Increase In Internal Pressure Research Articles

Flow–solid coupling analysis of underground reinforced concrete forked pipe enclosing rock and structure

The stability of the surrounding rock for the construction excavation and the reinforcement of the lining structure during operation in the water-rich area is a difficult problem for the design of high-head underground turnout pipes. Firstly, according to the mechanism of excavation load release and surrounding rock damage evolution, the seepage effect of excavation in the construction of the forked caves is coupled to the surrounding rock stress damage, and an iterative method of numerical simulation of the coupled mutual feedback effect of excavation surrounding rock stress and seepage is proposed. Then, based on the cracking characteristics of the high internal water pressure reinforced concrete turnpike lining, a numerical analysis method of the coupling interaction between lining cracking and internal water seepage is proposed by coupling internal water seepage to stress damage in the lining by cracking the forked pipe structure. Applying the aforementioned method to a forked pipe project, the results show that: during the construction period, there is a significant increase in the damage zone, stress, and displacement of the rock around the cavern after considering the coupled iterations; during the operation period, with the increase in internal water pressure, the lining structure accelerates cracking due to the external infiltration of internal water; after the internal water is applied, the surrounding rock bears the main internal water pressure and the reinforcement bears only part of the circumferential force. The method provides theoretical support for the analysis and calculation of the reinforcement of similar underground high-pressure tunnels for rock support and lining structures and has certain theoretical and engineering significance.

Analytical method for deformation and stress calculation of bell-and-spigot joints in PVC-U pipes

The stable operation of water supply pipelines relies significantly on the structural safety of pipe joints. A novel analytical pipe joint structural calculation method based on the Novozhilov thin shell theory was proposed to calculate the deformation and stress of bell-and-spigot joints in unplasticized polyvinyl chloride (PVC-U) pipes under internal pressure. An equivalent stress index was established to investigate and evaluate the safety performance of pipe joints. The effects of various factors, including spigot insertion depth, the clearance between the bell and spigot, internal pressure, and different pipe nominal outside diameter (DN) and nominal pressure (PN) series, on the maximum equivalent stress of pipe joints, were thoroughly analyzed. The results indicate that the maximum equivalent stress under nominal pressure is located on the inner surface of the bell and consistently exceeds the design stress. The influence of spigot insertion depth on the maximum equivalent stress is minimal. However, as the clearance value between the bell and spigot decreases and the internal pressure increases, the maximum equivalent stress increases significantly. Pipes with smaller DN and PN series result in a higher maximum equivalent stress at the joint. The analytical method indicates that increasing pipe thickness and reinforcing the bell with continuous carbon fiber filament winding are two potentially effective methods to enhance the mechanical performance of the joint and reduce the maximum equivalent stress. This study's findings offer valuable theoretical support for designing and selecting joints in PVC-U pipelines.

Acoustic frequency analysis of the vibrational resonant frequencies of Special Nuclear Material containment

The increase of the resonant frequencies of a Magnox containment package that have been detected by an electromagnetic acoustic transducer and a microphone, are the result of an increase in internal pressure of the package. Therefore, it is possible to infer an internal pressure measurement of the Magnox package by measuring the shift of different resonant frequencies. A model of the Magnox package has been constructed to predict the acoustic vibrational resonant frequencies of the package wall and the corresponding mode shapes. Laser Doppler vibrometer measurements of the Magnox package wall have confirmed the presence of the predicted mode shapes and the resonant frequencies at which they occur have been reasonably estimated by the model.

Detection of the internal pressure in beer cans by measuring the force-displacement curves

Microbiological contamination of beer is manifested in many cases by the production of CO2 and an increase in its concentration. An increase in the concentration of CO2 in a closed package leads to an increase in internal pressure, which can cause the destruction of the package with dangerous consequences. This case study aimed to verify the applicability of force-displacement measurement for non-destructive monitoring of the internal pressure in beer cans.

Contact mechanical behavior and leakage prediction of metal lenticular gaskets in bolt flange joints of ultrahigh pressure pipelines

