, Toshio Haga, Tonica Bončina, 2022, original scientific article Abstract: In this investigation, strips of an experimental Al-Mn-Cu-Be alloy were manufactured by
high-speed single-roll and twin-roll casting to stimulate the formation of a quasicrystalline phase
during solidification. The strips were characterised by light microscopy, scanning and transmission
electron microscopy, microchemical analysis, and X-ray diffraction. Indentation testing was used to
determine the mechanical responses of the strips in different areas. A smooth surface was achieved
on both sides of the twin-roll-cast strip, while the free surface of the single-roll-cast strip was rough.
The microstructures in both strips consisted of an Al-rich solid solution matrix embedding several
intermetallic phases Θ-Al2Cu, Be4Al (Mn, Cu), Al15Mn3Be2 and icosahedral quasicrystalline phase
(IQC). The microstructure of the single-roll-cast strip was more uniform than that of the twin-roll-cast
strip. Coarse Al15Mn3Be2 particles appeared in both alloys, especially at the centre of the twinroll strip. These coarse particles adversely affected the strength and ductility. Nevertheless, both
casting methods provided high-cooling rates, enabling the formation of metastable phases, such as
quasicrystals. However, improvements in alloy composition and casting procedure are required to
obtain enhanced microstructures and properties.
Keywords: single-roll casting, twin roll casting, microstructure, quasicrystal, hardness, aluminium, characterisation
Published in DKUM: 24.03.2025; Views: 0; Downloads: 4
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4. Energy flexibility in aluminium smelting : a long-term feasibility study based on the prospects of electricity load and photovoltaic productionMarko Bizjak, Niko Uremović, Domen Mongus, Primož Sukič, Gorazd Štumberger, Haris Salihagić Hrenko, Dragan Mikša, Stanislav Kores, Niko Lukač, 2024, original scientific article Keywords: energy flexibility, aluminium smelting, renewable energy, virtual battery, solar production
Published in DKUM: 17.12.2024; Views: 0; Downloads: 18
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5. Dispersoids in Al-Mg-Si alloy AA 6086 modified by Sc and YFranc Zupanič, Sandi Žist, Mihaela Albu, Ilse Letofsky-Papst, Jaka Burja, Maja Vončina, Tonica Bončina, 2023, original scientific article Keywords: aluminijeve zlitine, toplotna obdelava, mikrostruktura, disperzoidi, dilatometrija, trdota, aluminium alloy, heat treatment, microstructure, dispersoids, dilatometry, DSC, hardness
Published in DKUM: 05.04.2024; Views: 183; Downloads: 21
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7. Microstructure, mechanical properties and fatigue behaviour of a new high-strength aluminium alloy AA 6086Franc 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: 281; Downloads: 31
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8. LCF behaviour of high strength aluminium alloys AA 6110A and AA 6086Jernej Klemenc, Srečko Glodež, Matej Steinacher, Franc Zupanič, 2023, original scientific article Abstract: The proposed research presents the comprehensive investigation of the Low Cycle Fatigue (LCF) behaviour of two high-strength aluminium alloys of series AA 6xxx: the conventional alloy AA 6110A and the newly developed alloy AA 6086. Both alloys were characterised in the as-cast condition after homogenisation, extrusion, and T6 heat treatment.
The quasi-static strength and hardness of the aluminium alloy AA 6086 were found to be significantly higher if compared to the AA 6110A alloys, while the ductility was a little bit smaller. The LCF tests showed that the AA 6086 alloy is more suitable for the high-cycle fatigue regime. On the other hand, the engineering advantage of the AA 6110A alloy is only for low-cycle fatigue applications if less than 100 loading cycles are expected in the service life of the analysed structure. The fatigue cracks formed predominantly on the α-AlMnSi intermetallic particles in both alloys, and, during LCF tests, exhibited small crack propagation. The area of the fatigue crack growth was much smaller than the area of the forced fracture. At smaller amplitude strains the fatigue striations were present at the fracture surface, while, at higher amplitude strains, they were not present. The obtained experimental results represent a good basis for engineering design applications of the analysed alloys AA 6086 and AA 6110A.
Keywords: aluminijeve zlitine, malociklično utrujanje, eksperimentalno testiranje, fraktografija, aluminium alloys, low cycle fatigue, experimental testing, fractography
Published in DKUM: 29.03.2024; Views: 197; Downloads: 16
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9. High strain-rate deformation analysis of open-cell aluminium foamAnja Mauko, Mustafa Sarıkaya, Mustafa Güden, Isabel Duarte, Matej Borovinšek, Matej Vesenjak, Zoran Ren, 2023, original scientific article Abstract: This study investigated the high-strain rate mechanical properties of open-cell aluminium foam M-pore®. While previous research has examined the response of this type of foam under quasi-static and transitional dynamic loading conditions, there is a lack of knowledge about its behaviour under higher strain rates (transitional and shock loading regimes). To address this gap in understanding, cylindrical open-cell foam specimens were tested using a modified Direct Impact Hopkinson Bar (DIHB) apparatus over a wide range of strain rates, up to 93 m/s. The results showed a strong dependency of the foam's behaviour on the loading rate, with increased plateau stress and changes in deformation front formation and propagation at higher strain rates. The internal structure of the specimens was examined using X-ray micro-computed tomography (mCT). The mCT images were used to build simplified 3D numerical models of analysed aluminium foam specimens that were used in computational simulations of their behaviour under all experimentally tested loading regimes using LS-DYNA software. The overall agreement between the experimental and computational results was good enough to validate the built numerical models capable of correctly simulating the mechanical response of analysed aluminium foam at different loading rates.
Keywords: Open-cell aluminium foam, Micro-computed tomography, High-strain rate, Direct impact hopkinson bar, Digital image correlation, Computer simulation
Published in DKUM: 06.12.2023; Views: 428; Downloads: 46
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10. Wear Behaviour of Multilayer Al-PVD-Coated Polymer GearsTonica Bončina, Brigita Polanec, Franc Zupanič, Srečko Glodež, 2022, original scientific article Abstract: A comprehensive experimental investigation of the wear behaviour of coated spur polymer gears made of POM is performed in this study. Three different thicknesses of aluminium (Al) coatings were investigated and deposited by the Physical Vapour Deposition (PVD) process. The Al coating was deposited in three steps: By plasma activation, metallisation of the aluminium by the magnetron sputtering process, and plasma polymerisation. The wear of the gears was tested on an in-house developed testing rig for different torques (16, 20, and 24 Nm) and a rotational speed of 1000 rpm. The duration of the experiments was set to 13 h, when the tooth thickness and, consequently, the wear of the tooth flank were recorded. The experimental results showed that the influence of metallisation with aluminium surface coatings on the wear behaviour of the analysed polymer gear is not significantly important. The results also showed that the gears with a thicker aluminium coating showed greater wear than gears with a thinner coating or even without a coating. This is probably due to the fact that the aluminium particles that started to deviate during gear operation represented the abrasive material, which led to the faster wear of the contacting surfaces of the meshing gear flanks.
Keywords: polymer gears, aluminium PVD coating, Physical Vapour Deposition process, multilayer coating, wear
Published in DKUM: 15.11.2022; Views: 580; Downloads: 467
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