1. A hybrid radial basis function-finite difference method for modelling two-dimensional thermo-elasto-plasticity : Application to cooling of hot-rolled steel bars on a cooling bedGašper Vuga, Boštjan Mavrič, Umut Hanoglu, Božidar Šarler, 2024, izvirni znanstveni članek Povzetek: This paper represents Part 2 of the parallel paper Part 1, where the strong form hybrid RBF-FD method was developed for solving thermo-elasto-plastic problems. It addresses the industrial application of this novel meshless method to steel bars cooling on a cooling bed (CB) where the formation of residual stress is of primary interest. The study investigates the impact of the distance between the bars and the distance to the heat shield above the CB on radiative heat fluxes and, consequently, on thermo-mechanical response. The thermal model is solved on bars cross-section with a RBF-FD method where augmented polyharmonic splines are used for the local approximation. View factors, computed with a Monte-Carlo method, are included in radiative heat fluxes. The thermal solution is incrementally applied on a mechanical model that assumes a generalised plane strain state and captures bars bending. The study employs a hybrid RBF-FD method to resolve a nonlinear discontinuous mechanical problem successfully. The simulation of the process shows how different process parameters influence the thermo-mechanical response of the bars.
Ključne besede: steel bars, cooling bed, thermo-mechanical modelling, hybrid radial basis function, generated finite differences, residual stresses
Objavljeno v DiRROS: 28.02.2024; Ogledov: 119; Prenosov: 69
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2. Complex interdependency of microstructure, mechanical properties, fatigue resistance, and residual stress of austenitic stainless steels AISI 304LPatricia Jovičević Klug, Matic Klug Jovičević, Michael Rohwerder, Matjaž Godec, Bojan Podgornik, 2023, izvirni znanstveni članek Ključne besede: stainless steel, AISI 304L, deep cryogenic treatment (DCT), microstructure, mechanical properties, fatigue, residual stress
Objavljeno v DiRROS: 02.02.2024; Ogledov: 168; Prenosov: 82
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3. The role of electricity mix and production efficiency improvements on greenhouse gas (GHG) emissions of building components and future refurbishment measuresTajda Potrč Obrecht, Sabina Jordan, Andraž Legat, Alexander Passer, 2021, izvirni znanstveni članek Povzetek: Purpose: An estimation of the environmental impact of buildings by means of a life cycle assessment (LCA) raises uncertainty related to the parameters that are subject to major changes over longer time spans. The main aim of the present study is to evaluate the influence of modifications in the electricity mix and the production efficiency in the chosen reference year on the embodied impacts (i.e., greenhouse gas (GHG) emissions) of building materials and components and the possible impact of this on future refurbishment measures.
Methods: A new LCA methodological approach was developed and implemented that can have a significant impact on the way in which existing buildings are assessed at the end of their service lives. The electricity mixes of different reference years were collected and assessed, and the main datasets and sub-datasets were modified according to the predefined substitution criteria. The influence of the electricity-mix modification and production efficiency were illustrated on a selected existing reference building, built in 1970. The relative contribution of the electricity mix to the embodied impact of the production phase was calculated for four different electricity mixes, with this comprising the electricity mix from 1970, the current electricity mix and two possible future electricity-mix scenarios for 2050. The residual value of the building was also estimated.
Results and discussion: In the case presented, the relative share of the electricity mix GHG emission towards the total value was as high as 20% for separate building components. If this electricity mix is replaced with an electricity mix having greater environmental emissions, the relative contribution of the electricity mix to the total emissions can be even higher. When, by contrast, the modified electricity mix is almost decarbonized, the relative contribution to the total emissions may well be reduced to a point where it becomes negligible. The modification of the electricity mix can also influence the residual value of a building. In the observed case, the differences due to different electricity mixes were in the range of 10%.
Conclusions: It was found that those parameters that are subject to a major change during the reference service period of the building should be treated dynamically in order to obtain reliable results. Future research is foreseen to provide additional knowledge concerning the influence of dynamic parameters on both the use phase and the end-of-life phase of buildings, and these findings will also be important when planning future refurbishment measures.
