Transient Response of Viscoplastic and Viscoelastic Shells Submerged in Fluid Media

1976 ◽  
Vol 43 (1) ◽  
pp. 137-143 ◽  
Author(s):  
T. A. Duffey
Keyword(s):  
Surrounding Medium ◽  
Viscoelastic Behavior ◽  
Rate Sensitivity ◽  
Viscoelastic Materials ◽  
Elementary Functions ◽  
Fluid Medium ◽  
Fluid Media ◽  
Viscoelastic Shells ◽  
Interaction Problem ◽  
Linearly Elastic Materials

The transient fluid-shell interaction problem is investigated for thin shells constructed of other than linearly elastic materials. Specifically, solutions are developed in terms of elementary functions for the transient responses of impulsively loaded, fluid-surrounded spherical shells constructed of either viscoplastic or viscoelastic materials. In all cases the fluid medium surrounding the shell is taken as inviscid and compressible and only spherically symmetric shell motions and radiation of sound into the surrounding medium are considered. It is found that the influence of material strain hardening and strain-rate sensitivity can be significant in reducing fluid-shell displacement responses. Further, limited investigations for viscoelastic materials indicate that for higher loss materials, displacement response of the shell is significantly altered by the inclusion of the viscoelastic behavior.

scholarly journals The Applicability of Different Fluid Media to Measure Effective Stress Coefficient for Rock Permeability

2015 ◽  
Vol 2015 ◽  
pp. 1-11
Author(s):  
Ying Wang ◽  
Guozhi Li ◽  
Min Li ◽  
Jing Zhang
Keyword(s):  
Clay Minerals ◽  
Effective Stress ◽  
Stress Sensitivity ◽  
Gas Reservoirs ◽  
Fluid Medium ◽  
Water Sensitivity ◽  
Stress Coefficient ◽  
Fluid Media ◽  
Sensitive Clay ◽  
Key Parameter

Effective stress coefficient for permeability (ESCK) is the key parameter to evaluate the properties of reservoir stress sensitivity. So far, little studies have clarified which ESCK is correct for a certain reservoir while rock ESCK is measured differently by different fluid media. Thus, three different fluids were taken to measure a fine sandstone sample’s ESCK, respectively. As a result, the ESCK was measured to be the smallest by injecting nitrogen, the largest by injecting water, and between the two by brine. Besides, those microcharacteristics such as rock component, clay mineral content, and pore structure were further analyzed based on some microscopic experiments. Rock elastic modulus was reduced when water-sensitive clay minerals were encountered with aqua fluid media so as to enlarge the rock ESCK value. Moreover, some clay minerals reacting with water can spall and possibly block pore throats. Compared with water, brine can soften the water sensitivity; however, gas has no water sensitivity effects. Therefore, to choose which fluid medium to measure reservoir ESCK is mainly depending on its own exploitation conditions. For gas reservoirs using gas to measure ESCK is more reliable than water or brine, while using brine is more appropriate for oil reservoirs.

VIBRIO CHOLERAE IN FLUID MEDIA

1950 ◽  
Vol 28e (6) ◽  
pp. 257-261
Author(s):  
L. E. Ranta ◽  
Mary McLeod
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Sodium Chloride ◽  
Sodium Bicarbonate ◽  
Inorganic Salts ◽  
Distilled Water ◽  
Hydrogen Phosphate ◽  
Fluid Medium ◽  
Dipotassium Hydrogen Phosphate ◽  
Fluid Media

Studies have been made of the growth of V. cholerae in fluid media of chemically defined compositions. The addition of three amino acids, tyrosine, asparagine, and glycine, to a fluid medium containing inorganic salts produced a growth of V. cholerae equivalent to a 450 p.p.m. silica standard. Under conditions of aeration with an air and carbon dioxide mixture, yields comparable to the turbidity of a 1600 p.p.m. silica standard were obtained with a medium composed of 0.67 gm. of tyrosine, 0.42 gm. of asparagine, 0.51 gm. of glycine, 5.0 gm. of sodium chloride, 5.0 gm. of ammonium sulphate, 0.75 gm. of dipotassium hydrogen phosphate, 0.1 gm. of magnesium sulphate, 10.0 gm. of glucose, and 15.0 gm. of sodium bicarbonate dissolved in one liter of distilled water.

