Showing papers on "Internal pressure published in 1975"

Aerodynamically Induced Pressure Oscillations in Cavities - Physical Mechanisms and Suppression Concepts

Abstract: : This report presents the results of an analytical and experimental research program to (1)improve the understanding of the physical mechanisms that control the occurrence of pressure fluctuations in long and shallow rectangular cavities, exposed to high-speed external flow, and (2)devise and evaluate devices that would either substantially reduce the amplitude of such pressure fluctuations, or totally suppress the occurrence of pressure fluctuations. During this investigation, the understanding of the complex interaction of the external shear layer and the cavity internal fluid medium, which constitutes the generating mechanism of high-intensity periodic pressure fluctuations was substantially furthered. Both the analysis and investigation of the physical mechanisms were aided through extensive shallow-water flow-simulation experiments. Large-scale experiments, using the NASA-Lewis Research Center 8 X 6 ft Supersonic Wind Tunnel were conducted to substantiate some of the analytical predictions and to study in detail the aeroacoustic behavior of cavities in the length-to-depth ratio range, L/D, of 2.3 to 5.5, and the Mach number range of 0. 8 to 2.0. Detailed information was obtained on the normalized levels of the first three resonant modes in the cavity for a range of cavity length-to-depth ratios and freestream Mach numbers. Several concepts for pressure oscillation suppression were developed and evaluated in wind tunnel experiments. The most promising concept utilizes a slanted trailing edge, which stabilizes the free shear flow above the cavity, thus effectively suppressing discrete-tone generation. (Author)

Collapse of Long Cylindrical Shells under Combined Bending and Pressure Loads

Abstract: The nonlinear collapse behavior of long cylindrical shell structures subject to a bending load only or combined bending and uniform normal pressure loads is studied using the STAGS computer code. Two modes of nonlinear collapse are investigated to determine maximum strength. One mode of collapse is described by circumferential flattening of the cylinder cross section, while the other mode is represented by axial wrinkling in the region of maximum compression. Results compare favorably with available published data for cylinders loaded by pure bending, and results are presented for combined loads which have not been previously reported. The collapse loads obtained in this study show that current design criteria are conservative except for a narrow range of length-to-radius ratios and pressures.

Solvent structure. The use of internal pressure and cohesive energy density to examine contributions to solvent-solvent interactions

Abstract: Internal pressures, (∂U/∂V)T, have been obtained at 25° for the solvents dimethyl sulphoxide, propylene carbonate, formamide, dimethylformamide, acetonitrile, methanol and hexamethyl-phosphoramide by measurement of the thermal pressure coefficients. Data in the literature suggest that values of the internal pressure and the cohesive energy density, (ΔU/Vm), are similar for a non-polar solvent. The observed divergence of the two properties in the polar solvents under investigation is discussed in terms of the nature of the solvent-solvent interactions.

Debonding along the interface of an elliptic rigid inclusion

Abstract: The two-dimensional problem of a crack lying along the interface of an elliptic rigid inclusion embedded in an infinite elastic matrix is theoretically studied. Based on the complex variable method of Muskhelishvili, closed form solutions of the stresses and displacements around the crack are obtained when both general biaxial loads at infinity and uniform normal internal pressure are applied. These solutions are then combined with the virtual work argument of Griffith to give a criterion of the crack extension, namely the growth of the debonding of the interface. The critical applied loads are expressed explicitly by a function of four parameters; the size, the ratio of the length of the minor axis to that of the major axis of the inclusion, the angle subtended by the crack arc and the polar angle of the middle point of the crack arc. It is shown that when the applied load is only a simple tension or only an internal pressure the critical load is inversely proportional to the square-root of the size of the inclusion. The variations of the critical load with the angle subtended by the crack arc and with the ratio of the length of the semi-axes are graphically shown and discussed.

Fluid transport in cartilage.

Abstract: Creep in cartilage is in quantitative agreement with fluid loss. The hydraulic permeability decreases steeply and the internal pressure increases as the fluid content of cartilage is reduced due to compressive loading. At any given water content the hydraulic permeability and the internal pressure are practically independent of the applied load. The ionic contribution to the osmotic pressure of femoral head cartilage has been found by a number of methods to be around 1 x 7 atm at full hydration.

Remote control of pneumatic tire pressure and its apparatus

Abstract: Apparatus for remotely controlling the pressure in a pneumatic tire in which a pneumatic chamber communicating with a tube inserted in a tire and a chamber whose internal pressure is remote-controlled from the cab are aligned on the same axle of a vehicle. The piston penetrates into both chambers and the internal pressure in the tube can be adjusted by changing the internal volume of the pneumatic chamber due to displacement of the piston.

