Showing papers on "Internal pressure published in 2002"

Analog experiments on magma-filled cracks: Competition between external stresses and internal pressure

Abstract: We have performed two series of analog experiments using gelatin to study the propagation of liquid-filled cracks in stressed medium. The first series was designed to study the competition between the external stress and the liquid excess pressure in controlling the propagation direction. We systematically controlled the external stress and the liquid excess pressure by changing the surface load and the liquid volume. An ascending crack progressively deflected to be perpendicular to the maximum tensile direction of the external stress. The degree of deflection depends on the ratio of the shear stress on a crack plane to the average liquid excess pressure. More deflection was observed for a crack with a larger ratio. No significant deflection was observed for the ratio less than 0.2. The volcanic activity in a compressional stress field might be understood in the context of this competition. The first series also demonstrated the importance of the gradient of the crack normal stress as a driving force for propagation. The vertical gradient of the gravitational stress generated by a mountain load can control the emplacement depth of magmas, and it might lead to the evolution of eruption style during the lifetime of a volcano. The second series was designed to study the three-dimensional interaction of two parallel buoyancy-driven cracks. The deflection of the second crack takes place, when the ratio of the shear stress generated by the first one to the average excess pressure of the second crack is larger than 0.2. If the second crack reaches the first one, the interaction can lead to the coalescence of two cracks. It has directivity: the region of coalescence extends more in the direction perpendicular to the first crack than in the direction parallel to it. It reflects the stress field around the first crack. This directivity might cause a characteristic spatial variation of magma chemistry through magma mixing.

Surface Tension and Melt Cohesive Energy Density of Polymer Melts Including High Melting and High Glass Transition Polymers

Abstract: Melt surface tensions and pressure−volume−temperature (PVT) data were obtained for many hydrophobic and hydrophilic polymers including high melting polyesters and polyamides such as poly(ethylene terephthalate) and nylon 66. A model is developed that uses surface tension to convert PVT data (from which the thermodynamic quantity “internal pressure” is calculated) into another thermodynamic bulk property, the cohesive energy density (CED). The errors inherent in assuming that the CED has the same proportionality factor to internal pressure independent of chemical structure are discussed. The results emphasize the difference between internal pressure and CED, where only internal pressure can be directly obtained from PVT data. The CED is the quantity that must be used for calculations of surface tension, and examples of the determination of melt surface tension are given for several polar or hydrogen-bonding polymers and semicrystalline or amorphous polymers of different molecular weights. Poly(2-vinyl pyri...

Evaporated fuel treatment device of internal combustion engine

Abstract: Disclosed is an evaporated fuel treatment device that includes a sealing valve installed between a fuel tank and a canister, a pump module pressure sensor for detecting the pressure on the canister side pressure, and a tank internal pressure sensor for detecting a tank internal pressure. Upon detection of a significant difference between the canister side pressure and tank internal pressure, the device concludes that no open failure exists in the sealing valve.

Limit-Load Analysis of Pipe Bends Under Out-of-Plane Moment Loading and Internal Pressure

Abstract: The purpose of this work is to study the load-carrying capacity of pipe bends, with different pipe bend factor (h) values, under out-of-plane moment loading; and to investigate the effect of internal pressure on the limit moments in this loading mode. The finite element method is used to model and analyze a standalone, long-radius pipe bend with a 16-in, nominal diameter; and a 24-in, bend radius. A parametric study is performed in which the bend factor takes ten different values between 0.0632 and 0.4417 Internal pressure is incremented by 100 psi for each model, until the limit pressure of the model is reached. The limit moments were found to increase when the internal pressure is incremented. However, beyond a certain value of pressure, the effect of pressure is reversed due to the additional stresses it engenders. Expectedly, increasing the bend factor leads to an increase in the value of the limit loads. The results are compared to those, available in the literature, of a similar analysis that treats the in-plane loading mode. Pipe bends are found to have the lowest load-carrying capacity when loaded in their own plane, in the closing direction. They can sustain slightly higher loads when loaded in the out-of-plane direction, and considerably higher loads under in-plane bending in the opening direction.

Internal pressure measurements during burst fracture formation in human lumbar vertebrae.

