Values Of Internal Pressure Research Articles

Influence of metal on the far-exploding surface on fragment deformation behavior under contact explosion

Metals exhibit diverse failure behavior under impact loading. In the context of fragment warheads, preformed fragments also undergo fracture and crushing behaviors when subjected to explosive loading, potentially diminishing the terminal effect and damage capability of the warhead. To address this issue, metal disks of varying impedance were applied to the far-exploding surface of the fragments, and their influence on fragment deformation behavior was examined. The experimental results revealed that when metal disks were attached to the far-exploding surface of the fragments, their fracture behavior changed, and the recovered fragments remained intact axially. Additionally, the axial length of the recovered fragments decreased as the impedance of the metal disk on the far-exploding surface increased. To elucidate the underlying mechanism of this experimental phenomenon, the variation in fragment pressure during the propagation process was calculated by employing theories of planar detonation waves and shock wave propagation in the study. The results indicate that when the impedance of the metal disks on the far-exploding surface is higher than that of the fragments, it leads to an increase in internal pressure and the formation of a compression zone within the fragments, thereby preventing fragment fracture. Conversely, lower impedance results in the formation of a tensile effect within the fragments. The theoretical and experimental results were consistent. Finally, based on the dimensional analysis, the dimensionless models were established to predict fragment deformation and internal pressure values influenced by the metal disk on the far-exploding surface.

Analysis of Bending Deformation and Stress of 6063-T5 Aluminum Alloy Multi-Cavity Tube Filled with Liquid.

The production of aluminum alloy multi-lumen tubes primarily involves hot bending formation, a process where controlling thermal deformation quality is difficult. Specifically, the inner cavity wall of the tube is prone to bending instability defects under the bending stress field. To address these challenges in the bending deformation of aluminum alloy multi-lumen tubes, a multi-lumen liquid-filled bypass forming method is proposed in this paper. This study focuses on the 6063-T5 aluminum alloy double-lumen tube as the research object. The liquid-filled bending deformation behavior of the aluminum alloy double-lumen tube was investigated, and the deformation theory of the aluminum alloy double-lumen tube was studied. Through experimental and numerical simulation methods, the influence of support internal pressure, bending radius, and tube wall thickness on the liquid-filled bending deformation behavior of the double-lumen tube was examined. The results indicate that when the value of internal pressure was 7.5 MPa, the straightening of the outer wall was improved by 2.51%, the thinning rate of wall thickness was minimized, and the internal concave defect was effectively suppressed. The liquid-filled bending method provides a promising new approach for the integrated bending and forming of multi-lumen tubes.

Estimation of Ultrasonic Velocity, Density, Internal Pressure, and Thermophysical Parameters of Ionic Liquid Mixtures: Application of Flory's Statistical Theory.

Flory's statistical theory (FST) has been employed to estimate the ultrasonic velocity, density, internal pressure, and several important thermophysical parameters such as the energy of vaporization, the heat of vaporization, cohesive energy density, polarity index, and solubility for eight binary mixtures of ionic liquids and water within the temperature range of 288.15 to 308.15 K. The ionic liquids chosen for this investigation are [BMim][dca], [BMim][TfO], [BMpy][TfO], [BMpyr][dca], [BMpyr][TfO], [EEPy][ESO4], [HMim][dca], and [MPy][MSO4]. The predicted values of ultrasonic velocity and density show good agreement with the data reported in the literature. It endorses the applicability of FST to these binary mixtures. A comparative analysis of the internal pressure values (Pi) determined by using FST and the standard thermodynamic approach is also presented. The results obtained for Pi using both approaches show good agreement. Besides, for the mixtures under study, the correlation between ultrasonic velocity, density, and surface tension has also been examined. The variation of thermophysical parameters with concentration and temperature changes has been utilized to explore the nature and strength of the solute-solvent interactions prevalent in these mixtures. It is pointed out that A-A-type interactions dominate over A-B-type interactions in water-rich regions of the mixtures.

