Autor: Miszczak, A. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Determination of variable pseudo-viscosity coefficients for oils with the Rivlin - Ericksen properties
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/247350.pdf
Data publikacji:: 2013
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: pseudo-viscosity coefficients
apparent viscosity
Rivlin-Ericksen equation
viscosity curves
Opis:: Modern oils, that lubricate the sliding friction pairs, contain more and more additives. These additives change the oil properties to the non-Newtonian. Furthermore, the friction and wear products and also the products of combustion in internal combustion engines, result in a change of the oil properties, from Newtonian to the non-Newtonian. Frequently, researchers suggest to use so-called „smart fluids”, for example, the ferro-oils as lubricants of sliding friction pairs exposed to strong magnetic fields or the absence of gravity. The ferro-oils are also characterized by the non-Newtonian properties. The viscosity characteristics of these oils are described rather well by the Rivlin-Ericksen constitutive equation. The Rivlin-Ericksen constitutive equation contains the coefficients, which are difficult to estimate or determine experimentally. One of the possibilities to determine these coefficients is the method proposed by Prof. K. Wierzcholski [12]. This method requires the experimental results of dynamic viscosity changes as a function of shear rate. The measurements of dynamic viscosity should be conducted for the widest possible range of shear rates. Then, using the viscosity curves and nonlinear system of equations, the auxiliary coefficients are determined. These coefficients generate the equations that describe the variable pseudo-viscosity coefficients. Not all oils have an intensive exponential character of viscosity changes in dependence on shear rate. In these cases it is possible to determine the constant coefficients of pseudo-viscosity [1, 3, 7, 8]. This paper presents the examples of determination of the variable pseudo-viscosity coefficients for the selected lubricating oils and ferro-oils.
Źródło:: Journal of KONES; 2013, 20, 1; 201-208
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Analysis of the influence of the changes in the value of dynamic viscosity coefficient in the direction of oil film thickness on the journal bearing load carrying capacity
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/243539.pdf
Data publikacji:: 2018
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: slide journal bearing
load carrying capacity
friction force
friction coefficient
numerical calculation
Opis:: This article presents the results of numerical calculations of the hydrodynamic pressure distribution, load carrying capacity, friction force and friction coefficient of the slide journal bearing, if the assumed model of hydrodynamic lubrication takes into account the dependence of oil viscosity values on its temperature in all three directions of the adopted coordinate system, in particular, also across the thickness of the lubricant layer. This research considered the slide journal bearing lubricated with the Newtonian oil. The flow of oil was modelled as laminar and stationary. The bearing bushing had a full angle of wrap and its surfaces were smooth. In order to obtain hydrodynamic pressure distributions, the Reynolds type equation was numerically solved by application of the finite difference method (FDM). The numerical procedures for this research were prepared with the Mathcad 15 software. When adopting the classic models and simplifications for the hydrodynamic lubrication and a thin boundary layer, it is assumed, that the hydrodynamic pressure of lubricating oil does not depend on the position measured across the height of the lubrication gap. On the other hand, it is known, that the dynamic viscosity strongly depends on the temperature, which is a function of all three spatial variables. The aim of this work is to include, in the hydrodynamic lubrication model, the changes of viscosity in the direction of oil film thickness, and to investigate how it will affect the hydrodynamic pressure distribution and load carrying capacity of the journal bearing.
Źródło:: Journal of KONES; 2018, 25, 3; 355-362
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Analysis of the load carrying capacities and the friction force in the gap of the slide journal bearing lubricated with a non-Newtonian oil described by a power-law model
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/244543.pdf
Data publikacji:: 2016
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: numerical calculation
load carrying capacities
friction forces
non-Newtonian oil
power law model
Opis:: In this paper, the author presents the results of numerical calculations of load carrying capacities and friction forces in the gap of the slide journal bearing lubricated with an oil on the non-Newtonian's properties. In the studies, the power-law model has been assumed to describe the relationship between the stress tensors and shear rate tensors. The analytical and numerical calculations have been performed for the plain bearing, non-porous with a full wrap angle. It has been assumed isothermal, laminar and steady flow of lubricant in the gap of a slide bearing. Numerical calculations have been performed for the Gumbel’s boundary conditions and dimensionless lengths of the bearings like L=b/R =2;1.5;1; ½ and ¼. The flow-rate index and coefficient of consistency have been adopted based on the results of experimental studies of changes of dynamic viscosity in terms of a shear rate. It has been assumed that the apparent viscosity depends only on the shear rate. Dynamic viscosity of the engine oil, used in a gasoline engine with a capacity of 1800 cm3, has been tested on the Haake Mars III rheometer. The analytical solutions presented in the paper were based on more general derivations carried out by Professor K. Wierzcholski in his article: ‘Non-linear hydrodynamic lubrication in conjugated fields’ (publication in printing). In this paper, the key quantities such as components of vector of the velocity, hydrodynamic pressure and temperature were presented in the form of convergent power series. The values of load carrying capacities and friction forces were determined and compared for the event where the oil has properties of Newtonian and non-Newtonian. Calculations have been made for the dimensionless quantities.
