scholarly journals Effects of internal pore pressure on closed-cell elastomeric foams

2012 ◽  
Vol 49 (19-20) ◽  
pp. 2793-2798 ◽  
Author(s):  
Oscar Lopez-Pamies ◽  
Pedro Ponte Castañeda ◽  
Martín I. Idiart
Keyword(s):  
Pore Pressure ◽  
Closed Cell ◽  
Internal Pore ◽  
Elastomeric Foams

The Influence of Internal Pore Pressure During Roll Forming of Structurally Porous Metals

1998 ◽  
Vol 521 ◽  
Author(s):  
D. M. Elzey ◽  
H. N. G. Wadley
Keyword(s):  
Pore Pressure ◽  
High Pressures ◽  
Hot Isostatic Pressing ◽  
Matrix Material ◽  
Porous Metal ◽  
Roll Forming ◽  
Dense Matrix ◽  
Porous Metals ◽  
Noticeable Effect ◽  
Internal Pore

ABSTRACTStructurally porous metal sandwich panels consisting of dense face sheets and porous cores of controlled relative density can be manufactured by trapping inert gas during hot isostatic pressing and modifying its distribution via subsequent thermo-mechanical forming. At high pressures, the internal gas is expected to influence the forming response. This paper describes a model for the roll forming of a porous metal panel and its use to explore the effects of internal pore pressure upon rolling response. It is shown that for gas pressures below about half the yield strength of the fully dense matrix material, there is essentially no influence on the forming response. Only in the case of very high initial pore pressures or at relative densities approaching full theoretical does a noticeable effect arise. In this case, a limiting upper density is attainable which depends on the specific rolling conditions and geometry.

Analysis of Space Shuttle External Tank Spray-On Foam Insulation With Internal Pore Pressure

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Brett A. Bednarcyk ◽  
Jacob Aboudi ◽  
Steven M. Arnold ◽  
Roy M. Sullivan
Keyword(s):  
Pore Pressure ◽  
Polymer Material ◽  
Space Shuttle ◽  
Micromechanical Model ◽  
Constitutive Models ◽  
Ideal Gas ◽  
Material Creep ◽  
Parametric Studies ◽  
Gas Expansion ◽  
Internal Pore

The polymer spray-on foam insulation used on NASA’s Space Shuttle external fuel tank is analyzed via the high-fidelity generalized method of cells micromechanical model. This model has been enhanced to include internal pore pressure, which is applied as a boundary condition on the internal faces of the foam pores. The pore pressure arises due to both ideal gas expansion during a temperature change as well as outgassing of species from the foam polymer material. Material creep and elastic stiffening are also incorporated via appropriate constitutive models. Due to the lack of reliable properties for the in situ foam polymer material, these parameters are backed out from foam thermomechanical test data. Parametric studies of the effects of key variables (both property-related and microstructural) are presented as is a comparison of model predictions for the thermal expansion behavior of the foam with experimental data.

Effect of Overburden Pressure on Some Properties Of Sandstones

1962 ◽  
Vol 2 (04) ◽  
pp. 360-366 ◽  
Author(s):  
Valery M. Dobrynin
Keyword(s):  
Experimental Data ◽  
Physical Properties ◽  
Pore Pressure ◽  
Clay Minerals ◽  
Elastic Waves ◽  
Water Saturation ◽  
Porous Rocks ◽  
Overburden Pressure ◽  
Pore Compressibility ◽  
Internal Pore

