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1

Research of Tribological and Thermodynamic Parameters of the WC-Cu Braking System of the Experimental Modular Electric Vehicle

Varecha Daniel, Galik Jan, Kohar Robert, Gajdosik Tomas, Gajdac Igor, Jenis Jozef

Production Engineering Archives

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2023

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Vol. 29, Iss. 2

116--127

EN

The authors of this manuscript present the development of a braking system with friction material baseWC-Cu coating for the electric vehicle. This manuscript follows on from the original development of an AGV multi-disc braking system and an experimental investigation of the friction factor of WC-Cu coatings. In addition to developing the mechanical elements and construction of the electric vehicle, the tribological parameters of three samples of the steel substrate, the C45 with WC-Cu coating, were investigated in the tribological laboratory. A metallic coating of the WC-Cu base was applied on theC45 steel substrate using electro-spark deposition coating technology. The experiment used three samples with different percentage ratios of chemical elements in the coating structure. The tribometer working on a “Ball on Plate” principle was an investigation of the friction factor of all samples duringthe experiment. Subsequently, the surface of the samples was modified structure WC-Cu with laser technology. The microhardness of modified and unmodified coatings according to the Vickers methodology was investigated in the next stage. At the end of the experimental investigation, a braking simulation was created in the programming environment of the Matlab® software, considering all driving resistances. The researchers also focused on the simulation of heat conduction during braking for some considered driving modes with braking on a level and with a 20% slope roadway. The simulation of heat flow was carried out in the Matlab® programming environment using the Fourier partial differential equation for non-stationary heat conduction.

2

Assessment of Slurry Transport Efficiency after Applying Deflocculant in the Lime Production Process

Jaworska-Jóźwiak Beata J.

Management and Production Engineering Review

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2023

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Vol. 14, No. 4

48--55

EN

The paper presents a method for improving the lime production process by increasing the efficiency of the lime slurry transport that occurs in it. The aim of the study was to reduce the energy demand of the pump installed in the discharge line. The presented solution consists of applying an additive called deflocculant to the transported slurry in order to reduce its viscosity while increasing the concentration of solids content. The deflocculant applied to the slurry is composed of waste material from the lime slaking process and an environmentally neutral chemical substance in the form of sodium-water glass. The rheological studies conducted confirm the positive effect of the selected deflocculant on the properties of the slurry tested. As a result of the analysis, it has been shown that the proposed solution has a substantial effect on reducing the friction factor of the transported slurry, thus reducing the energy consumption in the investigated process.

3

Optimization of geometric and flow parameters of solar air heater roughened with artificial roughness by Taguchi method

Sahu Mukesh Kumar, Mishra Shivam, Kumar Avinash

Archives of Thermodynamics

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2023

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Vol. 44, no 3

3--33

EN

The paper presents the investigation of the optimum design parameters of a solar air heater (SAH) having wire ribs as artificial roughness by using the Taguchi method. The solar air heater has arc shape roughness geometry with apex upstream flow on the absorber plate. The objective of this paper is to obtain a set of parameters that deliver maximum thermo-hydraulic performance. For this objective, a new parameter the thermo-hydraulic improvement parameter (ηTHIP), has been introduced. For the present analysis, the effects of Reynolds number (Re), relative roughness pitch (P/e), angle of attack (α), and relative roughness height (e/Dh), denoted by A, B, C, and D, respectively, have been considered. An (L18 = 61 · 3 2 ) orthogonal array (OA) was chosen as an experimental plan for applying the Taguchi method. The set of control factors for the solar air heater SAH which delivers the maximum Nusselt number (Nu), and minimum friction factor (fr) – are A6B2C2, and A1B1C3 respectively. To obtain the maximum THIP the experimental set-up requires only one single run using the parameter A6B2C2, hence there is no need to run it all 54 times.

