STN EN Research Articles

The Effect of the Carbon Fiber Content on the Flexural Strength of Polymer Concrete Testing Samples and the Comparison of Polymer Concrete and U-Shaped Steel Profile Damping.

This article explores the effect of carbon fiber content on the flexural strength of polymer concrete testing samples and compares the damping of polymer concrete and U-shaped steel profiles. The experiments involved and described herein consisted of flexural strength testing according to STN EN 12 390-5 Testing of Hardened Concrete, Part 5: Flexural Strength of Test Samples. The test results were evaluated graphically and by calculations and were further processed in various programs. The experimental results indicated that the highest flexural strength value was obtained by the test samples containing 12% of carbon fibers while culminating at 17.9 MPa. The results showed that the highest increase of flexural strength was caused by the addition of 3% of carbon fibers to the mixture, which increased the flexural strength by 4.2 MPa, or 26.75%. The results indicated that, based on the shape of the regression curve, flexural strength culminated at 13% carbon fiber content. The experimental results demonstrated that the tested polymer concrete test sample had a 6.87 times higher attenuation coefficient than the U-shaped steel profile. The results showed that the polymer concrete test sample No. 4 reduced vibration acceleration deviation by 93.5% in 0.005 sec and the U-shaped steel profile by 32.9%.

Failure of Slender Concrete Columns Due to a Loss of Stability

Abstract The European standard for the design of concrete structures that are likely to lose stability requires taking into account the effects of second order theory. This effect increases the impact of a bending moment due to member deformation and additional eccentricity. Slender members can be calculated by the use of a non-linear method. This approach shows a deficit in global reliability for cases where the concrete columns fail due to the loss of stability before reaching the design resistance in the critical cross-sections. Buckling is a brittle failure which occurs without any warning, and the probability of its formation is markedly influenced by the slenderness of the column. Here, the calculation results are presented and compared with the results from an experiment which was carried out in cooperation with STRABAG Bratislava LTD at the Central Laboratory of the Faculty of Civil Engineering SUT in Bratislava. The columns were designed according to the methods stated in STN EN 1992-1-1, namely, a general non-linear method. The focus of this study is to compare multiple approaches based on codes used in Germany (DIN 1045-1, 2001) and Austria (ÖNORM B 4700, 2001) with the present European code mentioned above. The paper aims to compare the global reliability of slender concrete columns with variable slendernesses of 90 and 160.

Illumination simulation of working environment during the testing of cutting materials durability

Abstract Illumination in the workplace is one of factors, which substantially acts on worker, his performance, error rate and last but not least his health. It is necessary to create the suitable illumination of environment for the sake of interpretation of needed working performances and provision of efficiency. The suitable illumination is possible to ensure by modelling in various simulation tools. It is one of low – economically. Presented article is focused on illumination simulation of working environment during testing of cutting materials durability by simulation software Dialux. On the basis of input data, it is created the model of indoor illumination of real working environment which is subsequently optimized in accordance with standard: STN EN 12464 – 1: Light and lighting; Lighting of workplaces. Part 1: Indoor workplaces. Then this optimized model is compared with real state before optimization. The results are presented in the results section of this article.

The quality standardization in suburban bus transport by the transformation of the service quality loop

Abstract The article is dealing with the standardization of quality level in total approach it means the transformation of the service quality loop by STN EN 13816. The quality loop reflects the rating of the service provided from the point of view of the customer as well as from the operators (authorities) point of view. Individual quality aspects are closely related. The aim is to minimize the differences between the expected and the provided quality in order to stabilize the passenger demand. The article includes the possible approaches and methods for determining the standard service quality level in suburban bus transport which are based on the results of real measurements in Žilina self-governing region in specific years.

