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1
Content available Determining of Maximum Stress in Circular and Circular Hollow Rod by Measurement of Strains
100%
LABAŠ V. , ĎURIŠ R. , LABAŠOVÁ E.
Edukacja-Technika-Informatyka
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2015
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tom 6
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nr 2
173-178
EN
The contribution deals with determining of stress from measured values of strains. Gauge strains, which were linked in half-bridge, and the universal measurement system QuantumX MX840 were used to experimentally obtain the strains. Rods with circular section and hollow circular section serve as tests samples. Students within the educational process will have the opportunity to acquaint with the universal measuring system and see the interconnectedness of theory and practical application.
2
Content available remote Exact solutions for the longitudinal flow of a generalized Maxwell fluid in a circular cylinder
100%
Siddique I.
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2010
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tom Vol. 62, nr 4
305-317
EN
This paper deals with the longitudinal flow of a generalized Maxwell fluid in an infinite circular cylinder, due to the longitudinal variable time-dependent shear stress that is prescribed on the boundary of the cylinder. The fractional calculus approach in the constitutive relationship model of a Maxwell fluid is introduced. The velocity field and the resulting shear stress are obtained by means of the Laplace and finite Hankel transforms and satisfy all the imposed initial and boundary conditions. The solutions corresponding to ordinary Maxwell fluids as well as those for Newtonian fluids are obtained as limiting cases of our general solutions. Finally, the influence of the fractional coefficient on the velocity and shear stress of the fluid is analyzed by graphical illustrations.
3
Content available remote Projektowanie kanalizacji w oparciu o naprężenia ścinające na granicy kanał - ścieki
100%
Dąbrowski W.
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2011
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tom nr 4
38-41
PL
Dobrze znany wzór na określenie przeciętnych wartości naprężenia ścinającego wzdłuż obwodu zwilżonego został wyprowadzony, a następnie użyty dla uzasadnienia empirycznego wzoru Imhoffa, dotyczącego wyznaczania minimalnych spadków poszczególnych kanałów. Podsumowano, że w celu uzyskania takich samych wartości naprężeń ścinających w kanałach o tym samym kształcie i napełnieniu względnym, ale o różnych wielkościach, należy spadki kanałów dobrać odwrotnie proporcjonalnie do ich wysokości. Następnie przedyskutowano i zilustrowano graficznie wpływ wysokości napełnienia na średnią wartość naprężenia wzdłuż obwodu zwilżonego.
EN
The well known formula for predicting the average shear stresses along the wetted perimeter has been developed and used for supporting the empirical I mhoff equation for minimal slopes of sewers. I t has been concluded that to obtain the same shear stress along walls of large and small sewers their slopes should be inverse to the height of sewers of the same shape and the same relative depth of flow. The impact of depth of flow on the average shear stress along the wetted perimeter has been described in details and illustrated in figures.
4
Rheological peculiarities of microcrystalline cellulose gels
88%
Laka M. , Chernyavska S. , Faitelson L. , Jakobsons E.
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1999
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tom Vol. 4, no spec.
351-355
EN
Rheological properties of MCC hydro- and alcogels have been studied. MCC gels were obtained by way of dispersing in water, ethyl alcohol and propyl alcohol media the wood pulp destructed to the levelling-off degree of polymerization (LODP) of cellulose by a method developed by us. At a sufficiently high cellulose concentration which was dependent on the liquid medium, MCC gels with rheological properties typical for liquid crystalline polymers (flow curves with three characteristic regions, viscosity concentrations curves with a local maximum, etc.) were obtained. These properties are more pronounced for hydrogels. MCC hydrogels are characterized also by a higher liquid phase retention volume (~ 380%), which is an important characteristic of a stable gel. For MCC alcogels, it makes up 40-65%. Inferior properties of MCC alcogels are connected with the chemical structure of alcohol molecules which, as compared to water molecules, are less favourable for bonds formation among cellulose microcrystallites and the liquid medium.
5
Content available remote Application of a constitutive equation for softening, yield and permanent deformation to finite plane simple shear
88%
Huntley H. , Wineman A. , Rajagopal K.
