| 1. |
- Belov, Ilja, et al.
(författare)
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Simulation and Experimental Methodology for Virtual Prototyping of Annealed Industrial Coils
- 2023
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Ingår i: Heat Transfer Engineering. - : Taylor & Francis. - 0145-7632 .- 1521-0537. ; 44:4, s. 353-367
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Tidskriftsartikel (refereegranskat)abstract
- The finite element three-dimensional transient model of the annealing process, including conductive and convective heat transfer in an aluminum (Al) coil was developed, implemented, and validated. It combines winding force dependent effective radial thermal conductivity model and the novel convective heat transfer modeling methodology. Experimental validation of the finite element model was performed for two industrial coils having different dimensions, strip thickness and crowning depth. The general agreement between the predicted and measured temperatures for most of the probes was better than 10% at the target material temperature. A series of measurements were configured and performed to supply both the input and validation data for the simulations. The effect of the additional wetted area on the convective heat transfer at the coil base was quantified. The guidelines on the virtual prototyping of the Al coil annealing process were provided, which can be of interest for the process designers.
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| 2. |
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| 3. |
- Jones, C. A., et al.
(författare)
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A mathematical examination of the impact of mould transparency to infrared radiation on solidification during the investment casting process
- 2023
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Ingår i: IOP Conference Series. - : Institute of Physics (IOP). - 1757-8981 .- 1757-899X. ; 1281:1
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Tidskriftsartikel (refereegranskat)abstract
- Investment casting is a highly dynamic process during which multiple competing physical phenomena are at work. Those seeking to understand and simulate such processes computationally are confronted with a considerable task, balancing accuracy with efficiency. Approximations and models based on well-understood and documented fundamental physics are powerful tools in a modeller’s arsenal. Driven by observed discrepancies between experimental thermocouple measurements and simulation predictions of casting temperatures, this work explores the additional alloy cooling mechanism of mould transparency to infrared radiation, targeting a new mathematical approximation applicable in such situations. Direct attenuation, scattering from coarse sand, sand distribution in the mould and material temperatures play a role in the extent of radiation transparency that must be considered. From this model, estimation of the additional cooling rate resulting from expected mould transparency can be determined and applied as a corrective measure to computation fluid dynamics (CFD) simulation results that do not capture this phenomenon.
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| 4. |
- Matsushita, Taishi, et al.
(författare)
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Influence of contact pressure on the thermal contact conductance of layered metallic sheets
- 2022
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Ingår i: High Temperatures-High Pressures. - : Old City Publishing. - 0018-1544 .- 1472-3441. ; 51:1, s. 63-82
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Tidskriftsartikel (refereegranskat)abstract
- For the optimisation of the annealing process of aluminium coils, simulation of the process is often performed. To simulate the process with higher accuracy, reliable input parameters are required, and thermal conductivity (thermal contact conductance) is one of them. In the present study, a method to measure the thermal conductivity and thermal contact conductance of metallic sheets were developed based on the steady-state comparative longitudinal heat flow. The apparatus was built with a compression test machine, and thus it allows to control the pressure to the sample and carry out the measurements at different contact pressure. An equipped heater allows to heat the sample to 573 K. To evaluate the thermal conductance at the interface, a thermal resistance network model was applied. The measurements were carried out with an aluminium alloy (AA3003 sheets). In addition to the thermal contact conductance measurements, the surface roughness of the sheets was also investigated. The semi-empirical equation for the relationship between thermal contact conductance and contact pressure was obtained based on the measurement results.
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| 5. |
- Sujakhu, S., et al.
(författare)
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On the fatigue damage micromechanisms in Si-solution-strengthened spheroidal graphite cast iron
- 2018
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Ingår i: Fatigue & Fracture of Engineering Materials & Structures. - : John Wiley & Sons. - 8756-758X .- 1460-2695. ; 41:3, s. 625-641
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Tidskriftsartikel (refereegranskat)abstract
- Graphite nodules in spheroidal graphite cast iron (SGI) play a vital role in fatigue crack initiation and propagation. Graphite nodules growth morphology can go through transitions to form degenerated graphite elements other than spheroidal graphite nodules in SGI microstructure. These graphite particles significantly influence damage micromechanisms in SGI and could act differently than spheroidal graphite nodules. Most of the damage mechanism studies on SGI focused on the role of spheroidal graphite nodules on the stable crack propagation region. The role of degenerated graphite elements on SGI damage mechanisms has not been frequently studied. In this work, fatigue crack initiation and propagation tests were conducted on EN-GJS-500-14 and observed under scanning electron microscope to understand the damage mechanisms for different graphite shapes. Crack initiation tests showed a dominant influence of degenerated graphite elements where early cracks initiated in the microstructure. Most of the spheroidal graphite nodules were unaffected at the early crack initiation stage, but few of them showed decohesion from the ferrite matrix and internal cracking. In the crack propagation region, graphite/ferrite matrix decohesion was the frequent damage mechanism observed with noticeable crack branching around graphite nodules and the crack passing through degenerated graphite elements. Finally, graphite nodules after decohesion acted like voids which grew and coalesced to form microcracks eventually causing rapid fracture of the remaining section.
