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1

Young’s modulus of a carbon-reinforced composite at an elevated temperature

Szczepaniak Robert, Przybyłek Paweł, Komorek Andrzej, Sapiński Przemysław, Rowicki Artur, Tkaczuk Sławomir, Rypulak Andrzej, Stabryn Sebastian

Technologia i Automatyzacja Montażu

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2021

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nr 4

29--33

PL

Konstrukcje lotnicze są eksploatowane w zmiennych warunkach środowiskowych wpływających na właściwości kompozytów polimerowych, z jakich często wykonywane są elementy samolotów i śmigłowców. Jednym z takich czynników jest temperatura użytkowania, zmieniająca się podczas lotu w bardzo szerokim zakresie. W artykule zaprezentowano wpływ temperatury eksploatacji na właściwości kompozytu wyznaczane podczas próby rozciągania. Dodatkowo kompozyty przeznaczone do badań wygrzewano w trakcie przygotowania w różnych temperaturach (zgodnie z zaleceniami producenta żywicy będącej osnową). Kompozyty składały się z 7 warstw tkaniny węglowej przesyconych żywicą epoksydową L285 z utwardzaczem. W wyniku badań zauważono, że zmiana temperatury eksploatacji wywiera istotny wpływ na właściwości wytrzymałościowe kompozytu bez względu na temperaturę wygrzewania. Materiały wygrzewane w wyższych temperaturach cechowała większa wartość współczynnika sprężystości wzdłużnej i wytrzymałości na rozciąganie.

EN

Aviation structures are operated under varying environmental conditions, affecting the properties of polymer composites, which are often used to manufacture components for airplanes and helicopters. One of such factors is an operating temperature that changes during a flight in a very wide range. This paper presents the influence of an operating temperature upon composite properties determined during a tensile test. In addition, composites which are intended for the research were post cured during their preparation at different temperatures (in accordance with the recommendations of the resin manufacturer which constitutes a matrix base). The composites consisted of 7 layers of carbon fabric, and matrix of L285 epoxy resin, with a hardener. As a result of the testing it was noted that a change in the operating temperature exerts a significant effect on composite strength properties regardless of the post curing temperature. The materials post cured at higher temperatures were characterized by a greater value of the modulus of elasticity and tensile strength.

2

FEM modelling of the static behaviour of reinforced concrete beams considering the nonlinear behaviour of the concrete

Pazdan Maciej

Studia Geotechnica et Mechanica

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2021

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Vol. 43, nr 3

206--223

EN

This paper presents a finite element (FE) method of modelling reinforced concrete beams. The proposed model takes into account the phenomena characteristic of reinforced concrete structures, such as the interaction between two materials (concrete and steel), the cracking caused by mechanical loads and the variation of the Young's modulus under increasing load. A relevant numerical FE analysis was carried out in the ABAQUS system using the concrete damaged plasticity (CDP) model. The character of Young's modulus variation due to increasing stress intensity level was taken from the author’s own research. The results of the FE calculations were compared with the results yielded by the author's numerical bar model.

3

The application of digital image correlation to investigate the heterogeneity of Achilles tendon deformation and determine its material parameters

Kohut Piotr, Holak Krzysztof, Ekiert Martyna, Młyniec Andrzej, Tomaszewski Krzysztof A., Uhl Tadeusz

Journal of Theoretical and Applied Mechanics

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2021

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Vol. 59 nr 1

43--52

EN

The challenge for researchers is to develop measurement techniques that can deal with biological specimens (e.g. the human Achilles tendon) characterized by high deformation during examination. The relevant quantity which has to be investigated in laboratory experiments is the deformation or strain field of the specimen subjected to a given load. In experimental mechanics, the most remarkable technique used for strain field computation is the Digital Image Correlation (DIC) method. In the paper, the DIC method is employed to study biomaterial parameters of human Achilles tendons (AT) subjected to tensile uniaxial loadings. The application of DIC allows the heterogeneity of tendon deformation to be taken into consideration. Young’s modulus of AT based on the strain field obtained from a vision-based measurement is estimated and the results are discussed. A map of Young’s modulus (YM) is demonstrated as well.