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2000
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tom Vol. 52, nr 3
443-479
EN
The finite homogenous simple shear deformation of an incompressible material is considered. The response is modeled with a constitutive equation that reflects a continuous process of microstructural transformation as the deformation increases beyond a threshold value. The original and transformed portions of the material are both taken to respond as incompressible elastic solids. It is shown that the transformation can lead to softening of the response with increasing deformation and to a local maximum in the shear stress-shear strain curve. The existence of permanent deformation after release of the shearing traction is demonstrated. It is confirmed that a process of increasing deformation followed by decreasing deformation to the point of zero shear traction is a dissipative cycle. A special case is then considered in which both the original and transformed materials are assumed to respond as neo-Hookean solids. The critical volume fraction of transforming material at which the shear stress-shear strain curve loses monotonicity is found analytically. Representations are obtained for the dependence of the residual shear deformation on the fraction of transforming material; on the ratio of moduli of the original and transformed materials; and on the maximum shear reached before unloading.
6
Content available remote Some exact solutions for the rotational flow of a generalized second-grade fluid between two circular cylinders
88%
Mahmood A. , Saifullah , Bolat G.
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2008
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tom Vol. 60, nr 5
385-401
EN
The velocity field and the associated tangential stress corresponding to the flow of a generalized second-grade fluid between two infinite coaxial circular cylinders, are determined by means of the Laplace and Hankel transforms. At time t=0, the fluid is at rest and at t=0+ the cylinders suddenly begin to rotate about their common axis with a constant angular acceleration. The solutions that have been obtained satisfy the governing differential equations and all the imposed initial and boundary conditions. The similar solutions for a second-grade fluid and Newtonian fluid are recovered from our general solutions. The influence of the fractional coefficient on the velocity of the fluid is also analyzed by graphical illustrations.
7
Wpływ naprężeń hydrodynamicznych na komórki żywe
75%
Pohorecki R. , Bałdyga J. , Malepszy S. , Ryszczuk A. , Golis W. , Motyl T. , Porębska A.
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1999
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tom Z. 26
127-132
PL
Przeprowadzono badania doświadczalne i analizę teoretyczną wpływu naprężeń hydrodynamicznych na komórki żywe. Badania doświadczalne potwierdziły możliwość zastosowania multifraktalnej teorii burzliwości do interpretacji zjawisk zachodzących w bioreaktorze.
EN
Response of plant and animal cells to high shear environment has been investigated during in vitro cultivation in a bioreactor with Rushton type impeller. Investigations have shown that agitation affects regrowth ability and viability of cells as well as cell aggregate structure and size distribution. A multifractal theory describing the fine scale structure of turbulence, including its intermittency, is employed to describe the cell-aggregate breakage process. The model predicts transient aggregate size distributions in agreement with experimental data.
8
Content available remote Bending analysis of laminated composite and sandwich beams according to refined trigonometric beam theory
75%
Sayyad A. S. , Ghugal Y. M. , Naik N. S.
Curved and Layered Structures
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2015
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tom 2
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nr 1
EN
A trigonometric beam theory (TBT) is developed for the bending analysis of laminated composite and sandwich beams considering the effect of transverse shear deformation. The axial displacement field uses trigonometric function in terms of thickness coordinate to include the effect of transverse shear deformation. The transverse displacement is considered as a sum of two partial displacements, the displacement due to bending and the displacement due to transverse shearing. Governing equations and boundary conditions are obtained by using the principle of virtual work. To demonstrate the validity of present theory it is applied to the bending analysis of laminated composite and sandwich beams. The numerical results of displacements and stresses obtained by using present theory are presented and compared with those of other trigonometric theories available in literature along with elasticity solution wherever possible.
9
Content available remote Wpływ rodzaju materiału ścianki, gradientu prędkości ścinania i temperatury na wartość naprężeń stycznych w smarach plastycznych
75%
Biernacki K.