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| 6. |
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| 7. |
- Awe, Samuel A., et al.
(författare)
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Development of new Al-Cu-Si alloys for high temperature performance
- 2017
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Ingår i: Advanced Materials Letters. - : VBRI Press. - 0976-3961 .- 0976-397X. ; 8:6, s. 695-701
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Tidskriftsartikel (refereegranskat)abstract
- In a quest to develop new light metal alloys that can perform excellently at elevated-temperatures (from 300°C to 400°C), a ternary eutectic Al-Cu-Si alloy was exploited to gain a deeper understanding of the alloy system and its suitability for high temperature applications. The alloys studied, with chemical composition of Al-27%Cu-5%Si (by weight percent) with Ni addition in the range of 0 to 1.5%wt, were cast in a rapid solidification casting technique. The solidification characteristics of the alloy was studied using the Thermo-Calc software. Microstructures were characterized in a scanning electron microscope coupled with energy dispersive spectrometry (SEM-EDS). Finally, the elevated-temperatures tensile properties of the alloys were investigated. Comparing the microstructures and mechanical properties of these Al-Cu-Si(-Ni) alloys with conventional Al-Si alloy A319, the refined microstructure with dispersed Ni intermetallic particles formed in the as-cast Al-Cu-Si(-Ni) alloys deliver improved elevated temperature properties. In particular, the yield strength and ultimate tensile strength of the new alloy with 1.5% Ni at 400?C were observed to be 220% and 309% higher, respectively, than for conventional A319 alloy.
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| 8. |
- Belov, Ilja, et al.
(författare)
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Effect of fillets on heat transfer in a rheocast aluminium heatsink
- 2016
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Ingår i: 2016 17th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE). - : IEEE. - 9781509021062
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Konferensbidrag (refereegranskat)abstract
- The effect of fillets formed between the base and plate fins of rheocast aluminium heatsinks on the thermal resistance of the heatsinks has been quantified by simulation. Simulation methodology, including sequential optimization has been developed in order to determine hotspot distributions where the fillets have the maximum effect. Combination of different fillet dimensions with various base thickness levels and aluminium alloys having inhomogeneous thermal conductivity have been investigated. For the studied cases, the effect of fillets on heatsink thermal resistance differs from negligible to 6%. The results would guide thermal designers on contribution of fillets to the heat transfer in multi-fin heatsinks for natural convection.
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| 9. |
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| 10. |
- Bjurenstedt, Anton, 1979-
(författare)
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On the influence of imperfections on microstructure and properties of recycled Al-Si casting alloys
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are great energy savings to be made by recycling aluminium; as little as 5% of the energy needed for primary aluminium production may be required. Striving to produce high quality aluminium castings requires knowledge of microstructural imperfections, which is extra important when casting recycled aluminium that generally contains higher levels of imperfections compared to primary aluminium. Imperfections include amongst others Si, Fe, and Mn as well as oxides. Si is needed for castability, but it may also initiate fracture. There are different types of Fe-rich intermetallics influencing properties of castings, generally in a negative direction. Oxides constitute cracks and they are elusive because they are difficult to quantify.This thesis aims to increase knowledge about imperfections in recycled aluminium castings originating from alloying elements and the melt. Experiments were performed in advanced laboratory equipment, including X-radiographic imaging during solidification and in-situ tensile testing in a scanning electron microscope. Experiments were also performed at industrial foundry facilities.The experiments showed that the nucleation temperature of primary α-Fe intermetallics increased with higher Fe, Mn, and Cr contents. Primary α-Fe are strongly suggested to nucleate on oxides and to grow in four basic morphologies. Lower nucleation frequency of α-Fe promoted faster growth and hopper crystals while higher nucleation frequency promoted slower growth rates and massive crystals. Results also showed that a decrease in the size of the eutectic Si and plate-like β-Fe intermetallics improved tensile properties, foremost the elongation to fracture. In β-Fe containing alloys the transversely oriented intermetallics initiated macrocracks that are potential fracture initiation sites. In alloys with primary α-Fe foremost clusters of intermetallics promoted macrocracks. In fatigue testing, a transition from β-Fe to α-Fe shifted the initiation sites from oxides and pores to the α-Fe, resulting in a decrease of fatigue strength. Oxides in Al-Si alloys continue to be elusive; no correlations between efforts to quantify the oxides and tensile properties could be observed.
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