Experimental Quantification of Air Permeability of Building Envelope with Installed Controlled Ventilation System - Case Study

To meet the increasingly stringent requirements of standard energy consumption and thus reducing operating costs of buildings, it is necessary to use energy-saving elements of technical equipment and eliminate heat loss through the building envelope. The biggest losses are caused by heat transmission and ventilation in the form of uncontrolled air infiltration through the building envelope. Their elimination can be achieved by improving the thermal technical quantification of building envelope and increase its airtightness. Determination of air permeability as a measure of quality building envelope is possible using the method of measuring devices Blower-Door test. Any defects can be detected by detection tools, then propose a suitable method for their removal and thus prevent unwanted unregulated air infiltration into the interior. On the other hand, are opposed to the health requirements required air exchange in the room, which is a significant reason for the transformation of this mode of ventilation by uncontrolled air infiltration to a controllable ventilation system. The subject of the paper is in-situ measurement of air permeability of specific apartment envelope by Blower-Door test method and comparison the efficacy of the installed controlled ventilation system and hygiene requirements of the ventilation intensity for residential buildings. Laboratory verification of façade ventilation unit parameters in big pressure chamber - measurement of inlet ventilation flap airflows at variable pressure differences. Methodology for the measurement by Blower-Door test method to determine the air permeability of building envelope structures and functionality of controlled ventilation system was based on a series of 10 measurements in 5 regimes. The overall air permeability of the building envelope or its integrated part may be verified using the total air exchange rate n50at 50 Pa pressure difference, determined experimentally according to STN EN 13829. Comparison of measured values with standard values recommended by some European countries with a similar climate with sealed and with unsealed ventilation flaps, which can determine the impact on the overall airtightness of the building envelope. Calculation of total hygiene required air exchange rate of the apartment and its comparison with actual measured values by Blower-Door test method.

Effect of Copper and Molybdenum on Microstructure and Fatigue Properties of Nodular Cast Irons

The aim of this paper is to compare the microstructure, mechanical and fatigue properties of three types of the nodular cast irons - unalloyed nodular cast iron, nodular cast iron alloyed by Si and Mo and nodular cast iron alloyed by Si and Cu. For all the types, microstructure, mechanical properties and fatigue properties were investigated. Microstructure of the specimens was evaluated according to STN EN ISO 945 and by automatic image analysis. The image analysis system NIS Elements, interfaced with the light microscope, was used for the evaluation of the shape factor, equivalent diameter of graphite, count of graphitic nodules and content of ferrite. The mechanical properties were evaluated by the tensile test, impact bending test and Brinell hardness test. Fatigue tests were realised at sinusoidal cyclic push-pull loading (stress ratio R = -1) at ambient temperature (T = 20 ± 5 °C). They were carried out in the high cycle fatigue region (from 105 to 107 cycles) at frequency f ≈ 75 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100. The relationship between the amplitude of stress σa and the number of cycles to failure N, as well as the fatigue strengths, were determined.

Hardness Tests and Dimensional and Shape Precision Analysis of Construction and Agricultural Machinery Components

The article deals with hardness tests and dimensional and shape precision analysis of construction and agricultural machinery components, namely with the clamping head and case of hydraulic hammer. The clamping head is made of 41 4220 class (1.7131, 16MnCr5) construction stainless steel and the case is made of 41 5130 class (1.7218, 25CrMo4) construction stainless steel. The micro hardness was measured on VICKERS LM 700 AT hardness tester, according to the national standard STN EN ISO 6507-1: this procedure includes injection of a diamond regular four-bladed pyramid with a 136° peak angle into the tested material with following parameters: objective lens X50, load 10 N, indentation time 10 s. The average HV micro hardness value was determined from 10 measuring points (distances) on 70 samples of the hydraulic hammer case and from 10 measuring points (distances) on 200 samples of the hydraulic hammer clamping head. To measure dimensional and shape accuracy, Perthometer MAHR, equipped with PCV 350 slider unit with sensors with 350 mm length range and a mobile 6-axis 3D measuring arm Romer Absolute Arm 7535 with a working range of 3.5 m were used. This way, basic contour elements were determined: radii, distances and angles. Using the mobile 3D measuring arm, the tolerances of circularity, coaxiallity and perpendicularity were also measured. Technical drawings, contourrograph measuring protocols and tables of dimensional and shape precision deviations are listed in the conclusion of the article.