4

An evaluation of the mechanical properties of 13MnSiCr7 steel by digital image correlation

Kempny Maciej, Rozmus Radoslaw

Computer Methods in Materials Science

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2021

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Vol. 21, No. 2

75--82

EN

In this paper, the possibility of replacing tensile extensometers with a non-contacting device for measuring elongation has been analyzed. An example of a non-contacting device is a Digital Image Correlation System (DIC). Such systems are widely used in various areas, for example, biology or modern engineering. DIC systems have several advantages that seem to be promising for testing modern materials. The most important is the fact that there is no physical contact between the sample and the DIC and therefore no additional force is applied during the experiment. On the other hand, a lack of contact with the sample can cause large measurement inaccuracies. Another advantage would be that a DIC can measure strain on the whole surface of the sample in all directions, instead of measuring part of the surface in one direction like in other extensometers. Because of these abilities, the environment impact on test bench (DIC + load device), and differences between conducted experiment with normalized tensile test needed to be investigated. The testing machine was replaced by a DIC system cooperating with a tension-compression module. The proposed method was used to monitor and record the images to determine the basic properties of 13MnSiCr7 grade steel. Twelve tests were performed. The analysis was done by comparing the values of mechanical properties obtained in a static tensile test, such as yield strength, tensile strength, Young’s modulus, elongation of the material; with the values of these properties determined experimentally. For each sample, stress-strain curves were evaluated. To check if the results were correct, a Q-Dixon test was performed in each case, confidence intervals were also calculated. Finally, the obtained properties were compared with those from the standard tensile test acquired from the manufacturer’s material card.

5

Effect of thermal treatment on mechanical properties of sustainable composite: experimental and simulation study

Ouchte I, Ait El Fqih M, Chafiq J, Matadi Boumbimba R, Mikdam A, Chakir H

Composites Theory and Practice

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2021

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R. 21, nr 3

102--106

EN

The aim of this work is to accurately characterize the thermomechanical behavior of jute-polyester composites. The thermal characteristics and the mechanical properties are determined over a temperature range from ambient to 100°C. The effect of temperature on the tensile breakage of specimens was investigated in order to determine the ability of this composite to maintain its mechanical resistance. It was observed that Young’s modulus and the tensile strength undergo an increase of about 80% when the temperature rises from ambient temperature to 60°C and a decrease for a temperature range from 60°C to 100°C. Numerical simulations, based on FEM analysis, provided results in good agreement with the experimental data in terms of the stress-strain curves. These simulations were achieved using Abaqus explicit finite element code. The increase and decrease in the mechanical properties were attributed to modification of the adhesion forces at the fiber/matrix interface.

6

Relation between geometry of FSW tools and formation of nano- dispersed zones in macrostructure EN AW 6082-T6 alloy welded joints

Krasnowski Krzysztof, Khokhlova Julia, Khokhlov Maksym, Kostin Valery

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2021

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Vol. 65, No. 5

7--16

EN

An article present the result of macrostructure formation with distribution of mechanical properties in cross-sections of 8 mm-thick one-sided butt-welded FSW joints of EN AW 6082-T6 alloy which were obtained using three types of specially designed tools: C-type – conventional tool consisting of a housing, cylindrical threaded probe and a shoulder with a grooved spiral, T-type – Triflute-type tool consisting of a housing, cylindrical threaded probe with three grooves and a shoulder with a grooved spiral, S-type – simple tool consisting of a housing, smooth cylindrical probe without a thread and a flat shoulder. Friction stir welding was performed using equipment of the Institute of Welding in Gliwice of Poland, and mechanical tests in the E.O. Paton Electric Welding Institute of the NAS of Ukraine. Mechanical test by indentation was performed using Micron-gamma device, which allows experimental identification of structural state of metal and determination of the strain hardening presence by limiting values of ratio of hardness to Young’s modulus of elasticity. It was found that for all three specimens the HAZ hardness decreases, and in the zone of thermomechanical effect the hardness increases. Maximum hardness values are inherent to the central part of welded joint nugget, as well as to light-coloured oval concentrated fragments of structure in the nugget upper and lower part. Judging by the presence of nanosized hardened structure and uniformity of its distribution in the nugget, as well as good dispersion of oxide films and absence of discontinuities, the friction stir welding with C-type tool can be regarded as the optimum variant. An assumption was made that formation of a uniform structure in welds can be achieved at three–four revolutions of the tool in friction stir welding in one place. The model of thermal fields distribution in Al-plate during FSW using a C-type tool visualized the metal’s thermal condition when formated hardened nano-dispersed weld zones.