Źródło:: Journal of KONES; 2016, 23, 3; 327-335
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Viscoelastic unsteady lubrication of radial slide journal bearing at impulsive motion
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/259407.pdf
Data publikacji:: 2004
Wydawca:: Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:: viscoelastic unsteady lubrication
analytical and numerical calculation
capacity forces
hydrodynamic pressure
Opis:: This paper presents an analytical solution of velocity components of unsymmetrical oil flow and pressure distribution in radial journal bearing gap for hydrodynamic unsteady lubrication with viscoelastic oil. Numerical calculations are performed in Mathcad 11 Professional Program, with taking into account the method of finite differences. This meŹthod satisfies stability conditions of numerical solutions of partial differential equations and values of capacity forces occurring in cylindrical bearings. Exact calculations of presŹsure in journal bearing and its load capacity may be useful to prevent from premature wear tribological units of self ignition engines, especially those applied in ships.
Źródło:: Polish Maritime Research; 2004, 2; 9-21
1233-2585
Pojawia się w:: Polish Maritime Research
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Experimental values of temperature distribution in a sliding bearing sleeve lubricated with non-Newtonian oils
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/259545.pdf
Data publikacji:: 2005
Wydawca:: Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:: ferro-oil
non-Newtonian oil
temperature distribution
test stand
Opis:: This paper presents results of experimental investigations of temperature distributions on inner surface of a sleeve of transverse sliding bearing lubricated with non-Newtonian oils. The measurements were performed by means of Pt100 miniature sensors placed close to internal surface of the sleeve. To measure sleeve temperature distributions use was made of a test stand installed at Gdynia Maritime University. Delo 1000 Marine 30 oil, SAE 15W40 basic oil, and aferro-oil made of the SAE 15W40 basic oil were used as a lubricating medium. During measuring temperature distributions for the ferro-oil different intensity values of external magnetic field generated by electromagnets were applied.
Źródło:: Polish Maritime Research; 2005, 3; 16-26
1233-2585
Pojawia się w:: Polish Maritime Research
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: The analysis of hydrodynamic pressure distribution and load carrying capacity in the gap of slide journal bearings with micro-grooves
Analiza rozkładu ciśnienia hydrodynamicznego oraz siły nośnej w szczelinie poprzecznego łożyska ślizgowego z mikrorowkami
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/190378.pdf
Data publikacji:: 2017
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:: slide bearing lubrication
journal bearings
hydrodynamic pressure
non-classical surface
micro-grooves
load carrying capacity
friction force
smarowanie łożysk ślizgowych
poprzeczne łożysko ślizgowe
ciśnienie hydrodynamiczne
nieklasyczna powierzchnia
mikrorowki
siła nośna
siła tarcia
Opis:: The purpose of this paper is to analyse the distribution of hydrodynamic pressure, load carrying capacities, and friction force in the gap of the slide bearing on account of the type, number, and size of micro-grooves on the surface of the sleeve. It was assumed that micro-grooves were distributed equally on the circumference of the sleeve as well as parallel to its axis. Micro-bearings with micro-grooves are more and more of ten utilized in the technical applications, e.g., in HDD disks or in computer fans. It is advisable to carry out a numerical analysis on the influence of the number and the size of micro-grooves on the value of the Basic flow parameters in the slide micro-bearing. A laminar flow of lubricating fluid and an isothermal model of the lubrication of the slide bearing was used for the analysis. A classical Newtonian model was applied as the constitutive equation. A cylindrical slide Bering with the finished length and smooth sleeve, and a full wrap angle was used for the research. The density and thermal conductivity of the oil were considered to be constant in the thin film of oil. The results of measurements of shape and sizes of micro-grooves in real micro-slide bearings were presented by the author in the previous publications. The results of that research are used at present to determine the preliminary assumptions concerning the shape and the size of the micro-grooves. The results obtained in the research show the minor influence of micro-grooves on the value of the friction force and a few percentages rate influence of micro-grooves on the value of load carrying capacity.