Analysis and Evaluation of Risks from Exposure to Noise in a Working Environment

This paper deals with a proposal of assessment of hearing impairment risk from the point of view of long-term exposure to noise in a selected plant in the Slovak Republic. Measurement and monitoring noise was carried out at two workshops of a mechanical engineering plant: in a Cutting Center and in a Welding Center. A Norsonic sound analyser was used to measure noise exposure. Evaluation of the noise measurement results consisted of the comparison of the measured values with the required values, which are specified, in the relevant legislative regulation (Government Regulation No. 115/2006 Coll., technical standard (STN EN ISO 9612:2010) and Directive (Council Directive 2003/10/EC). The measured results show that the normalized levels of noise exposure, extended by the uncertainty of measurement (U = ± 2,1 dB) at the all workplaces, exceed the limits stipulated by the Slovak Government, all measured professions fall within the fourth category of work activities categorized according to the noise factor. Long-term exposure of the human organism to noise pollution can cause, in addition to hearing impairment, a wide range of other diseases. Very high levels of noise cause hearing impairment, lower levels affect the control system in our body. This paper presents the results of a study aimed at assessing the risks associated with acoustic noise in connection with exposure to noise at the workplace and with its possible negative effects (a risk event) to health and hearing of workers in the engineering industry.

Determination of Explosion Characteristics of Sugar Dust Clouds

Abstract A dust explosion occurs when an airborne combustible dust cloud encounters an effective ignition source. The resulting pressure and temperature increase can severely injure people and damage surrounding equipment and buildings, and therefore needs to be prevented or controlled (Taveau, 2016). The article deals with the measurement of maximum explosion pressure and maximum rate of explosion pressure rise of sugar dust cloud. The measurements were carried out according to STN EN 14034-1+A1:2011 Determination of explosion characteristics of dust clouds. Part 1: Determination of the maximum explosion pressure pmax of dust clouds, the maximum rate of explosion pressure rise according to STN EN 14034-2+A1:2012 Determination of explosion characteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/dt)max of dust clouds and Determination of explosion characteristics of dust clouds. Part 3: Determination of the lower explosion limit LEL of dust clouds. The sugar dust cloud in the chamber is achieved mechanically. The testing of explosions of sugar dust clouds showed that the maximum value of the pressure was reached at concentrations of 1000 g/m3 and its value is 6,89 bars.

Microstructure, mechanical and fatigue properties of SiMo- and SiCu- nodular cast irons

Fatigue has been a predominant fracture mode of load-bearing machine members. Therefore, through the years its prevention has become a fundamental design criterion. The objective of this study was to compare the microstructure, mechanical and fatigue properties of two types of the nodular cast irons – ferrite-pearlitic nodular cast iron alloyed by Si and Mo and pearlite-ferritic nodular cast iron alloyed by Si and Cu. Microstructure of the specimens was evaluated according to STN EN ISO 945 and by automatic image analysis. The image analysis system NIS Elements, interfaced with the light microscope, was used for evaluation of the shape factor, count of graphitic nodules and content of ferrite. Fatigue tests were realised at sinusoidal cyclic push-pull loading (stress ratio R = –1) at ambient temperature (T = 20 ± 5 °C). They were carried out in the high cycle fatigue region (from 105 to 107 cycles) at frequency f ≈ 75 Hz using the fatigue experimental machine Zwick/Roell Amsler 150HFP 5100. The relationship between the amplitude of stress σa and number of cycles to failure Nf, as well as the fatigue strength, were determined.

Microstructural features evaluation of age-hardened A 226 cast alloy by image analysis

Abstract Age-hardening provides one of the most widely used mechanisms for the strengthening of aluminum alloys. The age-hardening involves three steps: solution treatment, quenching and aging. The temperature of solution treatment and aging is very important in order to reach desired properties of castings. The optimum temperature of solution treatment and aging led to formation microstructural features in form which does not lead to decreasing properties, but increasing ones. The major micro-structural features in A 226 cast alloys which are responsible for increasing properties are: eutectic Si particles, Cu-rich phases, Fe-rich phases and porosity. The increase of properties depends on morphology, size and volume of microstructural features. In order to assess age-hardening influence on microstructural features in A226 cast alloys were used as possibilities of evaluation by means of image analysis. Quantitative analysis decelerate changes in microstructure includes the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe-rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu) further increase in the hardness and tensile strength in the alloy. Changes of mechanical properties were measured in line with STN EN ISO.