PL

W artykule przedstawiono wyniki badań nad tworzeniem się nanostruktury z rozkładem właściwości mechanicznych w przekrojach poprzecznych złączy FSW o grubości 8 mm ze stopu EN AW 6082-T6 zgrzewanych jednostronnie doczołowo. Połączenia uzyskano przy użyciu trzech rodzajów specjalnie zaprojektowanych narzędzi. Stwierdzono, że dla wszystkich próbek twardość w SWC zmniejsza się, a w strefie oddziaływania termomechanicznego wzrasta. Maksymalne wartości twardości są charakterystyczne dla środkowej części jądra zgrzeiny, a także dla jasno zabarwionych, owalnych fragmentów w strukturze części górnej i dolnej jądra zgrzeiny. Oceniając obecność utwardzonej struktury nanometrycznej i równomierność jej rozmieszczenia w strefie zmieszania oraz dobre rozproszenie warstewek tlenkowych i brak nieciągłości, zgrzewanie tarciowe z przemieszaniem narzędziem konwencjonalnym można uznać za wariant optymalny. Można przypuścić, że podczas zgrzewania tarciowego z mieszaniem zgrzeiny uzyskuje się jednorodną strukturę zgrzein przy czterech i więcej obrotach narzędzia FSW w jednym miejscu. Model rozkładu pól termicznych w płycie aluminiowej podczas FSW, przy użyciu narzędzia konwencjonalnego, zwizualizował stan termiczny metalu podczas formowania utwardzonych stref nanodyspersyjnych w zgrzeinach.

7

The Effects of Grain Boundary Structures on Mechanical Properties in Nanocrystalline Al Alloy

Jang Jin Man, Lee Wonsik, Ko Se-Hyun

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

971--975

EN

This study investigates the effects of grain boundary structures on mechanical properties of nanocrystalline Al-0.7Mg-1.0Cu alloy using nanoindentation system. Grain boundary structure transforms to high angle grain boundaries from low angle ones with increase of heat treatment temperature and the transformation temperature is about 400°C. Young’s modulus and hardness are higher in sample with low angle grain boundaries, while creep length is larger in sample with high angle ones. These results indicate that progress of plastic deformation at room temperature is more difficult in sample with low angle ones. During compression test at 200°C, strain softening occurs in all samples. However, yield strength in sample with low angle grain boundaries is higher twice than that with high angle ones due to higher activation energy for grain boundary sliding.

8

Mechanical strength indicators of polyurethane adhesive in lightweight floor systems

Karpiesiuk Jacek

Technical Transactions

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2020

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Vol. 117, iss. 1

art. no. e2020024

EN

The article describes the basic features of the lightweight floor system with heat-dissipating lamellas (LFS-L) that do not require screeds and are used in the design of radiant heating. It was assumed that reactive polyurethane adhesive constitute the connection layer between the ceramic tile floor and the thermal insulation substrate, which is covered with aluminium foil. This type of construction has not been fully tested for mechanical strength. To define it, for example, using the finite element method, strength indicators of the tested adhesives which were not used in any of the previous studies discussed in this paper should be determined, such as Young's modulus E, Poisson's ratio ν and linear thermal expansion coefficient α. This article presents research methods by which these data were determined. Module E and the ν ratio were determined in the compression strength test of cylindrical samples of polyurethane adhesive. Coefficient α was determined by using digital image correlation in the Aramis system, placing the prepared adhesive samples in a thermal chamber.

9

Mechanical properties and sound velocity of gold copper (AuCu) II superlattice: 3D molecular dynamic (MD) simulation

Aish Mohammed Mahmoud

Journal of Theoretical and Applied Mechanics

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2020

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Vol. 58 nr 4

901--909

EN

Young’s modulus, yield stress and Poisson’s ratio are studied for different size and tem- perature. The temperature dependence of simulated Young’s modulus is quite similar to experimental results. Transverse sound velocity is estimated from the simulated elastic con- stants at each temperature. The dislocation speed reaches up to 75% of the transverse sound velocity. The dislocation speed decreases with increasing temperature linearly. The tempera- ture dependence of macroscopic deformation behavior and the possibility of the existence of supersonic dislocations are discussed. The transverse sound velocity and rigidity G is calcu- lated from Young’s modulus, Poisson’s ratio and density ρ which changes with temperature.