Tube Mechanism With 3-Axis Rotary Joints Structure to Achieve Variable Stiffness Using Positive Pressure

Studies on soft robotics have explored mechanisms of switching the stiffness of a robot structure. The hybrid soft-rigid approach, which combines soft materials and high-rigidity structures, is the most commonly-used method for the variable stiffness mechanism. The positive-pressurization method, in particular, has attracted significant attention in recent years as it can remove the limit on the driving pressure. Moreover, it can change the shape holding force according to the value of internal pressure. In this study, a variable stiffness mechanism, consisting of 3-axis rotary ball joints and a single chamber, is devised via frictional force using positive pressure. The prototype can change joint angles arbitrarily when not pressurized and can hold joint angles when a positive pressure is applied. By using a theoretical model of the torque required to hold the joint angle, we simulated the holding torque using finite element modeling analysis and measured the holding torque in the pitch and roll directions when internal pressure was applied. Based on the interaction of the theoretical model, measurement, and FEM analysis, it was confirmed that the value of the holding torque in the roll direction was approximately π/2 times larger than that in the pitch direction for each value of the internal pressure. Further, we evaluated the FEM value, theoretical value, and measured value of holding torque by numerical comparison with each other. We believe that our approach will aid the design of effective stiffening mechanisms for soft robotics applications.

Experimental research of stress state and residual stresses of the hydropower pipeline branch model

The paper presents experimental research of branch model in laboratory conditions. The branch model is, in fact, a reduced real branch whose basic dimensions are interrelated on the basis of similarity theory which arise from the conditions of stress equality on the branch model and the real branch. Using numerical methods - finite element methods, measuring points on the branch model, were determined. At the defined measuring points, experimental measurements of stress were performed, namely using: strain gauges and recording with 3D cameras. The branch model was quasi-statically loaded with different values of internal pressure during the experiment. The values of the internal pressure reached such a level that the maximum stress at the measuring point with the highest measured stress reached values far above the yield strength of the branch model material. The most important results of experimental research on the branch model can be expressed through the following items:- Verification of the fact that in the field of elasticity, there is a linear relationship between stress and internal pressure.- Disclosing what happens when the stresses exceed the value of the yield strength of the branch material, whether there are plastic deformations of the branch model.- Defining the dependence of stress on internal pressure in the field of elasticity and the zone of residual stresses.- Coming to conclusions regarding the distribution of stresses and residual stresses on the branch model.

Influence of curvature and geometrical parameters on internal pressure in cylindrical Insulating Glass Units

The application of curved glass provides exceptional freedom in the design of modern wavy shapes of building enclosures. The stiffness resulting from curvature has been identified as a remarkable advantage over flat glass, decreasing support requirements, and improving esthetics or increasing spans. However, many constraints arise regarding its design, manufacture, and performance during operation. Due to improved stiffness, curved Insulating Glass Units (IGUs) have a limited ability to equalize internal and atmospheric pressure changes by pillowing, compared to flat IGUs. High internal pressure values may lead to visible visual distortions or failure of the secondary seal. This paper presents the results of experiments, Finite Element (FE) and analytical simulations of flat and cylindrically curved insulating glass units. The study involved seven IGU specimens with 4 mm component panes and a 16 mm cavity. All specimens had a constant width (500 mm) but differed in length (500, 1000 and 1500 mm), and arc radius (two radii of curvature were used, 1500 and 2500 mm). In this study, the main focus was on the influence of geometric parameters on internal pressure in the cavity. The study uses a rarely used technique to simulate varying pressures in the IGU cavity by injecting or withdrawing of a defined volume of gas into/from the cavity.

