• Structural analysis of Formula Student vehicle chassis using Ansys software

    pg(s) 52-56

    Formula Student is a student engineering competition. Students all over the world compete to build a racing vehicle. One of the main elements of this vehicle is the vehicle chassis. The chassis is one of the most important elements from the aspect of driver safety. There are different chassis design concepts. The two most common are the monocoque chassis and the tubular chassis. In this paper, a detailed structural analysis of the tubular chassis of the Formula Student vehicle was performed using the software. The chassis model was created in the CATIA software, and then the structural analysis was done in the ANSYS software. By applying modern software, it is possible to better understand the problems during construction, and significant financial and time savings can be made. ANSYS software can also be of great help in chassis optimization.

  • Heat-insulating lightweight concretes and composite materials on the basis of inorganic binders with application in construction

    pg(s) 47-51

    A general overview of a number of thermal insulation materials and products made on the basis of inorganic binders (mainly Portland cement) is presented. The technological methods of production, the main operational indicators and the application in construction of various heat-insulating and structural-heat-insulating lightweight concretes are examined. The structure of various cellular concretes (foam concretes and aerated concretes), composite materials and lightweight aggregate concrete was analyzed. The role of the origin, technological processing, characteristics and composition of different types of light additive materials for the formation of the final operational properties of the products has been traced.

  • Robust Control With Fuzzy Based Neural Network For Robot Manipulators

    pg(s) 42-46

    The utilization of robotic systems is prevalent in various industries, such as defence and automotive, and is commonly utilized in industrial settings. The movements of these systems can be controlled through software programming, allowing for the manipulation of objects and modification of trajectory as desired. However, it is important to exercise caution during these operations as improper manipulation may result in undesired outcomes. As a result, the control of robotic systems has become a crucial aspect in modern industry.
    The parameters of robotic systems are subject to change based on the loads they carry. Robust control is a method that adapts the control system to accommodate these changes in parameters, thereby maintaining stability and performance. This control method allows for the desired level of control to be maintained even in the presence of changing system parameters. In contrast to traditional robust control methods, robust control utilizes variable parameters with a constant upper limit for parameter uncertainty. Control parameters are updated over time using cosine and sine functions, however, determining appropriate values for these parameters can be challenging. To address this issue, a neural network model utilizing fuzzy logic compensator is employed to continuously calculate the appropriate control parameter values. The effectiveness of this proposed control method is demonstrated through graphical representation.

  • Conceptual design and 3D modeling of a microfluidic device for liver cells investigation

    pg(s) 39-41

    The cell engineering is one of the most developing fields during the last decade needing specially fabricated polymer microfluidic devices and systems. One of the main functionalities of the microfluidic devices is to mimic the in-vivo environment where the cells and tissue live. The various types in-vitro microfluidic devices and systems could replace the experiments with animals in the biomedical investigations. The aim of this publication is 3D modeling and simulation of a microfluidic device for liver cells investigation. Suitable materials could be used with main properties related with fully transparency and bio-compatibility of the selected polymers. A new technology for development of the microfluidic device will be proposed, incorporating a thin layer of liver cells for investigation of their behavior during treatment with different substances. The conceptual work principle of the developed bio-chip will be presented. The future investigations, related to the fabrication of a real physical prototype and research experiments will be mentioned briefly in conclusions.

  • Determining normalized friction torque of an industrial robotic manipulator using the symbolic regression method

    pg(s) 21-24

    The goal of the paper is estimating the normalized friction torque of a joint in an industrial robotic manipulator. For this purpose a source data, given as a figure, is digitized using a tool WebPlotDigitizer in order to obtain numeric data. The numeric data is the used within the machine learning algorithm genetic programming (GP), which performs the symbolic regression in order to obtain the equation that regresses the dataset in question. The obtained model shows a coefficient of determination equal to 0.87, which indicates that the model in question may be used for the wide approximation of the normalized friction torque using the torque load, operating temperature and joint velocity as inputs.

  • Application of the mathematical model of Johnson-Kendall-Roberts in the study of the Young’s modulus of erythrocytes in patients with type 2 diabetes mellitus

    pg(s) 12-18

    The goal of the present study is to evaluate the elastic properties (Young’s modulus) of erythrocytes from healthy donors and patients with type 2 diabetes mellitus (T2DM), by using an atomic force microscope (AFM). Morphological and mechanical characteristics of red blood cells are studied in parallel by PeakForce QNM (Quantitative NanoMechanical Mapping) mode of AFM Dimensional ICON Bruker NanoScope V9 Instrument. Young’s modulus is calculated based on the mathematical model of Johnson-Kendall-Roberts by the application of the “two-point method”. AFM images of the erythrocytes from the healthy donors show that erythrocytes with a normal biconcave shape predominate. In patients with T2DM, the so-called erythrocyte polymorphism is studied. The Young’s modulus of erythrocytes, in patients with T2DM, significantly statistically increases by 27% (p≤0,001), compared to the data of healthy donors. The studied Young’s modulus by AFM can be used in clinical practice as a precise biomarker for the state of the red blood cells in T2DM.

