Volume 14 (2016)
  Special Issue I

Journal Full Text: Vol14_S1

Contents


Pages

975–983 R. Chotěborský and M. Linda
Determination of chemical content of soil particle for abrasive wear test
Abstract |

Determination of chemical content of soil particle for abrasive wear test

R. Chotěborský¹ and M. Linda²*

¹Czech University of Life Sciences in Prague, Faculty of Engineering, Department of material Science and Manufacturing Technology, Kamýcka 129, CZ 165 21 Praha – Suchdol, Czech Republic
²Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamýcka 129, CZ 165 21Praha – Suchdol, Czech Republic
*Correspondence: linda@tf.czu.cz

Abstract:

 Soil is an extremely abrasive environment that causes a change in the part dimension of agricultural tools like as chisels or ploughshares. Dry rubber wheel test according to ASTM G65 is one of standard to wear testing. For this test is used Ottawa sand (SiO2 particles) which have a spherical shape. The actual soil contains sand, but also particles of other minerals with higher or lower abrasion than sand. This article is focuses on identifying the abrasive particles in the soil by electron microscopy with EDS analysis. The results should be used for mixing the abrasive particles to the rubber wheel test, but also to identify the mineral composition of the soil profile. The aim of the research is closer to the real test of wear on the field and laboratory tests on the device with a rubber disc. Results shown that the soil contents alumina oxide particles with high hardness or silumina complex chemical composition with sharp shape. The ratio of amount these abrasive particles in the soil is influenced by geological position in earth and this ratio of particle amount influence wear rate in actual soil.

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984–993 P. Hrabě, M. Müller and Č. Mizera
Mechanical properties of polymer matrix composites filled with Jatropha Curcas L.
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Mechanical properties of polymer matrix composites filled with Jatropha Curcas L.

P. Hrabě¹*, M. Müller¹ and Č. Mizera²

¹Czech University of Life Sciences, Faculty of Engineering, Department of Material
Science and Manufacturing Technology, Kamýcká 129, 165 21 Prague, Czech Republic
²Czech University of Life Sciences, Faculty of Engineering, Department of Mechanical
Engineering, Kamýcká 129, 165 21 Prague, Czech Republic
*Correspondence: hrabe@tf.czu.cz

Abstract:

 Polymers and their composites are widely used for their specific properties. This paper deals with composite materials based on Jatropha oil cake. Seeds of Jatropha Curcas L. plant are pressed for gaining oil. A cake is a by-product.
A polymer composite was a subject of performed experiments. A continuous phase was in a form of a two-component epoxy adhesive and Jatropha oil cakes were a discontinuous phase (reinforcing particles).
Using Jatropha oil cake as the by-product after the mechanical extraction of the oil decreases a price of the composite system. Jatropha oil cake is the waste which is not further utilized.
The research was focused on various weight concentrations from 5 to 30%. The volume energy, the strength characteristics and the impact resistance were tested at these composite materials. Results were evaluated by means of the statistical program ANOVA. The filler moisture was 4.59 ± 0.22% WB. Mechanical properties were not changed using of the filler.
The negative influence of the filler was ascertained at the tensile strength. The positive influence was ascertained at the impact strength until 20 wt% of the filler concentration.
Owing to the high complexity of the failing process of the composite material the grid electron microscopy in the area of the fracture surface was used.

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994–1003 H. Kallakas, M. Martin, D. Goljandin, T. Poltimäe, A. Krumme and J. Kers
Mechanical and physical properties of thermally modified wood flour reinforced polypropylene composites
Abstract |
Full text PDF (525 kB)

Mechanical and physical properties of thermally modified wood flour reinforced polypropylene composites

H. Kallakas¹*, M. Martin¹, D. Goljandin², T. Poltimäe¹, A. Krumme³ and J. Kers¹

¹Tallinn University of Technology, Faculty of Chemical and Materials Technology, Department of Polymer Materials, Chair of Woodworking, Teaduspargi 5, EE 12618 Tallinn, Estonia
²Tallinn University of Technology, Faculty of Mechanical Engineering, Department of Materials Engineering, Chair of Materials Science, Ehitajate tee 5, EE19086 Tallinn, Estonia
³Tallinn University of Technology, Faculty of Chemical and Materials Technology, Department of Polymer Materials, Ehitajate tee 5, EE 19086 Tallinn, Estonia
*Correspondence: heikko.kallakas@ttu.ee

Abstract:

 Heat treatment of wood helps to lower the hydrophilicity and polarity of wood fibres used in wood-plastic composites. By means of heat treatment it is possible to reduce the access to wood hydroxyl (OH) group, which causes hydrophilic and polarity of wood fibres. Therefore improving compatibility between the wood and polymer matrix. In this research, the effect of wood flour (WF) heat treatment and chemical modification with 3-aminopropyltriethoxysilane (APTES) were investigated. WPC test samples were prepared using alder (Alnus incana) WF with mesh size of 0.05 mm as a filler material and polypropylene (PP) as the matrix material. WF was chemically modified with NaOH and APTES to increase the adhesion and compatibility of WF to polymer matrix. The composites were manufactured using a twin-screw extruder and the test samples were made by injection molding. The composites mechanical properties were tested using three-point flexural test and Charpy impact test. The composite physical properties were investigated with Fourier transform infrared spectroscopy (FTIR). The effect of silane (APTES) and NaOH modification on thermally treated and untreated WF was examined with contact angle measurement. Comparisons were made between the untreated WF and thermally treated WF. Also the effect of NaOH and silane (APTES) modification on the properties of thermally modified and unmodified WF composite were investigated. Using WF as a filler material increased flexural strength, while impact strength decreased thus making the material more rigid and brittle. The test results revealed that there was no significant difference in the mechanical properties between thermally treated and untreated composites. However, chemical modification improved the mechanical properties of the composites.