Procedure to categorize wheelchair cushion performance using compliant buttock models

Purpose: Wheelchair cushion prescription often seeks to address tissue integrity in addition to other clinical indicators. Because hundreds of wheelchair cushion models are available, a benefit would result if cushions were classified in a more valid manner to help guide selection by clinicians and users. The objective of this research was to develop an approach to evaluate and classify wheelchair cushion performance with respect to pressure redistribution. Materials and methods: Two anatomically-based buttock models were designed consisting of an elastomeric shell that models overall buttock form and a rigid substructure that abstracts load-bearing aspects of the skeleton. Model shapes were based upon elliptical and trigonometric equations, respectively. Two performance parameters were defined, pressure magnitude and pressure redistribution. The pressure magnitude parameter compared internal pressure values of the test cushion to a flat foam reference material, resulting in three classifications, superior, comparable, and inferior. Surface sensors were used to distinguish cushions with high, moderate or low pressure redistribution performance. Ten wheelchair cushions were evaluated by both models using two loads that represent a range of body weights expected for 41–43 cm wide cushions. Results and Conclusion: A classification matrix is proposed using both models and performance parameters. Two cushions met criteria for the highest level of performance, and one cushion was deemed to have inadequate performance for therapeutic value. The proposed method has a sensitivity to discern differences, compatibility with different sized cushions, and a versatility in classification. As such, it stands as an improvement over existing classification approaches.

Modeling thermophysical properties of several liquid adipates

The densities and several derived thermodynamic properties of 6 liquid adipates were correlated and predicted through a proposed perturbed hard-chain equation of state (PHC EoS) containing a term of Yukawa tail. The adipates under study comprised the diesters of methyl and ethyl types. The EoS was constructed through correlating it with densities and isothermal compressibilities of studied systems in 288–403 K range and pressure at 0.1Mpa. Then the EoS was applied to predict densities and several first derivative thermodynamic properties including isobaric expansivities, thermal pressure coefficients and internal pressure values for pressures up to 140 MPa. The average absolute relative deviations (AARD) of densities and isothermal compressibilities were found to be 0.21 % and 8.58 %, respectively. Then, the rest of derived thermodynamic properties of the aforementioned systems were predicted and compared with a Tait-type equation cited in literature. Further, a rough hard-sphere-chain (RHSC) model in conjunction with the proposed EoS has been successfully employed to correlate and predict the viscosities of 4 selected liquefied adipates, for which the experimental values were available in the literature. The model could correlate/predict 1075 experimental viscosity data points of the above-mentioned adipates in 283–373 K range and pressures up to 65 MPa with the AARD of 2.14 %. The accuracy of the results from the RHSC-based model has also been compared with those obtained from other RHS-based model of literature.

Elastic-plastic solution of circular hydraulic pressure tunnel based on D-P criterion

This work provides new findings on the theory of D–P failure criterion applied to the study of the analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of hydraulic pressure tunnel under uniform ground stress field. It focuses on elasto-plastic rock masses with the stage of construction and operation. The results that are obtained are compared to other calculation techniques and show that: The elastic-plastic solution calculated based on the theoretical model is larger than that based on the D-P Criterion, indicating safer conditions. The principal stress varies with the internal water pressure, and it firstly decreases to zero and then gradually increase in the plastic zone. With the internal water pressure keeping increasing to a high level, the principal stress in the elastic zone changes from tangential stress to radial stress in the radial distance-enlarging direction, which tends to reach the geostress. In this condition, the radial distance is related to the value of internal water pressure. The calculation results of this study are demonstrated to be in good agreement with those of numerical simulation under the same conditions.

Relationship between mattress internal air pressure and interface pressure distribution in the lateral position.

Previous research shows that maximum interface pressure increases when the patient is lying in the lateral position. However, it was unclear whether it was better to increase or decrease the internal air pressure to reduce the maximum interface pressure in the lateral position; thus, this study investigated this issue. In this study, we investigated the change in pressure redistribution because of the difference in internal air pressure between the supine and lateral positions on an active air mattress for pressure ulcer prevention management. Each participant's five internal air pressure values served as the independent variables. The interface pressure on the active air mattress was measured for 20 minutes. The sacral left iliac crest and left greater trochanteric interface pressures were measured using a portable pressure-measuring device. When seven of the 10 participants switched from the supine position to the left lateral position, there was a decrease in the maximum interface pressure as the internal air pressure increased. The maximum interface pressure in the greater trochanter in the lateral position was twice that in the sacral region in the supine position. These results show that increasing the internal air pressure in the lateral position might help reduce the maximum interface pressure.