Celem niniejszej pracy jest analiza rozkładu ciśnienia hydrodynamicznego, siły nośnej i siły tarcia w szczelinie poprzecznego łożyska ślizgowego ze względu na rodzaj, liczby i wielkość mikrorowków na powierzchni panewki. Do analizy przyjęto mikrorowki rozłożone równo po obwodzie panewki i równoległe do osi panewki. Mikrołożyska ślizgowe z mikrorowkami są coraz częściej stosowane w technice, np. w dyskach HDD czy też wentylatorach komputerowych. Celowym jest dokonanie analizy numerycznej, jaki wpływ na wartość podstawowych parametrów przepływowych ma liczba i wielkość mikrorowków. Do analizy hydrodynamicznego smarowania przyjęto laminarny przepływ cieczy smarującej oraz izotermiczny model smarowania łożyska ślizgowego. Jako równanie konstytutywne zastosowano klasyczny model newtonowski. Do rozważań przyjęto walcowe łożysko ślizgowe o skończonej długości z gładką panewką o pełnym kącie opasania. W cienkiej warstwie filmu olejowego przyjęto niezmienność gęstości i współczynnika przewodzenia ciepła oleju. Wyniki pomiaru kształtu i wymiaru mikrorowków w rzeczywistych mikrołożyskach ślizgowych autor przedstawiał we wcześniejszych publikacjach. Wyniki tych badań służą obecnie do określenia wstępnych założeń dotyczących kształtu i wielkości mikrorowków. Uzyskane wyniki badań wskazują na znikomy wpływ mikrorowków na wartość siły tarcia i kilkuprocentowy wpływ mikrorowków na wartość siły nośnej.
Źródło:: Tribologia; 2017, 272, 2; 119-126
0208-7774
Pojawia się w:: Tribologia
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Structure analysis of the surface of plunger and barrel assembly in the injection pump pumping section
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/246030.pdf
Data publikacji:: 2014
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: atomic force microscope
surface topography
roughness
plunger
barrel
injector pump
pumping section
Opis:: Precision surfaces in a diesel engine’s fuel system are used in the two components. First one is the pumping section in the injection pump. The second ones are injectors. In this paper authors present results of the topography measurements of the surface of plunger and barrel assembly in the injection pump pumping section. The measurements were performed using the atomic force microscopy (AFM) NT-206. The measured surface topographies were shown in the form of two and three-dimensional views of selected areas of the investigated surfaces. There are also presented the profiles of the selected area cross-sections as well as roughness height distribution and cumulative height distribution of roughness. Additionally, the basic parameters describing the surface roughness, such as: a roughness average Ra, a root mean square value Rq of roughness, a skewness Ssk (Rsk) and kurtosis Sku (Rku), are also specified. The samples (plungers and barrels), which have been measured, come from the injection pump pumping section as a new ones and after estimated period of operation time. The lateral precision surfaces have been measured. The atomic force microscope NT-206 allows to perform scanning of the measured surface with maximum are dimensions of 32 μm x 32 μm and maximal roughness height of ± 1 m. Scanned surfaces was divided into 256x256 measuring points and the measurements were performed in the static (contact) mode. After surface scanning on the atomic force microscope, the data was calculated in the SurfaceXplorer® 1.311 or Gwyddion 2.35 software. In this paper, only selected surfaces from the several dozen performed scans are shown. The obtained results allow to determinate the degree and type of wear of tested surfaces at the micro-level.