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1004–1014 A. Kešner, R. Chotěborský and M. Linda
Determination of the heat flux of steel for the heat treatment model of agricultural tools
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Full text PDF (405 kB)

Determination of the heat flux of steel for the heat treatment model of agricultural tools

A. Kešner¹*, R. Chotěborský¹ and M. Linda²

¹Department of Material Science and Manufacturing Technology Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ 165 21 Prague – Suchdol, Czech Republic
²Department of Electrical Engineering and Automation, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ 165 21 Prague – Suchdol, Czech Republic;
*Correspondence: kesner@tf.czu.cz

Abstract:

 Chisels and tines for agricultural machinery are mechanically worn. Mechanical wear depends on the microstructure of the material. The desired microstructure of the material, specifically steel is obtained by heat treatment. Microstructure after heat treatment can be determined in two ways. The first one is the experimental determination, which is timeconsuming and not economically efficient. The second is to build the thermal model during the heat treatment. Microstructure is affected during the heat flux during heat treatment. This research was focused on the boundary conditions of the model heat flux during quenching. The heat flux was measured during quenching with solid cylindrical samples (ø25–50 mm) by means of two thermocouples. The first temperature was measured in the axis of the sample and the second temperature was measured near the sample surface. The results of the heat flux were appointed to the model and experimentally verified. In this way it is possible to construct a model of tines and chisels for agricultural machine, which shows the progress of the heat flux during quenching.

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1015–1022 T. Koppel, A. Shiskin, I. Hussainova, H. Haldre and P. Tint
Electromagnetic shielding properties of ceramic spheres coated with paramagnetic metal
Abstract |
Full text PDF (601 kB)

Electromagnetic shielding properties of ceramic spheres coated with paramagnetic metal

T. Koppel¹*, A. Shiskin², I. Hussainova¹, H. Haldre³ and P. Tint¹

¹Tallinn University of Technology, Ehitajate 5, EE 12616 Tallinn, Estonia
²Faculty of Material Science and Applied Chemistry, Riga Technical University, 3 Paula Valdena str, LV-1048 Riga, Latvia
³Institute of Environmental Health and Safety, Jaam 14, EE 11615 Tallinn, Estonia
*Correspondence: tarmo.koppel@ttu.ee

Abstract:

 This study utilized a setup of radiofrequency generating and metering instruments to measure the reflective and pass-through properties of the innovative material of paramagnetic metal coated ceramic hollow spheres (MCS). The dimensions of the spherical articles reside around 50–250 μm, the thickness of metal (Cu) coating is 0.5–1.3 μm. The radiofrequency field was of 2.4 GigaHertz (GHz) frequency and radiated towards the material via a waveguide-horn antenna at 100 mWt power output. Two additional waveguide-horn antennas connected to a radiofrequency analyzer measured the reflection and pass-through characteristics of the material. Reflection and pass-through coefficients (from 0 to 1) were calculated to each tested sample. The material was tested at different thicknesses: from single – to multi (up to 5) mono-layers and 5 mm layer in bulk condition of MCS.
The measurement results show insignificant shielding characteristics for 1 to 5 layer thickness samples: pass-through coefficient from 0.96 to 0.92. Noteworthy shielding characteristics were starting to show in case of MCS mixed with graphite emulsion: transmission coefficient dropped to 0.16.
The latter sample demonstrates the prospective shielding characteristics of the material, since most of the radiofrequency radiation was not allowed to pass through the material neither to be reflected, but absorbed within the structure of the material.

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1023–1033 V. Krasnyy, V. Maksarov and J. Olt
Improving fretting resistance of heavily loaded friction machine parts using a modified polymer composition
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Improving fretting resistance of heavily loaded friction machine parts using a modified polymer composition

V. Krasnyy¹, V. Maksarov¹* and J. Olt²

¹Saint-Petersburg Mining University, 21st Line 2, RU 199106 St. Petersburg, Russia
²Institute of Technology, Estonian University of Life Sciences, Kreutzwaldi 56, ЕЕ51014 Tartu, Estonia
*Correspondence: maks78.54@mail.ru

Abstract:

 The application of coatings based on fluorocarbon polymer composition, frictionmechanical brass, fullerene C60 and surface treatment of vibrorolling with the regular roughness for the protection of heavily loaded mating parts of machines, working in conditions of frettingcorrosion. Studied the mechanisms of friction of coating, which will considerably reduce the fretting-wear mechanisms of friction in engineering products. It is established that in all studied for the protection of heavily loaded mating parts of machines is a single mechanism of increasing wear resistance when fretting in the area of the contact layer of the fine particles through the use of thin-layer coatings. Their presence may be due to either structural self-organization material, or forming of composite structures with small wear particles when using the polymeric composition. At that the protective coating virtually eliminates component corrosion mechanism of fretting – wear.

