STN EN Research Articles

Experimental verification of the compressive stiffness of high-damping rubber bearings (HDRB) according to STN EN 1337-3 and their effectiveness in seismic isolation for cable-stayed bridges

Experimental verification of the compressive stiffness of high-damping rubber bearings (HDRB) according to STN EN 1337-3 and their effectiveness in seismic isolation for cable-stayed bridges

The Effect of Artificial Ageing on the Changes in Selected Properties of Organic Coated Sheets.

This contribution presents the results of research focused on changes in selected properties of organic-coated steel sheets in a corrosive environment of salt mist. The aim of this study was to characterise coated sheets and to analyse the influence of elevated temperature on changes in their selected properties. The methodology and experiments were chosen to simulate the accelerated ageing and to evaluate the surface of organic-coated steel sheets. During the research, the effect of artificial ageing due to increased temperature on changes in mechanical properties of coated sheets was monitored, which were determined by tensile testing according to STN EN 10002-1. The fracture surface of the test samples was analysed using a SEM. The following observations were made for the evaluation of coating by cross-cut tests according to EN ISO 2409. Corrosion tests were carried out by conducting salt spray corrosion tests according to EN ISO 9227. The test specimens were artificially sectioned using a laser beam. The results of the research experiments confirmed the assumption that the utilisation of the laser beam was convenient for the creation cross-cut test of the material. After the ageing test, only small significant changes in the basic mechanical properties of the tested materials were observed. It is necessary to take into account that there were changes in the appearance of the coating. The cross-cut test confirmed the results that the plastic-coated sheets could be utilised in salt corrosion environments.

Energy usage of spruce with waste face masks and spent coffee grounds as fuel in a pellet boiler

It is necessary to reduce dependency on fossil fuels for heating and waste generation, while also utilizing the energy potential of waste materials. One possibility is to create fuel pellets where waste makes up a small proportion so that the properties of the wood are not significantly altered with. This article investigates the energy usage of pellets containing spent coffee grounds (5 % or 10 %) and waste face masks (5 % or 10 %), with spruce sawdust as the primary input material (80 % or 90 %). The elemental, thermogravimetric, calorific value, mechanical durability, emission and performance characteristics, and ash melting temperatures of the pellets were evaluated during the experiment. The results were compared with respect to pure spruce sawdust pellets and the specified limit values for wood pellets in commercial and residential applications as specified in ISO 17225 [18]. Both tested samples met the element content limit (N, S, Cl, As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) for the highest quality grade (A1). No significant amounts of harmful elements were detected. The samples also complied with the limits of moisture content, ash content, and net calorific value (also known as lower calorific value). All samples met the emission limits in their respective classes (3, 4, or 5) according to STN EN 303-5+A1 [35]. However, the samples failed to meet the limit values for mechanical durability and ash melting temperatures. Despite this, the manufactured pellet samples represent a suitable fuel product for combustion purposes as a more sustainable thermal energy fuel.

A device for dynamic testing of the refractory ceramic resistance to biomass ash

The corrosive effects of biomass ash on refractory materials in combustion chambers pose challenges. Development of new castable refractory materials which are more resistant to corrosion requires tests that accurately reflect the conditions occurring in real devices. This article describes the Computational Fluid Dynamics (CFD) design and construction of a device for evaluating the corrosion of refractory materials in dynamic regime. The device allows to simulate combustion chamber conditions accurately, to regulate an injection of corrosive medium on the tested material surface under the specified conditions (temperature, time, and flow). In the present investigation the conventional refractory material was exposed to attack of biomass ash at the temperature of 1300 °C for 3 h to test the functionality of the device. A burner with technology oxygen–enriched combustion was used to heat the device. The corrosion tests were conducted in accordance with the standard P CEN/TS 15,418 and the standard STN EN ISO 21404. The operational state required for corrosion tests at 1300 °C was achieved within 1.12 h. The extent of refractory material degradation in the dynamic corrosion regime was evaluated using electron microscopy-energy dispersive spectroscopy (EM-EDS) and compared with the results of a static crucible test (3 h at 1300 °C). The dynamic test provided sufficient information on the interactions of corrosion medium with the refractories. Its main advantages are the maintenance of non-equilibrium conditions by controlled deposition of the corrosion medium in quantity from 1 to −100 g/h, fast heating rate to operating temperature (20 °C/min), and the possibility of conditions variability during tests (temperature, ox-red. atmosphere, fuel gas flow etc.).

