Temat: coefficients - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Determination of pseudo-viscosity coefficients for visco-elastic lubricants
Autorzy:: Wierzcholski, K.
Powiązania:: https://bibliotekanauki.pl/articles/247504.pdf
Data publikacji:: 2010
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: pseudo elastic coefficients
method of determination
Opis:: In this paper we assume determination of pseudo-viscosity coefficients of visco-elastic non-Newtonian fluid flow directly near the cooperating micro-bearing surface. We show the constitutive stress-strain dependencies of non-Newtonian visco-elastic media with regard to the content of addition of nano-particles. The greater content of nano-particles and influences of superficial layer of cooperating surfaces on the dynamic oil viscosity, the more distinct non-Newtonian properties. The non-Newtonian properties create non-linear dependencies between strain and stress. Moreover the dynamic viscosity or apparent dynamic viscosity of oil often decreases along with shear rate increasing during motion. dynamic viscosity of oil inside very thin boundary layers depends on Young's modulus of the cell body being in contact with the oil. Considered visco-elastic oils with nano-particles have non-Newtonian pseudo-plastic properties, described in the beginning by means of Rivlin-Ericksen constitutive relations. Hence their stress-strain dependencies presented in this paper have the modified Rivlin-Ericksen form. Scientific efforts brought into this elaboration represent an impact to the considered domain by providing for some data on comparisons between boundary conditions for lubrication flow in super thin boundary layer lying on the external surface of biological cells of joint cartilage and boundary conditions for lubrication of micro-bearing of shaft diameter smaller than 2 mm.
Źródło:: Journal of KONES; 2010, 17, 2; 491-496
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Dimensional constraints in ship design
Autorzy:: Charchalis, A.
Powiązania:: https://bibliotekanauki.pl/articles/245380.pdf
Data publikacji:: 2013
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: ship principal dimensions
hull volumetric coefficients
hull design
Opis:: The paper presents general rules for calculations of ship’s hull principle dimensions at preliminary stage of design process. There are characterized and defined basic assumptions of design process and limitations for calculations of dimensions and some criteria numbers. Limitations are an outcome of shipping routes what is related to shipping restrictions, diminishing of hull drag, achieving of required strength of hull and safety of shipping requirements. Shipping limitations are because of canals and straits dimensions or harbours drafts. In order to diminish propulsion power, what is related to economically justified solution, selected form and dimensions of hull must ensure minimizing of resistance, including skin friction and wavemaking resistance. That is why proper selection of coefficients of hull shape and dimensional criteria according to ship owner’s requirements i.e. deadweight (DWT) or cargo capacity (TEU), speed and seakeeping. In the paper are analyzed dimensional constraints due to shipping region, diminishing of wavemaking and skin friction resistance or application of Froude Number, ships dimensional coefficients (block coefficient, L/B, B/T, L/H) and coefficients expressing relations between capacity and displacement. The scope of applicability above presented values for different modern vessels construction were analyzed.
Źródło:: Journal of KONES; 2013, 20, 2; 27-32
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Determination of coefficients of energy losses occurring in a constant capacity pump working in a typical hydrostatic drive
Autorzy:: Skorek, Grzegorz
Powiązania:: https://bibliotekanauki.pl/articles/245612.pdf
Data publikacji:: 2019
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: coefficients of losses
energy losses
hydrostatic system
axial piston pump
Opis:: In order to assess possibilities of energy saving during hydrostatic drive system operation, should be learned, and described losses occurring in system. Awareness of proportion of energy, volume, pressure, and mechanical losses in elements is essential for improving functionality and quality of hydrostatic drive systems characterized by unquestionable advantages. In systems with too low efficiency there is increase of load, mainly in case of pump load, which can lead to higher risk of failure, necessity of repair or replacement, as well as to shorten service life of system. Coefficients ki, given in subject literature by Paszota, describe relative value of individual losses in element. They make it possible to assess proportions of losses and assess value of energy efficiency (volumetric, pressure, mechanical) resulting from losses occurring at nominal pressure pn of system in which element is used. As a result, thanks to knowledge of coefficients ki of individual losses, it is possible to determine losses and energy efficiency of components operating in hydraulic system as well as efficiency of system with defined structure of motor speed control as function of speed and load coefficient of motor. Knowledge of coefficients of energy losses occurring in system elements (pump, hydraulic motor, conduits, and motor) allows building models of losses and energy efficiency of element working in system and energy efficiency of system as whole composed of elements. Mathematical models of losses and energy efficiency in system must take into account conditions resulting from applied structure of system, from level of nominal pressure, from rotational speed of motor driving pump shaft, from viscosity change of applied hydraulic oil. Article presents method of determining coefficients of axial piston pump used in typical hydrostatic drive system with proportional control. Values that can be assumed for these loss coefficients for other hydraulic pumps are also given.
Źródło:: Journal of KONES; 2019, 26, 1; 159-166
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Solutions of recurrences with variable coefficients for slide bearing wear determination
Autorzy:: Wierzcholski, K.
Powiązania:: https://bibliotekanauki.pl/articles/247289.pdf
Data publikacji:: 2013
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: wear anticipation after exploitation
slide bearings
recurrence equation
variable coefficients
Opis:: The numerous methods of numerical calculations occurring in power-train tribology and transport concerning wear bearing determination problems demand the more and more information referring the slide bearing wear anticipation in succeeding years of machine operations. Therefore this paper presents the methods of solutions of some specific class of ordinary non-homogeneous recurrence equations of second and higher order with variable coefficients occurring in hydrodynamic theory of bearing wear problems. Contrary to linear recurrence equations with constant coefficients, linear recurrence equations with variable coefficients rarely have analytical solutions.. Numerical solutions of such equations are always practicable. In numerous analytical methods of solutions of linear recurrence equations with variable coefficients there are usually three research directions. The first of them depend upon the successive determination of the linear independent particular solutions of the considered recurrence equation. The second direction to be characterized by the reduction of the order of recurrence equation to obtain an always solved, first order recurrence equation. The third direction of solutions of recurrence equations with variable coefficients, contains the methods of analytical solutions by means of a summation factor. The majority of the general methods of analytical solutions of linear recurrence equations with variable coefficients constitute an adaptation of the methods applied in solutions of suitable differential equations In final conclusions the application of presented theory in this paper contains the the examples referring the wear values determination of HDD bearing system in the indicated period of operating time.
Źródło:: Journal of KONES; 2013, 20, 3; 427-433
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