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1034–1042 A. Krofová, P. Kic and M. Müller
Influence of dust pollution in the laboratory on the strength of adhesive bond
Abstract |

Influence of dust pollution in the laboratory on the strength of adhesive bond

A. Krofová¹*, P. Kic² and M. Müller¹

¹Czech University of Life Sciences Prague, Faculty of Engineering, Department Material Science and Manufacturing Technology, Kamýcká 129, CZ 165 21, Czech Republic
²Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ 165 21, Czech Republic
*Correspondence: kofovaa@tf.czu.cz

Abstract:

The main aim of this paper is to evaluate the influence of microclimate conditions on the bond strength in the research laboratory in the Faculty of Engineering at the Czech University of Life Sciences Prague. The main attention is paid especially to the contamination of the working environment with dust particles. In the frame of this research the concentration and size of dust particles in the air was measured by the aerosol monitor DustTRAK II Model 8530 with impactors for measurement of size fractions PM1, PM2.5, PM4 and PM10. The adhesive bonds were created according to the ISO standards from Duralumin material specimens with different type of twocomponent epoxy adhesives under different conditions of ventilation (0%, 50% and 100% of ventilation rate). The tensile strength of created specimens was measured by universal testing machine for tensile strength measurement – LABTest 5.50ST. The results of measurement were evaluated by statistical methods and summarized in the conclusions. There is no significant difference in the strength of the bond when applied various performance of ventilation.

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1043–1052 V. Maksarov, A. Khalimonenko and J. Olt
Effect of porosity on the performance of cutting ceramics
Abstract |
Full text PDF (619 kB)

Effect of porosity on the performance of cutting ceramics

V. Maksarov¹*, A. Khalimonenko¹ and J. Olt²

¹Saint-Petersburg Mining University, 21st Line 2, 199106 St. Petersburg, Russia
²Institute of Technology, Estonian University of Life Sciences, Kreutzwaldi 56, ЕЕ51014 Tartu, Estonia
*Correspondence: maks78.54@mail.ru

Abstract:

 The article examines the forecasting performance of the cutting tool equipped with interchangeable plates of carbide oxide ceramics (A2 – mixed ceramic), by definition porous ceramic tool material affecting its cutting properties. Set correlation of porosity ceramic tools from electrical resistivity removable ceramic plates. Cutting tools having larger electrical resistivity values and, respectively, smaller porosity percentages should be used for machining the most precise components of machine part blanks, since their performance will be better than that of the tools whose ceramic bits have small electrical resistivity values. Based on the established correlation selects ceramic plates for the required machining conditions.

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1053–1062 V. Mironovs, I. Boiko, T. Koppel and M. Lisicins
Cellular tubular structures from perforated metallic tape and its application
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Cellular tubular structures from perforated metallic tape and its application

V. Mironovs¹, I. Boiko²*, T. Koppel³ and M. Lisicins¹

¹Riga Technical university, Faculty of Civil Engineering, Institute of Building Production, Azenes street 16/20–331, LV-1048 Riga, Latvia
²Riga Technical University, Faculty of Mechanical Engineering, Transport and Aeronautics, Institute of Mechanical Engineering, Ezermalas street 6k, LV-1006 Riga, Latvia
³Tallinn University of Technology, Department of Labor Environment and Safety, SOC351, Ehitajate tee 5, EE19086 Tallinn, Estonia
*Correspondence: irina.boiko@rtu.lv

Abstract:

 The objectives of performed research were the following: 1) check out the possibility of effective formation of the tubular and planar structures from the perforated steel tapes, which were obtained as a waste during stamping of fine-sized details, by cutting and bending; 2) testing of achieved tubular and annular structures for fixing up of the electrical cables and as electromagnetic shielding solutions; 3) analysis of achieved results and elaboration of the recommendations for using of lightweight tubular shields for the electrical cables. The actuality of research is connected with the re-using of metallic wastes and shielding solutions against electromagnetic fields. All objectives were reached successfully using bending for formation of the tubular structures. The bending strength of achieved structures and the shielding efficiency in a controlled environment was examined. The measurement results have shown that perforated steel will exhibit noticeable shielding properties against both the electric and magnetic field. Such results open up wide possible application of the planar and cellular tubular structures from perforated metallic tapes.

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1063–1068 V. Mironovs, O. Ozernovs, V. Lapkovskis and D. Golyandin
Production of Crumb Rubber – Iron Powder Mixture for perspective synthesis of Carbon-Iron powder sorbent
Abstract |
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Production of Crumb Rubber – Iron Powder Mixture for perspective synthesis of Carbon-Iron powder sorbent

V. Mironovs¹, O. Ozernovs¹, V. Lapkovskis¹* and D. Golyandin²

¹Riga Technical University, Laboratory of Powder Materials, Kipsalas Str. 6, LV-1048 Riga, Latvia
²Tallinn Technical University, Tallinn University of Technology, Ehitajate tee 5, EE 19086, Tallinn, Estonia
*Correspondence: lap911@latnet.lv

Abstract:

A sustainable technique for conversion of end-of-life tyres (ELTs) to products with added value is of a great importance for resource-efficient circular economy. However, obtaining products with added value often requires multi-stage procedures, which include traditional and emerging technological approaches. In current paper, the authors suggest an efficient approach for recycling of ELT tyres, obtaining products which can be subsequently used for environmental applications. This approach introduces a synthesis path for new materials by transformation of industrial wastes i.e. ELT rubber wastes to crumb rubber and further mixing with iron powder. Particular attention is driven to perspective processing of obtained crumb rubber-iron powder mixture by means of microwave pyrolysis for synthesis of carbon-iron powder mixture and its use as a composite absorbent material along with emerging application for electromagnetic and microwave irradiation protection.