The Differences in Shape Stability for Hornbeam (Carpinus betulus L.) Lumber with and without Spiral Grain

Spiral grains are one of the most important tree growth defects that can remarkably affect the shape stability of lumber. This growth defect is observed by an oblique arrangement of axially oriented cell elements in the wood. This research focused on identifying and measuring selected shape changes caused by the spiral grains in the log. Hornbeam logs with spiral grain and with no spiral grain aged 60 and 52 years were selected to detect shape changes. Following the research and the norms of STN EN 1309-3 (49 1013), DIN (4074-5), and ASTM D245, it can be stated that spiral grain is an essential factor affecting the shape stability of hornbeam lumber. In the case of lumber with spiral grain, the spiral grain increased by up to 8° within three months. The warp of both types (bow, crook) increased exponentially throughout the study, peaking between the third and fourth week with an increase in warp bow of 26 mm and 17 mm in warp crook.

Effect of selected bacteria of the genus Pseudomonas on the quality of raw cow’s milk

Pseudomonas spp. are a psychrotrophic species associated with milk spoilage caused by its enzymatic activities. The aim of this study was to identify Pseudomonas spp. in raw cow’s milk and to investigate their associated enzymatic properties and the ability to produce pyoverdine pigment. For microbiological analysis, 2 ml of milk samples was taken in sterile sample boxes. Milk sampling was carried out according to the principles of STN EN ISO 707. By identification using the PCR method, of n=320 samples of raw cow milk a total of 73 isolates of Pseudomonas spp. were identified as P. putida (34.25%); P. fragi (13.70%); P. lundensis (9.59%) and Pseudomonas spp. (42.47%). Proteolytic activity determined at a temperature of 7°C was positive from n=20 selected isolates of Pseudomonas spp. (60%) isolates and a temperature of 25°C was positively detected (85%). Lipolytic activity determined at a temperature of 7°C was confirmed in 35% of isolates and a temperature of 25°C it was confirmed in 70% isolates. Pyoverdine pigment production was detected in 65% of isolates. The results reveal the enzymatic activity of Pseudomonas spp. present in raw cow’s milk and its spoilage potential at different temperatures in relation to pigment production.

IMPLEMENTATION OF IO-LINK TECHNOLOGY INTO THE HANDLING AND SORTING SUB-STATION OF THE FESTO FMS 500 AUTOMATED LINE

The article deals with implementing IO-LINK components in the sorting station of the FESTO FMS 500 automated line and their experimental verification based on the principles of IO-LINK technology. The implementation of such technology also includes the upgrade of the PLC control to PLC S7-1500 (SIEMENS), the addition of an IO-LINK device (BALLUFF BNI005H), and a signaling light device from the same company (SMARTLIGHT BNI007F), which ensures the indication of workplace state. Communication between the PLC device and the IO-LINK devices is carried out via the PROFINET communication network. Installing the signaling light device at the sorting station of the automated line provides light signaling messages for the operator (concerning the standard STN EN 61310-1). For example, the indication of the filling of the reserve warehouse using a light signaling message means the operator needs to empty the individual warehouses to repeat the sorting operation. In addition, part of the article is the implementation and evaluation of experimental measurements, the aim of which is to determine both the individual sorting times of various components, as well as determining their maximum number during the sorting process in connection with increasing the level of automation of the sorting station as such.

An Experimental Study of High-Damping Rubber Bearings (HDRB) and Their Implications for the Seismic Performance of Cable-Stayed Bridges

This article investigates the efficiency of high damping rubber bearings (HDRB), which are made of special rubber with excellent damping attributes and layers of steel. HDRB isolators have excellent flexibility, vibration reduction ability, and high restoring ability for controlling the seismic response of long-span cable-stayed bridge systems under near-fault ground motions. The seismic isolation of cable-stayed bridges is achieved using high-damping rubber bearings (HDRB). High-damping rubber bearings have excellent seismic effects during earthquakes. The elastic stiffness of the bearing depends on the degree of deformation. When the deformation is small, the stiffness will be large. Therefore, compressive stiffness is one of the key parameters in the design of seismic isolation bearings for cable-stayed bridges. For this reason, predicting the behavior of high-damping rubber bearings under compressive loads is highly important for their design. Therefore, the experimental verification of high-damping rubber bearings (HDRB) for compressive loading was tested according to the standard assumptions in STN EN 1337-3. Firstly, periodic vertical compression tests are performed, and the high damping rubber (HDRB) capabilities and energy dissipation are analysed, taking into account the effect of vertical compression and loading frequency. Secondly, a corrected calculation of the vertical stiffness for high-damping rubber bearings is proposed based on experimental data to provide a more accurate and realistic tool for measuring the vertical mechanical properties of rubber bearings. The test results prove that HDRB has the most advanced performance. For the fatigue property, the hysteresis curves of the HDRB plump both vertically, which provides a good energy dissipation effect. DOI: https://doi.org/10.52783/pst.431

A Case Study of Ergonomic Risk Assessment in Slovakia with Respect to EU Standard.

