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This paper offers a study regarding regression and correlation analysis and intercomparison of stress concentration factors obtained from FEM analysis with factors imported from external sources. The procedure for obtaining the stress concentration factors is implemented and demonstrated on the shape configuration of an axially symmetric structural element with offset, tension loading. It is a typical representation of stress concentrators of the shape-discontinuity-dimension-load configuration applied in structural elements mainly from the engineering and construction fields. The data thus obtained are then subjected to regression and simple correlation analysis. Three regression models based on 2nd- and 3rd-degree polynomials and power function are applied. These results are further subjected to a detailed procedure of comparison with the values of the stress concentration factors obtained from two other independent sources. Finally, a detailed analysis of the possible reasons for the registered value deviations is performed.

The present paper discusses a new approach for the experimental determination of modal parameters (resonant frequencies, modal shapes and damping coefficients) based on measured displacement values, using the non-contact optical method of digital image correlation (DIC). The output is a newly developed application module that, based on a three-dimensional displacement matrix from the experimental measurement results, can construct a frequency response function (FRF) for the purpose of experimental and operational modal analysis. From this frequency response function, the modal parameters of interest are able to be determined. The application module has been designed for practical use in Scilab 6.1.0, and its code interfaces directly with the ISTRA4D high-speed camera software. The module was built on measurements of a steel plate excited by an impact hammer to simulate experimental modal analysis. Verification of the correctness of the computational algorithm or the obtained modal parameters of the excited sheet metal plate was performed by simulation in the numerical software Abaqus, whose modal shapes and resonant frequencies showed high agreement with the results of the newly developed application.

The presented paper dealt with the concept of an innovative manifold header for evacuated tube solar collectors. The proposed concept eliminates the drawbacks of conventional manifold headers, especially the serial connection of heat pipes that operate under uneven conditions. The advantage of the proposed design of the manifold header is also an increase in the heat exchange surface and the possibility of conducting the heat transfer media flow in a parallel flow arrangement, which increases the overall efficiency. The concept of the manifold header was evaluated on five variations of design with the use of the computational fluid dynamics (CFD) analysis. The results of the CFD analysis confirmed the functionality of the concept and also enabled the selection of the most suitable design elements, which were incorporated into the final design of a manifold header in the pre-prototype phase of manufacturing.

Structural element shape optimization based on the biological growth method is increasingly used nowadays. This method consists of two main methods: topological optimization (soft kill option—SKO) and shape optimization (computer-aided optimization—CAO). This paper presents the solution procedures for both shape optimization and topological optimization. In applying these methods, first of all, a certain stress norm must be established, where the most appropriate and most used criterion is the equivalent stress according to von Mises. The application of the mentioned optimization methods is illustrated by several examples. The aim was to compare the change in volume or mass and the maximum stress of the structural elements between the different designs: the initial design, the design after topological optimization, and the design after shape optimization.

Isogeometric analysis (IGA) represents a relatively new method of problem-solving in engineering practice. A huge advantage of this method over the finite element method (FEM), is the reduction of the simulation execution time. Non-uniform rational B-splines (NURBS) allow the use of higher-order basis functions, thus increasing the accuracy of the solution. This paper deals with the comparison of structural analysis of thin-walled structural elements using isogeometric analysis and the finite element method. The investigated objects are modelled using a single patch in MATLAB. The basic functions are created from NURBS, which were previously used in the creation of an accurate geometric model. The paper contains a comparison of the results obtained by the above-mentioned methods. All computations are performed in the elastic domain.

The object of the upgrade presented in this paper was an older analogue-based universal testing machine preferably designed for tensile testing. The objective of the upgrade was to create a new digitized measurement chain capable of also operating in the mode of simple fatigue tests with cyclic tensile stresses. The upgrade of the equipment mainly included the processes of calibration, creation of related calibration jigs, creation of transformation dependencies and digitization, creation or completion of missing parts of chain-signal conditioning modules, A/D converters, special jigs, etc., as elements of the experimental hardware. The degree of correctness of the calibration and of the transformation dependencies created was verified by regression analysis, and this was verified by simple correlation analysis. The correctness of the proposed modifications, was verified on the basis of the fatigue tests performed for cyclic loading. Thus, it was possible to design, develop and functionally verify a new measurement chain based on an older universal testing machine. Thus, a partially digitized pulsator was created for the possibility of fatigue testing in a technically or functionally limited mode, mainly for educational purposes as a temporary replacement for the order of magnitude more expensive commercially produced test systems.

Technological units of water reservoirs and power plants include sluice gates which are designed to completely seal the inflow or outflow of water in supply or discharge channels. This article describes the issue of technical assessment of a sluice gate made in the 1950s. Such structures are characterised by states of significant corrosive wear, permanent deformations of contact and sealing surfaces as well as increased levels of residual stresses. In such cases, it is difficult to determine service life using only numerical modelling methods, mainly due to problematic definition of material properties and boundary conditions. Therefore, for safety assessment, it is necessary to verify these facts experimentally. This article presents the procedure for assessing safe operation of the sluice gate on which places with permanent deformation and a broken part of the guide wheel flange were identified. By means of numerical modelling, we identified critical stress values at the locations of reinforcing elements, which were modified, and the stress values were reduced by about 15%. The results of numerical modelling were verified at select locations by experimental measurements during operation using strain gauges. The maximum values of operational normal stresses in the assessed places reached about 27 MPa. Based on the comparison of obtained results and taking into account values of residual stresses reaching up to 190 MPa made by shielded metal arc welding, it can be stated that, for safe operation of the sluice gate, it is necessary to follow the proposed procedure during its lowering and to modify the reinforcing elements structurally.