An analytical evaluation method to estimate effects of void induced errors on the stresses of pressurized fiber reinforced composite tube

This study investigates the effects of voids on the internally pressurized tangentially fiber reinforced tube with open and closed ends. As known, voids-induced errors in the fiber reinforced composites bring about degradation of the mechanical properties of the material. Due to the property degradations, the failure limits of the tube reduce. Herein, analytical approaches are performed to model elastic solutions and the material properties. Employing two different failure criteria, Tsai-Wu and Hoffman, the limit internal pressure values are found for the tube containing various void volume fractions. It has been observed that, as the void volume fraction in the composite rise, in other words, when void-induced defects increase in the tube, corresponding directional stresses and the limit pressure values of the tube decrease. Moreover, the location of the voids through the thickness of the tube may change the radial position of the failure.

Numerical Study on Dimensions and Orientation Effect of Semi-Elliptical Cracks in PE100 Pipelines

The through-thickness crack or surface crack in PE100 pipes subjected to internal pressure represents a serious risk to the structural integrity of HDPE pipes, which has attracted wide attention in modern industry. Although experimental research offers reliable predictions of surface crack influence on pipes, the relatively high cost hinders its application. The numerical simulation, as a cost-effective alternative, has been widely applied to assess stress displacement and strain to the entire pipe structure. This is the initial approach adopted in recent decades. This article provides simulations tests of an uncracked pipe and cracked PE100 pipe under different internal pressure values, with varying each time the dimensions of the crack with 1 mm rate for minor and major radius and 0.<i>5mm</i> rates for the largest contour radius, using ANSYS MECHANICAL STRUCTURAL STATIC for simulation.

Determination of an allowable value of internal uniform pressure on the underground horisontal working contour with a trapezoidal form of its cross-section

The paper presents the study results of the stress state at the contour points of an underground horizontal working carried out by the methods of the complex variable theory. This study is the basis for solving the problem of determining an allowable value of the uniform pressure transmitted to the contour of the working, with predetermined values of the depth of its laying. The condition proposed by the authors of the paper is used as a criterion of strength (stability), according to which the working’s contour strength is ensured if at any point the amount of the tangential normal stress does not exceed the tensile and compressive strength of the host soil (rock), i.e. σt ≤ σe ≤ σc . As a result of the solution, an assessment of the stress distribution on the contour of an underground horizontal working has been made. The working has a cross-section in the form of a curved trapezoid, which is under the action of uniform all-round stretching of a given intensity with a varying depth and various values of the host mass lateral expansion coefficient. The allowable values of the tensile internal pressure on the contour of an underground horizontal working of a trapezoidal cross-section have been determined at the given values of its depth and a constant coefficient value of the lateral expansion of the host mass μ = 0.25. The materials presented in the paper can be used when choosing the maximum or minimum allowable depth of the working used as a storage facility for liquid or gaseous hydrocarbons.

CREEP OF A THICKWALLED QUASILINEAR VISCOELASTIC TUBE UNDER A CONSTANT EXTERNAL AND INTERNAL PRESSURE

We consider the creep problem for a quasilinear viscoelastic model of a thickwalled tube, loaded with constant internal and external pressure; the material is supposed to be incompressible. An exact solution to this problem was received by one of the authors in previous papers, assuming the state of a tube to be plain deformation; hereby we study properties of this solution for arbitrary material functions of quasilinear viscoelasticity constitutive relation. A criterion of stress stationarity is derived; the stress field of a thickwalled tube under a constant pressure evolves in time in the case of unbounded creep function and arbitrary nonlinearity function, except some particular types. The monotonicity of stress field components is studied: the radial stress monotonicity depends only on internal and external pressure values (for internal pressure, greater than an external one, it is negative and increases in radii). For other stress components, there are derived sufficient conditions of monotonicity. For an exponential nonlinearity function and unbounded creep function, a creep curve is determined to be concave up at the initial moment, and concave down during prolonged observation; the creep curve of a bipower nonlinearity function model may change its convexity. The stressstrain state of a model with a bounded creep function is proved to be bounded.