Attention on work-related musculoskeletal disorders (WMSDs) involves statistical surveys showing an increasing trend in the incidence of WMSDs. Technological development has led to new tools and methods for the assessment of physical load at work. These methods are mostly based on the direct sensing of appropriate parameters, which allows more precise quantification. The aim of this paper is to compare several commonly used methods in Slovakia for the assessment of ergonomic risk reflecting current EU and Slovak legislative regulations. A Captiv wireless sensory system was used at a car headlight quality control assembly workplace for sensing, data acquisition and data processing. During the evaluation of postures and movements at work, we discovered differences in the applicable standards: Decree 542/2007 Coll. (Slovak Legislation), the STN EN 1005-4+A1, and the French standards default in the Captiv system. Standards define the thresholds for hazardous postures with significant differences in several evaluated body segments, which affects the final evaluation of the measurements. Our experience from applying improved risk assessment methodology may have an impact on Slovak industrial workplaces. It was confirmed that there is a need to create uniform standards for the ergonomic risk assessment of body posture, including a detailed description of the threshold values for individual body segments.

MONITORING OF PESTICIDE RESIDUES IN GRAPEVINE LEAVES UNDER VARIANT FUNGAL DISEASE MANAGEMENT

Food contamination is the result of over-reliance on fungicides in crop production. The presence of pesticide residues in agricultural commodities needs to be strategically solved by applying gentle agrotechnical procedures. The research aimed to evaluate the effect of the treatment of grapevine with fungicides on the content and mobility of 4 active substances in the leaves of the variety Hibernal. The experiment included a control variant treated with fungicides and an untreated variant. We focused on monitoring the active substances of fungicides used in the first half of the vegetation: azoxystrobin, cyflufenamid, difenoconazole, myclobutanil, and another 25 active substances, in terms of multi-residue analysis methodologies. Grape leaves for analysis were collected on two dates: in the phenological phase of berry development BBCH 73 and 14 days after grape harvest – BBCH 91. Samples were prepared according to STN EN 15662. For qualitative analyzes of residues, we used the QuEChERS method in combination with liquid (LC-MS/MS) and gas (GC-MS/MS) chromatography with tandem mass spectrometry. In the untreated variant, the contents of residues from both leaves collection were in undetectable values. In the leaf samples of the treated variant collected in BBCH 73, we established higher values of residues than the MRL determines, namely for azoxystrobin 0.083 mg/kg (MRL – 0.01 mg/kg). Azoxystrobin is the active substance of the Quadris max fungicide, and we applied this preparation 41 days before the first collection of leaves. In the analyzes of leaf sampling from the treated variant after grape harvest in BBCH 91, we found a decrease in the content of all monitored residues below detectable values. We consider the gradual degradation of residues in biological materials to be a very favorable result from the point of view of their impact on consumer health and the environment. Through visual observations of the vegetation, we found out that even the untreated variant had a perfect state of health. Hibernal is a variety suitable for biological production systems, and we assume that even in vintages with high pressure of fungal diseases, it is possible to maintain the health of the grapevine with ecological products. Using the appropriate grape variety combined with the right agrotechnical interventions makes it possible to use safer ecological practices to produce healthy food, maintaining sustainability and a healthy natural environment. The research will continue in the early Table grape varieties, where the vegetation period is shorter, and space for breaking down the residues is more difficult.

MEASUREMENT OF MICROBIOLOGICAL QUALITY OF RAW GOAT´S MILK BY LASER FLOW CYTOMETRY

The popularity of goat's milk and its products is growing in Slovakia. Among the mandatory health safety features of raw goat's milk is the total bacterial count. It can be determined by the anchor plate-cultivation method, which is, however, tedious, and laborious. Laser flow cytometry is a modern alternative method for measuring the microbiological quality of raw milk. To use the results from laser flow cytometry method for legislative purposes, it is necessary to create a representative conversion of the primarily measured results obtained by this method into the CFU/mL scale. This work describes the creation of such a conversion for raw goat's milk, which will be valid for the Slovak region. After measuring several hundred individual and bulk tank samples of raw goat's milk on a BactoScan FC laser flow cytometer and at the same time using the anchor method according to STN EN ISO 4833-1 and after their subsequent logarithmic transformation, such a conversion was created in the form of log10(CFU/mL) = 1.0174 x log10(IBC/ml) + 2.7483. Subsequently, this was verified by comparing the recalculated and directly measured results in CFU/mL, using additional data set of samples. The influence of the somatic cell count in raw goat's milk, as a possible interfering factor, was also assessed.