scholarly journals THE DRUG-FASTNESS OF SPIROCHETES TO ARSENIC, MERCURIAL, AND IODIDE COMPOUNDS IN VITRO

1917 ◽  
Vol 25 (3) ◽  
pp. 349-362 ◽  
Author(s):  
Seinai Akatsu ◽  
Hideyo Noguchi
Keyword(s):  
Culture Media ◽  
Treponema Pallidum ◽  
Chemotherapeutic Agents ◽  
Inhibitory Influence ◽  
Fluid Medium ◽  
Rate Of Increase ◽  
Fluid Media ◽  
Pure Cultures ◽  
Free Media

In the foregoing experiments we attempted to determine whether or not, by subjecting several varieties of spirochetes to increasing doses of certain chemotherapeutic agents, a gradual increase of resistance to the latter could be shown. For this purpose, pure cultures of Treponema pallidum, Treponema microdentium, and Spirochœta refringens were used against the action of salvarsan, neosalvarsan, bichloride of mercury, and iodine-iodide potassium solution in vitro. For culture media, the usual ascites-broth-tissue medium as well as solid ascites-agar-tissue medium was used. After permitting the spirochetes to grow for a fortnight in media containing certain quantities of each drug, transfers were made from tubes showing various degrees of growth to the next series of tubes containing the same drug in still higher concentrations, and similar transfers repeated every 2 weeks. The results of the experiments may be briefly summarized as follows: 1. Treponema pallidum and Treponema microdentium have, within 3 to 4 months, increased their tolerance to salvarsan and neosalvarsan to five and one-half times their original mark. With Spirochata refringens the increase was about three times. 2. Against the action of bichloride of mercury, the amount of increased tolerance of Treponema pallidum was about 35 to 70 times the original, while that of Treponema microdentium was about 10 times as much and was reached within 10 weeks. Spirochata refringens resisted 30 times the original dose. 3. There was an unmistakable increase of resistance of these spirochetes to the action of the iodine-iodide solution (Lugol's solution) when they were grown for several generations in fluid media containing the iodine solution, but the rate of increase between the initial and the acquired tolerance was slight. In general, the addition of Lugol"s solution to fluid media has a weak inhibitory influence upon the growth of the spirochetes, requiring for the total suppression of growth a quantity of over 0.7 cc. to 5 cc. of the culture media. The tolerance reached was for about three times that amount. 4. A similar tolerance phenomenon has not been established when employing a solid instead of a fluid medium containing the drugs. No explanation is offered except a suggestion that the drugs held in the agar do not enter into combination with certain tissue constituents of the medium as they are able to do with tissue elements in fluid media. This may be a factor necessary for inducing drug tolerance in these organisms in vitro. 5. The increased drug-fastness in vitro has a limit beyond which no further advance can be made. This limit varies with different species of spirochetes. 6. The acquired drug-fastness in vitro gradually disappears when the spirochetes are cultivated again in the drug-free media for several generations.

scholarly journals Viscoelastic Behavior of Drug-Loaded Polyurethane

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2608
Author(s):  
Navideh Abbasnezhad ◽  
Mohammadali Shirinbayan ◽  
Fatiha Chabi ◽  
Stephane Champmartin ◽  
Abbas Tcharkhtchi ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Drug Carriers ◽  
Tensile Tests ◽  
Release Time ◽  
Fluid Medium ◽  
Free Volume Fraction ◽  
Drug Eluting ◽  
Loading Ratio