10

Influence of maturing conditions of steel-fibre reinforced concrete on its selected parameters

Czajkowska Agnieszka, Raczkiewicz Wioletta, Bacharz Magdalena, Bacharz Kamil

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

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2020

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Vol. 9 Nr 1

47--54

EN

In the article the impact of varying humidity conditions on selected strength properties of hardened steel fibre-reinforced concrete (such as Young’s modulus and the compressive strength of concrete) were analysed. The analysis shows that the value of the Young’s modulus of concrete cured under 100% humidity conditions is the highest; 35% higher compared to concrete hardening in the laboratory hall and about 18% higher than modulus measured in the concrete samples maturing in the chamber. A much higher compressive strength of approx. 25% was observed in samples hardening under 100% humidity conditions than in the other two environments. It was also observed that the non-uniform distribution of samples in the chamber and opening and closing the chamber during sample maturation had an impact on the dispersion of the results and due to the coefficient of variation, results can be even worse than in free-maturing samples.

11

Mechanical characterization of millimetric agarose spheres using a resonant technique

Yescas J., Mandal P., Sinha J., Snook R., Hawkes J., Moreno Garibaldi P., Carrera-Espinoza R.

Archives of Mechanics

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2020

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Vol. 72, nr 3

217--233

EN

This paper presents a methodology for the mechanical characterization of agarose millimetric spheres using resonant principles. Detection of the modes of vibration was conducted using a low-cost experimental setup based on an electret microphone adapted with a thin latex elastic membrane for the sensing stage and a piezoelectric actuator driven by a conventional transformer for the excitation stage. The identification of vibration modes is supported through an ANSYS Finite Element model of the experimental setup. Experimental and numerical results demonstrate that two modes of vibration, known as Quadrupole and Octupole, appear in the amplitude spectrum and can be used to obtain stiffness values for the samples. Following this approach, Young’s modulus of 209 ± 19.80, 338 ± 35.30 and 646 ± 109 kPa for 2%, 3% and 4% agarose millimetric spheres were calculated.

12

Nondestructive characterization of elastic modulus of APS Ni–5Al/10hBN coating on stainless steel 304 under high temperature

Yeh Cheng‑Hung, Jeyaprakash N., Yang Che-Hua

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

116--130

EN

The failure mechanisms of coatings, under high thermo-mechanical loads, can be examined through finite element simulations. However, mechanical properties such as Young’s modulus and Poisson’s ratio are necessary to achieve an accurate model. In this study, nickel–aluminum with hexagonal boron nitride (NiAl/hBN) is deposited on stainless steel 304 substrate using atmospheric plasma spray technique. The effect of the hydrogen content in the plasma-formed gas on the microstructure, hardness, and porosity of the deposited layers is examined. Also, the mechanical properties of the coating are measured at ambient temperatures using non-contact laser ultrasound technique. Results indicated that the flow rate of hydrogen has a major impact on the coating structure and elastic properties. The inhomogeneity in the coating can be minimized by decreasing the hydrogen flow rate. The coating Young’s modulus was increased at room temperature, which slowly decreased while increase in atmospheric temperature. The behavior of Young’s modulus at high temperature causes decrease in flexural strength. In addition, the back calculations are well agreed with experimental results.