4

Effect of artificial coarseness on the performance of rectangular solar air heater duct: a comparative study

Dubey Manoj Kumar, Prakash Om

Archives of Thermodynamics

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2023

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Vol. 44, no 3

325--358

EN

Solar air heater is regarded as the most common and popular solar thermal system and has a wide range of applications, from residential to industrial. Solar air heater is not viable because of the low convective heat transfer coefficient at the absorber plate which contributes to decreasing the thermal efficiency. Artificial coarseness on the plain surface is the most effective method to enhance heat transfer with a moderate rate of friction factor of flowing air in the design of solar air heater duct. The different parameters and different artificial coarseness are responsible to alter the flow structure and heat transfer rate. Over the years different artificial roughness and how its geometry affects the performance of solar air heater have been thoroughly studied. Various investigators report the correlations between heat transfer and friction factors. In the present study, a comparison of several artificial coarseness geometries and methods with a view to enhancing the performance of solar air heater has been made. A brief outline has also been presented for future research.

5

Effect of serrated circular rings on heat transfer augmentation of circular tube heat exchanger

Kharkwal Himanshi, Singh Satyendra

Archives of Thermodynamics

|

2022

|

Vol. 43, no 2

129--155

EN

Limiting energy resources has led researchers to find new innovative ways to enhance heat exchanging devices thermal performance in power generating systems. Thus, the present paper analyzes passive techniques of enhancing the thermal performance of a single tube heat exchanger. Experimental and numerical investigation on heat transfer enhancement using aserrated circular ring with twisted tape is carried out. The work incorporates the determination of Nusselt number, friction factor, thermal performance factor for serrated circular ring with twisted tape with variation in diameter ratio (0.8 and 0.85) and pitch ratio (2 and 3). Air is used as a working fluid with Reynolds number 6000–24000. The experiment is conducted by providing a constant wall heat flux of 1000 W/m2 to the system and thereby taking results at a steady state. The experimental and computational findings obtained for the smooth tube case are compared with the standard correlations of Dittus–Boelter and Blasius. Based on experimental and numerical investigation, there is 5.16 times augmentation in heat transfer and 3.05 times improvement in thermal performance factor over the smooth tube heat exchanger. In addition, the study of entropy generation rate for every geometrical parameter has been conducted, and their influence on the system’s thermal behaviour is presented. The results obtained in the present study may help the researchers of the same research area to find similar inserts and new ways of enhancing the thermal performance of heat exchangers.

6

Numerical simulation of flow through microchannels of technical equipment with triangular and rectangular elements of roughness

Kmiotek Małgorzata, Iwan Tomasz

Technologia i Automatyzacja Montażu

|

2021

|

nr 4

16--23

PL

Celem pracy jest określenie wpływu chropowatej powierzchni na przepływ płynu w mikrokanałach stosowanych w różnych mikrourządzeniach technicznych złożonych wyrobów. Rozpatrywano dwuwymiarowy osiowo-symetryczne mikrokanały o przekroju kołowym. Chropowatość została zasymulowana jako proste figury geometryczne tj. trójkąt i prostokąt o różnej wysokości h i różnej odległości s między sobą. Równania przepływowe zostały rozwiązane za pomocą oprogramowania Ansys/Fluent. Przeprowadzana jest analiza linii prądu w celu zbadania przepływów w strefie recyrkulacji za elementami chropowatości. Stwierdzono, że współczynnik tarcia wzrasta wraz ze wzrostem wysokości elementów chropowatych. Współczynnik tarcia jest większy dla elementów prostokątnych niż trójkątnych i zmniejsza się wraz ze zmianą geometrii elementu. Straty tarcia maleją wraz ze wzrostem liczby Reynoldsa. Autorzy wskazują, że w produkcji mikrokanałów złożonych wyrobów do modelowania chropowatości zaleca się używać elementów trójkątnych.