Laser marking as environment technology

AbstractThe contribution deals with the laser marking as one of the progressive and environment friendly technologies with utilisation in many branches of industry. Engraving and other types of laser marking of different types of materials are very actual technologies these days. Laser marking decreases the waste creation in comparison with the other classical marking technologies, which use paintings or created chips. In this experimental investigation the laser marking surface texturing of material AL99,7 according to STN 42 4003:1993-08 (STN EN 573) has been conducted. The laser marking machine TruMark 6020 and software TruTops Mark were used. Laser surface texturing after laser marking has been realised under different combinations of process parameters: pulse frequency, pulse energy and laser beam scanning speed. The morphological characterization of engraving or annealing surfaces has been performed using scanning electron microscopy (SEM) technique. The evaluation of roughness of engraved surfaces has been realized according to STN EN ISO 4287 by using Surftest SJ 301. The aim of the contribution was to show how different laser parameters affect the surface texture and colour change of metallic materials while creating minimal waste.

Study of Explosion Characteristics of Wood Dust Clouds in Dependence of the Particle Size Distribution

Abstract The article deals with the measurement of explosion characteristics of wood dust. The measurements were carried out according to STN EN 14034-1+A1:2011 Determination of explosion characteristics of dust clouds. Part 1: Determination of the maximum explosion pressure pmax of dust clouds and the maximum rate of explosion pressure rise according to STN EN 14034-2+A1:2012 Determination of explosion characteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/dt)max of dust clouds. On the basis of measurements, we found that the distribution of the particles has a significant impact on the parameters of wood dust samples.

Determination of the Explosion Characteristics of Wheat Flour

Abstract The article deals with the measurement of explosion characteristics of wheat flour. The measurements were carried out according to STN EN 14034-1+A1:2011 Determination of explosion characteristics of dust clouds. Part 1: Determination of the maximum explosion pressure pmax of dust clouds, the maximum rate of explosion pressure rise according to STN EN 14034-2+A1:2012 Determination of explosion characteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/dt)max of dust clouds and LEL according to STN EN 14034-3+A1:2011 Determination of explosion characteristics of dust clouds: Determination of the lower explosion limit LEL of dust clouds. The testing of explosions of wheat flour dust clouds showed that the maximum value of the pressure was reached at the concentrations of 600 g/m3 and its value is 8.32 bar/s. The fastest increase of pressure was observed at the concentration of 750 g/m3 and its value was 54.2 bar/s.

Analysis of the Overall Reliability Slender Concrete Columns

Standard for designing of concrete structures STN EN 1992-1-1 offers three methods of analysis of second order effects with axial load. Namely, a general method based on non-linear second order analysis and two simplified methods: Method based on nominal stiffness and method based on nominal curvature. According to three series of the experiments of slender concrete columns and after calibration of the non-linear calculations, the authors in following paper compare the global reliability of above mentioned design methods with parametric study. According to executed research is possible to say that the differences in reliability of the design methods are considerable in several cases of the slender concrete columns design.The experiments were executed in the Central laboratory of Faculty of Civil Engineering STU in Bratislava in cooperation with company STRABAG ltd. The series of columns differed only in strength class of concrete (C45/55 for S1, C70/85 for S2, C80/95 for S3) and each series included six tested samples. The geometry and reinforcement of the columns as well as the initial eccentricity of the axial force were design so, that the buckling failure of the columns occurred earlier than the design strength of materials in the most stressed cross-section ran out.

Optimalization of Tempering Temperature of 9CrNB Steel in Železiarne Podbrezová Steelworks