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1069–1077 Č. Mizera,, D. Herák and P. Hrabě
Relaxation and creep behaviour of false banana’s fibre (Ensete ventricosum)
Abstract |
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Relaxation and creep behaviour of false banana’s fibre (Ensete ventricosum)

Č. Mizera¹,*, D. Herák² and P. Hrabě³

¹,²Czech University of Life Sciences Prague, Faculty of Engineering, Department of Mechanical Engineering, Kamýcká 129, CZ 165 21 Praha 6 Suchdol, Czech Republic
³Czech University of Life Sciences Prague, Faculty of Engineering, Department of Material Science and Manufacturing Technology, Kamýcká 129, CZ 165 21 Praha 6 Suchdol, Czech Republic
*Correspondence: mizera@tf.czu.cz

Abstract:

This study was focused on the analysis of viscoelastic behaviour of fibres of false banana (Ensete ventricosum). The aim of the experiment was to describe the short term creep and relaxation behaviour under tension loading. The fibers of Ensete ventricosum, originally from Ethiopian region Hawasa, were used in this experiment. Moisture content Mc = 8.40 ± 0.67% (d. b.) and true density ρt = 668 ± 44 kg m-3 of the samples were determined. The specimens had initial gauge length of L0 = 100 ± 1 mm and the average yarn breaking load (YBL) after 20 tests was σr = 14.3 ± 1.7 N. To determine the relationship between tension force and deformation, tension device (Labortech, MPTest 5.050, Czech Republic) was used to record the course of deformation function. All tests were performed using a constant rate α = 3.1 N s-1. The short term creep tests were performed using constant loads of 30%, 60% and 90% of the average YBL. The short term relaxation tests were performed using constant strain of 30%, 60% and 90% of maximal strain. Measured data were analysed by computer software Mathcad 14. Experimental reep and stress relaxation curves at different load levels were determined. Experimental creep lifetimes tr for different load levels: 24,311 ± 7,489 s (30% YBL), 1,831 ± 462 s (60% YBL) and 17.6 ± 5.5 s (90% YBL) were determined. Initial modulus of elasticity, finite modulus of elasticity and initial energy of stress relaxation and creep of Ensete fibres were determined.

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1078–1087 M. Müller and R. Chotěborský
Impact strength behaviour of structural adhesives
Abstract |
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Impact strength behaviour of structural adhesives

M. Müller* and R. Chotěborský

Department of Material Science and Manufacturing Technology, Faculty of
Engineering, Czech University of Life Sciences, Kamýcká 129, CZ 165 21 Prague,
Czech Republic
*Correspondence: muller@tf.czu.cz

Abstract:

A cohesive force at an adhesive bond is one of the limit for a strength of an adhesive bonding. This study is focused on an impact force of an adhesive. Samples without a notch were cast in the casting mould at a laboratory temperature with a normal pressure. The instrumentation microcharpy test equipment was used for the evaluation of the impact force. The samples were tempered at a laboratory temperature, 40 °C and 60 °C. Results showed that the temperature of the specimens influenced the impact strength, the toughness and the maximum deformation of the adhesives. Higher temperature decreased the impact force but it increased the toughness. The hardness Shore D of commercial filled two-component epoxies is comparable. A nonhomogeneity of adhesives distinguished for a porosity was found by the investigation of a fracture surface.

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1088–1098 V. Osadcuks and A. PeckaV. Osadcuks and A. Pecka
Electrical field based detection of fruits and vegetables for robotized horticulture
Abstract |
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Electrical field based detection of fruits and vegetables for robotized horticulture

V. Osadcuks* and A. PeckaV. Osadcuks* and A. Pecka

Latvia University of Agriculture, Faculty of Engineering, Department of Energetics, Cakstes blvd. 5, LV-3001 Jelgava, Latvia; *Correspondence: vtl@tvnet.lv

Abstract:

In this research authors study possibilities of using transmitting-type electric field based sensors for recognition of fruits and vegetables. The main idea is to detect distortions of electrical field between electrodes of sensors by measuring capacitance changes for these electrodes. Electrical field is strongly affected by relative permittivity of medium, which is several times larger for fruits and vegetables consisting mainly of water than for surrounding air, leaves and other low-mass non-conductive objects. This could help to develop electrical field sensing device with number of electrodes for detection of fruits or vegetables and determining their position thus serving as additional sensor in multi sensor system with optical camera or as stand alone device. The research covers both theoretical aspect of proposed approach and experimental evaluation of prototype device based on mixed signal controller MGC3130 originally intended for electrical field based gesture sensing periphery for consumer electronics. Main results show that in worst condition when an electrode is fully covered with a physical model of leaf 43% of signal value in comparison to sensor output without obstacle is still usable. Thus this type of sensors potentially can be an integral part of complex fruit or vegetable recognition system in robotized horticulture applications. 