Analysis of Normative Requirements and Technical Specifications of a Structural Design of the Mechanical Device Operating in the Amusement Industry

In current hectic times, people should be able to slow down and diversify their free time. Therefore, the contribution of the amusement industry should not be negligible but, on the contrary, should be seen as something where whole families can seek respite from ordinary worries and problems. For this reason, the presented paper was written, which represents an intermediate step in the design of an amusement facility suitable for amusement parks that respects the normative requirements. Technical standardization represents a set of rules, characterizations, guidelines, and results of activities necessary for mutual understanding when solving technical problems in production. Adherence to standards is essential when launching a product on the market. The main standard indicating the full functioning of an amusement device is STN EN 13814. Its analysis and the resulting technical specifications of the proposed equipment are the chief objectives of the paper.

Design of low-pressure transportable steel tanks for storing hydrogen for an electric tractor

The presented contribution offers a theoretical analysis of the possibilities of implementing hydrogen technologies in agricultural machines and tractors. It discusses in more detail the structural designs and strength calculations of low-pressure transportable steel tanks for hydrogen storage for the ET 3000 electric tractor, in which the accumulators will be replaced by designed metal hydride tanks. The structural design of low-pressure tanks meets the requirements of the STN EN 13322-2 standard, which deals with the technical and structural design of transportable pressure tanks. The design and construction of tanks are key from the point of view of the real implementation of hydrogen technology in a fully functional small tractor for the purpose of its long-term testing.

Comparison of Surface Roughness of Beech Wood after Sanding with an Eccentric and Belt Sander

The presented paper deals with a mutual comparison of the roughness of the sanded radial surface after an eccentric and a belt sander. The beech wood (Fagus sylvatica L.) was sanded with an eccentric sander ETS 125 REQ-PLUS and a belt sander BS-75 E-set from Festool with the grit sizes P40, P60, P80, P100, P120 and P150. The evaluation of the roughness parameters Ra, Rp, Rv, Rz, and Rt was carried out using a digital microscope with a 2.5 mm L-filter and an 8 μm S-filter under the conditions of the technical standard STN EN ISO 21920. The measured results were supported using microscopic analysis of the surface topography especially for surfaces with very high roughness. The experiment shows a lower surface roughness of beech wood sanded with an eccentric sander. The sander created a surface with smaller grooves, removed more protruding fibers and created a more homogeneous surface suitable for subsequent surface treatment.

The use of the acoustic tomograph and digital image analysis in the qualitative assessment of harvested timber – case study

Abstract Accurate qualitative evaluation of grown and harvested wood is a key issue from the point of view of its subsequent economic evaluation. With the current trend of global climate change and large volumes of wood damaged by harmful agents, automated methods of wood quality assessment are becoming more and more important. The work aimed to verify the applicability and significance of the results of using the acoustic tomograph for the qualitative assessment of selected tree species logs. Ten samples of log sections of non-coniferous and coniferous trees were evaluated, on which an image analysis of qualitative features was performed on a cross-section from their digital photograph and the image output of an acoustic tomograph software. The results were compared with each other and the accuracy of qualitative feature identification by acoustic tomograph was evaluated. At the same time, the results of the image analysis of the qualitative feature were compared with its assessment through STN EN 1309-3. It was shown that, when evaluated according to the Standard, qualitative features were overestimated by an average of 29.19% compared to the acoustic tomograph and by 28.22% compared to the digital photograph. The use of the acoustic tomograph confirmed a good level of accuracy in the identification of qualitative features even on logs of harvested wood, although it is primarily intended for the qualitative evaluation of standing trees.

Formation of Alpha-Case Layer during Oxidation of Ti6Al4V Surface by Annealing at 1050 °C and Change of Microstructure after Different Cooling Rates

The two-phase titanium alloy Ti6Al4V (often referred to as GRADE 5 or Ti64) is currently probably the most widely used type of Ti alloy. It is characterized by an excellent combination of strength - toughness - chemical stability. However, at temperatures above 500 - 800 °C it is prone to the diffusion of oxygen into surface layers, where the increased oxygen content creates the so-called “alpha-case” layer. The formation of this layer is associated with a reduction mainly in the deformation characteristics of the alloy. The paper focuses on the metallographic analysis of the "alpha-case" layer after annealing at 1050 °C with a holding time of 3 hours and cooling at different cooling rates (500 °C/s, 1 °C/s and 0.08 °C/s). Microstructure changes were observed by light microscopy using polarized light – PL, dark field – DF and phases were identified by SEM methods. The influence of changes in the microstructure on the mechanical properties was determined by measuring the microhardness HV0.2 /10 (STN EN ISO 6507) with Zwick / Roell ZHµ and measuring the resistance to impact stress KU (Charpy system STN EN 10045-1). Based on the microhardness measurement, an increase in the microhardness of the surface layers was observed at all cooling rates and at the same time, a decrease in the impact resistance was observed compared to the initial state.