EN

This paper presents a computational study on an influence of a rough surface on the fluid flow in a microchannel used in various technical microdevices of complex products. Two-dimensional axially symmetrical microchannels with a circular cross-section were considered. The fluid flow were simulated as simple geometric figures, i.e. a triangle and a rectangle with different height h and different distance s between each other. The flow equations were solved with Ansys / Fluent software. A streamline analysis is performed to investigate the flows in the recirculation zone behind the roughness elements. It was found that the friction factor increases with increasing height of rough elements. The coefficient of friction factor is greater for rectangular elements than for triangular elements, and decreases as the geometry of the element changes. Friction factor decreases as the Reynolds number increases. The authors indicate that in the production of microchannels of complex products, it is recommended to use triangular elements to model roughness.

7

Heat transfer and friction factor correlation for inclined spherical ball roughened solar air heater

Murmu Ramesh, Kumar Parmanand, Singh Hari N.

Archives of Thermodynamics

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2020

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Vol. 41, no 2

3--34

EN

Flow mechanism under roughened solar air heater is quite complex. This paper is an effort towards determining the governing equations for heat transfer and friction factor for inclined spherical balls roughened ducts. With the availability of these equations, it is easier to predict the thermal and thermohydraulic performance of such roughened solar air heaters. The governing equations are derived based on the experimental data generated under actual outdoor condition at the test rig designed and fabricated at the terrace of the Mechanical Engineering Department, the National Institute of Technology Jamshedpur in India, in terms of roughness and flow parameters. Maximum augmentation in Nusselt number and friction factor for varying relative roughness pitch, relative roughness height, spherical ball height to diameter ratio, and angle of attack was respectively found to be of the order of 2.1 to 3.54 times, 1.87 to 3.21 times, 2.89 to 3.27 times and 1.74 to 3.56 times for Nusselt number and 0.84 to 1.79 times, 1.46 to 1.91 times, 1.67 to 2.34 times and 1.21 to 2.67 times for friction factor in comparison to non-roughened duct. The optimum roughness parameters under present investigation have been found.

8

Augmentation in heat transfer and friction of three sides over one side dimple roughened solar duct

Kumar Vikash

Archives of Thermodynamics

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2020

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Vol. 41, no 3

57--89

EN

Providing roughness is an effective method to heat fluids to high temperature. Present paper make use of concave dimple roughness on one and three sides of roughened ducts aimed at determining rise in heat transfer and friction of three sides over one side roughened duct. Three sides roughened duct produces high heat transfer compared to one side roughened. Results are shown as a rise in Nusselt number and friction factor of three sides over one side roughened duct. Experimental investigation was conducted under actual outdoor condition at National Institute of Technology Jamshedpur, India to test various sets of roughened collectors. Roughness parameter varied as relative roughness pitch 8–15, relative roughness height 0.018–0.045, dimple depth to diameter ratio 1–2, Reynolds number 2500– 13500 at fixed aspect ratio (width/hight) 8. Highest enhancement in Nusselt number for varying relative roughness pitch, height, and diameter ratio was respectively found as 2.6 to 3.55 times, 1.91 to 3.42 times and 3.09 to 3.94 times compared to one side dimple roughened duct. Highest rise in friction for three sides over one side roughened duct for these varying parameters was respectively found as 1.62 to 2.79 times, 1.52 to 2.34 times and 2.21 to 2.56 times. To visualize the effect of roughness parameter on heat transfer and friction factor, variation in Nusselt number and friction factor for varying roughness parameters with Reynolds number is shown.

9

Features of hydrates transportation in a fluid flow

Vozniak Lidiia V., Kryvenko Galyna M.

Journal of New Technologies in Environmental Science

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2019

|

Vol. 3, nr 2

84--88

EN

Significant deposits of natural gas are in a gas-hydrated state. One of the options for a possible solution is the transport of hydrates in a fluid flow. The stability of crystalline hydrates, namely, their presence in the solid state, affects both temperature and pressure. The influence of the concentration of solid particles on the reduction or increase of the friction factor is shown, which leads to a decrease or increase in pressure drop during the flow of liquid with solid admixtures. The analytical dependences of the friction factor from the Reynolds number on a certain concentration of solid admixtures in a liquid are proposed A plot of the dependence of the friction factor from the Reynolds number on a certain concentration of rubber crumb and different granulometric composition was constructed.