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1099–1106 J. Sander and T. Jehlička
Use of spiral conveyor in the processing of granular waste materials
Abstract |
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Use of spiral conveyor in the processing of granular waste materials

J. Sander¹* and T. Jehlička²

¹Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ 165 21 Prague 6 – Suchdol, Czech Republic
²Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ 165 21 Prague 6 – Suchdol, Czech Republic
*Correspondence: sander@tf.czu.cz

Abstract:

The work presents a construction solution, verification of operation function and evaluation of the efficiency of a spiral separator in processing of agricultural, food industry and other granular waste. The common method of processing waste is based on crushing and subsequent sorting by various physical and mechanical properties. Crushing waste results in a heterogeneous mix of particles with a substantial size and weight difference and major share of dangerous powder particles. Thus, specific requirements are put on the conveying and manipulation of the mixture. The solution is using pneumatic conveying and closed sub-pressure separators. Under laboratory pilot conditions a sub-pressure spiral separator was designed and tested. The separator is designed as an immobile drum sieve in which a rotating axis-free helix is inserted. The inside space of the drum sieve is linked axially to the sub-pressure pipe of the combined conveyor. A light aspiration proportion (dust particles) are carried by the air flow while the granular particles with big specific weight and specified size make the sieve fraction. The particles larger than the separation apertures of the sieve are carried mechanically by the helix. The separating efficiency was observed on a mix of granular materials at same operation conditions. The contents of the mix of granular materials varied in size, specific weight and in the proportion of dust particles. Evaluation of the separating possibilities of the spiral separator verified the operation applicability of the system for separation and conveying of various agricultural, food and other granular materials. 

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1107–1115 R. Šemjakin, A. Ruus, K. Kirtsi and E. Tungel
Water vapour transmission properties of linseed oil paint
Abstract |
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Water vapour transmission properties of linseed oil paint

R. Šemjakin, A. Ruus*, K. Kirtsi and E. Tungel

Tallinn University of Technology, Tartu College, Department of Technology, Puiestee 78, EE 51008 Tartu, Estonia; *Correspondence: aime.ruus@ttu.ee

Abstract:

Linseed oil paint has been in use in indoor and outdoor decorating for a long period of time. It is not easy to date the first findings but there are signs of using linseed paint at least in VIX century in some areas of Afghanistan and during the renaissance period in Europe. It is also known as a good preservative material for wood. Indoor finishing materials considerably influence the indoor climate (temperature, RH, ventilation rate) because of their moisture buffering ability. Moisture buffering occurs because of the sorption and diffusion properties of materials (wood, plaster, gypsum board etc.). As paint is a cover for those materials, the knowledge about material water vapour transmission properties is essential for evaluating hygrothermal properties of boarders and the co-action of paint and substrate (plaster). There could be products with different properties referred to as ‘linseed oil paint’.
In the current study six handmade paints with different recipes including two primers and two commercial paints were under investigation. As for interior works, one layer of paint could be used as well therefore the samples were covered with both – one and two layers of paint. The thickness of paint layers varied from 0.8 and 6.2 μm for one-layer primers, from 11.3 to 26.9 μm for one-layer paints and from 17.8 to 40.7 μm for two-layer paints. Water vapour transmission properties were determined by using EVS-EN ISO 7783 standard.
Water vapour diffusion equivalent air layer thickness sd was estimated as 0.1 and 0.2 m for 1-layer primers, 0.2 to 0.9 m for 1-layer paints and 0.4 to 0.9 m for 2-layer paints. The information gathered from the experiment enables to get an overview of the different properties of ‘the same product” and use the data in hygrothermal calculations.

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1116–1122 P. Valášek
Study on impact strength of sisal fibers reinforced epoxy composites using experimental methods
Abstract |
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Study on impact strength of sisal fibers reinforced epoxy composites using experimental methods

P. Valášek

Department of Material Science and Manufacturing Technology, Faculty of Engineering, Czech University of Life Sciences Prague, Kamýcká 129, CZ 165 21 Prague; e-mail: valasekp@tf.czu.cz

Abstract:

 Among the advantages of composite materials is their ability to exploit the properties of partial phases that creates the composite. Common materials used as matrix materials include polymeric composites. The properties of these matrices can be optimized by using synthetic or also natural fibers. Natural fibers are inexpensive, ranks among renewable resources and when respecting their biological nature, they can replace synthetic fibers in many applications. This paper describes the impact strength of epoxy resins filled with unordered short sisal fibers with a length of 2–6 mm. From the experimental results it is evident that the presence of fibers of sisal examined as epoxy resins, increases the impact strength, up to 143%. SEM (scanning electron microscopy) was used to assess the failure of mechanism of these composites.

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1123–1129 J. Volf, V. Novák and V. Ryzhenko
Effect of conductive ink on transfer characteristics of pressure into electric signal for tactile sensors
Abstract |
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Effect of conductive ink on transfer characteristics of pressure into electric signal for tactile sensors

J. Volf*, V. Novák and V. Ryzhenko

Czech University of Life Sciences Prague, Faculty of Engineering, Kamýcká 129, CZ165 21 Prague, Czech Republic
*Correspondence: volf@tf.czu.cz

Abstract:

The article deals with tactile sensors with circular electrodes in which conductive ink was used as a converter converting pressure into an electric signal. The article briefly describes theoretical background of this issue and presents several appropriate converters, from which the tested ink was selected. The measurement process is described in detail, and subsequently the dependence of resistivity on the thickness of the deposited ink layer is studied and the properties of various setups were compared. Finally, the results are summarized and the main issues are pointed out.

