Internal Pressure Research Articles

Analysis of hole wall stability in saturated clay using undrained solution for cylindrical cavity contraction

To investigate the stress state of soil during the instability of the hole wall (hole shrinkage) in saturated clay, the theory of cylindrical cavity contraction in an infinite medium is applied, utilizing the modified Cam-Clay (MCC) model. By employing intermediate variables, the issue of cylindrical cavity contraction is reformulated into a first-order ordinary differential equation in Lagrangian form, with three effective stress components and pore pressure as the unknowns. In MATLAB, the stress conditions at the elastoplastic boundary serve as the initial values for solving the initial value problem of the differential equation system. After determining the correlation between the stress distribution around the cavity and the diameter reduction ratio, the analysis proceeds to evaluate the internal support pressure required for stabilizing the hole wall according to various stability criteria. This pressure is then integrated into the hole wall stability coefficient formula within the soil pressure model, facilitating the evaluation of hole wall stability. The effectiveness and accuracy of the proposed semi-analytical elastic–plastic solutions were subsequently confirmed through comparison with finite element analysis results, underscoring its relevance for addressing hole wall stability challenges.

Soft Sensory-Motor System Based on Ionic Solution for Robotic Applications.

Soft robots claim the architecture of actuators, sensors, and computation demands with their soft bodies by obtaining fast responses and adapting to the environment. Sensory-motor coordination is one of the main design principles utilized for soft robots because it allows the capability to sense and actuate mutually in the environment, thereby achieving rapid response performance. This work intends to study the response for a system that presents coupled actuation and sensing functions simultaneously and is integrated in an arbitrary elastic structure with ionic conduction elements, called as soft sensory-motor system based on ionic solution (SSMS-IS). This study provides a comparative analysis of the performance of SSMS-IS prototypes with three diverse designs: toroidal, semi-toroidal, and rectangular geometries, based on a series of performance experiments, such as sensitivity, drift, and durability. The design with the best performance was the rectangular SSMS-IS using silicon rubber RPRO20 for both internal and external pressures applied in the system. Moreover, this work explores the performance of a bioinspired soft robot using rectangular SSMS-IS elements integrated in its body. Further, it investigated the feasibility of the robot to adapt its morphology online for environment variability, responding to external stimuli from the environment with different levels of stiffness and damping.

Experimental and numerical study of a fluidic oscillator frequency domain characteristics

Fluidic oscillators are fluid devices that provide steady flow at the inlet while generating unsteady flow at the outlet. This paper aims to investigate the frequency domain characteristics of internal pressure fluctuations in a specific type of fluidic oscillator to gain a deeper understanding of its dynamic behavior. The following conclusions were drawn: (1) Within a certain range, as the inlet-to-outlet pressure ratio increases, the oscillation frequency of the fluidic oscillator continuously rises, and the oscillation amplitude strengthens. (2) As the jet nozzle velocity increases within a certain range, the jet oscillation frequency exhibits a linear upward trend. These research findings provide essential academic and engineering guidance for designing and applying fluidic oscillators, assisting engineers in better understanding and controlling the device’s performance to meet the requirements of various application domains.

Cavern spacing of CAES cavern group in hard rock based on plastic zone and deformation analysis

Existing research on layout parameters of compressed air energy storage (CAES) cavern groups in hard rock has indicated that the key influential factors for group stability include buried depth, diameter, and cavern spacing. Among these, in contrasting to other factors, the research on cavern spacing is limited. This paper focuses on the issue of safe spacing and proposes a numerical method to determine it. By establishing a series of finite element models, the stress state of surrounding rock, changes in shape, equivalent plastic strain of plastic zone, and cavern wall deformation under different spacing have been studied. When a group of air storage caverns in rows is subjected to high internal pressure, for a small spacing, the plastic zone of the surrounding rock between two caverns is connected. Here, the size of the plastic zone, equivalent plastic strain value, and deformation of the cavern wall are relatively large, making the surrounding rock highly susceptible to damage. As the spacing increases, the horizontal width of the plastic zone, the maximum equivalent plastic strain value, the displacement changes of the cavern wall remain stable. This spacing is virtually the same as that when the plastic zone of the surrounding rock is no longer connected and can be selected as a safe spacing. This study explores the design of cavern safe spacing of underground CAES cavern groups and discusses several influencing factors, which can provide references for follow-up energy storage engineering and research.