Metal lenticular gaskets have been widely applied in the bolt flange joints of high and ultrahigh pressure pipelines due to their semi-self-tightening sealing properties. However, research on the leakage prediction of the metal lenticular gaskets is still lacking, which limits their further optimal design and sealing performance improvement. In this paper, an elastoplastic contact mechanics analysis of a metal lenticular gasket used in the bolted flange joint of ultra-high pressure polyethylene pipelines was firstly carried out. The analytical formulas of contact stress and contact width were derived and compared with corresponding numerical results. Then, based on the surface topography measurement, a leakage model was established, in which the pipe surface was simplified to a smooth rigid flat surface, and the gasket surface was simplified to an equivalent rough surface composed of identical wedges. Finally, an analytical leakage prediction formula for the metal lenticular gasket was proposed. In addition, the effects of influence factors on leakage rate were discussed. It is shown that the analytical formulas can accurately calculate the contact stress and contact width in elastoplastic contact. The leakage rate increases with the decrease of the bolt load and the increase of internal pressure. For the ultrahigh pressure pipeline with internal pressure of 200 MPa, the minimum bolt load should be ensured to be higher than 120 kN in order to meet the T5 tightness level. In addition, the initial contact diameter is basically proportional to the leakage rate, while the change of gasket inclination angle has little effect on the leakage rate. Therefore, the contact diameter can be designed to be as small as possible within a reasonable range. This work can provide a theoretical basis for the sealing optimal design of metal lenticular gaskets.

Study by finite element modeling of hydrogen atom diffusion and distribution at a dent on existing pipelines for hydrogen transport

Pipelines, especially existing natural gas pipelines, provide an efficient and economical means for hydrogen transport, accelerating realization of a full-scale hydrogen economy. However, the existing aged pipelines usually contain dents, which serve as effective traps to accumulate hydrogen atoms, potentially causing hydrogen embrittlement and pipeline failures. To date, there has been a strong interest in development techniques for assessment of hydrogen atom distribution at a dent on pipelines. In this work, a three-dimensional nonlinear finite element-based model was developed to investigate the hydrogen atom diffusion and distribution at a constrained dent on an X52 steel pipe. Parametric effects, including dent depth and internal pressure, were determined. The presence of a dent on pipelines drastically changes the local stress and strain distributions, facilitating diffusion and accumulation of hydrogen atoms at the dent. The minimum hydrogen atom concentration at the crystalline lattice sites, (i.e., 3.8 mol/m3) is located on the outer surface of the dent center, and the maximum hydrogen atom concentration (i.e., 12.1 mol/m3) is found on both sides of the dent with 103 mm from the dent center in the circumferential direction. The hydrogen atom concentration at trap sites at the dent is much lower than that at the lattice sites. The diffusion and accumulation of hydrogen atoms at the dent area is affected by two competitive mechanisms, i.e., hydrostatic stress and plastic strain, depending on the initial concentration of hydrogen atoms entering the interior of the pipe steel. At a low initial concentration such as 0.001 mol/m3, the equivalent plastic strain dominates the distribution of hydrogen atoms at the dent, and the hydrogen atom concentration at the lattice sites is much lower than the concentration at the trap sites. At high initial hydrogen atom concentrations such as 0.1 and 1 mol/m3, the hydrostatic stress is the dominant factor to determine the distribution of hydrogen atoms, which mainly accumulate at the lattice sites. With an increased depth of the dent, both the von Mises stress and plastic strain concentrations increase, and so is the hydrogen atom concentration. The increase of internal pressure from 5 MPa to 15 MPa only slightly elevates the von Mises stress, equivalent plastic strain and the hydrogen atom concentration.

Large-scale CAES in bedded rock salt: A case study in Jiangsu Province, China

To efficiently utilize renewable energy sources primarily consisting of wind and solar power, large-scale compressed air energy storage (CAES) can be implemented using underground salt caverns. In this paper, the abundant wind and solar energy resources and the geological conditions of the three major salt mines in Jiangsu Province are introduced. A geomechanical model is established based on the Huai'an rock salt formation. The simulation results show that as the internal air pressure (IAP) increases, the safety factor increases, and the displacement, plastic zone, volume shrinkage, and equivalent strain decrease. Based on the above results, the minimum IAPs of caverns AN 13 and AN 21 are recommended to be 10–12 MPa. According to estimates, to store 15% of wind and solar power in Jiangsu Province through CAES by 2050, a 9894.0 × 104 m3 salt cavern volume is needed, of which at least 77.8 million m3 can be provided by salt mining enterprises. The cost of reconstructing an underground salt cavern is 12.1 billion yuan, while the investment in surface equipment is 746.7 billion yuan. We provide an economical and feasible solution for achieving carbon neutrality in Jiangsu Province in this study.

Consumption of a polarized membrane reservoir drives asymmetric membrane expansion during the unequal divisions of neural stem cells.