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1130–1137 A. Yonetken and A. Erol
Production and characterization of Ni-Co (WC) composites materials
Abstract |

Production and characterization of Ni-Co (WC) composites materials

A. Yonetken¹* and A. Erol²

¹University of Afyon Kocatepe, Faculty of Engineering, Department of Electrical Engineering, ANS Campus, TR 03200 Afyonkarahisar, Turkey
²University of Afyon Kocatepe, Faculty of Technology, Department of Metallurgy and Materials Engineering, ANS Campus, TR 03200 Afyonkarahisar, Turkey
*Correspondence: yonetken@aku.edu.tr

Abstract:

Ceramic-Metal Composite such as NiWC, CoWC are among advanced technology materials that have outstanding mechanical and physical properties for high temperature applications. Especially low density and high hardness properties stand out in such ceramic-metal composite. The microstructure, mechanical properties of %60Ni, %20Co and %20WC powders have been sintered by using tube furnace at 1,000–1,100–1,200–1,300–1,400 °C temperature. Mecahnical proporties and metalograhphic analysis were investigated after sintering. NiCo phases observed after metallographic analaysis. XRD, SEM (Scanning Electron Microscope)results showed us best microhardness of composites 174.16 HV, 8,563 g cm-3 density were obtained at 1,400 °C sintering tempareture.

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1138–1146 J. Zavrtálek, M. Müller and V. Šléger
Low-cyclic fatigue test of adhesive bond reinforced with glass fibre fabric
Abstract |

Low-cyclic fatigue test of adhesive bond reinforced with glass fibre fabric

J. Zavrtálek¹*, M. Müller¹ and V. Šléger²

¹Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Material Science and Manufacturing Technology, Kamýcká 129, CZ 165 21 Prague, Czech republic
²Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Mechanical Engineering, Kamýcká 129, CZ 165 21 Prague, Czech republic
*Correspondence: zavrtalek@tf.czu.cz

Abstract:

Epoxy resins are widely used polymers, which are popular due to their workability, high tensile strength and a chemical resistance. The glass fibre fabric interlayer was used for improving the tensile and the quasi-.static lap shear strength of joints bonded with an epoxy adhesive.
The aim of the experiment is to clarify a fatigue behaviour (low-cyclic tests of the fatigue) of structural two-component epoxy adhesive applied to a constructional steel S235J0. The fabric was composed from type E glass fibres in a plain weave. For optimization of properties of the composite bond it was used various weights in grams of the fabric in the extent of 80, 110, 160 g m-2 for the fabric treated by a wax, where this treatment is determined for better spinning of fibres at the production of the fabric, and weights of grams of 80, 110, 163 g m-2 at the fabric with a chemical dressing determined for improving the adhesion between the fibres and the epoxy resin. The specimens for quasi-static and lap shear strength tests were made in accordance with EN 1465:2009. The difference of the saturation of the various types of fabrics with the epoxy adhesive was observed with SEM (Scanning Electron Microscopy). It is obvious from the experiment results that it came to the improvement of the quasi-static loading at all adhesive bonds reinforced with glass fibres. The adhesive bonds specimens A110, A160, B110 and B160 resisted to required 200 cycles at 80% loading. The test specimens without the fabric showed worse properties. 

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1147–1152 M. Zeps, A. Gailis, J. Smilga, O. Miezite, L. Sisenis2 and I. Zariņa
Hybrid aspen clone wood mechanical properties
Abstract |
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Hybrid aspen clone wood mechanical properties

M. Zeps¹*, A. Gailis¹, J. Smilga¹, O. Miezite², L. Sisenis2 and I. Zariņa¹

¹Latvian State Forest Research Institute ʻSilava’, Rigas 111, Salaspils, LV 2169, Latvia
²Latvia University of Agriculture, Forest Faculty, Akademijas 11, LV 3001 Jelgava, Latvia
*Correspondence: martins.zeps@silava.lv

Abstract:

 The hybrid aspen is believed to be a suitable alternative to the European aspen for raw material supply, but information on its wood properties and their variations among clones is lacking. Nevertheless, its fast growth is associated with a decrease of wood density and mechanical strength. The aim of the study was to assess wood mechanical properties of the hybrid aspen clones and their relationship with growth traits. The tree height and diameter at breast height (DBH), basic wood density, compressive strength, modulus of rupture (MOR), and modulus of elasticity (MOE) were measured for three sample trees from 22 hybrid aspen clones and one common aspen clone. Significant (all P < 0.001) differences of assessed wood properties and growth traits were found among the hybrid aspen clones. At the clone mean level, compressive strength ranged from 26.6 ± 1.3 to 36.7 ± 0.8 N mm-2 and MOR and MOE were from 57.9 to 74.5 N mm-2 and from 7338.5 to 9734.6 N mm-2, respectively. The mean wood density was 383 ± 3.1 kg cm-2. It correlated significantly (P < 0.001) with MOR (r = 0.66), MOE (r = 0.63), and compressive strength (r = 0.71) at the individual tree level. All mechanical properties of the wood showed non-significant (all P > 0.05) correlation with growth traits. Therefore, selection of fast-growing clones will not interfere with the mechanical quality of wood. However, the suitability for structural applications should be cautiously tested due to the clonal variations.

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1155–1160 M. Bloch-Michalik and M. Gaworski
Practical usage of additional heat from biogas plant
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Practical usage of additional heat from biogas plant

M. Bloch-Michalik* and M. Gaworski

Warsaw University of Life Sciences, Department of Production Management and Engineering, Nowoursynowska str. 164, PL 02-787 Warsaw, Poland
*Correspondence: marta_michalik@sggw.pl

Abstract:

Biogas plants are one of the most stable and cost-effective energy sources. The better volume of produced biogas is used for parallel electricity and heat production in CHP gas engines. The heat from the engine is conveniently used for heating the digester but the additional amount causes lot of problems and is wasted despite its large potential. The inefficiency in energy use is a bottleneck in current biogas production, causing macroeconomic and microeconomic losses and challenges in the context of increasing land use competition. As a major output of the biogas management process research provide by authors, this article was elaborated in order to introduce the results of theoretical heating system analysis.