10

Ocena właściwości tribologicznych wybranych substancji smarujących na podstawie charakterystyk Herseya–Stribecka

Aranowski Arkadiusz, Kałdoński Tadeusz, Gocman Krzysztof, Kałdoński Tomasz Jan

Biuletyn Wojskowej Akademii Technicznej

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2019

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Vol. 68, nr 2

109--143

PL

W pracy przedstawiono wyniki badań dotyczących właściwości tribologicznych - na podstawie charakterystyk Herseya–Stribecka, substancji smarujących takich jak syntetyczna baza olejowa PAO-6, olej perfluoropolieterowy PFPE Fomblin Y 04 oraz ciecz jonowa CJ 006, tj. bis(trifluorometylosulfonylo)imid-3-metylo-1-propylopirydynowy. Badanie przeprowadzono w Zakładzie Tribologii, Inżynierii Powierzchni i Logistyki Płynów Eksploatacyjnych Wydziału Mechanicznego Wojskowej Akademii Technicznej na uniwersalnym nano/mikrotesterze UNMT, wyprodukowanym przez CETR (Centrum for Tribology) w USA. Badania zostały zrealizowane przy różnych obciążeniach, a mianowicie 0,25 N, 5 N i 50 N. Zróżnicowały one substancje smarujące pod względem właściwości tribologicznych, ukazując wpływ zmiany prędkości tarcia oraz obciążenia węzła tarcia na wartość współczynnika tarcia. Najlepsze właściwości tribologiczne, szczególnie przy większych obciążeniach, wykazała ciecz jonowa.

EN

The content of the paper presents the results of investigations of selected lubricants. The study led to obtaining Hersey’s-Stribeck’s curves and to comparison of the lubricating properties of lubricants belonging to different groups such as hydrocarbon oils, perfluoropolyether oils (PFPE), and ionic liquids. The following liquids were evaluated for tribological properties: PAO-6 polyalphaolefin oil base, CJ 006 ionic liquid (3-methyl-1-propylpyridinium bis(trifluoromethylsulphonyl)-imide) and Fomblin Y 04 synthetic perfluoropolyether oil. The research was carried out using the universal nano/micro tribotester (UNMT-CETR, CA, USA) at the Department of Tribology, Surface Engineering and Service Fluids Logistics, Faculty of Mechanical Engineering, Military University of Technology. The study consisted of friction of a ball bearing steel (100 Cr 6) with a round specimen of a certain roughness (ball-on-disc). Friction occurred in rotational motion of the specimen, at different rotational speeds at constant radius and at constant load (0.25 N; 5 N; 50 N). The friction node was lubricated with the tested liquid.

11

Badanie warunków tarcia w procesie walcowania pierścieni na gorąco

Surdacki P., Gontarz A.

Hutnik, Wiadomości Hutnicze

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2018

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Vol. 85, nr 6

182--185

PL

Efektywną metodą kształtowania wyrobów pierścieniowych o dużych średnicach w stosunku do wymiarów przekroju poprzecznego jest walcowanie pierścieni na gorąco. Z uwagi na złożony charakter tego procesu przy projektowaniu celowe jest stosowanie symulacji numerycznych. Istotnym zagadnieniem jest odpowiedni opis warunków tarcia. Najczęściej w obliczeniach stosuje się model tarcia stałego, w którym czynnik tarcia charakteryzuje parę trącą narzędzie – odkształcany materiał. Celem badań przedstawionych w opracowaniu było wyznaczenie czynnika tarcia dla pary trącej rolka główna – walcowany pierścień, który zastosowany w symulacjach zapewni najlepszą zbieżność wyników obliczeń i doświadczenia. Badania laboratoryjne przeprowadzono na walcarce pionowej. Podczas badań zmieniano prędkość dosuwu rolki głównej w celu określenia wartości granicznej w aspekcie poślizgu. Uzyskano dwie prędkości charakterystyczne (z poślizgiem i bez poślizgu), dla których przeprowadzono symulacje numeryczne z parametrami odpowiadającymi warunkom eksperymentu. Zmieniano czynnik tarcia poszukując wartości, przy której uzyska się zgodność z doświadczeniem tj. dla jednej prędkości charakterystycznej wystąpi poślizg, a dla drugiej nie wystąpi. Na podstawie zastosowanej metodyki badawczej wyznaczono czynnik tarcia m=0,61 jako najbardziej odpowiedni do analiz numerycznych przy użyciu programu Simufact.forming v. 14.0.