This paper deals with the optimalization of tempering temperature of 9CrNB steel in Železiarne Podbrezová Steelworks, where hot-rolled tubes were produced with dimensions of 88.9 x 12.51 mm. Austenitising at 1070°C/12m/hr was carried out after rolling, and samples were subsequently tempered at 790°C, 760°C and 720°C/4m/hr. The results of testing the mechanical properties show that only tempering at 790°C fulfilled all of the mechanical properties requirements (Rp0,2, Rm, A5, HBW, KV2). The mechanical properties of grade P92 were used for comparison with 9CrNB mechanical properties, according to the relevant standard of STN EN 10216-2+A2. Yield strength requirements (Rp0,2) were also fulfilled in the temperature range from 100 to 600 °C. Microstructural analysis showed that tempering at 720°C, and also at 760°C does not lead to the complete tempering of martensite microstructure. We observed segregation of secondary phases at the grain boundary, but cementite films between individual laths did not coagulate to form carbide phases. By tempering at 790°C the intensity of formation of carbide phases, coagulation and growth of carbide phases is very high and leads to disintegration of laths. Despite satisfactory results, theoretical studies with respect to the selected chemical composition of 9CrNB steel show that to achieve sufficient dissolution of carbide or nitride phases (especially BN), it is necessary to use high temperature austenitization up to about 1200°C, followed by tempering below Ac1.

Calculation of Emissions from Transport Services and their use for the Internalisation of External Costs in Road Transport

Impact of transport operations on the environment is an important criterion of quality services. Requirements for environmental acceptability has recently escalated, manufacturing and trading companies require the carriers to declare the impact of their activities on the environment. Area of concern are the emission factors used for calculating emissions and their unification. For this reason it was accepted norm STN EN 16258, which deals with the methodology of calculation and declaration of energy consumption and greenhouse gas emissions from transport services. Existing emission calculators do not allow the calculation of the external costs of transport services in the area of transport services impacts on the environment. Article deals with the design and application of the calculator of external costs of transport services as an extension, respectively another important function, emission calculator for field of transport services.

Case Study of the Straw Bale House

Straw is renewable material both from the ecological and environmental point of view. It is almost always available at construction sites. Straw is used mainly as filling thermal insulation in structures. This paper deals with design of a two-generation family house. The family house is located in the eastern Slovakia. There is the temperature zone -14 °C. The first goal of this project was to specify the optimal ratio between solid and glazed surfaces in distribution of the specific heat use for space heating. The second goal was to achieve the specific heat use for space heating lower than 15 kWh·m-2·a-1. The specific heat use for space heating has been calculated according to STN EN ISO 13 790 Energy performance of buildings. The project analysed forced ventilation with the heat recovery unit, orientation towards cardinal points, optimal ratio of glazed and solid surfaces of the designed house and their impact on energy performance of buildings. Individual parameters were mutually combined and required goal has been achieved. The specific heat use for space heating was less than 15 kWh·m-2·a-1 in 13 of the evaluated combinations.

Comparison of Driving Rain Index Calculated According to EN 15927-3 to the CFD Simulation and Experimental Measurement

Wind-driven rain or driving rain is a rain which has given a horizontal velocity component by the wind. It can be the important moisture source for building façades and has been of the great concern in building science. In this article, the normative method described in STN EN ISO 15927-3:2009, was used for calculation of driving rain impact on vertical surfaces. This amount of rain was compared to the CFD simulation for selected location and to the experimental measurement carried out by wind-driven rain gauge.

Cladding of Wear-Resistant Layers in Metallurgy and Engineering

The paper presents the application of weld layers used in renovations of functional surfaces of components that are exposed to several tribodegradation factors in operation of metallurgical and engineering industries. Surfaces of selected components are renovated using arc welding processes, namely: (MMAW) Manual Metal Arc Welding, (SAW) Submerged Arc Welding methods, (GMAW) Gas metal arc welding and (FCAW) Flux cored wire metal arc welding without gas shield. Claddings were made always three-layered directly on the surfaces of renovated components using dedicated cladding machines in operations and laboratory conditions respectively. Their quality was assessed using non-destructive tests, namely (VT) visual testing by STN EN ISO 17637 and (UT) Ultrasonic testing STN EN ISO 11666. Within the destructive tests the quality of claddings was evaluated using the metallographic analysis conducted on a light microscope Olympus BX and electron microscope Jeol where the impact of mixing the weld metal as well as heat treatment after cladding on the final structure of claddings was observed. Using the Shimadzu HMV 2 device the microhardness of cladding layers was evaluated on metallographic samples by STN EN ISO 9015-2. In laboratory conditions the resistance of cladding layers to abrasive wear was verified on the device Di-1. Experimental testing of the claddings confirmed that the selected additives and cladding parameters witting individual technology were chosen correctly as in cladding layers no presence of internal defects was observed.