Drug-eluting stents are desirable platforms for local medicine delivery. However, the incorporation of drugs into polymers can influence the mechanical and physicochemical properties of said matrix, which is a topic that is still poorly understood. In fact, this is more noticeable since the apposition is most often accompanied by mechanical stresses on the polymer coating, which can induce therapeutic failure that can result in death. It is therefore necessary to better understand their behavior by examining their properties in conditions such as those in living beings. We studied polyurethane drug carriers made in-house. Diclofenac epolamine was chosen as a model hydrophilic medicine. We used thermal measurements (DMTA) and tensile tests. The aim was to establish the influence of the loading and release of the drug on the physicochemical properties of this polymer in the presence of a stagnant or circulating fluid medium, phosphate-buffered saline (PBS). For the two PU/drug loadings studied, the effect of the initial drug load was more marked. The free volume fraction and the number of pores in the samples increased with the increasing percent of the drug and with release time. The kinetic profiles were accelerated with the loading ratio and with the presence of flow. Young′s modulus and ultimate stress were not significantly influenced by the release time. A relevant relationship between the tensile properties and the viscoelastic behavior of the samples was developed. Our results have implications for optimizing the performance of drug coatings for stents.

The Effect of a Surrounding Fluid on Pressure Waves in a Fluid-Filled Elastic Tube

1955 ◽  
Vol 22 (2) ◽  
pp. 227-231
Author(s):  
M. C. Junger
Keyword(s):  
Sound Velocity ◽  
Surrounding Medium ◽  
Elastic Tube ◽  
Pressure Waves ◽  
End Effects ◽  
Fluid Medium ◽  
Phase Velocities ◽  
Radiation Losses ◽  
Surrounding Fluid ◽  
Theory Of Shells

Abstract The analysis of the transmission of pressure waves in a fluid-filled elastic tube has been extended to the case where the tube is surrounded by a fluid medium. The sound pressure inside the tube is the resultant of a number of modes, some of which are nonpropagating, while others propagate at their own characteristic phase velocities. Neglecting end effects, and for continuously generated waves, it is found that only the modes whose velocity is larger than the sound velocity of the surrounding medium radiate sound energy radially outward. These modes will be damped out by radiation losses, while modes having a phase velocity smaller than this sound velocity are propagated without attenuation (if viscous and heat-transfer losses are neglected). Consequently, if the fluid is the same in the surrounding medium and in the tube only the lowest mode, which resembles a plane wave, propagates unattenuated. In any case, the mass-loading of the surrounding fluid lowers the phase velocities of the propagating modes, particularly at intermediate frequencies. It is shown that in this application the membrane theory of shells will lead to incorrect results, even in thin-walled tubes. This is illustrated by comparison with experimental data.

scholarly journals Complex Eigenvalue Analysis for Structures With Viscoelastic Behavior

2011 ◽  
Author(s):  
G. Chevallier ◽  
F. Renaud ◽  
J.-L. Dion ◽  
S. Thouviot
Keyword(s):  
State Space ◽  
Viscoelastic Behavior ◽  
Maxwell Model ◽  
Accurate Method ◽  
Eigenvalue Analysis ◽  
Theoretical Development ◽  
Complex Eigenvalue ◽  
Viscoelastic Materials ◽  
Space Problem ◽  
Internal States

This document deals with a method for eigenvalue extraction for the analysis of structures with viscoelastic materials. A generalized Maxwell model is used to model linear viscoelasticity. Such kind of model necessitates a state-space formulation to perform eigenvalue analysis with standard solvers. This formulation is very close to ADF formulation. The use of several materials on the same structure and during the same analysis may lead to a large number of internal states. This article purpose is to identify simultaneously all the viscoelastic materials and to constrain them to have the same time-constants. As it is usually possible, the size of the state-space problem is therefore widely reduced. Moreover, an accurate method for reducing mass and stiffness operators is proposed; The enhancement of the modal basis allows to obtain good results with large reduction. As the length of the paper is limited, only theoretical development are presented in the present paper while numerical results will be presented in the conference.