Abstract Experimental data demonstrate that physical properties of porous rocks change under pressure. In this paper an assumption is made and proved that under pressure the changes of physical properties such as porosity, density, permeability, resistivity and velocity of elastic waves are controlled to a large extent by the pore compressibility of rocks. It is also shown that the pore compressibility of rocks can be determined, within the range of pressures from 0 to 20,000 psi, by knowing the maximum pore compressibility and the magnitude of the pressure. Mathematical equations were developed which permit one to define changes in physical properties of porous rocks under pressure. These equations were verified by experimental data obtained from the study of sandstones. Introduction In studying the behavior of porous rocks under pressure in the field of petroleum technology, the most interesting aspect is the observation of those properties which characterize the rocks as possible reservoirs for example, porosity, permeability, resistivity, density and be velocity of elastic waves. The literature dealing with this problem mainly contains data concerning the study of only one or at most two of these parameters, but not of the group as a whole. An attempt is made in this paper to find general equations involving each of these parameters, which will permit the study of the behavior of rocks under pressure. All experimental data used here were obtained from the investigation of consolidated sandstones. EXPERIMENTAL In addition to the use of published experimental data, an experiment was carried out which studied the main physical properties of sandstones under pressure. Two homogeneous quartz sandstones were chosen for this purpose:the Torpedo sandstone bona Kansas, andthe Medina sandstone from Ohio. The porosity of the Torpedo sandstone was 20.2 per cent, and that of the Medina 8.7 per cent. Permeabilities were 45 md and less than 1 md, respectively. Each sandstone contained about 5 per cent clay minerals, consisting mostly of kaolinite and chlorite, which were distributed quite evenly throughout the samples. One cylindrical sample 2 in. in diameter and 5 in. in length was cut from each sandstone and then saturated in a vacuum with a 3N solution of NaCl. This high concentration was used in order to obtain true formation factors and to decrease the swelling of the clay minerals. The methods of mounting the samples and measuring the changes in porosity and resistivity were practically the same as those described by Fatt and Mann. Changes of resistivity under pressure were studied for sandstones with 100 per cent water saturation, and for sandstones with the irreducible water saturation. The irreducible saturation was obtained by enclosing the saturated rock samples in relatively fine silicate powder so as to remove the water by capillary action. This procedure is described by Orkin and Kuchinski. Changes of permeability with pressure were determined at room temperature using nitrogen as the flowing medium. In studying the effects of pressure, one series of measurements was made using an internal pore pressure Pi equal to the atmospheric pressure, while the overburden pressure P. ranged from 0 to 20,000 psi. A second series of measurements was used over the same range of overburden pressure, but with an internal pore pressure of 1,800 psi When the results were compared on the basis of net overburden pressure (P, - 0.85 Pi ), there was practically no difference for these two sandstones. The origin of the factor 0.85 in the expression for net overburden pressure is given by Brandt, Fatt and Geertsma. SPEJ P. 360^

The Microstructural Response of Articular Cartilage at Peak Internal Pore Pressure: A Comparison Between Normal and Degenerate Matrices

2008 ◽  
Author(s):  
James M. Fick ◽  
Ashvin Thambyah ◽  
Neil D. Broom
Keyword(s):  
Articular Cartilage ◽  
Pore Pressure ◽  
Direct Compression ◽  
Pore Pressures ◽  
The Relationship ◽  
Internal Pore

This study was aimed at investigating the relationship between the microstructural responses of healthy (normal) versus mildly osteoarthritic articular cartilage and their associated peak internal pore pressures, when subjected to direct compression.

ULTRASONIC SHEAR‐WAVE VELOCITIES IN ROCKS SUBJECTED TO SIMULATED OVERBURDEN PRESSURE AND INTERNAL PORE PRESSURE

Geophysics ◽  
1965 ◽  
Vol 30 (1) ◽  
pp. 117-121 ◽  
Author(s):  
B. S. Banthia ◽  
M. S. King ◽  
I. Fatt
Keyword(s):  
Hydrostatic Pressure ◽  
Pore Pressure ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Overburden Pressure ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
The Matrix ◽  
Internal Pore