A thin-walled pipe exposed to corrosion under pressure and nonuniform heating

The paper concerns assessment of the durability of a thin-walled elastic pipe subjected to uniform corrosion under internal and/or external pressures of different media with generally different temperatures. Stress-assisted corrosion of thin-walled pipes under pressure was earlier studied by other authors. Being based on the Laplace law, their solutions do not reflect the effect of internal and external pressure values themselves but only the pressure difference. However, as it is known, hydrostatic pressure may affect the corrosion rate. Unlike the solutions based on the Laplace law, we present a solution taking into account the effects of both internal and external pressures (not only their difference), a difference in the elastic stresses through the pipe wall thickness, and thermal stresses. In accordance with available experimental data, the rate of corrosion is supposed to be linearly dependent on the maximal principal stress at the corresponding surface and exponentially dependent on the temperature. Being presented in a closed form, the obtained solution can serve as a benchmark for numerical analysis and for design purposes.

Finite element analysis and optimization of tube hydroforming process

Tube Hydroforming is one of the most effective manufacturing processes used in modern times since it satisfies the current robust requirements of the manufacturing industry. It finds enormous applications in the automobile and aerospace sectors owing to the inherent advantages over conventional forming processes, like consumption of less material with no compromise on the part strength. Complex geometries can be developed with high accuracy in less number of manufacturing stages, which would, in turn, reduce the overall manufacturing cost. Such an ability of this process to fabricate products with high strength-to-weight ratios at economical costs make it energy-efficient and it does push a step further towards sustainable and modern innovative manufacturing.This paper presents the development of a detailed nonlinear finite element model for the tube hydroforming process that uses Abaqus/Explicit as a computational tool. Elastic-plastic material constitutive behavior is defined using a flow-stress equation, and the Arbitrary Lagrangian-Eulerian technique (ALE) is used to determine the material flow. Input parameters like applied pressure, initial tube thickness, and die-corner radius are considered against output parameters like formed tube thickness, final part dimensions, and stress concentration. The developed model is validated with a previously published literature by Rakesh A. Shinde et al. (2016), and the results are found to agree for the case of percentage of thickness reduction.Following the work done by Rakesh A. Shinde et al., three different numerical cases are created with different die corner radii and tube thicknesses, for 3 different internal pressure values, viz., 41 MPa, 43 MPa, and 45 MPa. The results obtained in the paper are first replicated, and the research is further extended for different loading/unloading rates and peak load holding times (loading paths). Results indicate the sufficiency of only lower loads to produce the required formability. Accordingly, simulations are also performed for cases of lower pressures. Results show that accurate part dimensions at much lower stress concentrations could be obtained at lower values of pressure. The presented work also looks into the optimisation of the process using a well-established DOE technique – Response Surface Methodology. Accordingly, a multi-objective optimisation is performed, considering 20 simulations for the cases of three parameters and three levels. The significant influencing parameter is also identified.