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2007
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tom nr 6
75-85
PL
Praca poświęcona jest badaniom nad właściwościami reologicznymi smarów plastycznych: wapniowego, litowego, aluminiowego i polimerowego. Do wyznaczenia wartości naprężeń stycznych w smarach wykorzystano reometr rotacyjny. Przeprowadzone badania wykazały, że zarówno rodzaj zagęszczacza, jak też rodzaj materiału ścianki wpływają na właściwości reologiczne smarów plastycznych. Badania wykazały także, iż wpływ warstwy przyściennej ujawnia się w zakresie niskich wartości prędkości ścinania i w niższej temperaturze.
EN
The presented research deals with the rheological properties of greases such as: calcium, lithium, aluminum soap and polymer thickened ones. The shear stress in these compounds has been determined by means of the rotational rheometer. Both the type of the thickener and the type of material of cylinder affected the rheological properties of greases. The study shows also that the influence of boundary layer appears in the low shear rate and low temperature area.
10
Influence of laminar shear stress on cytoskeleton and ICAM-1 expression of endothelial cells
75%
Muller S. , Sun R. , Legrand S. , Labrador V. , Wang X. , Stoltz J. F.
|
1999
|
tom Vol. 4, no spec.
151-156
EN
The aim of this work was to study the morphological behavior and the surface adhesion molecules expression and localization of a human endothelial cell line subjected in vitro to a laminar flow in a parallel plate flow chamber, by a 3-D fluorescence microscopy and cytofluorimetry. At rest, endothelial cells showed an array of microfilament bundles of the actin fibers, and a peripheral distribution of ICAM-1 molecules. After shear stress (1 to 30 dyne/cm2, 1 to 24 hours), the stress fibers appeared and were oriented related to the flow direction but also to the shear. The ICAM-1 expression varied according to the shear stress characteristics and their distribution at the cell surface appeared also modified and related to the stress fibers formation.
11
Deformation of a model endothelial cell in flow: A two-dimensional numerical simulation
75%
Wang X. , Wache P. , Maurice G. , Lucius M. , Stoltz J. F.
|
1999
|
tom Vol. 4, no spec.
185-190
EN
Mechanical forces induced by blood flow influence largely endothelial cells' behavior. Also they can modify the expression and distribution of biological receptors, orient cytoskeleton, modify vasoactive factors, etc.. The objective of this study was to determine the deformation of a model endothelial cell exposed to a laminar flow. The cell was supposed to be a two dimensional elastic material. The interaction between the flow and cell deformation was simulated numerically by finite element method. Thus the distributions of mechanical forces on cell surface were obtained. The numerical results showed that the cell deformation depended on imposed flow velocity and that the mechanical stresses on cell surface were not uniform and lower with deformation than without. These numerical results suggest that it'll be interesting to study eventual correlation between the distribution of cell's biological receptors and that of mechanical factors.
12
Content available Theoretical and experimental analysis on the interaction properties between tracks and sediments considering sand content for unmanned underwater tracked bulldozer
75%
Li Y. , He D. , Si Q. , Li Y. , He D. , Si Q.
|
|
nr 1
13
Content available Experimental investigations on punching shear of flat slabs made from lightweight aggregate concrete
75%
Gołdyn M. , Krawczyk Ł. , Ryżyński W. , Urban T. , Gołdyn M. , Krawczyk Ł. , Ryżyński W. , Urban T.
|
|
nr 4-I
14
Content available Elasticity solution of adhesive tubular joints in laminated composites with axial symmetry
71%
Selahi E. , Selahi E.
|
|
nr 3
15
Content available remote Wpływ zawartości zagęszczacza na zjawisko tiksotropii smarów plastycznych
63%
Paszkowski M.
|
2007
|
tom nr 3-4
85-96
PL
Praca dotyczy wpływu udziału procentowego zagęszczacza na zjawisko tiksotropii smarów plastycznych. Badaniom poddano czyste (bez dodatków) smary litowe zagęszczane 12-hydroksystearynianem litu na bazie oleju mineralnego. Wyniki eksperymentu pokazały, że zarówno udział procentowy zagęszczacza, jak i gradient prędkości ścinania mają istotny wpływ na odbudowę mikrostruktury zagęszczacza litowego po procesie ścinania. Badania zostały przeprowadzone z wykorzystaniem reometru rotacyjnego - Rheotest 2.1 ze zmodyfikowaną głowicą pomiarową.