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: 6.

Tytuł:: Wear process in successive time units described by first order recurrences
Autorzy:: Wierzcholski, K.
Powiązania:: https://bibliotekanauki.pl/articles/244485.pdf
Data publikacji:: 2014
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: wear determination during slide bearings operating process
first order recurrence equation
class of variable coefficients
Opis:: The numerous tribology problems occurring in power-train and transport industry lead to wear bearing determination solutions. Especially the project designer demand the more and more information referring the slide bearing wear anticipation in succeeding years of machine operations. In this paper a perspective will be provided on what is known about various types of influences which are caused wear effects. Some machinery eventually fails or becomes uneconomical to operate because of single causes for example types of wear, but most mechanical devices succumb to combinations of causes. A direct parallel is seems in the human machine. Therefore this paper presents the methods of solutions of some specific class of ordinary non-homogeneous recurrence equations of first order with variable coefficients occurring in hydrodynamic theory of bearing wear problems. The various coefficients occurring in considered recurrent equations are determined from experimental measurements where the influence of various operating parameters on the wear effects is taking into account. The influence of numerous operating parameters on the wear effects is experimentally determined in the case if mentioned parameters are independent as well if are mutually connected. Moreover in this paper the theorems will be presented of the existence, determination and an algorithm construction of discrete solutions of non-homogeneous, linear, first order recurrent equations with variable coefficients. The Lemmas and Theorem are formulated and proved by means of the Unified Operator of Summation (UOS operator) with a unitary translation operator, where the operator properties and features are taking into account. In the case of the space of solution functions, the above mentioned wear problems determination are attributed to practical applications related to the non-homogeneous, linear, first order differential equations. The examples presented in this paper for various variable coefficients i.e. for various operating conditions determine the wear values of micro- bearing system during the indicated time units of operating time.
Źródło:: Journal of KONES; 2014, 21, 3; 285-292
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Wear cumulating process for friction pair implemented by first order recurrences
Autorzy:: Wierzcholski, K.
Powiązania:: https://bibliotekanauki.pl/articles/245033.pdf
Data publikacji:: 2014
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Tematy:: cumulative wear values
operation after finite and infinite time units
first order recurrence implementation
variable coefficients after experiments
Opis:: Wear determination engages a major part of our efforts in considered numerous tribology problems including animal teeth and joints, human joints, cams, piston, rings, tires, brakes, dirt seals, belts, shoes, fabrics, electrical contacts, tape and CD reader heads and others. At times it seems after numerous observation, that the rate of progress in the knowledge of wear is very slow. Modern design activities are mostly concern in the wear cumulative values determination rather than the wear values determination in successive time units of friction nods during the operation time. Therefore, presented paper determines in analytical way the cumulative wear values of friction nods after specified finite and infinite units of operation time. Therefore are considered the convergences and divergences of wear value cumulative processes for various friction nods. The kind of friction nods depends on type of wear process propagation. Such propagation is described in this paper by the recurrence first order equation. Mentioned equation is formulated with constant or variable parameters. This parameters are determined by virtue of experimental measurements and depend on: bearing materials properties, environmental conditions, roughness of cooperating surfaces, vibration effects, electrical conductivity of materials, hardness of materials, deformations mode of cooperating surfaces, temperature, air humidity, kind of the friction, sliding velocity, loading of the friction nod and others. The range of wearing influence components and devices is endless. Therefore, this paper presents the methods of solutions of numerous specific class of ordinary non-homogeneous recurrence equations of first order with variable coefficients occurring in hydrodynamic theory of bearing especially micro-bearing wear problems. The obtained solutions are examined by means of the UOS operator. The examples presented in this paper determine the abrasive wear cumulative values of micro-bearing system after the indicated time units of operating time. Moreover, after infinite time units of micro-bearing operation are considered the convergences and divergences of the obtained sums of cumulative wear process.
Źródło:: Journal of KONES; 2014, 21, 1; 287-294
1231-4005
2354-0133
Pojawia się w:: Journal of KONES
Dostawca treści:: Biblioteka Nauki

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