13

Spiekanie ceramiki azotkowej metodą SPS

Wyżga Piotr, Klimczyk Piotr, Cyboroń Jolanta, Figiel Paweł

Mechanik

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2019

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R. 92, nr 5-6

366--370

PL

Ze względu na wyjątkowe właściwości ceramiki azotkowej jest ona bardzo często wykorzystywana w szeroko pojętej technice. Otrzymywanie wyrobów z azotku krzemu wiąże się jednak z koniecznością stosowania zaawansowanych metod, gdyż ten materiał jest trudno spiekalny. W wyniku spiekania prądem impulsowym SPS/FAST (spark plasma sintering/field assisted sintering technique) otrzymano gęste spieki ceramiczne z układu Si3N4-Al2O3-Y2O3. Parametry spiekania mieszanki zoptymalizowano tak, aby uzyskać możliwie najwyższe parametry spieków, takie jak: gęstość, moduł Younga, twardość i odporność na pękanie. W ramach pracy analizowano wpływ ciśnienia i prądu impulsowego, stosowanych w metodzie SPS/FAST, na spiekalność oraz na wybrane właściwości fizyczne i mechaniczne otrzymanych materiałów. Celem wprowadzenia do osnowy Si3N4 dodatków Al2O3 i Y2O3 była aktywacja trudno spiekalnego proszku azotku krzemu i w konsekwencji – osiągnięcie wysokiej gęstości otrzymanego spieku. Najlepszymi właściwościami charakteryzował się spiek otrzymany w temperaturze 1700°C i pod ciśnieniem 63 MPa; czas wytrzymania w temperaturze spiekania wynosił 15 min. Gęstość uzyskanej próbki osiągnęła 98% wartości teoretycznej, a pozostałe parametry wynosiły: moduł Younga – 298 GPa, twardość Vickersa – 17,7 GPa, odporność na pękanie powierzchniowe – 6 MPa∙m1/2.

EN

Due to the unique properties of ceramics materials based on nitride, it could be used in the broadly understood technique. However, obtaining silicon nitride materials requires it to use the advanced methods of manufacturing, mostly because this material is difficult to sinter. Dense ceramic sinters were obtained from the system Si3N4-Al2O3-Y2O3 by applied pulsed current – SPS/FAST method (spark plasma sintering/field assisted sintering technique). The sintering parameters of the initial mixture were optimized to obtain the highest possible sinter properties, such as: density, Young’s modulus, hardness and fracture toughness. In the presented work the influence of pressure and pulse current, used in the SPS/FAST method, on sinterability and on selected physical and mechanical properties of the obtained materials was analyzed. The purpose of introducing the Al2O3 and Y2O3 additions to the Si3N4 matrix was to activate the hard-to-sinter silicon nitride powder and consequently to achieve a high density of the sintered samples. The best properties were characterized by sinter obtained in 1700°C and under pressure 63 MPa; the holding time at sintering temperature was 15 min. The density of the obtained sample has reached 98% theoretical value, and the other parameters were: Young’s modulus – 298 GPa, Vickers hardness – 17,7 GPa, fracture toughness – 6 MPa∙m1/2. KEYWORDS: Si3N4, SPS sintering, Young’s modulus, hardness

14

Mechanical properties of cement mortar with graphene oxide

Krystek Małgorzata

Architecture Civil Engineering Environment

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2019

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Vol. 12, no. 1

91--96

EN

These days, nanotechnology has already influenced many fields of science and technology, including civil engineering. Cementitious composites incorporating various nanomaterials have emerged as novel materials with improved microstructure, mechanical properties and durability. Over the past decades, graphene oxide has appeared as one of the most promising nanomaterials for civil engineering applications. However, the effect of graphene oxide addition on the properties of cementitious composites has not yet been fully investigated. The paper presents the studies on the mechanical properties of cement mortar reinforced with the 0.03 wt.% of graphene oxide (dosage by weight of cement). Graphene oxide proved to accelerate the cement hydration, in particular at the early stages of mortar hardening, hence improving the mortar performance during mechanical tests. The significant enhancement of the flexural, cubic and cylindrical compressive strength has been reported, thus showing the great nanotechnology potential for concrete structures.

15

Analysis of bone wedge dimension selectionmethods in high tibial osteotomy

Urbanowski S., Łuczkiewicz P., Grymek S.

Advances in Materials Science

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2019

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Vol. 19, nr 2(60)

15--27

EN

The article presents the analysis of methods for selecting dimensions of bone wedge for high tibial osteotomy. The existing methods are described along with the procedure. In the following paragraphs, deficiencies in the selection of bone wedge dimensions and global trends in this field have been demonstrated. Based on the numerical analysis, the problem appearing in the wrong choice of bone wedge dimensions was illustrated.