Structural response analysis of a solid rocket motor charge under temperature and internal pressure loads

To study the structural integrity of a solid rocket motor under low temperature load, internal pressure load, and two combined loads, based on the linear viscoelastic model, the structural response of a solid rocket motor under low temperature load, internal pressure load and two combined loads were analyzed by ANSYS finite element software, and the temperature field and strain field of charge loading were obtained. The Von Mises strain distribution of the solid rocket motor along the axial characteristic line is obtained. The results are: Under the combined action of low temperature load, internal pressure load, and two kinds of loads, the maximum Von Mises strain appears at the transition position between the blade joint and the barrel section, which is the most dangerous position for charging.

IMPACT OF FREEZE-THAW CYCLES ON BACTERIAL VIABILITY IN CONCRETE

Calcium carbonate precipitating bacteria can improve mechanical and physical properties of building materials. Most commonly, bacteria are used for the crack repair, production of self-healing concrete, or as a cementitious agent for low-strength materials. The favorable effect of bacterial metabolism can only be achieved if the sufficient number of cells remain viable in the structural material. Besides the limited amount of oxygen, extremely high pH level and mechanical pressure on cell walls, bacteria must survive the repetitive freezing and thawing in concrete-type materials. Freezing water may generate additional internal pressure damaging the bacterial cells and suppressing the bacterial activity. In present study, the viability two of bacteria strains (Bacillus pseudofirmus and Bacillus cohnii), was studied under repeated freezing and thawing conditions. It was shown that concrete-embedded bacteria may survive fluctuations of low temperatures and freeze-thaw cycles, compromising approximately 50% of viable spores. This survivability may only be achieved if bacterial spores are protected from the concrete environment itself, for example, spores could be injected to the expanded clay particles and coated with the styrene-acrylate emulsion. These findings confirm that Bacillus pseudofirmus and Bacillus cohnii bacteria could be used in cold climatic regions, retaining viable bacteria spores within the concrete.

Experimental study on the coupled flow field and thrust characteristics of tail cavity and jet

During the launch process of underwater vehicles, a tail cavity is formed at the bottom, which plays a crucial role in the engine ignition stage. The flow state within this tail cavity significantly impacts the engine's operational efficiency. Moreover, the evolution of the tail cavity and jet coupling, along with hydrodynamic characteristics, influences the motion attitude of the vehicle. This article delves into the effects of initial tail cavity length, Froude number, and pressure ratio on cavity morphology and hydrodynamic characteristics, utilizing water tunnel experiments to explore these dynamics at the vehicle's bottom. The experimental findings suggest that while the length of the initial tail cavity influences the jet's coupling mode, it does not significantly affect the cavity's ultimate morphological evolution. A larger initial cavity scale correlates with a lower initial pressure peak following nozzle activation; similarly, an increase in the Froude number leads to a decrease in the initial pressure peak. When the cavity morphology remains intact, the pressure pulsation amplitude and frequency are relatively low. In contrast, partially broken cavities and pulsating foam cavities differ in morphological structure and peak internal pressure oscillations, though their pressure pulsation frequencies are similar. During the initial phase of nozzle activation, the thrust produced by the nozzle plays a more significant role than the bottom thrust. Notably, in the initial phase of nozzle activation, the nozzle-generated thrust is more influential than the bottom thrust. The thrust pulsations from pulsating foam cavities are especially strong, with peak values surpassing the initial peak thrust. These insights offer a new insight on the dynamic behavior of underwater vehicles, crucial for refining engine startup strategies.

IMPACT OF FREEZE-THAW CYCLES ON BACTERIAL VIABILITY IN CONCRETE

Calcium carbonate precipitating bacteria can improve mechanical and physical properties of building materials. Most commonly, bacteria are used for the crack repair, production of self-healing concrete, or as a cementitious agent for low-strength materials. The favorable effect of bacterial metabolism can only be achieved if the sufficient number of cells remain viable in the structural material. Besides the limited amount of oxygen, extremely high pH level and mechanical pressure on cell walls, bacteria must survive the repetitive freezing and thawing in concrete-type materials. Freezing water may generate additional internal pressure damaging the bacterial cells and suppressing the bacterial activity. In present study, the viability two of bacteria strains (Bacillus pseudofirmus and Bacillus cohnii), was studied under repeated freezing and thawing conditions. It was shown that concrete-embedded bacteria may survive fluctuations of low temperatures and freeze-thaw cycles, compromising approximately 50% of viable spores. This survivability may only be achieved if bacterial spores are protected from the concrete environment itself, for example, spores could be injected to the expanded clay particles and coated with the styrene-acrylate emulsion. These findings confirm that Bacillus pseudofirmus and Bacillus cohnii bacteria could be used in cold climatic regions, retaining viable bacteria spores within the concrete.