Bifurcation of elastic-plastic spherical shells subject to internal pressure

Abstract: The bifurcation of elastic-plastic spherical shells subject to internal pressure loading is investigated. Two cases are considered; in one case, the pressure is prescribed, while in the other, the change in volume enclosed by the shell is prescribed. Attention is restricted to axisymmetric bifurcations. Separation of variables is employed to introduce a complete set of bifurcation modes. For one of these modes a simple approximate bifurcation criterion is obtained. A numerical method is then employed to investigate the bifurcation of elastic-plastic spherical shells in a variety of modes. A comparison is made between the numerical results and the predictions of the approximate criterion. Of particular interest is whether bifurcation can occur prior to the maximum pressure point. The numerical results obtained here show that this does not occur for the axisymmetric modes considered.

Energy absorber with internal pressure relief valve

Abstract: Energy absorbing unit for vehicle bumper support having inner and outer telescoping cylinders with primary valve for metering fluid between a pair of contractible and expansible fluid chambers to dissipate impact energy. An auxiliary pressure relief valve internal of the unit in parallel with the primary valve opens in response to predetermined pressure buildup in one of the chambers to control pressure and prevent damage to the unit. A gas spring in the unit moves the two cylinders in their extended position on removal of bumper impact load.

Elliptical cutouts in cylindrical shells

Abstract: The stress concentrations due to an elliptical cutout in a shallow cylindrical shell are determined by means of a system of singular integral equations, solved numerically. Three loading conditions are considered: tension, and internal pressure. Results confirm those obtained by previous authors by other methods and extend the range of parameters over which results are available.

Pass level tester for glass bottles

Abstract: An apparatus for testing the internal pressure strength of glass bottles is described. The system utilizes water as a pressure test medium which is introduced into the test bottles and pressurized to predetermined pressure levels in stepped increments. Pressurization of the water is effected by a gas driven piston in the water supply line. A plurality of pressure control switches in the water supply line step the water pressure through said predetermined levels. A control circuit is provided for sequentially actuating said pressure switches for predetermined durations. Indicator means are provided on a control panel to indicate the test pressure level under which the test apparatus is operating at any given time, (i.e., guage), as well as the test pressure levels passed (i.e., lamps).

The Yield, Flow and Creep Behaviour of Annealed En24 Steel under Combined Stress

Abstract: Constant stress-ratio tests under combinations of tension, torsion and internal pressure have been performed on annealed En24 steel. The initial yield locus conformed to the Maxwell Mises criterion...

Ambient pressure probe

Abstract: Ambient or static pressure in a fluid stream is sensed with a hollow circr cylinder placed normal to the fluid stream. A shroud is mounted on the cylinder for adjustment over a ring of ports provided in the cylinder. In this manner, the relationship between the internal pressure in the cylinder and the ambient pressure is controllable. Ideally, the internal and ambient pressures are exactly equal. Further, extension of the cylinder above and below the shroud provides symmetry for positive and negative angles of attack.

Bursting pressure of thick-walled cylinders subjected to internal and external pressures, axial load and torsion

Abstract: A finite-total-strain, incompressible, analytical solution is presented to predict load-deformation relations for loads from zero to failure for thick-walled cylinders subjected to internal pressure, external pressure, axial load and torsion. The solution assumes that the material is an isotropic hardening material that obeys the von Mises yield condition. The flow law incorporates the prandtl-Reuss stressstrain relations and a loading function represented by the tension true-stress vs. true-strain diagram. Poisson's ratio is assumed to be equal to one-half for both elastic and plastic strains. The difference between the strains given by the incompressible solution and the correct strains are calculated for one set of elastic loads; the strains given by the incompressible solution are then corrected based on the assumption that each correction is proportional to the increase in the given component of load. Good agreement is indicated between the corrected incompressible solution and data obtained from cylinders made of either SAE 1045 steel, OFHC copper, or aluminum alloy 1100.

Fuel injection device for internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To improve exhaust gas characteristics by evening out the injection quantities of injection valves, taking into consideration their individual variations in injection characteristics. SOLUTION: Pressure varying means 8a, 32 first varies the internal pressure of an accumulator 3 to a first pressure, whereupon injection quantity computing means 31 meters the actual injection quantity of each cylinder, and next varies the internal pressure of the accumulator 3 to a second pressure, whereupon the injection quantity computing means 31 calculates the actual injection quantity of each cylinder gain. From the two actual injection quantities when the internal pressure of the accumulator 3 is set at the first and second pressures, injection characteristic estimating means 40 estimates the injection characteristics of each injection valve 4 in relation to the internal pressure of the accumulator 3, on the basis of which the result, correcting means 36 corrects the drive state into which injection control means 37 drives each injection valve 4.

