Showing papers on "Internal pressure published in 1971"
TL;DR: In this article, the dependence of energy on distance on a molecular scale was examined and the expected relationship between internal energy and molar volume was discussed, and it was shown that the dependence on internal energy on the distance between two points is not independent.
Abstract: In order to discuss the expected relationship between internal energy and molar volume, it is first necessary to look at the dependence of energy on distance on a molecular scale.
59 citations
TL;DR: In this paper, an exact buckling criterion for multilayered circular cylindrical shells made of materials with different orthotropic moduli in tension and compression was derived. But this criterion is valid for arbitrary combinations of axial and circumferential loading, including axial compression and internal pressure as well as axial tension and lateral pressure.
Abstract: An exact buckling criterion, within the framework of classical buckling theory, is derived for eccentrically stiffened multilayered circular cylindrical shells made of materials that have different orthotropic moduli in tension and compression. Such behavior is typical of many current composite materials. The buckling criterion is valid for arbitrary combinations of axial and circumferential loading, including axial compression and internal pressure as well as axial tension and lateral pressure. The material model (stress-strain relationship) involves a bilinear stress-strain curve that has a discontinuity in slope (modulus) at the origin. A numerical example of buckling of a ring-stiffened two-layered circular cylindrical shell is given to illustrate application of the buckling criterion.
38 citations
TL;DR: In this article, the authors apply Vlasov-Ambartsumyan shell theory to anisotropic and laminated cylinders and develop equations for calculating the stresses in a composite tube under combined axial load, torsion, and internal pressure.
Abstract: Applying Vlasov-Ambartsumyan shell theory to anisotropic and laminated cylinders, equations are developed for calculating the stresses in a composite tube under combined axial load, torsion, and internal pressure. Comparison to results obtained from exact elasticity theory shows that the shell equations are capable of predicting, with a reasonable degree of accuracy, the large stress gradients found in highly anisotropic tubes. Thus the shell theory provides the experimentalist with a set of closed form expressions for readily defining the proper specimen dimensions for precise characterization of unidirectional and laminated composite tubes. A modification to the shell theory, in which the effects of transverse normal strain are included is also discussed. Numerical results show that such a modification is necessary for determining stresses induced by free thermal expansion. It is also shown that certain classical thin shell kinematic relations are incapable of predicting stresses in composite tubes.
38 citations
TL;DR: In this article, it was shown that axial normal stress under axial loading and the hoop stress under internal pressure are somewhat different from the respective isotropic results for laminated cylinders.
Abstract: In a recent paper [1], (see also [2]) it was shown that extremely severe stress gradients can exist in the wall of a unidirectional, helical-wound cylinder under the common loadings applied in the laboratory, i.e., axial loading, internal pressurization, and torsion. In that study it was found that the stress gradients were drastically reduced in an orthotropic, symmetric laminated cylinder, such as an angle-ply. In fact, for the case of torsion, the shear stress distribution almost coincides with that which occurs in an isotropic cylinder. While an analogous smoothing of the stress field occurs under other loadings, the axial normal stress under axial loading and the hoop stress under internal pressure are somewhat different from the respective isotropic results. For example, refer to Figure 12 in [1]. In order to complete the treatment of the geometric design of tubular characterization specimens, the remaining stress components, e.g., the hoop and shear stresses induced in the axial loading experiment, should be considered. It is therefore the purpose of this note to present some results in this regard for laminated cylinders.
30 citations
TL;DR: In this paper, the effects of initial elastic loading followed by stress redistribution due to creep leading to a stationary stress state were analyzed for a range of thick-walled tubes (1·11⩽ diameter ratio ⩽ 10 ) operating under creep conditions.
30 citations
TL;DR: Longitudinal edge stiffness and internal pressure effects on buckling and initial postbuckling behavior of axially compressed stringer reinforced cylindrical panels, discussing imperfection sensitivity were discussed.
Abstract: Longitudinal edge stiffness and internal pressure effects on buckling and initial postbuckling behavior of axially compressed stringer reinforced cylindrical panels, discussing imperfection sensitivity
30 citations
TL;DR: In this article, a general velocity field, satisfying constitutive requirements at a generic instant, is constructed and employed to investigate the possibility of loss of steady-state deformation in closed-end cylinders under internal and external pressure.
Abstract: Rigid -plastic strain-hardening flow in closed-end cylinders under internal and external pressure is examined from the view-point of obtaining criteria for uniqueness and stability of finite deformation. A general velocity field, satisfying constitutive requirements at a generic instant, is constructed and employed to investigate the possibility of loss of steady-state deformation. Earlier stability bounds, for the case of internal pressure, derived under the assumption that instability occurs in a continuation of the steady-state mode, may then be verified, although with some restrictions as it is shown that, for certain combinations of cylinder geometry and material hardening properties, non-unique deformation might precede a stability loss. For the case of external pressure, a general criterion is established from which the accuracy of the classical tangent-modulus buckling load may be confirmed in the thin-shell approximation.