Numerical analysis of stress and deformation characteristics of compressed air energy storage chambers developed from a modified coal mine tunnel

The use of abandoned coal mine tunnels as underground compressed air energy storage (CAES) facilities has garnered significant attention given that it effectively repurposes unused underground space and enhances the efficiency of renewable energy utilization. However, existing coal mine tunnels, without optimization and retrofitting, may not meet the stability requirements of compressed air energy storage repositories. Sectional transformation is a retrofitting method with excellent optimization effects. In this study, numerical simulation based on Midas software was employed to create a three-dimensional model of straight-wall arched mine tunnels. The stress and displacement deformation of the tunnel sections were simulated under internal pressure of 10 MPa, and scenarios with no modification and circular-section backfilling were compared. The outcomes of the study are (1) For deeply buried soft rock mines, the existing structure without modification may not meet the stability requirements of compressed air storage facility due to low rock strength. (2) In the unmodified scenario, stress concentration effects and excessive floor tensile stress occur near the tunnel closure. (3) Backfilling straight-wall arched tunnels into circular shapes effectively reduces stress and displacement along the tunnel walls, preventing stress concentration near the tunnel closure. This study provides a retrofitting approach for repurposing abandoned mines into compressed air energy storage facilities, providing guidance for future projects facing complex geological conditions.

Creep analysis of a cylinder subjected to 2D thermoelasticity loads and boundary conditions with inner heat generation source

This paper presents an in-depth investigation of the creep behavior of a thick-walled cylinder subjected to thermomechanical loads with internal heat generation under various boundary conditions. The cylinder is subjected to internal pressure with the incoming heat flux in the inner layer and the outgoing heat flux from the outer layer accompanied by heat generation. The displacement field follows the kinematics of the first-order shear deformation theory (FSDT). Simultaneously, the temperature field is treated as two-dimensional, exhibiting variations both along the thickness and the length of the cylinder, with a linear temperature gradient across the cylinder's thickness. Using the energy method, the equilibrium equations and general boundary conditions are derived for the cylinder. Norton's model is incorporated into rate forms of the above-mentioned equations to obtain time-dependent stress and strain results using an iterative method. The redistribution, displacements, strains and stresses over time have been obtained by the semi-analytical iteration method. Moreover, the effectiveness of the proposed method in addressing axisymmetric cylindrical shells under various boundary conditions and thermo-mechanical loading is demonstrated. A parametric study on the creep behavior has also been carried out which reveals critical insights. Notably, the study demonstrates that effective stress and radial displacement during creep can be effectively managed by optimizing the external cooling profile or the internal heating profile. Furthermore, the investigation reveals that the presence of a heat source markedly influences the effective stress and displacement within structure, highlighting the interplay between thermal and mechanical factors in determining the structural integrity. To validate the findings of this study, the finite element method was employed, with the results indicating good agreement between the two approaches.

Analysis of internal pressure and vibration of a flexible expansion ratio elongation nozzle shape

The nozzle made of flexible materials can expand and elongate its profile at different flight altitudes, greatly improving the engine’s endurance and ballistic accuracy. However, this also introduces the problem of structural vibration in the nozzle, which adversely affects engine performance. This paper introduces a high-precision hyperelastic material constitutive model for the flexible elongation nozzle and uses numerical simulation to conduct a detailed analysis of the internal pressure and structural vibration under aerodynamic pressure loads. As the flight altitude increases, the pressure magnitude and distribution on the inner wall of the same elongated flexible expansion section do not change. The pressure distribution on the inner wall of the flexible elongation expansion section exhibits certain nonlinear characteristics, and its magnitude decreases gradually along the axial position. The vibration of the elongated expansion nozzle profile becomes more intense with the increase in flight altitude. At high characteristic flight altitudes, the elongation length of the longer expansion section approaches an undamped vibration state.

Numerical study on altitude-compensating mechanism of a permeable nozzle

A conceptual adaptive altitude compensation nozzle with a permeable wall (permeable nozzle for short) is proposed in the present study. The typical operating states of the nozzle are demonstrated using numerical methods and the underlying mechanism of its altitude compensation is interpreted. The numerical results show that, at low nozzle pressure ratios, the external atmosphere enters the nozzle through its permeable wall section, which inhibits the backflow at the nozzle wall, weakens the strength of the separated oblique shock, thus improves the low-altitude thrust performance of the nozzle. However, at high nozzle pressure ratios, the exhaust gas leaves the nozzle through its permeable wall, which weakens the expansion of the exhaust gas and reduces the thrust performance. The permeable nozzle is considered to possess altitude compensation ability when the enhancement in its low-altitude thrust performance surpasses the deterioration in high-altitude thrust performance. The thrust composition analysis of the permeable nozzle reveals that its altitude compensation ability derives from the internal pressure rise due to the atmospheric air penetration into the nozzle at low nozzle pressure ratios.