The asymmetric divisions of Drosophila neural stem cells (NSCs) produce unequally sized siblings, with most volume directed into the sibling that retains the NSC fate. Sibling size asymmetry results from the preferential expansion of the NSC sibling surface during division. Here, we show that a polarized membrane reservoir constructed by the NSC in early mitosis provides the source for expansion. The reservoir is formed from membrane domains that contain folds and microvilli that become polarized by apically directed cortical flows of actomyosin early in mitosis. When furrow ingression begins and internal pressure increases, the stores of membrane within the apical reservoir are rapidly consumed. Expansion is substantially diminished in NSCs that lack a reservoir, and membrane expansion equalizes when the reservoir is not polarized. Our results suggest that the cortical flows that remodel the plasma membrane during asymmetric cell division function to satisfy the dynamic surface area requirements of unequally dividing cells.

On the evolution of supercavity geometry and unsteady behavior of supercavitation flow during the development of a twin-vortex supercavity

To investigate the evolution of supercavity geometry and the unsteady characteristics of the supercavitation flow from the initial generation to full development. A three-dimensional numerical model with the inhomogeneous multiphase model and SST k−ω turbulence model was established. The numerical model was validated by experimental results. The ventilated supercavitation flow was performed under the different gas entrainment coefficients and Froude numbers. The results show that the initial supercavity closure mode is the re-entrant jet, then the closure mode changes to the twin-vortex induced by the gravitational effect. For the fully developed twin-vortex supercavity, a flow structure with gas recirculation exists inside the supercavity, which includes the reverse flow region and downstream flow region. Compared to the supercavity with the twin-vortex closure mode, the increment in the supercavity dimension with the re-entrant jet closure mode increases drastically, and the oscillation characteristic of internal pressure increases, leading to the significant supercavity deformation and gas shedding. The difference of the supercavity dimension is revealed by analyzing the gas leakage behavior. Further, a theoretical model describing the strength of re-entrant jet is established to reveal the transition mechanism of the supercavity closure mode and analyze the unsteady flow characteristics during the supercavity development.

Pretest analysis of a prestressed concrete containment 1:3.2 scale model under thermal-pressure coupling conditions

In nuclear power plant (NPP) accidents, the containment is subject to high temperatures and high internal pressures, which may further trigger serious chain accidents such as core meltdown and hydrogen explosion, resulting in a significantly higher accident level. Therefore, studying the mechanical performance of a containment under high temperature and high internal pressure is relevant to the safety of NPPs. Based on similarity principles, the 1:3.2 scale model of a prestressed concrete containment vessel (PCCV) of a NPP was designed. The loading method, which considers the thermal-pressure coupling conditions, was used. The mechanical response of the PCCV was investigated with a simultaneous increase in internal pressure and temperature, and the failure mechanism of the PCCV under thermal-pressure coupling conditions was revealed.

Pressure-induced damage monitoring in prestressed concrete of nuclear containment wall segments using acoustic emission technique – Application to VeRCoRs containment building

This paper reports benchmark findings of an experimental study of pressure-induced damage monitoring in a nuclear containment building (NCB) reproducing realistic conditions of internal pressure increase accidents. The leak-tightness of NCBs is assessed every 10 years during integrated leak-rate tests (IRLT). For double-wall containments, which have no metallic liners, the leak-tightness is strongly influenced by the degree of cracking of concrete and opening of the cracks. This paper is focused on assessing the effectiveness of the Acoustic Emission (AE) technique to evaluate the damage evolution of a reinforced concrete containment wall under pressure loading test. Piezoelectric accelerometers were mounted on the internal containment wall of the VeRCoRs mockup, which constitutes the containment building of a Nuclear Power Plant in a 1:3 scale. The Akaike criterion (AIC) as an AE hit picking method and the adaptive meshing algorithm (AMA) as an AE events localization algorithm have been applied for damage and cracking monitoring. A benchmark analysis based on the distribution of AE events and energy is presented for the detection of damages and the monitoring of crack propagation in correlation with the known locations of main cracks. The potential and limitations of the AE technique for in situ damage sources estimation are discussed upon two experimental campaigns (2017 and 2019), and the main conclusions of the benchmark survey are given. The results show that the AE technique is adequate for damage evaluation in large-scale concrete structures. It provides important information about the integrity of the structure and the assessment of damage evolution with time.

FORM-FINDING ANALYSIS FOR CABLE-REINFORCED MEMBRANE STRUCTURE BASED ON MINIMAL SURFACE

This paper applies a discretization formulation of the finite element method using the minimal surface for membrane structures and denotes an initial shape analysis procedure for a cable-reinforced HP-type suspension membrane structure and a cable-reinforced pneumatic membrane structure as numerical analysis model. In the computation process of cable introduction, moving boundaries are set and the cable is introduced step by step to denote a stable numerical computation procedure. In addition, finite elements of the initial shape obtained assuming a time history response analysis by wind are subdivided to compute the minimal surface again. To verify the equally tension property of the initial shape obtained based on minimal surface, a stress deformation analysis using the finite element method with the coordinate assumption is performed. For the pneumatic membrane structure, an example of stress deformation analysis due to an increase in internal pressure assuming strong winds is shown. The above clarifies the validity of this numerical procedure.