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1161–1168 A. Gedzurs
Operation reliability of induction motors at egg processing plant ‘Balticovo’
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Operation reliability of induction motors at egg processing plant ‘Balticovo’

A. Gedzurs

Latvia University of Agriculture, Faculty of Engineering, Institute of Energetics, J. Cakstes blvd. 5, LV-3001 Jelgava, Latvia; e-mail: aleksejs.gedzurs@llu.lv

Abstract:

In hen houses air quality plays an important role in egg production volume. However, failure of fan induction motors often occurs and it is important to improve reliability of these. A motor reliability study was conducted in the egg processing plant ‘Balticovo’ in Iecava. Results show that 86% of failed number from 2010–2015 occur in hen houses and more than 50% of them were failures of motors which drive the fan. Annual failure rate of fan induction motors each year was increasing and in 2015 it was 6%. Investigations of the faulty motors showed the following defects – stator turn to turn failure of stator winding insulation leadwire and stator winding insulation thermal stress and mechanical damage of stator core resulting in the damaged stator winding leading to a short circuit. Results show that conditions that could contribute to such defects are excessive heating and vibrations.

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1169–1179 V. Malijonytė,, E. Dace, F. Romagnoli and M. Gedrovics
Methodology for determining the mixing ratio of selected solid recovered fuels
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Methodology for determining the mixing ratio of selected solid recovered fuels

V. Malijonytė¹,², E. Dace¹*, F. Romagnoli¹ and M. Gedrovics¹

¹Riga Technical University, Institute of Energy Systems and Environment, Azenes 12/1, LV-1048 Riga, Latvia
²Kaunas University of Technology, Institute of Environmental Engineering, Donelaičio g.20, LT-44239 Kaunas, Lithuania
*Correspondence: elina.dace@rtu.lv

Abstract:

Energy recovery is a preferable waste management method for waste that cannot be reused or recycled. For energy recovery, various types of waste with differing properties are being used, e.g. mixed municipal solid waste or end-of-life tires. To achieve a more stable and homogeneous characteristics of the waste derived fuels (RDF, SRF), they can be mixed in a number of ratios. The paper presents a methodology for determining the optimal mixing ratio of three selected waste derived fuels (mixed municipal solid waste, sewage sludge, end-of-life tires) considering environmental and economic aspects. The developed method is based on combining life cycle assessment method, mass balance calculations and multi-criteria analysis (the technique for order of preference by similarity to ideal solution – TOPSIS). The results show that mixing the various waste derived fuels allows obtaining a more sustainable solution than in the case of each separate waste derived fuel.

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1180–1190 M. Mimra, M. Kavka and R. Renfus
Analysis and Evaluation of the Waste Management in the Municipality
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Analysis and Evaluation of the Waste Management in the Municipality

M. Mimra*, M. Kavka and R. Renfus

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Machinery Utilisation, Kamýcká 129, CZ 165 21 Prague 6–Suchdol, Czech Republic
*Correspondence: mimra@tf.czu.cz

Abstract:

Objective of this paper was to analyse the waste management on an example of the municipality Nový Bor in the Czech Republic. The analysis is performed on comparison of Municipal Solid Waste (MSW) production in Nový Bor which systematically separates between mixed and sorted waste as commodities with a second life span. It was noted that the average amount of mixed MSW came to approximately 200 kg person-1 year-1 in Nový Bor in 2014 which was 24% below the Czech average value of 263 kg person-1 year-1 from the identical year. Comparison of the sorted waste production in 2014 showed that Nový Bor achieved better results than the Czech average of 39.7 kg person-1 year-1; a common resident of Nový Bor separated 24.4% more waste via recycling containers (= 49.5 kg person-1 year-1) and 11.6% more via Bag Collecting System (BCS) which means 54 kg person-1 year-1 in total. Unfortunately, approximately 80% of MSW from Nový Bor is landfilled so its energy producing utilisation is totally neglected. Generally, the decision how to dispose of waste depends more or less on price: disposal of MSW by landfill costs about 700 CZK t-1, whereas in an incinerator about 2,000 CZK t-1. The personalised, registered BCS clearly ensures a better, diligent waste separation (impurity only max. 10%) compared to the mixture found in ‘anonymous’ recycling containers placed all over the city where the impurity of sorted waste varies between 20–40%. 

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1191–1199 A. Mäkiranta, J.B. Martinkauppi and E. Hiltunen
Correlation between temperatures of air, heat carrier liquid and seabed sediment in renewable low energy network
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Correlation between temperatures of air, heat carrier liquid and seabed sediment in renewable low energy network

A. Mäkiranta*, J.B. Martinkauppi and E. Hiltunen

University of Vaasa, Faculty of Technology, Electrical Engineering and Energy Technology, P.O. Box 700, FI-65101 Vaasa, Finland
*Correspondence: anne.makiranta@uva.fi

Abstract:

The low energy network based on renewable seabed sediment heat has been monitored for several years in Vaasa, Finland. In this study the temperatures of air, heat carrier fluid and seabed sediment are compared to each other and correlations between them are investigated. In this study data from one year 2014, was used. Correlations between these subjects clearly exist. The sizing of installed network seems to be correct; no overuse was detected.