The energy storage field is nowadays a highly ranking topic. This research deals with the installation and analysis of the ice storage system which combines heat pump, solar absorber, and ice storage tank (phase change material—PCM). This system uses a special kind of solar absorber – header pipes (HDP), which have no thermal isolation compared to the common solar absorber. Thanks to that the HDP, pipes can absorb thermal energy not only from the sun but also from the environment. The rain or snow also affects heat exchange. All that is provided by one technical device. The system can store thermal energy gained from the solar absorber into the ice storage tank for future usage. Research works with data from the real operation, for a period of the year covering all working phases/modes of the system. The analysis of the data led to the identification of several specific modes of the system, especially from the processes taking place in the PCM storage tank during its charging and discharging at various time stages of operation of the whole system. The installation and analysis of the ice storage system probably took place for the first time in Slovakia and Slovak Republic’s conditions. Besides, this system was not installed on a new low-energy house, but on an older family house with thermal insulation. The aim of this installation was also to demonstrate the usability of the ice storage system in an older house and potentially reduce the homeowner’s fees thanks to new technology with higher efficiency. We managed to comprehensively analyze and describe the operation of this system, which also appears to be highly efficient even in a family house with a lower energy certificate, than today’s new low-energy buildings. The results showed a significant efficiency difference in favor of the ice storage system compared to conventional heating systems. The total analysis time was 1616 h and the total efficiency of this heating system—the seasonal coefficient of performance (SCOP) was 4.4. Compared to the average SCOP 3.0 of conventional heating systems for new low-energy houses, the total efficiency increased by 46.6%. These results could therefore be considered as beneficial, especially if we take into account that this system was installed on an approximately 40-year-old family house. The analyzed ice storage system is still working today. The main goals of this paper were to describe the heat pump’s duty cycle with ice storage (PCM) based on real-life data and bring a detailed description of the heat transfer medium behavior at various phases of storing/utilizing heat in the vertical ice storage’s profile for increasing efficiency.

Sales of electric cars and vehicles (EVs) have recently been showing a rapidly growing trend. In connection with rising electricity prices as well as social pressure on the environmental impacts of electromobility, there is also increasing interest of EV owners in the ecological source of electricity. The largest group of owners of EVs are residents of family houses, so, logically, they focus their attention on the possibility of using photovoltaic (PV) charging systems for EV charging. The design of the PV system for supporting EV charging is problematic due to several input parameters in the calculation of energy needs and due to the inconsistencies of electricity generation with normal electric vehicle (EV) charging time. While the PV system produces electricity during the day, family homeowners require charging EVs mainly at night. This requires batteries as part of a PV system. The optimal design of the PV of the battery system must take into account the real consumption of EV, the average daily distance traveled, the location, the weather bridging time, and, last but not least, the investor’s financial situation. The timing mismatch of electricity needs and generation may result in the oversizing or sub-scaling of the PV system depending on the time period for which the investor claims full coverage. With an average daily EV consumption of 10 kWh/day, the overproduction of electricity may be at 8620 kWh per year if it is required to fully cover PV systems in January. Conversely, for the installation of PVs for full coverage in August, the year-round electricity deficit will be 1500 kWh per year. For the analyzed geographical conditions, i.e., Latitude 48.8, the optimum performance of PV system for one-day electricity storage is 3.585 kW. This corresponds to the full coverage of EV consumption in March, the price of the whole system varies from EUR 9000 to EUR 20,000 depending on the type of battery. In addition to the battery price, the required accumulation time for electricity to overcome adverse weather increases the required performance of a photovoltaic system (PVS), which again results in system overshooting and financial loss by not using the generated electricity. This cycle of interdependencies is usually very difficult to adjust optimally. In the contribution, we analyzed the mutual relationships of calculating the performance of a PVS according to the daily consumption of EV and required time of overcoming adverse weather. The input data for the analyses were normal average EV consumption and the number of daily km traveled from 10 to 100 km/day scaled to 10. The optimization process consisted of determining the necessary performance of the PVS and its production in the event of a requirement to ensure full energy demand in each month. In addition, different types of batteries that influence the investment price enter into optimization analyses. This depends on the energy density of a given battery, the depth of discharge, capacity, and type. The result of this research is a computational model for determining a new indicator—we called it the monthly deviation factor. This indicates the degree of oversizing or undersizing of the PV system in relation to the stated factors.

This paper describes a problem related to a casting bridge crane with a combined load of 200/50/12.5 t and a span of 18.6 m, working in a heavy metallurgical operation. Due to the specific stress of the structure after its long-term operation, longitudinal fillet welds between the upper flange and the web of the main box beam on the rail side of the 200 t trolley were irreparably damaged. As a result, the cross-section of the main beam had opened, thereby substantially reducing its strength and stiffness. This resulted in a disproportionate increase and undesirable redistribution of stresses in the beam and, at the same time, an increase in the probability of acute fatigue or the loss of stability of the elastic beam shape. Therefore, the rectification of the damaged load-bearing structure was carried out by specific structural modifications. Critical load-bearing elements were subjected to complicated strength and fatigue life analyses before and after rectification. These analyses were supported by experimental measurements. The applied modifications resulted in a partial strengthening of the lifting device with the possibility of its further operation, but only in a limited mode, with a limited period of operation with a time limit of 2 years and a reduced total load capacity of 150 t. The applied methods are also applicable for the fatigue analysis of load-bearing elements and equipment for bridge, gantry and tower cranes, crane tracks, road and railway bridges and support structures under machinery and other devices with a dominant transverse and rotating effect.