Źródło:: Journal of KONES; 2014, 21, 3; 227-234
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Analysis of surface topography of slide journal bearings and micro - bearings
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/247394.pdf
Data publikacji:: 2013
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: surface topography
atomic force microscope
static contact mode
height distributions of surface roughness
Opis:: In this paper, the author presents the results of measurements of the slide journal bearings and micro-bearings sleeves and journal surfaces. The study was performed with the atomic force microscope (AFM) NT-206. The results of measurements of surface topography are presented in the form of a 2D and 3D map of surface topography and also in the form of profiles for selected cross-sections of examined surfaces. Additionally, the height distributions of surface roughness are presented. The Atomic Force Micsroscope NT-206 allows investigating the surface of sample with maximum scanning area 32μm x 32μm and with the maximum value of roughness ±1μm. The measurements can be carried out in three modes: static (contact) mode, dynamic (non-contact) mode, dynamic intermittent mode. The author used the contact mode. The application of this mode of operation, in the case of samples with a hard surface, for example, the journal of a bearing, enables to obtain a good mapping of the measured surface. The presented in this paper results of surface topography measurements, include the calculated values of the Ra and Rq parameters and also the maximum value of the distance between the lowest and the highest surface inequality. The obtained results allow evaluating the amount and type of wear of researched elements in the micro-scale and they also are useful in the design of such surface layers of co-operating components, in order to obtain optimum tribological properties. When considering the impact of the surface roughness on the change of height of bearing gap, and consequently the change of flow and operating parameters, the information about average distribution of roughness value is required. With such measurements, it is possible to obtain these data. In the presented research the micro-bearings from personal computers hard drives, as well as classic bearings and sleeves, were investigated.
Źródło:: Journal of KONES; 2013, 20, 4; 285-292
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Operating parameters of slide micro – bearings with consideration of oil temperature changes and micro - grooves on sleeve surface
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/247490.pdf
Data publikacji:: 2012
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: HDD micro-bearings
micro-grooved surfaces
oil viscosity changes in gap height
hydrodynamic pressure
friction forces
load carrying capacity
Opis:: In this paper author presents results of numerical calculations of hydrodynamic pressure distribution in bearing gap, load-carrying capacity, friction force and friction coefficient of slide micro-bearing considering the influence of lubricating oil temperature changes and also taking into account the influence of micro-grooves, which occur on sleeve internal surface. The micro-grooves on that surface are in longitudinal direction. The equation, which describes a bearing gap with micro-grooves on sleeve surface, was adopted from prof. K Wierzcholski's investigations. In very thin gap height of cylindrical micro-bearings, large gradients of temperature can be observed. This causes significant changes of oil dynamic viscosity in the gap height direction. According to this, oil flow velocity, friction forces, and a hydrodynamic pressure during the micro-bearing operation are changing. Up to now the influence of temperature on oil viscosity changes and due to this, on hydrodynamic pressure and on load carrying capacity in cylindrical micro-bearing gap in numerical way were not considered yet. The numerical calculations were performed with the use of Mathcad 14. The finite differences method and own computational procedures were implemented. The calculations were begun by solving the Reynolds' equation, assuming, that the dynamic viscosity is constant. After calculating the hydrodynamic pressure distribution, the temperature distribution in lubricating oil was determined. The obtained function of temperature was used to describe the viscosity changes with temperature. Next step involved determining the hydrodynamic pressure distribution taking into account the viscosity dependence on temperature, and then new distribution of temperature and again new values of viscosity were calculated. Calculations were repeated until assumed convergence and accuracy were reached. The friction force depends on pressure gradient and rotational motion of bearing journal. Part of friction force, which resulting from the pressure gradient, is determined for the area, where the oil film occurs, i.e. from omega p to omega k. Part of friction force, which is related to journal motion, is determined for full wrap angle, i.e. from 0 to 2 pi. The results were presented in the form of graphs, for eccentricity ratio gamma from 0.1 to 0.9, for dimensionless length of the bearing L1=1/4. In numerical calculations were used the theoretical considerations and solutions presented in papers of K. Wierzcholski and A. Miszczak.