COMPARISON OF QUANTITATIVE METHODS FOR DETERMINING THE ANTIBACTERIAL EFFECTIVENESS OF NON-WOVEN TEXTILES

This contribution is aimed at comparing two quantitative methods for determining the antibacterial effectiveness of non-woven textiles and assessment of permanence of the antimicrobial finish of the nonwoven textile materials prepared from polypropylene fibers. Experience and results obtained by the quantitative test methods specified in AATCC TM 100 and STN EN ISO 20743 intended to evaluate the effectiveness of the antibacterial finish are published in the contribution. Emphasis is placed on comparability of the selected test methods, on the test microorganism used in the study as well as on evaluation of the results of antibacterial effectiveness. The non-woven fabrics, that were the subject of the evaluation, were pre-treated by surface activation with low-temperature plasma at atmospheric pressure and subsequently finished using antimicrobial (AMB) nanosol solution with a concentration of 15 ppm Ag+, 30 ppm Ag+, 60 ppm Ag+ and 120 ppm Ag+. Antibacterial effectiveness before washing and after 5 washing cycles is demonstrated on the specific examples obtained from practice.

Impact of Road Tunnel Consumption on the Power Quality, Power Factor and Reactive Power Flow

In recent years there has been an increase in reactive power flow from lower voltage levels to higher voltage levels due to changes in the power grid. Road tunnels also contribute to the reactive power flow by their nature of loading. Tunnel consumption is mostly made up of lighting sources. Currently, the most commonly used lighting is LED-based, which includes current sources with non-linear volt-ampere characteristics and high capacitance. As a result, they draw distorted current from the grid and also generate reactive power to the grid. This paper analyzes the overall power quality based on STN EN 50 160, the total harmonic distortion of current, power factor, and reactive power of the road tunnel. The paper especially shows the effect of harmonic distortion of current on the difference between the fundamental harmonic power factor and the total power factor, and also the difference between the reactive power of the fundamental harmonic and the total reactive power.

THE INFLUENCE OF LOW-TEMPERATURE PLASMA ON PERMANENCE OF ANTIMICROBIAL NANO-FINISH

This paper describes the effect of low-temperature plasma on increasing permanence of surface finish of textile materials using an antimicrobial nanosol. Selected textile materials (polyester and polyamide woven fabrics, polypropylene non-woven fabric) were pre-treated by surface activation with low-temperature plasma at atmospheric pressure and subsequently finished using an antimicrobial (AMB) nanosol with a concentration of 60 ppm Ag+, 120 ppm Ag+ in the application solution. The goal was to increase the permanence of AMB nano-coating of textiles after washing and drying. To verify the effect of low-temperature plasma on increasing the permanence of the nanolayer, washing and drying was performed in accordance with the STN EN ISO 6330 standard. To determine antibacterial activity and effectiveness of the nano-coated textile materials, a quantitative test method was used in accordance with the technical standard AATCC TM 100. Evaluation of the antibacterial activity of the textile materials was performed before washing and after 20 washing cycles.

New test equipment for testing the watertightness of facade structures in-situ

With the current trend of construction of high-rise buildings in urban agglomerations, ensuring watertightness of their facade structures exposed to the effects of high-intensity wind-driven rain is coming to the fore. Laboratory experimental testing of water impermeability of elements of building envelope structures and their joints is performed in the process of preparation of the facade implementation in accordance with STN EN 1027: 2002 in rain chamber equipment. Due to the fact that the quality and functional properties of the finished facade are significantly influenced by the assembly technology and work discipline in its implementation, successful testing of the facade and its components in the rain chamber may not guarantee the watertightness of the finished facade. For this reason, the investor has the opportunity to check the finished facade in terms of its hydrodynamic safety and reliability by a functional test of its watertightness according to the standard regulation STN EN 13051 Curtain walling - Watertightness - Site test. The article describes in detail the new technological device for the implementation of the in-situ watertightness test of the facade, the measurement methodology, including its functional verification on the facade of the high-rise administrative building Nivy Tower in Bratislava.