Carrying capacity of rings formed by winding composites with high-modulus anisotropic fiber reinforcement

Abstract: The characteristics of composites associated with the essential anisotropy of the reinforcing fibers are studied. The effect of distortion and pretensioning of the reinforcement on the axisymmetricity of the strain field, the moduli of elasticity, and the strength in the direction of the fibers under external and internal pressure are investigated with allowance for the high compliance of the material in the transverse direction. Numerical estimates are obtained for the moduli of elasticity Eθ and Er, expansion coefficient αθ and αr, and initial temperature stresses σ r 0 and σ θ 0 for a model material. The dependence of the bursting pressure on the thickness of the rings is described and strength criteria are formulated. In all the problems considered it is necessary to make allowance for the high compliance of the composites in the transverse direction.

Pressure Effects in Sealed Liquid-Crystal Cells

Abstract: Liquid crystal cells are hermetically sealed glass containers completely filled with liquid. Two plane-parallel plates are sealed all around the edges to a frit glass spacer. The cell is then filled with liquid through two holes and sealed off with plugs of fusible metal. This construction gives rise to some internal pressure effects, because the thermal expansion coefficient of the liquid is about 100 times that of the glass. If the cell is filled and sealed off at room temperature, the liquid will exert a pressure at all higher temperatures. At lower temperatures it will be under tension. The pressure will deform the cell, making the walls bow out. This makes the volume enclosed by the cell a little larger and reduces the pressure but does not eliminate it completely. Some pressure or tension will always remain for temperatures different from the filling temperature. Repeated expansion and contraction may lead to loss of hermeticity or other cell failure. In what follows, the magnitude of the effect is calculated and the important factors are analyzed.

Pressure device for quality testing earthenware pipes - has ring with inflatable sleeve placed in pipe to apply bursting stress

Abstract: Pressure in the sleeve (11) is increased to a value which applies to the pipe a radial pressure almost reaching its ultimate stress limit; the elastic sleeve can stand without external support an internal pressure of at least 25 kp/ cm2; It is connected to a pressure tank for liquid; the tank is partly filled with liquid, and has at its upper part an inlet for compressed air, at its lower part there is an outlet for the liquid and an inlet for the liquid is provided at middle portion of the tank. The sleeve is supported by a broad metal ring (10).

Analysis of thick cylinders with internal semicircular grooves subjected to internal pressure

Abstract: Introduction S propellant rocket motor grains are generally thick cylinders with internal axisymmetric grooves. Certain analysis and design modifications to reduce the effects of such grooves were investigated in Refs. 1 and 2. Essentially, the propellant grain is a viscoelastic material and a rigorous viscoelastic analysis is to be performed to assess the performance of the grain. Since the numerical procedure involved in the viscoelastic analysis is a series of elastic analyses in the time domain, a very accurate and reliable elastic analysis tool is necessary to get a satisfactory viscoelastic solution. And for configuration involving internal grooves, the continuum analysis becomes tedious and finite element methods can be advantageously used to get accurate stress pictures around the grooves. For this purpose, a six-degree-offreedom triangular solid ring element is available in the literature, but it is the authors' experience that the use of this element does not give satisfactory stress picture around the grooves even with a very fine mesh division. Then the alternative is to use the complex isoparametric elements or highprecision triangular solid axisymmetric ring element, to get a realistic solution around the grooves. The main aim of the present Note is to get the elastic stress distribution using the high-precision triangular ring element along the semi-circular internal grooves of a thick cylinder subjected to internal pressure, which is a typical sample of a rocket grain, for various groove geometries. As the emphasis given in the Note is the study of the variation of stress concentration along the groove, a typical configuration of a thick cylinder with internal grooves is considered and groove geometries alone are varied.

Plug for testing cylinder under pressure - segmented portion expanded by pressure to wedge against interior

Abstract: The closure used when subjecting a vessel to high internal pressure, partic. for testing, consists of a sealing component with an upper conical face over which is fitted an internally tapering cylinder whose diameter is smaller than that of the pressure cylinder. This smaller cylinder is divided into segments which hold the closure in place as a result of the inside pressure. Each segment has a corrugated surface for contact with the inside of the cylinder, and is suspended from a plate by bolts which pass through slotted holes to enable it to move under pressure.