Assessment of Buckling Failure in Oil Storage Tanks: Finite Element Simulation of Combined Internal and External Pressure Scenarios

Investigating the structural behaviour and buckling susceptibility of cylindrical oil storage tanks is crucial for ensuring their safe and reliable operation. In this study, the structural behaviour and buckling susceptibility of closed roof-top cylindrical oil storage tanks under combined internal and external pressure scenarios were investigated using the finite element analysis (FEA) technique. By utilizing the FEA technique, the combined effect of wind-induced pressure of 250 Pa, applied on the outer surface of the tank and internal pressure of 0.5 MPa, applied on the outer surface of the storage was analysed. The result reveals significant stress concentrations and deformation patterns, particularly on the windward side of the tank, thus, emphasizing the susceptibility of the storage tank to buckling under the specified operating conditions for both the filled and half-filled tank; with internal pressure emerging as the primary contributor to mechanical strain and deformation experienced in the tank, while the wind load plays a secondary but significant role in the deformation of the tank. The fe-safe predicted useful life shows that under the specified operating conditions, the filled storage tank will survive 1 429 hours (2 months) while the half-filled tank will survive 3 551 hours (5 months) before failure due to buckling. Thus, the useful life estimation results show the importance of varying oil levels and operating conditions in the structural assessments of storage tanks.

Bio-Inspired Pressure-Dependent Programmable Mechanical Metamaterial with Self-Sealing Ability.

Self-sealing is one of the fascinating functions in nature that enables living material systems to respond immediately to damage. A prime plant model is Delosperma cooperi, which can rapidly self-seal damaged succulent leaves by systematically deforming until the wound closes. Inspired by this self-sealing principle, a novel programmable mechanical metamaterial has been developed to mimic the underlying damage management concept. This material is able to react autonomously to changes in its physical condition caused by an induced damage. To design this ability into the programmable metamaterial, a permeable unit cell design has been developed that can change size depending on the internal pressure. The parameter space and associated mechanical functionality of the unit cell design is simulated and analyzed under periodic boundary conditions and various pressures. The principles of self-sealing behavior in designed metamaterials are investigated, crack closure efficiency is identified for different crack lengths, the limitations of the proposed approach are discussed, and successful crack closure is experimentally demonstrated in the fabricated metamaterial. Although this study facilitates the first step on the way of integrating new bio-inspired principles in the metamaterials, the results show how programmable mechanical metamaterials might extend materials design space from pure properties to life-likeabilities.

Analyzing mechanical properties and loading performance of polypropylene sandwich pipes

Sandwich pipes are widely used in various piping applications owing to their exceptional pressure resistance and thermal insulation properties. In this paper, the mechanical properties and loading performance of sandwich pipes made of polypropylene material have been investigated under different loading conditions including lateral and axial compression, as well as hydrostatic internal and external pressures. For this purpose, finite element models of sandwich pipes with various designs have been developed. Material properties have been determined through standard experimental tests, and the finite element models have been validated using lateral compression experiments. The results indicate that incorporating annular cores with thinner thickness and greater numbers, along with using a thicker inner pipe in the sandwich pipe structure, improves its properties and performance.

A Thermodynamic Model for Cryogenic Liquid Hydrogen Fuel Tanks

Hydrogen is used as a fuel in various fields, such as aviation, space, and automobiles, due to its high specific energy. Hydrogen can be stored as a compressed gas at high pressure and as a liquid at cryogenic temperatures. In order to keep liquid hydrogen at a cryogenic temperature, the tanks for storing liquid hydrogen are required to have insulation to prevent heat leakage. When liquid hydrogen is vaporized by heat inflow, a large pressure is generated inside the tank. Therefore, a technology capable of predicting the tank pressure is required for cryogenic liquid hydrogen tanks. In this study, a thermodynamic model was developed to predict the maximum internal pressure and pressure behavior of cryogenic liquid hydrogen fuel tanks. The developed model considers the heat inflow of the tank due to heat transfer, the phase change from liquid to gas hydrogen, and the fuel consumption rate. To verify the accuracy of the proposed model, it was compared with the analyses and experimental results in the referenced literature, and the model presented good results. A cryogenic liquid hydrogen fuel tank was simulated using the proposed model, and it was confirmed that the storage time, along with conditions such as the fuel filling ratio of liquid hydrogen and the fuel consumption rate, should be considered when designing the fuel tanks. Finally, it was confirmed that the proposed thermodynamic model can be used to sufficiently predict the internal pressure and the pressure behavior of cryogenic liquid hydrogen fuel tanks.