Refined assessment of tire rolling resistance in the starting mode

Problem. Rolling resistance is one of the most important operational characteristics of a car tire. First of all, the fuel consumption, durability and service life of the tire depend on the rolling resistance. Of course, the higher the rolling resistance, the faster and more intensively the tire will wear out. Also, car braking parameters, such as deceleration and, accordingly, the braking distance, may indirectly depend on the rolling resistance characteristics. In turn, rolling resistance is influenced by the properties of the tire itself, as well as the condition of the road surface and weather conditions. It is especially important to evaluate the operational characteristics of a car tire in the starting period of movement, because at this time the behaviour of the tire is unpredictable. Goal. The purpose of this work is to improve the methodology for evaluating the rolling resistance of a car tire in the starting period of movement. Knowing how the rolling resistance changes during the starting movement, it is possible to evaluate the operational properties of the car. Methodology. Refined assessment is carried out with the help of dependencies obtained in previous scientific works. But in order for the result of the rolling resistance assessment to be correct, it is necessary to determine the necessary characteristics of the tire. Namely, we are talking about the characteristics of radial stiffness. In the work, these characteristics are determined both by conducting experimental studies and by using FEM. Results. Thanks to the conducted research, significant results were obtained on the change in rolling resistance during the starting motion. It was established that with an increase in internal pressure from 0.17 MPa to 0.225 MPa, as a result of the starting motion, the rolling resistance decreases by approximately 20-25%. Originality. From the analysis of the literature, it can be concluded that in most of the studied works, the peculiarities of the interaction of automobile tires with the supporting surface in the starting period are not taken into account during various studies. It can be said that the originality of this work, on the one hand, is that the rolling resistance is investigated during the starting motion, and on the other hand, that its assessment is carried out both on the basis of the results of experimental studies and with the help of FEM. Practical value. In this work, it is possible to highlight the obtained results, thanks to which we can estimate the rolling resistance of a car tire with sufficient accuracy. The methods of determining the operational characteristics of a car tire, presented in the work, can be used during its operation and at the design stage.

An Assessment of Seal Ability of Tubing Threaded Connections: A Hybrid Empirical-Numerical Method

Abstract Oil and gas development has strict requirements for the seal ability of premium threaded connections (PTCs) of tubing. Assessing the seal ability of joints can help reduce the risk of leakage after running the string. Using experimental methods to investigate thread sealing capability is time-consuming and expensive, and furthermore, the results of the finite element simulations are not accurate enough. To better address this issue, a hybrid method is utilized as an advanced solution: we establish a geometric nonlinear model and tie it to an empirical formula based on experimental data. With this method, we explore the variation of the seal ability of a PTC within the actual working load range. Our results indicate that the increase in internal pressure increases the contact pressure on the contact path to a certain extent, but reduces the seal ability of the joint. Also, an increase in the axial tensile load will significantly impair the performance of the joint to seal. Eventually, an economic appraisal is obtained by considering the seal ability of different type of joints. The described workflow may be adopted in other wells to predict the potential string leak problems induced by premium threaded connections with cheap computational costs, and to compare the seal abilities of different PTCs for optimal purposes of saving drilling costs.

Fatigue Life Calculation of Tubing for In Situ Drilling Rig

The severe bending strain that the tubing of the in-situ drilling rig is subjected to during the operation under pressure, which exceeds the elastic limit, will cause periodic plastic deformation of the tubing of the in-situ drilling rig, so that fatigue cracks will occur on the internal and external surfaces of the tubing of the in-situ drilling rig and expand rapidly, leading to the greatly shortened service life of the tubing of the in-situ drilling rig. Based on the stress analysis of the dangerous points of the tubing of the in-situ drilling rig, the relationship between the predicted and the standard measured tubing life of the in-situ drilling rig is obtained in this paper. The number of tubing cycles of in-situ drilling rig decreases sharply with the increase of internal pressure. The greater the internal pressure is, the greater the circumferential stress and uniaxial alternating stress are, which causes the number of tubing cycles of in-situ drilling rig to decrease when tubing fails. It shows that the fatigue life of tubing of in-situ drilling rig is significantly affected by internal pressure.