Change in shear‐wave velocity for four dry sedimentary rocks has been studied as a function of the variation of both external hydrostatic pressure and internal pore pressure in the range 0 to 2,500 psi. The experimental method employs a beam of ultrasonic energy passing through a liquid in which a copper‐jacketed parallel‐sided slab of rock is rotated. The shear‐wave velocity is calculated from the laws of refraction and reflection of waves at a liquid‐solid boundary applied to the angle at which minimum energy is transmitted. The variation of shear‐wave velocity with pressure has been found to be a function of net overburden pressure, [Formula: see text], where [Formula: see text] hydrostatic pressure on the jacketed sample, [Formula: see text] pore pressure and n = a pressure‐dependent factor less than unity. The values of n at several differential pressures were chosen to yield a smooth curve passing through the displaced data points when the shear‐wave velocities were plotted as a function of net overburden pressure. Using the n values so obtained, the matrix compressibility [Formula: see text] for two of the sandstones has been calculated from the relation [Formula: see text]. The bulk compressibility [Formula: see text] for these two rocks had previously been obtained experimentally as a function of differential pressure. The values obtained for the matrix compressibility are in the range expected from a knowledge of the grain and cementing materials for these sandstones.

scholarly journals Fluid pressure heterogeneity during fluid flow in rocks: new laboratory measurement device and method

2021 ◽  
Vol 225 (2) ◽  
pp. 968-983
Author(s):  
Nicolas Brantut ◽  
Franciscus M Aben
Keyword(s):  
Pore Pressure ◽  
Transient Flow ◽  
Fluid Pressure ◽  
Confining Pressure ◽  
Dead Volume ◽  
Low Permeability ◽  
Pore Fluid Pressure ◽  
Working Pressure ◽  
New Type ◽  
Internal Pore

SUMMARY We present a new type of transducer capable of measuring local pore fluid pressure in jacketed rock samples under elevated confining pressure conditions. The transducers are passive (strain-gauge based), of small size (7 mm in diameter at the contact with the rock and around 10 mm in length), and have minimal dead volume (a few mm3). The transducers measure the differential pressure between the confining fluid and the internal pore pressure. The design is easily adaptable to tune the sensitivity and working pressure range up to several hundred megapascals. An array of four such transducers was tested during hydrostatic pressurization cycles on Darley Dale sandstone and Westerly granite. The prototypes show very good linearity up to 80 MPa with maximum deviations of the order of 0.25 MPa, regardless of the combination of pore and confining pressure. Multiple internal pore pressure measurements allow us to quantify the local decrease in permeability associated with faulting in Darley Dale sandstone, and also prove useful in tracking the development of pore pressure fronts during transient flow in low permeability Westerly granite.

Pore-water pressure response during undrained isotropic load changes in layered soils

1999 ◽  
Vol 36 (3) ◽  
pp. 544-555
Author(s):  
K D Eigenbrod ◽  
W H Wurmnest
Keyword(s):  
Pore Pressure ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Coefficient ◽  
Shear Stresses ◽  
Pressure Equalization ◽  
Pore Water Pressures ◽  
Internal Pore ◽  
Varved Clay

Low pore-water pressure responses observed during undrained isotropic loading of thinly interbedded varved clay specimens were related to internal pore-water pressure equalization and internal shearing between soft clay seams and stiff silt layers of the varved clay. Both processes were analyzed in two separate models: a finite element analysis of the layered soil specimen with different elastic properties for each layer showed that shear stresses can develop along the layer interfaces during undrained isotropic loading. However, because the shear stresses are small and restricted to a narrow zone close to the surface of the cylindrical specimen, it appeared that the effect of shearing on the overall pore-water responses is negligible. The analysis of the pore-water pressures during undrained, isotropic loading demonstrated that hydraulic gradients between the two layers will develop. As a result, pore water will drain from the clay into the silt, leading to consolidation of the clay and swelling of the silt seams. The stabilized pore-water pressures should be the same as the pore-water pressures measured for the overall specimen, if the effect of internal shearing is negligible. Comparison of the computed with the measured overall pore-water pressure responses during testing for Skempton's pore-pressure coefficient B indicated reasonable agreement.Key words: Skempton's pore-pressure coefficient B, pore-water pressure response, varved clays, internal shearing, internal pore-water pressure equalization.

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