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Abstract: Štore Steel Ltd. is one of the biggest flat spring steel producers in Europe. The main motive for this study was to study the influences of non-metallic inclusions on mechanical properties obtained by tensile testing. From January 2016 to December 2021, all available tensile strength data (472 cases–472 test pieces) of 17 low alloy steel grades, which were ordered and used by the final user in rolled condition, were gathered. Based on the geometry of rolled bars, selected chemical composition, and average size of worst fields non-metallic inclusions (sulfur, silicate, aluminium and globular oxides), determined based on ASTM E45, several models for tensile strength, yield strength, percentage elongation, and percentage reduction area were obtained using linear regression and genetic programming. Based on modeling results in the period from January 2022 to April 2022, five successively cast batches of 30MnVS6 were produced with a statistically significant reduction of content of silicon (t-test, p < 0.05). The content of silicate type of inclusions, yield, and tensile strength also changed statistically significantly (t-test, p < 0.05). The average yield and tensile strength increased from 458.5 MPa to 525.4 MPa and from 672.7 MPa to 754.0 MPa, respectively. It is necessary to emphasize that there were no statistically significant changes in other monitored parameters.
Keywords: mechanical properties, tensile test, tensile strength, yield strength, percentage elongation, percentage reduction area, low alloy steel, modeling, linear regression, genetic programming, industrial study, steel making, optimization
Published in DKUM: 24.03.2025; Views: 0; Downloads: 2
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Abstract: This study investigates the optimization of the design of timber floor joists, taking into account the self-manufacturing costs and the discrete sizes of the structure. This non-linear and discrete class of optimization problem was solved with the multi-parametric mixed-integer non-linear programming (MINLP). An MINLP optimization model was developed. In the model, an accurate objective function of the material and labor costs of the structure was subjected to design, strength, vibration and deflection (in)equality constraints, defined according to Eurocode regulations. The optimal design of timber floor joists was investigated for different floor systems, different materials (sawn wood and glulam), different load sharing systems, different vertical imposed loads, different spans, and different alternatives of discrete cross-sections. For the above parameters, 380 individual MINLP optimizations were performed. Based on the results obtained, a recommended optimal design for timber floor joists was developed. Engineers can select from the recommendations the optimal design system for a given imposed load and span of the structure. Economically suitable spans for timber floor joists structures were found. The current knowledge of competitive spans for timber floor joists is extended based on cost optimization and Eurocode standards.
Keywords: structural optimization, cost optimization, discrete optimization, mixed-integer nonlinear programming, MINLP, timber floor joists
Published in DKUM: 12.03.2025; Views: 0; Downloads: 2
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Keywords: self-sufficiency, food supply chain, multi-objective optimization, mixed integer linear programming, sustainable development
Published in DKUM: 14.02.2025; Views: 0; Downloads: 5
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Abstract: Vertical addition to already-existing structures is an approach to energy-efficient building renovation. It presents an opportunity for the densification of built-up areas and the construction of new usable spaces. While many studies have dealt with the subject of renovating buildings with a focus on energy efficiency, far fewer studies have specifically examined the potential of vertically extending existing buildings, an approach which could be introduced in new sustainable building policies. The objective of this study is to redevelop optimal timber–glass upgrade modules, considering the ideal proportions of glazing for all cardinal directions, by using discrete Mixed-Integer Non-Linear Programming optimization. The novelty of the suggested method resides in the synchronous optimization of the upgrade modules’ daylighting and energy-efficiency performance, resulting in the creation of optimization methods that can determine the optimal glazing proportions for all cardinal directions and incorporate rational design and window measurement. The impact of the developed Mixed-Integer Non-Linear Programming-optimized upgrade modules is compared to previously designed optimized upgrade modules. Finally, a methodology for estimating the energy efficiency of building renovations incorporating vertical additions using the timber–glass upgrade modules was developed, supporting the quick assessment of the reduction in hybrid buildings’ energy consumption for heating and cooling according to boundary conditions, presuming that they undergo the suggested renovations. The findings are applicable (not exclusively) to Slovenia’s residential building stock, which makes up around 20% of the country’s current housing stock and was mainly constructed between 1946 and 1970. This offers a substantial opportunity to improve the overall sustainability and energy efficiency of the country’s housing stock. The proposed approach offers a holistic solution to drive sustainable development in the built environment by incorporating all three pillars of sustainability (environmental, social, and economic).
Keywords: energy efficient building renovation, energy efficiency, building vertical addition, timber–glass upgrade modules, mixed-integer non-linear programming, MINLP, optimization, visual comfort, energy sustainability
Published in DKUM: 16.01.2025; Views: 0; Downloads: 5
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Abstract: The aim of the Master’s thesis was to evaluate the current and potential applications of virtual reality technology in chemistry and chemical engineering, as well as to evaluate the use of virtual reality for educational purposes. First, we made an overview of the numerous applications of the virtual reality technology with a specific focus on its current use in the chemistry and chemical engineering fields, including research and educational environments as well as industrial applications. It was found that the use of virtual reality technology is growing in all areas, with training, remote collaboration, and interactive learning being the most prominent fields. To assess the effectiveness of virtual reality as an educational tool, we performed a study with second year students of Chemistry and Chemical Engineering programs at the Faculty of Chemistry and Chemical Engineering, University of Maribor. Students were divided into two groups, one undertaking a training on the proper use of fume hoods in virtual reality and the other group performing the same training in a real chemical laboratory. Students from both groups took a knowledge evaluation test and a personal experience survey after the training. The test results have shown that virtual reality can be just as effective or potentially even more effective than conventional training in the chemical laboratory. The average score of the virtual reality group was 2.5% higher than that of the group performing conventional training in a chemical laboratory, although we did not confirm a statistically significant difference between the scores. We also prepared a personal experience survey to evaluate the students’ personal experience and interest in using virtual reality as an educational tool. It was observed that there is a lot of enthusiasm from the students for the use of virtual reality technology and that the group performing the training in virtual reality reported a significantly better subjective experience scores, and due to fewer reported distractions remained more focused on the training content compared to the group that underwent the training in a real chemical laboratory. The results of the Master’s thesis suggest that virtual reality presents an effective alternative to traditional live training methods. Future research should be conducted with larger groups focusing especially on the long-term retention of the acquired knowledge and on the application in real-world scenarios, such as laboratory exercises, device training, and safety procedures training, to fully reveal the potential of virtual reality for educational purposes.
Keywords: virtual reality technology, Meta Quest, correct use of fume hoods in virtual reality, correct use of fume hoods in a chemical laboratory, R programming language
Published in DKUM: 20.11.2024; Views: 0; Downloads: 0