EN
The paper deals with influence of thickener fraction on thixotropy of lubricating greases. The research was done on pure (without any additives) lithium greases thickened by lithium 12-hydroxystearate witl mineral base oil. The results of the experiment showed that both the thickener fraction and shear rate have a significant influence on reconstruction of lithium thickener microstructure after the shearing process. The research was carried out by means of a rotary rheometer - Rheotest 2.1 with modified measuring head.
16
Content available remote Protodiastole and vessel damage in atherosclerosis
63%
Beraia M. , Todua F. , Khomeriki I.
|
|
tom Vol. 26, no. 3
65-75
EN
Hemodynamic forces are now known to be the localizing factors in atherogenesis, but conclusions as to the causes of the vessel wall damage are inconsistent. The purpose of the study was examination of the blood flow features in the aortic arch and establishment of the initial factors of atherogenesis. 15 men (age from 27 to 35 years) have been examined by magnetic resonance angiography on Siemens-Sonata-Cardio unit. Blood flow peak systolic velocity changes at the opposite walls of the aortic arch have been revealed. During protodiastole, the flow was found to form opposite directed streams, and a flow arrest with a flat flow profile was noted in discrete sites of the aorta. At these specified places, the peak systolic velocity was found to be low. Blood protodiastolic acceleration was 6 times higher than in the systole, and the shear stress was found to exceed the verge of the endothelial endurance. The circular blood flow at the aortic arch in protodiastole is characterized by a high acceleration, and the gradient pressure in the flat profile can damage the internal layers of the vessel.
17
Influence of the rotor's eccentricity on mixer power requirement
63%
Cherniuk V. , Zhuk V. , Pitsyshyn B.
|
2002
|
tom Nr 4
43-44
EN
In this article the results of the experimental research on the influence of a non-axial position of two cylinders, on the average shearing stress at the wall of the internal bob rotating in water are presented.
18
Content available remote Wpływ technologii sporządzania kompozytów na właściwości PA6 modyfikowanego montmorylonitem
63%
Mencel K. , Kelar K. , Jurkowski B. , Danch A.
|
2006
|
tom Vol. 26, nr 1
187-200
19
Content available remote Endothelial cell responses to fluid shear stress
63%
Kamiya A.
|
|
tom Vol. 20, no. 3
21-33
EN
Implications of vascular endothelial cell (EC) responses to flow-oriented wall shear stress are outlined from the bioengineering viewpoint. These responses regulate the adaptive remodeling of the vascular system including capilIary networks, in a negative feedback mechanism maintaining the shear stress level constant. The preserved set point of the stress is selected so as to optimize the mass transport function of the system. To initiate such shear-dependent responses, EC has a mechano-sensor conjugated with second messengers, one of which is cytoplasmic Ca(2+) transient. The evidence that wall shear stress is the real factor inducing the transient, is visualized from an in vitro flow loading experiment to cultured ECs using mediums differing in viscosity.
PL
W artykule przedstawiono implikacje występowania reakcji komórki śródbłonka na naprężenia ścinające w ścianie naczynia, związane z przepływem płynu. Reakcje te kontrolują adaptację systemu naczyń krwionośnych, łącznie z siecią kapilar, utrzymując naprężenia ścinające na stałym poziomie za pomocą mechanizmu ujemnego sprzężenia zwrotnego. Zadany poziom naprężeń jest tak dobrany, aby optymalizować funkcję transportu masowego układu naczyniowego. W celu inicjacji reakcji, zależnej od poziomu naprężeń ścinających, komórki nabłonka wykorzystują mechano-sensor połączony z innymi "przekaźnikami", z których jednym jest transport wapnia. Dowód, że naprężenia ścinające w ściance naczyń są czynnikiem uruchamiającym ten "transport" jest widoczny podczas badań in vitro mechanizmu przepływu medium o różnej lepkości w hodowli komórek śródbłonka.
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