Abstract: Study Design In a laboratory study, 21 human lumbar spine segments were used to determine whether intraosseous pressure increases occur during axial-compressive loading conditions under two displacement rates Objective To determine whether an intraosseous pressure rise is associated with burst fracture formation Summary of Background Data Burst fractures are high-speed injuries usually associated with neurologic deficit An internal pressure rise has been implicated as a critical factor in burst fracture formation The authors hypothesize that the internal pressure increases with increasing input velocity Methods The internal pressure changes were measured in spine segments using two displacement rates: 10 mm/s (slow speed) and 2500 mm/s (high speed) Failure load and energy absorption were determined for both groups The resultant fracture types were determined from postinjury radiographs Results The initial peak internal pressure decreased from slow- to high-speed tests (P < 001) Overall peak pressure, failure load, and energy absorbed at failure were not significantly different Slow-speed tests resulted in compression fractures, whereas high-speed tests resulted in burst and compression fractures Conclusions The current research did not support the current theory of burst fracture formation There was a decrease in measured internal pressure from the slow- to high-speed groups, and burst fractures still were produced The theory could be potentially modified to suggest that the nucleus entering the vertebral body acts as a wedge, splitting the vertebral body apart and enabling the bony fragments to the pushed into the canal space

Numerical simulation of sleeve repair welding of in-service gas pipelines

Abstract: The purpose of this study is to develop an appropriate numerical model for full encirclement, sleeve repair welding of in-service gas pipelines and to investigate the effects of in-service welding conditions. An axisymmetric finite element model was used to calculate the temperature distribution, maximum HAZ hardness, and the distribution of residual stress and plastic strain during multipass sleeve fillet welding of in-service API 5L X65 pipelines of 14.3 mm thickness. Experiments were also conducted for sleeve repair welding on pipe with internal pressure. The calculated geometry of the fusion zone and HAZ was in good agreement with the macrostructures of sleeve repair fillet welds. The calculated maximum HAZ hardness was in good agreement with the measured value. The effect of gas flow rate on the maximum HAZ hardness and the effects of internal pressure on residual stress and plastic strain distribution were investigated. Risk of melt-through and susceptibility to cold cracking were also estimated using a simplified analysis.

Review: the microhardness of non-crystalline materials

Abstract: Hardness is defined as a phenomenological measure of resistance of a material to shear stresses under local volume compression. It is shown that this definition may serve as a theoretical basis for existing empirical relationships between the Vickers microhardness HV and the various phenomenological, packing density-sensitive parameters of non-crystalline materials, including among them, the internal pressure, the glass transition temperature Tg, the excess enthalpy, and the free volume fraction at Tg.

Assembly of tire and rim

Abstract: An assembly of a tire and a rim allowing a stable running over a required distance even if a tire internal pressure is lowered after the tire gets damaged without sacrificing a rolling resistance and a riding comfortableness in normal running before the tire gets a damage, wherein the hollow donut-shaped tire is installed on an applicable rim, a large number of generally spherical particles formed of resin of continuous phase and independent bubbles and having an average bulk specific gravity under the atmospheric pressure of 0.1 or less are disposed in the tire partitioned by the tire and the applicable rim, and a pressure inside the tire at the temperature of 25 °C is set to 150 kPa or higher in absolute pressure.

Radial fictitious cracking of thick-walled cylinder due to bar pull-out

Abstract: A new analytical model is suggested to describe the radial cracking around a ribbed reinforcement bar embedded in a quasibrittle material such as concrete. The model is based on the partly cracked solution of a thick-walled cylinder, exposed to radial internal pressure. For the partly cracked inner ring of the cylinder an exponential softening model is applied to model the hoop stresses across the fictitious crack. The main advantage of applying an exponential softening relationship instead of a linear or a power-law model, which have been applied in previous investigations, is that the asymptotic behaviour of the exponential softening turns out to be a useful analytical feature. Another difference between the present analytical model and the previous solutions is that the radial displacements in the inner ring are assumed to be equivalent with the linear-elastic displacement field. Furthermore, the solution employs the brittleness number to give a dimensionless description of the problem. Through this br...