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1200–1211 V. Papez and S. Papezova
Optimization of a solar power station with LiFePO4 accumulators
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Optimization of a solar power station with LiFePO4 accumulators

V. Papez¹ and S. Papezova²*

¹Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Electrotechnology, Technicka 2, CZ 166 27 Pague 6, Czech Republic
²Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamycka 129, CZ 165 21, Prague 6 ˗ Suchdol, Czech Republic; *Correspondence: papezovas@tf.czu.cz

Abstract:

The paper describes the design and construction of an isolated solar power station supplying energy at weekends to a remote location. The system comprises two parts: a photovoltaic system generating electric energy in sunlight, and an accumulator accumulating energy to be permanently available and to be able to supply a peak power of several kW. The design of the system optimized with respect to maximum reliability, ease of operation and minimum purchase costs. The control circuits were therefore constructed by means of simple analog circuits. To use microcomputers, which are nowadays used in battery management systems most often available on the market, is not appropriate. Such a system, compared with a simpler analog system, is less reliable. Power circuits are again designed in order to ensure minimum complexity of the system. The resulting design is absolutely different from conventional designs offered by suppliers of photovoltaic systems. The photovoltaic part of the system is designed for optimum adaptation of the load characteristic of the photovoltaic generator to the charging characteristic of the accumulator. By selecting photovoltaic panels with appropriate parameters and their appropriate interconnection, possibly by an automatic change of their interconnection during the charging cycle, it is possible to achieve more effective utilization of the charging power of the photovoltaic generator than by using charging DC/DC converters. The accumulator used in the system is formed by an assembly of LiFePO4 accumulators which thanks to their outstanding durability in spite of their high price currently show the lowest cost per accumulated kWh. 

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1212–1221 S. Papezova and V. Papez2
Automated Measuring Station for Accumulator Testing
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Automated Measuring Station for Accumulator Testing

S. Papezova¹* and V. Papez2

¹Czech University of Life Sciences in Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamycka 129, CZ 165 21, Prague 6 ˗ Suchdol, Czech Republic
2Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Electrotechnology, Technicka 2, CZ 166 27 Pague 6, Czech Republic
*Correspondence: papezovas@tf.czu.cz

Abstract:

The paper describes the design and implementation of the system allowing the testing of the lithium-iron-phosphate (LiFePO4) cell parameters during long-term loading. Manufacturers and retailers, in particular, accentuate their beneficial properties – the possibility of charging and discharging by high currents, minimum influence of the discharge time on capacity, long durability. At the same time, their operational conditions are a lot more strictly defined than those for other types of accumulators. The proposed testing system enables loading the accumulators, consisting of several cells, by periodic discharging and charging processes with various operating currents and various levels of cell discharging. The charging and discharging process control is fully automated; the measuring of the cell operational state is performed automatically during charging and discharging. The data is recorded, and continuously evaluated for the purposes of process management. The measurements enable the comparison of the catalogue data with the parameters of the real products. The testing system design is based on the application of a digital control block, which is completed with an analog control block. The core of the digital control unit is a control computer equipped with a multifunctional input-output card and an array of logically controlled circuit breakers. An accumulator management algorithm, implemented as a control program of the computer, ensures the operation of the accumulator in subsequent charging and discharging periods. The actual accumulator control is based on the evaluations of voltage levels at the cell terminals. 

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1222–1231 Týbl, J. and P. Kic
Thermal properties and reduction of energy consumption of buildings
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Thermal properties and reduction of energy consumption of buildings

Týbl, J.* and P. Kic

Czech University of Life Sciences Prague, Faculty of Engineering, Kamycka 129, 16521, Prague 6, Czech Republic; *Correspondence: tybljiri@seznam.cz

Abstract:

The aim of this paper is to summarize and present all relations, which are essential in determination of winter heat balance of the buildings, and that enable a reduction of energy consumption or heating costs. These questions should be realized and taken into account already in the proposal of building design. This paper shows the methods of calculation of winter heat balance and results of measurements which verify theoretical conclusions in real conditions. These factors are applied on two existing buildings. There are due to their different shapes and constructions proposed different solutions of improvement. Two different buildings were selected for this research work: a large ground floor building and a high hall. In the case of the first building (the large ground floor building) it appears to be a major problem not sufficient thermal properties of the envelope constructions. The enormous heat losses caused high heating costs. The existing heating method of the second building (the high hall), is not suitable. The temperature distribution in the interior is undesirable, which results in very high energy consumption. The use of radiant ceiling panels could enable to achieve favourable conditions in the working area and considerable energy savings.

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1232–1240 Z. Vondrášek
Numerical Modelling of Transient Phenomena in a Synchronous Machine
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Numerical Modelling of Transient Phenomena in a Synchronous Machine

Z. Vondrášek

1Czech University of Life Sciences Prague, Faculty of Engineering, Department of Electrical Engineering and Automation, Kamýcká 129, CZ 16521 Praha 6 – Suchdol, Czech Republic; e-mail: vondrasek@tf. czu.cz

Abstract:

The present contribution deals with the idea of identification of electromagnetic transient phenomena pages in a synchronous machine – namely of distant short circuits – by numerical modelling. Phenomena in AC windings of a synchronous machine (stator) have a backswing effect on the phenomena in DC windings – namely the excitation one. Concerned is namely the current stress of the excitation circuit during the transient phenomenon. The computer model is created in the Famulus- vers. 3 – environment. The time behaviour of AC circuit currents in components d, q and the excitation circuit is monitored on the example of a 3-pole distant short circuit in a synchronous machine (via the impedances of connecting elements). The results are compared of models with a simpler structure (one damper circuit in the rotor) with those with a more complicated structure (two damper circuits in the rotor). 

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