23 citations
22 citations
TL;DR: In this article, six first-order differential equations have been solved to obtain the stress and deflexion distributions in both circular and elliptical toroidal shells, loaded by internal pressure.
21 citations
Patent•
29 Oct 1971
TL;DR: An underwater optical method and apparatus in which the pressure within a sealed optical chamber is balanced with external hydrostatic pressure by filling the optical compartment with a pressurized gas having a minimum index of refraction is described in this article.
Abstract: An underwater optical method and apparatus in which the pressure within a sealed optical chamber is balanced with external hydrostatic pressure by filling the optical compartment with a pressurized gas having a minimum index of refraction. The focal length of a lens within the optical compartment remains nearly constant throughout a range of changing internal pressure because of the low index of refraction of the gas (typically helium) as compared with other gases. The low-index gas is supplied from a pressurized gas bottle carried by the device.
17 citations
TL;DR: In this article, an exact solution for a star-shaped crack, formed by n equal line cracks intersecting at a common point with an angle 2 π / n between adjacent cracks, when each of the separate cracks is subjected to an equal but arbitrary pressure distribution is also examined.
TL;DR: In this paper, a hole theory of polymer glasses is presented, in which the glassy state is distinguished from the liquid state by the freezing of holes, and the equation of state, internal pressure, and cohesive energy density are derived.
Abstract: A hole theory of polymer glasses is presented, in which the glassy state is distinguished from the liquid state by the freezing of holes. The equation of state, internal pressure, and cohesive energy density are derived. The results of the theory are compared with experimental observations with the use of the molecular parameters obtained in the preceding paper. The hole theory can semiquantitatively explain the decrease of internal pressure on glass formation.The free volume at the glass transition temperature and the correlation of the glass transition temperature to cohesive energy density are also discussed.
Patent•
15 Nov 1971
TL;DR: In this article, a wire braid hydraulic hose is made according to certain specifications and the hose is subjected to an internal pressure of approximately 80 to 95 percent of the known burst pressure, maintaining said pressure momentarily and relieving the same whereby the individual wires of the braid will be realigned and repositioned into permanent close contact with each other so as to substantially increase the strength of the hose and increase the number of pressure impulse cycles it will withstand well above the known average.
Abstract: A method of making a wire braid hydraulic hose which when made according to certain specifications will have a known average burst pressure and a known average life of pressure impulse cycles wherein the hose is subjected, immediately after curing, to an internal pressure of approximately 80 to 95 percent of the known burst pressure, maintaining said pressure momentarily and relieving the same whereby the individual wires of the braid will be realigned and repositioned into a permanent close contact with each other so as to substantially increase the strength of the hose and increase the number of pressure impulse cycles it will withstand well above the known average to thereby increase the life expectancy of the hose.
TL;DR: In this article, the steady state creep of a pressurized circular cylindrical shell is analyzed on the basis of Mises' criterion and the power law of creep, where the representations of stress, membrane force and bending moment expressed in terms of the components of displacement are linearized by expanding them in the neighborhood of a certain approximate value of displacement.
Abstract: Numerical analysis of the steady state creep of a pressurized circular cylindrical shell is developed on the basis of Mises' criterion and the power law of creep. The representations of stress, membrane force and bending moment expressed in terms of the components of displacement are linearized by expanding them in the neighborhood of a certain approximate value of displacement. The equations of equilibrium substituted with these expressions are replaced by the corresponding difference equations, in order to obtain the simultaneous linear equations with respect to the small perturbation of the components of displacement. The approximate values assumed previously are improved by using the resulting solutions. More accurate values of these variables are obtained by repeating the procedure. This method may be interpreted as a modification of the Newton-Raphson method for non-linear simultaneous equations. Calculations are carried our for clamped circular cylindrical shells with open ends subjected to internal pressure. The effect of the shell geometry and that of non-linearity of the creep law are elucidated. The numerical results thus obtained are also compared with existing solutions for sandwich shells.
TL;DR: In this article, a stress analysis of a discontinuous pipe bend (a multi-mitred pipe bend) has been carried out for internal pressure loading, based on a previous analysis for in-plane bending of the same structure.
TL;DR: In this article, it was shown that the internal pressure of a polymer in the glassy state is about half the value expected from the behavior of the polymer just above the glass temperature, Tg.