EN

An effective method of producing ring products with large diameters in relation to the dimensions of the cross-section is hot rolling. Due to the complexity of the design process, the use of numerical simulations is advisable when designing. An important issue is an adequate description of the friction conditions. Most often, in the calculations, a shear friction model is used, in which the friction factor is characterized by a rubbing pair: tool - a deformed material. The purpose of the research presented in the paper was to determine the friction factor for the friction pair of the main roll - the rolled ring, which used in the simulations will ensure the best convergence of the results of calculations and experiments. Laboratory tests were performed on a vertical mill. During the tests, the infeed speed of the main roll was changed to determine the limit value in terms of slip. Two characteristic speeds were obtained (with slip and without slip), for which numerical simulations with parameters corresponding to the experimental conditions were performed. The friction factor has been changed, looking for a value at which compatibility with the experiment will be obtained, i.e. for one characteristic speed, slip will occur and for the other it will not occur. On the basis of the applied research methodology, the friction factor m = 0.61 was determined as the most suitable for numerical analyzes using the program Simufact.forming v. 14.0.

12

Niskie właściwości przeciwpoślizgowe nawierzchni – co można zrobić aby nie wymieniać warstwy ścieralnej?

Polecki A.

Drogownictwo

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2018

|

nr 4

118--122

PL

Właściwości przeciwpoślizgowe nawierzchni są jednym z głównych elementów decydujących o bezpieczeństwie ruchu drogowego. Podczas eksploatacji, wartość miarodajnego współczynnika tarcia obniża się do poziomu krytycznego. Należy wówczas przeprowadzić zabieg, który poprawi stan warstwy ścieralnej. Jest wiele metod, które umożliwiają poprawę właściwości nawierzchni. Jedną z nich jest śrutowanie – młotkowanie, którego efekty pozwalają na znaczące polepszenie i utrzymanie bezpiecznego poziomu przyczepności kół samochodowych do nawierzchni przez okres minimum 2 lat.

EN

Friction of the surface course is one of the most important component of the traffic safety. During operation and maintenance, friction factor is going critically down. There are many of methods to raise skid resistance. One of them is the blasting, which increases friction factor to a safe level of skid resistance. Results of that process lasts for two years or more.

13

Badania warunków tarcia w zakresie obróbki plastycznej na gorąco z wykorzystaniem smarów na bazie szkła

Bulzak T., Tomczak J., Pater Z.

Hutnik, Wiadomości Hutnicze

|

2017

|

Vol. 84, nr 8

298--300

PL

W artykule przedstawiono wyniki badań, w których określono warunki tarcia podczas kształtowania stali C45 w temperaturze 1150°C. Badania przeprowadzono z wykorzystaniem smarów na bazie szkła: szkło wodne, mieszanina szkła wodnego i grafitu oraz proszek szklany. Celem badań było wyznaczenie czynnika tarcia m. Wartości czynników tarcia wyznaczono na podstawie porównania wymiarów próbek spęczanych doświadczalnie z wynikami symulacji numerycznych. Szukaną wartość czynnika tarcia określano na podstawie minimalizacji funkcji celu.