Źródło:: Journal of KONES; 2012, 19, 2; 329-336
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Surface topography of operated slide journal micro - bearings used in HDD
Autorzy:: Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/242978.pdf
Data publikacji:: 2012
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: atomic force microscope
surface topography
microgrooves
herringbone grooves
micro bearing in HDD
Opis:: In this paper author present results of measurements of slide journal micro-bearings surface topography measured with an atomic force microscope (AFM). The results of measurements of surface topography were presented in the form of surface topography maps, three-dimensional graphs and some examples of selected cross-sections of investigated surface in the form of profile graphs. Measurements of surface topography were made for journals and sleeves of slide journal micro-bearings from personal computers' hard disc drives, with the Atomic Force Microscope NT-206 produced in MTM in Minsk, Republic of Belarus. In this research author used two identical sets of micro-bearings from 2.5" HDD Samsung HM160HI 5400rpm and 3.5" HDD Seagate Barracuda 7200.10 ST380815AS 7200 rpm hard disc drives. First set of those four microbearings worked for a year at rated RPM continuously (i.e. 24 hours a day). Second set of the same micro-bearings also worked for a year at rated RPM, but in intermittent mode (i.e. 15 minutes on, 15 minutes off). The values of profile roughness parameters Ra and Rq and the distance between maximum peak height and maximum valley depth are presented as well. The application SurfaceXplorer registered trademark was used for processing and visualization of the data obtained from AFM NT-206, which besides from generating 2D, 3D and profile diagrams, was used to calculate and draw graph of height distribution. Surface topography of investigated bearings sleeves was also measured using Hommeltester T8000-R60 profilometer. Those measurements give information about micro-grooves dimensions and location. On the surfaces of studied micro-bearings, some micro-grooves can be found in form of herringbone, with depth about 1.5..m and width 150..m. Received information about micro-grooves geometry will allow developing proper theory of hydrodynamic lubrication for micro-bearings with micro-grooves.
Źródło:: Journal of KONES; 2012, 19, 4; 449-456
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 11.

Tytuł:: Samooczyszczające się hydrofobowe systemy tribologiczne
Self-cleaning hydrophobic friction systems
Autorzy:: Wierzcholski, K.
Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/188012.pdf
Data publikacji:: 2010
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:: powierzchnie hydrofobowe
adhezja
samooczyszczanie
hydrophobic surface
anti-adhesion
self-cleaning
Opis:: Procesy adhezyjne lub mechanizmy tribologiczne są interesujące z wielu powodów. Biologiczne mechanizmy kontaktowe pomagają w zrozumieniu zasad funkcjonowania wielu technicznych adhezyjnych urządzeń. Zbadanie biologicznych stykowych powierzchni stało się źródłem rozwoju idei twórczych w zakresie przemysłowych zastosowań powierzchni samo-oczyszczających się. Na przykład powierzchnie samooczyszczające są bardzo pożądane w zbiornikach do magazynowania olejów, smarów, farb. Ponadto powierzchnie lemieszy pługa powinny też posiadać własność samooczyszczania się od pozostałości gleby po orce. Zdolność samooczyszczania powierzchni jest procesem tribologicznym. Powierzchnie hydrofobowe charakteryzują się specyficzną rzeźbą w postaci mikroi nanorowków. W pracy wyjaśniono mechanizm zanieczyszczenia powierzchni tworzony adhezyjnym wiązania nanoobiektów z rozpatrywanymi powierzchniami na skutek sił Van der Waalsa.
Adhesive or sticking tribological mechanisms are interesting in several respects. Biological sticking mechanisms may aid in understandding the principles of the functioning of other technical frictional and adhesive mechanisms. Biological sticking surfaces provide a rich source of ideas for the development of industrial applications, such as self cleaning surfaces. For example, the self-cleaning surfaces are very desirable for the internal surfaces of tanks for lubricants in contact with the oil. The shared surfaces of the plough ought to have self-cleaning properties too. Self cleaning-abilities of the surface are known as the hydrophobic properties. Hydrophobic surfaces have specific sculptured shapes with the nano-ridges and nano-grooves. Particle contaminating surface structures consists, in most cases, of material that is more readily wetted than hydrophobic wax components. Contaminants usually rest on the tips of the surface structures, so that the real contact area between the particles and sculptured surface is minimised. Thus, these particles can be easily removed by water droplets rolling over the surface. In this case, the adhesion between particles and water droplets is greater than between particles and the sculptured surface due to the reduced contact between the particles and surface. Therefore, we have the selfcleaning process of the surface.
Źródło:: Tribologia; 2010, 3; 241-250
0208-7774
Pojawia się w:: Tribologia
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 12.

Tytuł:: Algorytm wyznaczania zmiennych współczynników pseudolepkości olejów na bazie eksperymentu
Algorythm for variable pseudoviscosity coefficients under an experimental basis
Autorzy:: Wierzcholski, K.
Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/188532.pdf
Data publikacji:: 2013
Wydawca:: Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:: związki fizyczne
zmienne współczynniki pseudolepkości
wpływ prędkości deformacji
oleje smarujące
physical dependencies
changes of pseudo-viscosity coefficients
share rate influences
lubrication oils
Opis:: Obserwuje się coraz większy udział stosowania olejów częściowo i całkowicie syntetycznych w procesie smarowania węzłów tarcia ślizgowego. Oleje te charakteryzują się nienewtonowskimi właściwościami. Nienewtonowskimi olejami nazywa się takie ciecze, w których oprócz klasycznych zależności lepkości oleju od ciśnienia i temperatury występuje dodatkowo zależność lepkości od prędkości deformacji. Większość czynników smarujących ulepszanych chemicznie ma właściwości nienewtonowskie. Podobnie ciecze zanieczyszczone, np. substancjami organicznymi, kurzem ulicznym, sadzą lub też produktami zużycia i spalania w silniku spalinowym wykazują właściwości nienewtonowskie. Wymienione zanieczyszczenia i dodatki mogą powodować wzrost lub spadek lepkości czynnika smarującego w stosunku do bazowej cieczy smarującej. W niniejszej pracy przedstawiona została metoda analityczna wyznaczania zmiennych wartości funkcyjnych współczynników pseudolepkości na podstawie wyników eksperymentalnych dla olejów stosowanych w praktyce inżynierskiej.
Constitutive equations between stresses and deformations for oils with pseudo-viscosity properties are usually described by the Rivlin-Ericksen relations. In these relations two pseudo-viscosity coefficients occur. Up to now, in numerous scientific papers concerning the journal bearing lubrication with visco-elastic oils, the mentioned pseudo-viscosity coefficients have been treated as constant values. By virtue of performed measurements, it is evident that experimental curves describing visco-elastic oil dynamic viscosity versus shear rate had shapes that cannot be obtained for the constant pseudo-viscosity coefficients. In this case, only possible are the unknown dependences between oil dynamic viscosity and share rate. This paper shows the algorithm derivation for variable pseudo-viscosity coefficients as a function of shear rate using pseudo-viscosity oils and taking into account the experimental data obtained from viscosity measurements.
Źródło:: Tribologia; 2013, 4; 125-136
0208-7774
Pojawia się w:: Tribologia
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 13.

Tytuł:: Magneto-therapy of human joint cartilage
Autorzy:: Wierzcholski, K.
Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/306552.pdf
Data publikacji:: 2017
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:: magnetoterapia
pole magnetyczne
efekty magnetoterapii
magnetic induction variable field
magnetotherapy
magneto electronic devices
positive effects of magnetotherapy
negative effects of magnetotherapy
human joint cartilage diseases
Opis:: Purpose: The topic of the present paper concerns the human joint cartilage therapy performed by the magnetic induction field. There is proved the thesis that the applied magnetic field for concrete cartilage illness should depend on the proper relative and concrete values of applied magnetic induction, intensity as well the time of treatment duration. Additionally, very important are frequencies and amplitudes of magnetic field as well as magnetic permeability of the synovial fluid. Material and methods: The research methods used in this paper include: magnetic induction field produced by a new Polish and German magneto electronic devices for the therapy of human joint cartilage diseases, stationary and movable magnetic applicators, magnetic bandage, ferrofluid injections, author’s experience gained in Germany research institutes and practical results after measurements and information from patients. Results: The results of this paper concern concrete parameters of time dependent electro-magnetic field administration during the joint cartilage therapy duration and additionally concern the corollaries which are implied from reading values gained on the magnetic induction devices. Conclusions: The main conclusions obtained in this paper are as follows: Time dependent magnetic induction field increases the dynamic viscosity of movable synovial fluid and decreases symptoms of cartilage illness for concrete intensity of magnetic field and concrete field line architecture. The ferrofluid therapy and phospholipids bilayer simultaneously with the administrated external electromagnetic field, increases the dynamic viscosity of movable synovial fluid.
Źródło:: Acta of Bioengineering and Biomechanics; 2017, 19, 1; 115-124
1509-409X
2450-6303
Pojawia się w:: Acta of Bioengineering and Biomechanics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 14.