16

Influence of dental materials on hardness and Young’s modulus of the surface layers of tooth enamel formed as a result of friction

Wojda Sylwia, Sajewicz Eugeniusz

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 1

129--139

EN

The purpose of this work was to determine the influence of dental materials used as permanent fillings on the mechanical properties of the tooth enamel surface layer subjected to friction with these materials. Methods: Dental composite materials (five types) were differentiated in terms of size and shape of the filler particles and matrix type over the course of tests on the chewing simulator under two different loads set during friction. Next, it was measured values of wear and nanoindentation for the resulting friction rates on the enamel (3 different load ranges). Results: It was found that the enamel’s resistance to tribological wear is significantly higher than that of the tested dental materials. It is also important to note that, depending on the penetration depth of the indenter (depends on the indenter pressure), different hardness values and Young’s modulus of enamel were obtained after friction with different dental materials. This demonstrates the formation of a surface layer with different properties than the native material. Conclusions: Analysis of the obtained results suggests the existence of different tribological wear mechanisms, as evidenced by significant differences in the wear values of dental materials and enamel. The data show that the enamel surface layer modified by the contacting dental material is shaped to a certain depth, and different thickness ranges of the changed layer have different properties.

17

The Influence of Reducing Temperature on Changing Young’s Modulus and the Coefficient of Friction of Selected Sliding Polymers

Ptak A., Kowalewski P.

Tribologia

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2018

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nr 3

107--111

EN

For the polymeric materials, changing of the temperature causes changes in mechanical and tribological properties of sliding pairs. The goal of the present study was to determine the change in Young's modulus and kinetic friction coefficient depending of the temperature. Three thermoplastic polymers, PA6, PET and PEEK, were tested. These materials cooperated in sliding motion with a C45 construction steel disc. As part of the experiment, the Young's modulus tests (by 3-point bending method) and kinetic friction coefficient studies (using pin-on-disc stand) were carried out. The temperature range of mechanical and tribological tests was determined at T = –50°C±20°C. Comparing the results of mechanical and tribological properties, there is a tendency to decrease the coefficient of friction as the Young's modulus increases while reducing the working temperature.

PL

Zmiany temperatury w przypadku materiałów polimerowych są przyczyną zmian własności materiału, a co za tym idzie i właściwości tribologicznych par ślizgowych. Tematem podjętym w niniejszym artykule jest określenie zmiany modułu Younga oraz współczynnika tarcia kinetycznego materiałów polimerowych współpracujących ślizgowo ze stalą w zależności od temperatury. Do badań wykorzystano polimery termoplastyczne: PA6, PET oraz PEEK, które współpracowały ślizgowo ze stalą konstrukcyjną C45. W ramach eksperymentu zostały przeprowadzone badania modułu Younga (3-punktową metodą zginania) oraz badania współczynnika tarcia kinetycznego (wykorzystując stanowisko typu pin-on-disc). Zakres temperatury badań mechanicznych i tribologicznych określony został na poziomie T = –50°C±20°C. Porównując wyniki badań własności mechanicznych z właściwościami tribologicznymi, można zauważyć tendencję do zmniejszenia wartości współczynnika tarcia wraz ze wzrostem modułu Younga podczas obniżania temperatury otoczenia.

18

The Influence of the Bias on Mechanical Properties of a-C:H CVD Thin Films

Kottfer D., Marton M., Kaczmarek Ł., Kuffova M.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

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2018

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Vol. 9, Nr 1 (31)

23--30

EN

In this study a-C:H (hydrogenated amorphous carbon) thin films were deposited on the 7075 Al alloy without an interlayer using a DC CVD (direct current chemical vapor deposition) method with varied negative substrate bias in order to improve the hardness and Young´s modulus. The highest values of films hardness and Young´s modulus were 25.6±3.5 GPa and 140.3±4.6 GPa, respectively. The measured results show a promising potential of the a-C:H coated 7075 Al alloy for low load (up to 10 N) applications.

19

Mechanical properties of colored acrylonitrile-butadiene-styrene injection molded parts

Trzaskalska M., Palutkiewicz P., Bociąga E.

Polimery

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2018

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T. 63, nr 11-12

791--798

EN

This article presents the results of examination of processing conditions such as mold Tf and injection Tw temperature influence on mechanical properties of the moldings made of copolymer ABS (acrylonitrilebutadiene-styrene) without and with a coloring agent in the form of a pigment and its masterbatches. The pigment was added in the amount of 1 wt ‰ and 2 wt ‰, while the masterbatches were added in the amount of 1 wt % and 2 wt %. The mechanical properties of the molded parts were determined in hardness, impact strength and tensile strength tests. The analysis of the obtained results allowed to state that the addition of the coloring agent in a form of pigment does not significantly affect the values of hardness and impact strength. However, the change of the processing conditions, e.g., increasing the mold temperature, contributed to the decrease of hardness and, at the same time, to the increase of impact strength. The tensile strength of the moldings made of ABS without and with the addition of the masterbatch is similar, regardless of the injection molding parameters, whereas their strain at break and Young’s modulus change, depending on the injection molding parameters. When using the low values of the mold temperature (30 °C) and injection temperature (230 °C), lower values of Young’s modulus were found, however, the aforementioned temperatures allow for obtaining a higher strain at break (noticed for colored samples).