EN

The paper presents the results of investigations in which friction conditions were determined during forming of C45 steel at 1150 °C. The research was conducted using glass-based lubricants: water glass, a mixture of water glass and graphite, and glass powder. The aim of this research was determining values of friction factors m. The values of friction factors were determined on the basis of the comparison of the dimensions of the experimental samples with the results of numerical simulations. The target value of friction factor was determined on the basis of minimizing the objective function.

14

Cooling of High Heat Flux Flat Surface with Nanofluid Assisted Convective Loop. Experimental Assessment

Arya A., Shahmiry S., Nikkhah V., Sarafraz M.M.

Archive of Mechanical Engineering

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2017

|

Vol. LXIV, nr 4

519--531

EN

Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. % = 0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.

15

Nanostructural TiN/Cu coatings deposited from the separated plasma flows

Latushkina S.D., Kuis D., Zhizhchenko A., Posylkina O., Piskunova O., Opielak M.

Przegląd Elektrotechniczny

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2016

|

R. 92, nr 8

173--175

EN

The results of the structural and physical-mechanical properties investigation of TiN/Cu coatings, deposited from multicomponent separated vacuum arc plasma are shown in this paper. The characteristics of the nanosized TiN-based coatings generation alloying by the element not forming chemical compounds with titanium and nitrogen under the chosen technological parameters are examined. The regularities of the microhardness and friction properties of TiN/Cu coatings changing under different elemental composition are determined.

PL

W pracy przedstawiono wyniki badań strukturalnych oraz właściwości fizyko-mechanicznych powłok TiN/Cu, otrzymanych łukową metodą próżniowo-plazmowego osadzania warstw ze złożonych odrębnych źródeł. Zbadano charakterystyki nanorozmiarowych powłok na bazie TiN generowanych dopingowaniem elementu nie tworzącego związki chemiczne z tytanem i azotem przy wybranych parametrach technologicznych. Ustalono, że prawidłowości mikrotwardości oraz właściowści tarciowe powłok TiN/Cu zmieniają się przy różnym składzie pierwiastkowym.

16

Wpływ technologii wykonania oznakowania poziomego nawierzchni drogowych na ich właściwości przeciwpoślizgowe

Danielek M., Wiśniewski D., Słowik M., Kempa J.

Materiały Budowlane

|

2016

|

nr 8

110--111

PL

W artykule przedstawiono wpływ technologii wykonania oznakowania poziomego na właściwości przeciwpoślizgowe nawierzchni. Za miarę przyjęto współczynnik tarcia. Do badań na 120 odcinkach pomiarowych wybrano trzy rodzaje oznakowania poziomego: grubowarstwowe, gładkie chemoutwardzalne; cienkowarstwowe z farb oraz grubowarstwowe, gładkie termoplastyczne. Wyniki wykazały, że najlepszymi właściwościami przeciwpoślizgowymi charakteryzuje się oznakowanie cienkowarstwowe, następnie grubowarstwowe – gładkie chemoutwardzalne, a najgorszymi grubowarstwowe – gładkie termoplastyczne.

EN

The article presents the impact of traffic marking production technology on the skid resistance of a road surface. The value of a friction factor is recognized as the measure of skid resistance. Three types of traffic marking have been selected for tests: thick-film smooth chemically hardened; thin-film painted and thick-film smooth thermoplastic. The investigations were carried out on 120 test sections. Test results have shown that thin-film marking features the best skid resistance, followed by thick-film chemically hardened marking, while thick-film smooth thermoplastic marking features the worst skid resistance properties.

17

Influence of 65G steel microstructure on crack faces friction factor under mode II fatigue fracture

Ivanytskyj Y. L., Lenkovskiy T. M., Molkov Y. V., Kulyk V. V., Duriagina Z. A.

