• Statistical Analysis of the Mechanical Properties of Aluminum Alloys EN AW-6060 (AlMgSi0,5)

    pg(s) 97-100

    Aluminum belongs to the group of light metals, which as pure aluminum does not have good enough mechanical properties for most engineering requirements. Therefore, in order to improve the exploitation properties of aluminum, it undergoes an alloying process, where different chemical elements are added to it, each of which has its own different role. Alloying is carried out mostly to increase hardness and tensile strength, then to increase machinability and stiffness, and sometimes toughness and castability. The most important chemical elements used for alloying aluminum are magnesium, copper, silicon, zinc and manganese, while chromium, titanium and iron are used as impurities. This paper presents the parameters of descriptive statistic mechanical properties of aluminum alloys EN AW-6060 (AlMgSi0,5).

  • Processing and properties of polymer – mineral compositions

    pg(s) 93-96

    Recycled plastics find more and more applications. In addition to recycled bulky products, the number and type of products also being used in polymer -mineral composites based on recycled PE and PP. One of the paving products sought by investors are traditional concrete blocks. However, they have their drawbacks, they are heavy, so their transport, logistics must meet stricter requirements, are products that are not very resistant to cracking as a result of impact, are fragile. Mineral-polymer products are the solution to such problems. Innovative compositions for their processing are a polymer – mineral mixture, containing mainly recycled material and mineral fillers (sand, ceramic waste dust). They are therefore products made of waste materials from recycling, recyclates and flakes of polymer materials.
    The technology for producing the polymer – mineral composition is based on the extrusion and compression molding technology of the compositions obtained. Polymer compositions are secondary materials, after recycling in the form of recyclates, flakes, and waste plastics, mineral fillers, that is waste ceramic dust, sand as well as activating substances (dyes, plasticizers, adhesion compatibilizers, polymermineral wetting agents). As a result, plastic waste and ceramic waste that cannot be recycled will be effectively processed.
    The sprinklers were made of various polymer materials (PP, HDPE) as well as characterized by different shape of working elements and a variable degree of contamination with mineral sludge. The research on the structure of manufactured materials and melt flow rate are presented. The influence of the type of material and mineral deposits on the process ability of the tested polymer-mineral compositions was determined.

  • Determining the quality of renovation layers using laser technology

    pg(s) 90-92

    The paper presents the results of research aimed at determining the quality of renovation layers using laser technology. In order to repair and renovate shaped parts of molds for casting aluminum alloys under high pressure, samples of experimental welds were prepared on the base material quality 1.2343 (Dievar). The renovation layers were created using additional materials Dievar, UTP A 7002 and NIFIL NiCu7 res. NiCu7 with Dievar combination. The microstructures on the cross-sections of the deposits were checked using the light microscopy technique. The technique of scanning electron microscopy and semi-quantitative EDX microanalyses were analyzed distribution of alloys in deposits. The microhardness of the deposits was determined.

  • Major operational characteristics of an innovative ceramic beehive

    pg(s) 86-89

    Prototypes of an innovative collapsible beehive, built of long-lasting, structural elements of quartz ceramics with high atmospheric resistance and the presence of air cavities with thermal insulation properties, were prepared. Prescription compositions, an original set of molds, and an adequate heat treatment regime applicable to obtain the structural details were developed. The role of the various technological factors in the formation of the performance indicators of the end products was analyzed. The main characteristics of the prepared experimental prototypes and their major functional advantages in comparison with the existing standard and traditional hives were observed. The presented innovative beehive provides a favorable natural habitat for the normal and safe development of bee families and allows the full application of modern approaches for the efficient and ecological production of high-quality natural apian products.

  • Intelligent Energy Guardian for Polygeneration Devices: Design, Implementation, and Experimental Evaluation

    pg(s) 83-85

    The article presents an intelligent energy guardian for a polygeneration device. The proposed solution aims to optimize energy usage and minimize wastage by incorporating smart control algorithms that continuously monitor and adjust the energy flow between different subsystems of the device. The energy guardian utilizes machine learning techniques to learn the device’s energy usage patterns and adapt to changing conditions, such as varying energy demands and supply constraints. The article outlines the design and implementation of the energy guardian, and presents experimental results that demonstrate its effectiveness in improving energy efficiency and reducing operational costs. Overall, the intelligent energy guardian offers a promising solution for enhancing the performance of polygeneration devices and promoting sustainable energy use.

  • Analysis of the densification of a biomedical titanium alloy produced by powder metallurgy

    pg(s) 73-76

    Titanium as a raw material for production is very expensive due to its high price and the complex production process. One of the successful alternatives for the production of titanium alloys and final products is powder metallurgy technology. In this work, a Ti-20Zr alloy for biomedical applications was produced using the powder metallurgy process. The density values determined for the compacts depend on the compression pressure. Namely, the compressibility of the powder mixture increases with increasing compaction pressure. A higher sintering temperature as well as a longer sintering time are more favourable to obtain higher values for the sintered density. Similarly, the compression coefficient is lower for samples compacted at higher pressure, while its value increases with increasing sintering temperature. The volume change in the volume of the sample is more pronounced after sintering at higher temperature and shorter time.