High pressure gas supplying system

Abstract: A high pressure gas supplying system comprises a supplying line 4 for supplying high pressure gas from high pressure tanks 3a,3b The supplying line 4 includes a supply piping line 30 connected with the high pressure tank 3a, a supply piping line 31 connected with the high pressure tank 3b, and a piping joint section 32 connecting these supply piping lines 30 and 31 A check valve 34a is provided in the supply piping line 30 to establish a flowing passage on condition that the internal pressure of the high pressure tank 3a is higher than the pressure at the piping joint section 32 And a check valve 34b is provided in the supply piping line 31 to establish a flowing passage on condition that the internal pressure of the high pressure tank 3b is higher than the pressure at the piping joint section 32

Analysis and Multidisciplinary Optimization of Internal Coolant Networks in Turbine Blades

Abstract: The theoretical methodology, conceptual demonstration, and validation of a fully automated computer program for the inverse design and optimization of internal convectively cooled three-dimensional axial gas turbine blades is presented. A parametric computer model of the three-dimensional internal cooling network was developed, including the automatic generation of computational grids. A boundary element computer program was written to solve the steady-state, nonlinear heat conduction equation inside the internally cooled and thermal barrier coated turbine blade. A finite element algorithm was written to model an arbitrary network of internal coolant passages for the calculation of the internal pressure losses, flow rates, effects of centrifugal pumping, heating of the coolant fluid, and heat transfer coefficients from the thermal model of the solid to the coolant fluid. The heat conduction and internal flow analyses were strongly and iteratively coupled to account for the heat balance between the blade and the coolant fluid. A system of evolutionary optimization algorithms was used to modify the internal cooling configuration and internal heat transfer enhancements (boundary-layer trip strips and pedestals) to achieve the objectives of increased cooling effectiveness and greater durability against oxidation, corrosion, and creep. The computer-automated design and optimization system was demonstrated on the second high-pressure turbine blade row of the Pratt and Whitney F100 engine. The internal cooling optimization on the product definition of this blade yielded a 5% increase in average cooling effectiveness, with only a marginal increase in coolant flow rate, in addition to having the same corrosion life and a doubling of the creep life.

Stress Analysis and Determination of Bolt Preload in Pipe Flange Connections With Gaskets Under Internal Pressure

Abstract: The stresses of a pipe flange connection with a spiral-wound gasket under internal pressure are analyzed taking account a nonlinearity and a hysteresis of the gasket by using an axisymmetric theory of elasticity and the finite element method (FEM) The leakage tests were also conducted using an actual pipe flange connection with a spiral-wound gasket Using the contact stress distribution of the pipe flange connection with 3-in nominal diameter under internal pressure and the tightness parameter, the values of the new gasket constants are obtained by taking into account the changes in the contact stress A difference in the new gasket constants between the estimated values obtained from the actual pipe flange connection and the values obtained by the PVRC procedure is small In addition, a method to determine the bolt preload for a given tightness parameter is demonstrated The obtained results of the bolt preload for the pipe flange connection are in a fairly good agreement with those obtained by the PVRC procedure under a lower pressure application However, a difference in the bolt preload is about 10% when an internal pressure is increased

Internal pressure of a thermodynamically ideal mixture and the excess internal pressure

Abstract: The excess internal pressure is often discussed in terms of molecular interactions in liquid mixtures. The additivity of internal pressures in the mole fraction scale is often erroneously assumed for an ideal mixture. In this paper, a thermodynamically correct formula for the excess internal pressure is suggested and compared with that based on the mole fraction additivity.

Plastic Interaction Relations for Pipe Sections

Abstract: General interaction relations for pipe sections subjected to combinations of normal forces, internal or external pressure, twisting moments, biaxial bending moments, and biaxial shearing forces are developed. The derivations are based on the fully plastic capacity of the pipe as determined by the maximum distortional energy density yield criterion. Close form interaction relations are obtained for general load combinations and an accurate approximation is proposed. Previously established interaction relations for bending moments, axial forces and internal pressure are recovered as a special case of the general solution. The developments are expressed as universal nondimensional relationships suitable for limit states design. Consideration is given to the limits of applicability of the interaction relations and a systematic design procedure is proposed based on the interaction relations obtained and their limits of applicability. The relations are applicable in the design of elevated pipes, submerged pipes, supports of offshore platforms, and tubular structural steel members.