Archives of Materials Science and Engineering

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2016

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Vol. 82, nr 2

49--56

EN

Purpose: The aim of the paper is to evaluate the dependence of microstructure parameters, strength and plasticity of steel on crack faces friction factor. Design/methodology/approach: The specimens for the investigation were cut out from the 10 mm thick hot-rolled plate of 65G steel used as a model material for fatigue and durability testing of whole-rolled railway wheels. The mechanical characteristics of the steel were determined according to the state standard using cylindrical specimens of diameter 5 mm and effective length 50 mm. The specimens were heat-treated at the mentioned conditions. Fatigue testing under mode II loading was carried out on a special rigid loading machine in the standard laboratory conditions at symmetric sinusoidal cycle with a frequency of 12 Hz in the range of fatigue crack growth rates da/dN = 5∙10⁻⁸…5∙10⁻⁷ m/cycle until its reaches relative length l/b ≥ 0.8. The obtained microsections were investigated using the optical metallographic microscope Neophot 9 equipped with a digital camera Nikon D50 and electronic scanning microscope Zeiss EVO 40XVP. Hardness of the specimens with different microstructure was determined using durometer TK-2. The crack faces friction factor was determined using original device for fractured surfaces sliding under certain compression force realization. Findings: The dependences of microstructure parameters, strength and plasticity of steel on crack faces friction factor are obtained. Research limitations/implications: The investigation of the influence of microstructure parameters, strength and plasticity of real wheel steels on crack faces friction factor at the mode II fatigue crack growth will be carried out. Practical implications: The value of crack faces friction factor have strong impact on stress intensity at the crack tip and must be taken into account at crack growth rates curves plotting. Originality/value: Mode II fatigue crack faces friction factor of steel is firstly experimentally determined.

18

Application of acustic emission for detection of fatigue microdemage in main and crank bearings for diesel engines

Girtler J.

Journal of Polish CIMEEAC

|

2015

|

Vol. 10, no 1

63--74

EN

The article presents reasons for applying the acoustic emission (AE) to detect fatigue microdamage in main bearings and crank bearings of marine main engines. Problem of determination of fatigue life for slide bearing bushes was characterized in general. There were demonstrated properties of the objects of research, which were bushings made of the MB58 alloy, as well as an overall description of the research. It was shown that the frequency bands of AE signals can indicate fatigue damage to the sliding layer of a bearing bush. The fatigue damage in the tested bushes was depicted in figures. General features of the AMSY-6 measuring system, used in the research, were also provided herein.

19

Jakościowa i ilościowa analiza zjawiska redukcji oporów przepływu za pomocą dodatków surfaktantów

Matras Z.

Inżynieria i Aparatura Chemiczna

|

2015

|

Nr 6

340--341

PL

Przedstawiono wyniki badań doświadczalnych wpływu dodatków surfaktanta CTAB i soli NaSal na obniżenie strat ciśnienia przy przepływie wody w rurach. Stwierdzono, że największa redukcja dyssypacji energii występuje w stabilnej strefie przejściowej między ruchem laminarnym i turbulentnym. Zbadano wpływ średnicy rury i stężenia roztworu na wielkość i zasięg redukcji oporów. Zaproponowano równanie opisujące zmodyfikowaną krzywą oporów w stabilnej strefie przejściowej.

EN

Experimental results of the influence of CTAB surfactant and NaSal salt additives on the pressure losses reduction for water flow in pipes are presented. It was found that the greatest reduction of energy dissipation is observed in the stable transitional zone between the laminar and turbulent flow ranges. The influence of pipe diameter and additives concentration on drag reduction efficiency was investigated. The equation of modified flow resistance curve in the stable transitional zone is proposed.

20

The importance of the law of the wall

Mandal B. C., Mazumdar H. P.

International Journal of Applied Mechanics and Engineering

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2015

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Vol. 20, no. 4

857--869

EN

This paper reports some results of turbulent boundary layer computation. The calculation is made assuming that law of the wall is valid throughout the boundary layer. Simple relations are proposed for friction for a smooth pipe and a flat plate at zero incidence. The results are compared with recent measurements. Encouraging results are obtained for both the cases of flows.