Experimental Study on Construction Performance of Infilled-Type Fire Resistant Materials

In this study, the physical properties of the material were tested to ensure the applicability of the filling-type fireproof construction method when using spraying materials, and the changes in the material in different filling locations were evaluated. The filler, ET-1013 mixture without admixture, showed proper fluidity. When using the lower filling method, cracking and sagging occurred over time because of the increase in internal pressure. At the same time, cracking and deflection did not occur in the case of the upper filling method. The filling tests were performed using manufactured 1,000 and 3,000 mm columns. In the case of the lower filling method, cladding steel plates of the column underwent out-of-plane buckling, and the material separation occurred.

Study on structural integrity of reactor pressure vessel with various ablation under core meltdown accident

In-vessel retention is an important measure to alleviate the core meltdown accident in the third generation nuclear power plant. External Reactor Vessel Cooling(ERVC) is the key to the successful implementation of IVR. Due to the ablation caused by the molten pool in the lower head, the reactor pressure vessel(RPV) has various wall ablation and thinning, which poses a great threat to the integrity of the pressure boundary of the RPV. Based on the boiling water RPV as the research object, the model is established for the RPV with various ablation and local thinning by finite element method(FEM). The stress/strain response of the structure is calculated and analyzed under the core meltdown accident. The plastic and creep damage are assessed for the RPV in terms of its evolution and distribution with continuum damage mechanics(CDM). Due to the existence of internal pressure within the RPV, the effect of pressure on creep and plastic rupture is also studied within the required 72 h. According to the criterion of ductile exhaustion, the results show that the increase of internal pressure further reduces the load-bearing capacity of RPV.

Structural behavior of an ablated reactor pressure vessel wall with external cooling

In a severe accident scenario of a nuclear power plant involving core meltdown and relocation to the lower head of the reactor pressure vessel (RPV), the vessel may undergo serious deformation and even failure due to extreme thermo-mechanical loads from the relocated core melt. Proper material models and detailed structural analysis are paramount in predicting the timing and mode of possible vessel failure.This paper presents a strain hardening creep model with optimal parameters to simulate the material behavior of the reactor steel 16MND5 under extreme thermo-mechanical loads. First, validations against two experiments, a tensile-creep test and the EU-REVISA RUPTHER #14 test, show that the proposed model is best overall compared to three previous models. Next, the creep model is implemented for the thermo-mechanical analysis of an ablated RPV under a severe accident scenario with external vessel cooling as a mitigation strategy. The effect of internal pressures from 3 to 50 bars is investigated with the assumption that the corners of the ablated part of the vessel have sharp corners. In this case, we found that the vessel fails above 40 bars. However, if we model the corners with varying smoothness or fillet sizes, we found significant delay in failure time and an increase in failure internal pressure.

Proposed Role for Internal Lens Pressure as an Initiator of Age-Related Lens Protein Aggregation Diseases.

The process that initiates lens stiffness evident in age-related lens protein aggregation diseases is thought to be mainly the result of oxidation. While oxidation is a major contributor, the exposure of lens proteins to physical stress over time increases susceptibility of lens proteins to oxidative damage, and this is believed to play a significant role in initiating these diseases. Accordingly, an overview of key physical stressors and molecular factors known to be implicated in the development of age-related lens protein aggregation diseases is presented, paying particular attention to the consequence of persistent increase in internal lens pressure.

A Cycle Analysis of Flow and Thermal Parameters in the Hydrogen Charging System at the Pressure of 50 MPa

In the currently developed hydrogen compression cycle system, hydrogen is compressed through a compressor and stored in a tank at high pressure. In the filling process from A (tube trailer) to B (high-pressure tank), thermal stress in the B arises due to the temperature rise of hydrogen together with the internal pressure increase in the tank. In the study, in order to achieve safe filling, it is necessary to investigate the flow and thermal parameters of the system. Based on the principles of thermodynamics, a thermodynamic prediction model for the temperature change during the hydrogen cycle was established by comprehensively considering the real state of gas, convective heat transfer between hydrogen and the inner wall, heat conduction through the tank wall, and natural convection of the outer wall. Prediction values of temperature, hydrogen charge amountm and heat transfer to the outside were calculated. Additionally, by investigating the performance of the hydrogen refueling station heat exchanger, the heat of the heat exchanger needed to keep the hydrogen temperature within a safe range was calculated. Due to the Joule–Thomson effect, the hydrogen temperature passing through the pressure reducing valve changed, and the changed value in the hydrogen charging cycle was predicted and calculated by calculating the temperature change value at this time. This study provides a theoretical research basis for high-pressure hydrogen energy storage and hydrogenation technology.