PL

Oceniano wpływ warunków przetwórstwa: temperatury wtryskiwania Tw oraz temperatury formy Tf na właściwości mechaniczne wyprasek wytworzonych z kopolimeru akrylonitryl-butadien-styren (ABS) bez dodatku i z dodatkiem środka barwiącego w postaci koncentratu lub pigmentu. Koncentrat dozowano w ilości 1 % mas. i 2 % mas., a pigment w ilości 1 ‰ mas. i 2 ‰ mas. Badania właściwości mechanicznych wyprasek obejmowały twardość, udarność i statyczną próbę rozciągania. Na podstawie analizy otrzymanych wyników stwierdzono, że dodatek środka barwiącego nie wpływa w istotnym stopniu na twardość i udarność wyprasek. Natomiast zmiana parametrów przetwórstwa, np. podwyższona temperatura formy, przyczynia się do zmniejszenia twardości, a jednocześnie zwiększenia udarności. Bez względu na warunki przetwórstwa wytrzymałość na rozciąganie próbek z tworzywa ABS bez dodatku oraz z dodatkiem koncentratu barwiącego była zbliżona, natomiast w zależności od warunków wtryskiwania następowała zmiana ich odkształcenia przy zerwaniu oraz modułu sprężystości przy rozciąganiu. W wypadku wyprasek barwionych zastosowanie niskiej temperatury formy wtryskowej (30°C) oraz niskiej temperatury wtryskiwania (230°C) powodowało zmniejszenie wartości modułu sprężystości oraz, na ogół, zwiększenie wartości odkształcenia przy zerwaniu.

20

Analysis of Young's modulus for Carboniferous sedimentary rocks and its relationship with uniaxial compressive strength using different methods of modulus determination

Małkowski P., Ostrowski Ł., Brodny J.

Journal of Sustainable Mining

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2018

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Vol. 17, iss. 3

145--157

EN

Young’s modulus (E) is one of the basic geomechanical parameters used in rock engineering in practice. It is determined based on uniaxial compressive test (UCS). However, according to International Society of Rock Mechanics it can be calculated by three different ways: as the tangent, secant and average modulus. The results from each method are significantly different. The UCS tests was carried out on 237 rock specimens with the slenderness ratio 2 of Carboniferous claystones, mudstones and sandstones. The axial deformation was always measured automatically by the displacement measurement device (LVDT) built into the testing machine and connected to the hydraulic piston. Then the Young’s modulus was calculated for each test by all three methods. The analysis of the results is presented in this paper to show the difference between all the three moduli calculated for each specimen, and to recommend the best method of Young’s modulus determination. First, the typical range of the elastic linear deformability for the chosen rock types was determined as 25-75% of the peak strength at confidence interval 95% for these sedimentary rocks. The modulus value distributions obtained from each calculation method were compared using statistical parameters: mean value, median, minimum, maximum, standard deviation, mean difference at confidence interval 95%, and non-uniformity coefficient. The proportions between average-secant modulus (Eav/Esec) and average-tangent modulus (Eav/Etan) for the rock samples were estimated. For the studied rocks the obtained values were: 1.10-1.32% for Eav/Esec, 1.08-1.25% for Etan/Esec and 1.01-1.06 for Eav/Etan (for Etan with the range of 20-80% of peak strength). These values show low coherence between secant and average modulus (ca. 23% difference) and good consistency of average and tangent modulus. Based on the analysis, tangent Young’s modulus is recommended as the guiding one at the constant range of 30-70% of the ultimate stress. Secant Young’s modulus, as it comprises not only elastic strain but the pore compaction as well, should be named as modulus of deformability. This conclusion was further confirmed by the regression analysis between UCS and E. The highest regression coefficients and the lowest standard error of the regression was obtained for tangent Young’s modulus determination method. In addition, modulus ratio MR for claystones, mudstones and sandstones was studied and determined as 274, 232 and 223 respectively.