  • Binary logistic regression for defect-free electron beam welding

    pg(s) 9-11

    Using the method of binary logistic regression, the dependence of dichotomous variables on one or more, quantitative or qualitative independent variables is studied. In order to solve problems with binary dependent variables, binary choice model estimation methodologies, such as logistic regression (logit) and probit regression (probit), can be implemented. The logistic model is based on the logistic distribution, while the probit model is based on the normal distribution. In this paper the binary logistic regression methodology is applied for obtaining defect-free welds by electron beam welding process, based on experimental data.

  • Synthesis and characterization of nanostructured hematite for wastewater treatment

    pg(s) 232-233

    Removal of heavy metals ions from water sources still represents a challenge and different materials are being developed in order to overcome it. Iron oxide nanomaterials receive a lot of attention because of their small size, high surface area, biocompatibility and low cost. However, most of the reported synthesis methods are multi-step and time-consuming. We investigated the co-precipitation method for the synthesis of nanostructured hematite prepared at different temperatures and different calcination times. The obtained materials were characterized by X-ray powder diffraction, scanning electron microscopy and infrared spectroscopy. The adsorption capacity for Pb(II) ions was found to be about 6–12 mg of adsorbed Pb(II) per gram of adsorbent.

  • Development and Production of Molding Equipment and Plastic masses using new compounding formulations, plastic pressing, drying, high-temperature liquid-phase synthesis and properties of a prototype batch of “yellow” paving stones

    pg(s) 228-231

    The research is related to the creation of new compounding formulations for the production of “yellow” paving stones. This was necessary due to denied access to a potential source of suitable raw material from the deposit near the village of Svetlen, Popovo municipality. Marlstone raw material from this deposit has the necessary qualities for such production, as a result of which, after hightemperature liquid-phase synthesis, new petrurgic phases with high physicochemical and mechanical properties can be formed. The new compounding formulation of the molding mass was developed on the basis of marlstone sedimentary rock from the Alexandra deposit, located near the village of Lovets, Targovishte district. The use of this compounding formulation makes it possible to obtain appropriate physicochemical and mechanical properties and a yellow coloring equivalent to that of the reference samples.

  • Study The Influence of Immersion in The Synthesis of Thin Layers on a Composite Substrates.

    pg(s) 226-227

    Dip coating is a common liquid deposition technique used in research and also for industrial production to produce polymeric, hybrid, and inorganic thin films of controlled thickness. During liquid deposition, the substrate withdrawal rate allows, in principle, easy tuning of the deposited film thickness. However, experimentally, unexplained thickness irreproducibility or strong fluctuations of sol-gel films are often observed when coating large substrates, which is a critical problem for optical coatings such as anti-reflective/reflective coatings. In this study, we present improved coatings obtained by sol gel-like multilayer structures composed of ZrO2-Y2O3 coating. The phase composition and morphology were analyzed by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) suitable for characterizing the surface properties of the obtained materials.

  • Investigation on mechanical properties of Co-Cr-Mo alloy manufactured by selective laser melting

    pg(s) 222-225

    Additive manufacturing approach is thought to be a key element to meet the needs of Industry 4.0. Selective laser melting (SLM) is a powder bed fusion additive manufacturing method for producing fully functional components. It is critical to determine the fatigue behavior of components produced by selective laser melting in order to fulfill the needs of industries with rigorous norms and criteria, such as the aviation industry. However, the rapid heating and cooling cycle caused by the nature of the SLM process has a negative mechanical effect on the components manufactured by this process.. Mechanical properties such as hardness and fatigue behavior should be disclosed for Co-Cr-Mo alloy manufactured by SLM technique. In this study, hardness and fatigue tests were performed on Co-Cr-Mo alloy components manufactured by SLM, and microstructure images were acquired and evaluated. When the microstructure of the samples was analyzed, tiny precipitates localized at the grain boundaries were discovered, along with the dominating γ phase. The average hardness value of the samples subjected to the Vickers microhardness test was 482±10. The fatigue life of the samples at the maximum stress of 800 MPa was 47,351 cycles. At the minimum stress of 400 MPa, the fatigue life exceeded 107 cycles. When fatigue fracture surfaces were examined, flat fracture surfaces similar to semi-cleavage were detected. The results will contribute to the literature on the mechanical characterization of SLM manufactured Co-Cr-Mo alloy components.