  • Stress and stability calculation of the third pass module of the steam boiler during lifting

    pg(s) 69-72

    This paper presents the calculation of the stress and stability of a third-cycle module of a steam boiler during the lifting process. A steam boiler is a key element of a cogeneration plant, so all calculations are performed according to prescribed standards. Before the numerical analysis of the steam boiler, the characteristics, components and function of the boiler are described, as well as the required standards. The 3D model of the boiler was created using the Abaqus/CAE 2016 program package according to the manufacturer’s technical documentation. Using the finite element method, the stresses and stability during lifting of the boiler from the horizontal and vertical positions were calculated and presented. It was found that when lifting from a horizontal position, the structural stress values of the main elements do not exceed the allowable values. On the other hand, when lifting from a vertical position, the stresses exceed the allowable values. In this case, the connection point between the lug and the profile was checked and analytically dimensioned. The obtained values of the stability analysis of the boiler module are satisfactorily defined and there is no risk of buckling in both cases of lifting. The boiler conforms with the standard and fulfils the requirements handed over to the engineer.

  • Extended research on the efficiency of internal crystallization chemical admixtures for cement concrete – mechanical and structural characteristics

    pg(s) 64-68

    In recent years, the use of internal crystallization chemical admixtures for concrete and mortar to increase their water-tightness and other physical and mechanical characteristics has been of increasing importance in modern construction. These types of chemical modifiers allow for the effective replacement of conventionally performed waterproofing works (membranes, rolls, brushed or sprayed coatings, etc.) by purposefully improving the physical-mechanical characteristics of structural concretes, rendering them, to one degree or another, impermeable to water or/and aggressive agents from different origins. In the specialized world market for such products there are several leading competing companies – producers of internal-crystallization chemical admixtures, which have different activity in Bulgaria. The new extended research on such several new types of those admixtures were reported and discussed. The complex mechanical and structural tests are conducted and respective results are compared to predict the admixture’s efficiency of their ability to limit the ingress of water into concrete and reinforced concrete sections, as well as their ability to increase the durability of concrete as the main structural material.

  • Theoretical study of β-cyclodextrin inclusion complexes with vitamin K

    pg(s) 37-40

    One of the main problems in modern society is related to improper and insufficient nutrition, as a result of which various diseases develop, the treatment of which requires additional intake of vitamins in the form of nutritional supplements. Fat-soluble vitamins have important biological activities, but their application is limited due to their low solubility and stability. One way to improve their properties is to incorporate them into complexes with host molecules, such as cyclodextrins, the most commonly used host molecules in the pharmaceutical industry. The theoretical study presented here aims at delianating the interactions of vitamin K3 and its analog phthiocol with β-CD drug delivery system. To achieve this goal, 1:1 complexes of different forms of vitamin K with β-CD were modeled. The influence of various factors on the thermodynamics of interactions of the guest molecules with the macrocycle (host molecule) was evaluated.

  • Results from the plastic pressing of experimental ceramic pavers of “yellow” paving stone type

    pg(s) 34-36

    The results of the plastic forming of ceramic pavers with a large volume and size are observed to produce better compaction of the raw material. The used ceramic mixture is based on a sedimentary rock with relatively high moisture content and firing shrinkage which gives the common yellow colour after a high-temperature liquid phase synthesis. The results of one-fold pressing revealed the occurrence of deformation processes in the drying stage and during the temperature regime. As a consequence, the pressing pressure should be increased and the residual water amount needs to be reduced to an optimal content.

  • Investigation of the influence of the convergent part of the FSAE vehicle restrictor on the airflow using CFD

    pg(s) 30-33

    The Formula Student competition is the most challenging, complex, and attractive student engineering competition in the world. Students from universities around the world compete to build better vehicles. The competition consists of several different disciplines, which are divided into two groups. The first group consists of static disciplines, where students who are members of the team defend the vehicle project in front of eminent experts from the world of the automotive industry and auto-moto sports. The second group is the group of dynamic disciplines, which is made up of several disciplines related to the analysis of vehicle behavior in real conditions. One of the main challenges facing the team members is designing the vehicle’s propulsion system. At competitions in the IC engine class, power units from a certain class of motorcycles are most often used. The main limitation related to the power unit is that all intake air must pass through a 20 mm diameter. One of the solutions to the mentioned problem is the use of a convergent-divergent nozzle with a throat diameter of 20 mm. In this paper, the influence of the convergent part of the nozzle on the airflow through the nozzle itself was examined. Models were created for several restrictors and they were tested by CFD simulation in ANSYS Fluent software

  • Drilling mud properties with added egg shell

    pg(s) 26-29

    The use of biodegradable waste is interesting for many companies from different industries, and in the last few years, more detailed research about its usefulness in the oil and gas industry, specifically as potential additives for the preparation of water-based drilling mud, has begun. Given that this type of research is globally important, there are data on the use of different types of food waste for this purpose, and scientists have mainly researched the biodegradable waste that is generated in larger quantities in a certain part of the world. Among the different types of waste whose effect has been investigated through laboratory measurements of various properties essential for drilling mud, there is also some data on egg shell. In this article, detalied set of data shows how egg shell affects the filtration properties of the drilling mud, the rheological properties, as well as the swelling reduction of the clay component of the rock when it is in contact with drilling mud with added egg shell in its composition.