Viscoelastic Materials: Innovation and Development Countenance

2017 ◽  
Vol 266 ◽  
pp. 165-171 ◽  
Author(s):  
Koorosh Gharehbaghi ◽  
Farshid Rahmani
Keyword(s):  
Viscoelastic Behavior ◽  
Critical Factor ◽  
Material Behavior ◽  
Stress And Strain ◽  
Viscoelastic Materials ◽  
Design Specification ◽  
Load Bearing Capacity ◽  
Total Load ◽  
Elastic Characteristics ◽  
Innovation And Development

While performance and durability are the key features of any Material behavior, the greater the elasticity and flexibility ability the better the functioning capabilities. These Material functioning capabilities not only include improved Load Bearing Capacity (LBC), but also enhanced stress and strain abilities. In addition, these functioning capabilities are dependent on composition of the material, Total Load (TL) and Design specification requirements. A key mechanical behavior of materials is their Viscoelastic ability. While Viscous materials are objects that become deformed via shear and tensile stresses, elastic materials are those that change their shape under stress and strain. Furthermore, Viscoelastic materials are those which portray both elastic characteristics as well as viscous behavior when enduring deformation. This Viscoelastic ability is a critical factor for materials to be effectively Total Load (TL) resistant. Accordingly, this paper will discuss some of the more important Material innovation, and development countenances such as functionality to further demonstrate the overall Viscoelastic behavior.

Compressive Strain-Rate Tests on Six Selected Materials at Strain Rates From 10−3 to 104 In/In/Sec

1966 ◽  
Vol 33 (3) ◽  
pp. 496-504 ◽  
Author(s):  
C. J. Maiden ◽  
S. J. Green
Keyword(s):  
Strain Rate ◽  
Compressive Strain ◽  
Pyrolytic Graphite ◽  
Viscoelastic Behavior ◽  
Rate Sensitivity ◽  
Hopkinson Bar ◽  
Strain Rates ◽  
Reduction Methods ◽  
Split Hopkinson ◽  
Aluminum 7075

The results of compressive strain-rate tests on 6061-T6 aluminum, 7075-T6 aluminum, 6Al-4V titanium fully annealed, pyrolytic graphite, lucite, and micarta for rates of loading of 10−3 to 104 in/in/sec are presented. A medium strain-rate machine and a split Hopkinson bar apparatus used to conduct these tests are described, and the principle of operation, data-reduction methods, and a critique of techniques are given for each machine. Results of the tests show that the two aluminums exhibit no strain-rate sensitivity over the rates tested. Titanium, lucite, and micarta are rate sensitive with the titanium exhibiting a delayed yield and the lucite and micarta showing viscoelastic behavior. The pyrolytic graphite shows little rate sensitivity below 10 in/in/sec and slight sensitivity above this rate.

THE EXTENDED FOURIER PSEUDOSPECTRAL TIME-DOMAIN (PSTD) METHOD FOR FLUID MEDIA WITH DISCONTINUOUS PROPERTIES

2010 ◽  
Vol 18 (04) ◽  
pp. 297-319 ◽  
Author(s):  
MAARTEN HORNIKX ◽  
ROGER WAXLER
Keyword(s):  
Wave Propagation ◽  
Time Domain ◽  
Fourier Transforms ◽  
Gibbs Phenomenon ◽  
Fluid Medium ◽  
Inhomogeneous Fluid ◽  
Model Wave ◽  
Air Interface ◽  
Fluid Media ◽  
Fourier Pseudospectral

The Fourier pseudospectral time-domain (PSTD) method is an attractive method to efficiently model wave propagation through a weakly inhomogeneous fluid medium. The method fails, however, for fluid media with discontinuous properties. This failure is due to the well known Gibbs phenomenon which arises when Fourier transforming a discontinuous function. The extended Fourier PSTD method developed here can accurately and efficiently model wave propagation through weakly inhomogeneous fluid media with discontinuities in the media properties. Rather than using Fourier transforms to calculate the spatial derivatives in the wave equation, the method developed here uses a generalized eigenfunction expansion for which no Gibbs phenomenon arises. Two approaches to solving the resulting time-domain problem are explored and the accuracy of the method is demonstrated. Finally, results from an example calculation of transmission through the water-air interface are shown.

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