Ključne besede: global warming potential (GWP), production phase, electricity mix, production efciency, residual value, refurbishment, building components, life cycle assessment (LCA)
Objavljeno v DiRROS: 31.07.2023; Ogledov: 383; Prenosov: 193
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4. An LCA methodolody for assessing the environmental impacts of building components before and after refurbishmentTajda Potrč Obrecht, Sabina Jordan, Andraž Legat, Marcella Ruschi Mendes Saade, Alexander Passer, 2021, izvirni znanstveni članek Povzetek: Refurbishment is one of the most important measures for reducing the environmental impacts of the construction sector in the near future. According to the life cycle assessment (LCA) methodology for buildings, the environmental impacts of refurbishment measures should be assessed within the whole life cycle of the building and reflected in separate modules. However, in practice, refurbishment is often treated as the beginning of a new building life cycle. This leads to difficulties in correctly assessing the environmental impacts for the components that are reused or recycled after the refurbishment. The division of a building’s life cycle into two separate life cycles indicates that the environmental impacts must be divided between the life cycle before and the life cycle after the refurbishment for a correct assessment of the environmental impacts and a calculation of the residual value. We propose a newly developed methodology for calculating the environmental impacts and the residual value of refurbishment measures that also involves a division between life cycles. The new methodology is a combi-nation of already exiting methodologies that are innovatively combined and consists of four sequential steps. In the first step, the input, output and reuse flows between the life cycles before and after the refurbishment are defined. In the second step, the environmental impacts are assessed using the chosen allocation approach (i.e., the cut-off, cut-off with module D, avoided-burden, 50:50 and the product environmental footprint (PEF)). In the third step, a maintenance scenario is implemented according to the selected reference-service-life (RSL) database. In the fourth step, the residual value is estimated. The methodology was tested on selected building components. A sensitivity analysis for different allocation approaches and RSL databases was performed to show how the choice of these parameters can influence the results. The differences between the selected allocation approaches emerge if materials with recycled content are used or if the materials are being recycled or reused at the end of their life cycle. The developed methodology reliably estimates the environmental impacts as well as the residual value of the life cycle before and after the refurbishment. We expect that this research will stimulate practitioners to avoid the negligence of previous environmental flows, bringing scientific consistency to future assessments of refurbishment measures.
Ključne besede: Life cycle assessment (LCA), refurbishment, allocation approaches, residual value, reference service life (RSL)
Objavljeno v DiRROS: 28.07.2023; Ogledov: 326; Prenosov: 210
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5. Residual compressive behavior of self-compacting concrete after high temperature exposure - influence of binder materialsMarija Jelčić Rukavina, Ivan Gabrijel, Ivanka Netinger Grubeša, Ana Mladenovič, 2022, izvirni znanstveni članek Povzetek: This paper presents an experimental investigation of the compressive behavior of highstrength self-compacting concrete exposed to temperatures up to 600 C. Ten different concrete compositions were tested, in which part of the cement (by weight) was replaced by three different mineral additives (5–15% metakaolin, 20–40% fly ash and 5–15% limestone). The stress–strain curves, compressive strength, modulus of elasticity and strain at peak stress were evaluated from uniaxial compression tests. Scanning electron microscope micrographs were also taken to evaluate the damage caused by the high temperatures. A sharp decrease in mechanical properties and an increase in peak strain were observed already after 200 C for all mixes tested. The different mineral additives used in this study affected the variations of residual compressive strength by 24% and peak strain by 38%, while the variations of residual modulus elasticity were 14%. Comparing the obtained results with the recommendations for compressive strength given in regulatory code EN 1992-1-2 for high strength concrete, it can be concluded that the strength loss observed in EN 1992-1-2 at temperatures up to 400 C is too conservative. The Popovics model for the relationship between stress and strain provided a good approximation for the experimentally determined stress–strain curves at different temperatures.
Ključne besede: self-compacting concrete, mineral additives, high temperatures, residual mechanical properties, open access
Objavljeno v DiRROS: 28.04.2023; Ogledov: 361; Prenosov: 174
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6. Residual stress modeling and analysis in AISI A2 steel processed by an electrical discharge machineDinesh Kumar, Krishan Kant Singh Mer, Hoshiyar Singh Payal, Kapil Kumar, 2022, izvirni znanstveni članek Ključne besede: electro discharge machining, numerical simulation, residual stress, dielectric fluid, AISI A2 die steel, Gaussian distributed heat flux
Objavljeno v DiRROS: 22.06.2022; Ogledov: 531; Prenosov: 130
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7. Revealing the Pb whisker growth mechanism from Al-alloy surface and morphological dependency on material stress and growth environmentMatic Klug Jovičević, Tim Verbovšek, Patricia Jovičević Klug, Barbara Šetina, Bojan Ambrožič, Goran Dražić, Bojan Podgornik, 2022, izvirni znanstveni članek Ključne besede: aluminum alloy, metallic whiskers, residual stress, crystal growth, oxidation
Objavljeno v DiRROS: 06.05.2022; Ogledov: 589; Prenosov: 198
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