Tytuł:: Distribution of hydrodynamic pressure in the interspace of lateral sliding bearings lubricated by ferrofluid with different concentrations of magnetic particles
Autorzy:: Frycz, M.
Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/245424.pdf
Data publikacji:: 2011
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: hydrodynamic pressure distributions
capacity
ferrofluid
magnetic field
numeric calculation
Opis:: This paper presents the numerical results of hydrodynamic pressure distributions and capacity in the gap of ferrofluid-lubricated slide bearing with different concentrations of magnetic particles. Ferrofluid is a colloidal mixture of dispersing agent (base) and diffused (magnetic particles). The most common distracted factors are Fe3O4, Ge2O2 or NiO. Scattering factor is mostly water, mineral oil, synthetic oil. In addition, the magnetic particles are coated with a surfactant in the form of long chains of molecules or electrostatic coating. Reynolds-type equation has been derived from the equations of momentum and continuity equation for laminar, steady and isothermal flow. Viscoelastic model Rivlin-Ericksen type of lubricant has been adopted. It has been adopted also that the dynamic viscosity depends generally on the magnetic field. The equations of momentum, continuity and Maxwell's equation with a constitutive equation were made dimensionless, and then them small units of higher order have been omitted (units of the order of the relative radial clearance: i//=0.001). Such estimated system of equations of motion was divided into two subsystems by the small parameter method. The basic system of differential equations which consider the effect of the magnetic field has been received and the additional system which takes into account influences of non-Newtonian properties as well. Integrating the appropriate momentum equations and imposing boundary conditions the velocity vector components and the Reynolds-type equation have been obtained. While computer simulations of the magnetic field were assumed that the longitudinal component of magnetic induction vector does not change with the length of the bearing. Reynolds-type equation by which the hydrodynamic pressure distributions can be determined has been solved numerically using Mathcad and ourselves calculation procedures. The paper presents results of numerical calculations of hydrodynamic pressure distribution and lift force for the simulated values of the magnetic field and ferrofluid's dynamic viscosity and for different relative eccentricities and dimensionless length of the bearing. The results presented in the paper are the solutions of a basic system.
Źródło:: Journal of KONES; 2011, 18, 3; 83-89
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 15.

Tytuł:: A new problem of hydrodynamic lubrication with temperature and viscosity variations in gap height direction
Autorzy:: Wierzcholski, K.
Miszczak, A.
Powiązania:: https://bibliotekanauki.pl/articles/245652.pdf
Data publikacji:: 2016
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: liquid viscosity changes in thin gap height direction
temperature
adhesion or capillary forces variations in thin gap height direction new analytical solutions
Opis:: Numerous Authors of scientific papers occurring in hydrodynamic theory of slide bearing lubrication, up to now almost always had neglected the oil dynamic viscosity variations caused by temperature, adhesion forces, capillary forces, or hydrogen ion concentration across the film thickness by virtue of the statement of the constant temperature as well constant adhesion as capillary forces in the thin bearing gap height direction. In addition, simultaneously by virtue of boundary layer simplifications for energy equation and by virtue of new measurements performed in micro and nano- level follows that oil temperature gradients and its values differences and adhesion or capillary gradients of forces in bearing gap height directions are not negligible small. The contemporary hydrodynamic theory of lubrication for non-isothermal lubricant flow is unfortunately based on the assumption of constant viscosity values across the film thickness, despite abovementioned self-evident contradiction between the fact of constant viscosity and simultaneously temperature variations in gap height direction. Such problem was up to now not sufficient critical examined and explained in practical and theoretical sense. After Authors, knowledge by virtue of above problem the most scientific papers in the domain of non-isothermal and lamellar hydrodynamic slide bearing or biobearing lubrication were up to now not sufficient correctly solved. It denotes that the main hydrodynamic lubrication solutions presenting for example hydrodynamic pressure by the modified Reynolds equation and temperature by the energy conservation equation are not sufficiently correctly obtained and next not correctly solved. Therefore are assumed simultaneously the temperature T and oil dynamic viscosity variations in length, width and bearing gap- height directions. From this assumption follows, that the energy equation must be solved simultaneously with the equations of motion i.e. consequently with pressure equation where viscosity depends on temperature and temperature depends on the coordinate in gap height direction.
Źródło:: Journal of KONES; 2016, 23, 2; 423-430
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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