Effect of cladding thickness on brittle fracture prevention of the base wall of reactor pressure vessel

In case of a loss of coolant accident, the cooling water is injected into the downcomer of reactor pressure vessel (RPV) and produces a pressurized thermal shock (PTS). Considering that the current cladding thickness is small, thermal shock and neutron irradiation are easy to cause brittle fracture of base material. The transient stress intensity factors of the crack tips at the base-cladding interface are obtained by the interaction integral method. Since the test of the crack propagation on the cladding-base interface is quite difficult and dangerous, the allowable internal pressure values obtained from the K-T curves are verified by XFEM in the thermo-mechanical coupling fields. By increasing the cladding thickness, the resulting temperature fields are compared with each other to demonstrate the different embrittlement effects caused by thermal shock. Then the elastic-plastic fracture mechanics (EPFM) method and the linear elastic interaction integral method are used to study the structural integrity at relatively low and high nil-ductility reference temperatures respectively. Furthermore, the influence of the crack size on the ultimate bearing capacity of the structure is quantitatively analyzed for various thicknesses of cladding and base wall. The size effect of crack decreases obviously with the increase of cladding thickness.

ANALYSIS OF THE BASIC DIRECTIONS OF FIRE HOSES RUPTURE PRESSURES INCREASING

The analysis of the main ways to increase the rupture pressure of these technical products was made based on the rupture pressures dependence in fire pressure hoses from the parameters of their woven reinforcing frame previously obtained by the authors. From a scientific and practical point of view, the main directions for increasing the bursting internal pressures in the FPH (Fire pressure hoses) are identified and analyzed. The developed methodology for calculating and designing of FPH is based on a relationship connecting internal hydraulic pressure p-burst with a breaking load N-burst in the weft thread and a number of other parameters. To assess the influence of the parameters of the FPH woven reinforcing framework on the value of the internal bursting pressure, the latex FPH with a diameter of 77 mm manufactured by BEREG (Russia) made of polyester yarns and designed for a working pressure of 1.6 MPa, was chosen as the object of study. The dependences of the bursting pressures values on the bursting strength of weft threads of FPH woven reinforcing frameworks, designed for a working pressure of 1.6 MPa, for various diameters of the arms cross sections are obtained. The influence of geometric densities on the basis and weft of the woven reinforcing frame on the value of internal burst pressure in the FPH is investigated. When calculating the FPH strength under the action of internal hydraulic pressure, the effect on the value of the burst pressure in latex FPH manufactured by BEREG (Russia), designed for a working pressure of 1.6 MPa, such parameters as sleeve radius, geometric densities of base and weft was studied. When designing and creating new types of FPH, it is necessary to take into account the influence of these parameters on the burst pressure value.

Mechanism of Burst and Crack during Deep Frying

Expantion of foods during cooking sometimes causes crack and burst. Burst is undesirable, while crack is desirable in some cases. Karinto with no sugar occasionally causes burst involving danger and cracks in doughnuts are generally favorable. Crack during deep frying is caused when the internal pressure of sample exceeds the cracking pressure of outer layer. Factors of internal pressure of samples are temperature increase and expanding ratio, and those of cracking pressure are thickness, tensile strength, and size and shape of the sample. The value of both internal pressure and cracking pressure can be calculated by using these data. The predicted timing of cracks in doughnut were confirmed in the experiment under various conditions. Mechanism of burst and crack during deep frying was proposed and it was expected to be applicable to the prediction and control of crack in food processing.

Quantifying intermolecular interactions between 1‑Hexyl-3-methylimidazolium Nitrate and 1-alkanol: Internal pressure and cohesive energy density approach

For the binary mixtures of [Hmim][NO3] with (C6 to C10) 1-alkanol, values of cohesive energy density (ced), free volume (vf), and internal pressure (Pint) at 303.15 K and ambient pressure were calculated. To calculate the cohesive energy density and the internal pressure of the binary systems, the COSMO-RS model in combination with experimental densities, and Flory’s statistical theory was applied respectively. From the above results, the Pint/ced ratio was tested to study the ‘structuredness’ of fluids. Obtained values (0.2–0.8) are a feature of associated or ionic liquids and demonstrate the strong interactions in binary fluids. The variation of calculated parameters with the chain length of alcohols and the mole fraction of ionic liquid was considered from the standpoint of molecular interactions. It was found that increasing the alkyl chain of alcohol loosens the packing structure of binary liquids and reduces the strength of intermolecular forces.