Abstract: It has been well established in the literature that the internal pressure, Pi = (∂E/∂V)T, of a polymer in the glassy state is about half the value expected from the behavior of the polymer just above the glass temperature, Tg. Consideration of this behavior in terms of a recent analysis of factors affecting internal pressures leads to the conclusion that the expression for the total energy of a glass must include a volume-dependent stored energy term, a term not present above Tg. This stored energy could be associated with actual bond and segment deformations in the glassy state. Brittleness and solvent cracking behavior of glasses will be strongly dependent on this stored elastic energy which can be modified by altering the molding conditions under which the glass is formed.
TL;DR: The free volume, vf, of liquids is defined in many ways Comparison of solid and liquid behavior indicates that the definition for free volume in terms of the internal pressure of the liquid (∂E/∂V)T, is physically reasonable.
Abstract: The free volume, vf, of liquids is defined in many ways Comparison of solid and liquid behavior indicates that the definition for free volume in terms of the internal pressure of the liquid (∂E/∂V)T, is physically reasonable Application of the definition of free volume, vf = RT/(∂E/∂V)T, to polymethylenes, coupled with surface energy values, leads to an evaluation of both polymer segmental volume, Ṽs, and free volume per segment, (vf)s, as a function of temperature These equilibrium thermodynamic measurements of Ṽs and (vf)s lead to an energy of activation for viscous flow in good agreement with viscosity studies Information of this type could be of great use in considering many current problems in polymer flow such as the effect of pressure on viscosity
TL;DR: In this article, upper and lower bounds for a spherical shell subjected to internal pressure and external axial force were presented for various geometrical parameters, and compared with the experiment results.
01 Jan 1971
TL;DR: In this paper, a finite element code for the problem of a two-layered plane strain cylinder with a cracked inner bore under internal pressure loading is presented, and a simple approximate formula for K 1 is presented that compares well with the numerical results and reduces to certain limit cases.
01 Apr 1971
TL;DR: Determination of axial buckling load of circular cylindrical shells formed by process of plastic expansion due to internal pressure has been done in this paper, where the authors used a linear regression model.
Abstract: Determination of axial buckling load of circular cylindrical shells formed by process of plastic expansion due to internal pressure
01 Jan 1971
TL;DR: In this paper, the authors used an approximate value for the stress intensity factor, and considering the high local stresses at the crack due to pressurized oil, close correlation was obtained between the estimated and experimental fatigue lives.
Abstract: Experimental data available on fatigue crack growth may be described by an equation of the form da/dN = B(ΔK)m, where da/dN is the rate of crack growth per stress cycle, ΔK is the range of stress intensity factor, and B and m are material properties.This relationship has been used to estimate the fatigue crack propagation lives of thick-walled cylinders subjected to repeated internal pressure. By using an approximate value for the stress intensity factor, and considering the high local stresses at the crack due to pressurized oil, close correlation is obtained between the estimated and experimental fatigue lives.Design curves are obtained, by which the fatigue life of such a cylinder may be estimated from a knowledge of the transverse uniaxial fatigue limit and fracture toughness properties of the cylinder material, as well as the diameter ratio of the cylinder and the repeated pressure.
01 Jan 1971
TL;DR: In this paper, the behavior of imperfect cylindrical shells has been studied by various investigators, and both isotropic and anisotropic shells have been considered in these structures.
Abstract: In recent years orthotopic cylindrical shells such as stiffened or fiber reinforced cylinders have been used extensively in aerospace structures. These structures are often subjected to axial compression and internal pressure. The thin cylindrical shells are known to be imperfection sensitive, and their buckling loads are substantially reduced by the presence of small initial deviations from the circular shape of the shell. The behavior of imperfect cylindrical shells has been studied by various investigators [1–5]. Both isotropic and anisotropic shells have been considered in these structures. In most of these investigations Karman-Donnell strain-displacement equations were used.
TL;DR: In this article, the propagation of plastic zones in a thin-walled sandwich-type cylinder has been analyzed theoretically and the predicted result was verified experimentally, and four specimens were built by lamination of a hexcell core between two concentric cylinders.
Abstract: The propagation of plastic zones in a thin-walled sandwich-type cylinder has been analysed theoretically. Boundary conditions are clamped-clamped at both ends, i.e. no rotation is permitted. The material was assumed to behave isotropically and to obey the yieid criterion of Huber-Hencky-von Mises. Deformation was computed on the assumption that the vector of rate of strain was normal to the plastic-interaction curve.The predicted result was verified experimentally. Four specimens were built by lamination of a hexcell core between two concentric cylinders. In the two mild-steel specimens, the initial stage of plastic flow conformed well with the prediction. This proved that plastic flow is not initiated at the mid-position between the end constraints. In two aluminium specimens, this phenomenon of incipient plastic flow could not be observed owing to the absence of a pronounced yield point. The overall agreement was, however, satisfactory.