Extracorporeal membrane oxygenation (ECMO) assisted huge mediastinal tumor resection combined with superior vena cava replacement: A case report and literature review.

As to huge solid mediastinal tumor which direct compression or invasion of the superior/inferior vena cava (SVC/IVC), surgical resection remains the main lifesaving treatment. However, it would present formidable anesthetic challenges due to the extremely high risks of cardiorespiratory compromise, drastic hemodynamic fluctuations and death at all perioperative stages. Here, we report a case of huge anterior mediastinal tumor resection combined with SVC replacement under the assistance of venoarterial extracorporeal membrane oxygenation (VA ECMO), and stable hemodynamics were maintained as well as high internal jugular vein pressure being avoided during the operation procedure. He was weaned off ECMO successfully just after surgery and eventually discharged. No signs of postoperatively neurological complications occurred. Therefore, the use of ECMO assistance in huge mediastinal tumor resection combined with SVC replacement is feasible and safe, which may provide the possibility of surgical treatment for such patients and improve outcomes.

Investigating the Effects of Crack Orientation and Defects on Pipeline Fatigue Life Through Finite Element Analysis

Abstract In response to the steady rise in global demand for energy resources such as gas and oil, there is a pressing need to enhance the efficiency and safety of pipeline transportation systems. These systems, integral for transferring vast amounts of energy, must operate under increasingly higher pressures and larger diameters without compromising reliability. This study focuses on utilizing finite element analysis (FEA) to investigate the influence of crack orientation and the presence of defects on the fatigue life of pipelines. By simulating internal pressure scenarios and examining various defect characteristics with the AFGROW software, this research applies damage tolerance principles to offer insights into the fatigue behavior of pipelines. The findings can be applied to extend the operational life and ensure the integrity of these critical infrastructures, thereby supporting the sustainable and safe transport of energy resources.

Vibroacoustic analysis of submerged fluid-filled cylindrical shell

This study presents a comprehensive Chebyshev-Fourier spectral method for analyzing the free and forced vibroacoustic characteristics of submerged fluid-filled cylindrical shells in heavy fluids. The vibroacoustic interaction system of submerged cylindrical shells consists of three discrete regions: The Sanders shell theory is applied for the shell structure, whereas the wave equation is used to determine the fluid inside. The external fluid pressure on the shell is described using the Helmholtz boundary integral equation. The governing equations for the shell's motion, the formulation of the external fluid pressure on the fluid-structure-interaction (FSI) surface using first-class Chebyshev polynomial and Fourier series expansions, and the internal sound pressure employing two-dimensional Chebyshev polynomial and Fourier series expansions, are seamlessly integrated with Gauss-Chebyshev-Lobatto sampling techniques. Artificial springs are implemented to replicate the boundary conditions of the cylindrical shell. The precision of the proposed methodology is corroborated by comparisons with existing literature and finite element method (FEM) results. Furthermore, the research examines how the properties of the acoustical medium on the vibroacoustic responses of the cylindrical shell. Results indicate that the presence of air inside the shell slightly influence on its acoustic radiation. However, replacing the internal medium with water significantly alters the shell's original radiation characteristics.

Numerical modelling of different airbag folding patterns and their influence on occupant responses in frontal vehicle impact

This paper presented a procedure for airbag folding for the application in occupant safety studies and analysed the influence of different airbag folding patterns on the occupant severity in frontal impact. Airbags were folded in two patterns: zig-zag and top-roll, using two folding techniques: Initial Metric Method and Explicit Folding. The explicit folding was found to be more expensive in terms of preparation time. However, this approach provided more control over the whole folding process. The Initial Metric Method was more robust, however, it’s hard to apply for complex folding patterns. Deployments of airbags were validated against experimental data of pendulum tests. Those airbag models were applied to 2006 Ford F250 pickup truck. This vehicle was used for simulations of frontal vehicle impact where the 50th male Hybrid III crash test dummy was an occupant. Results of this simulation were compared with an actual test with a similar vehicle, under the same impact conditions. Results showed the head and chest accelerations were lower for top-roll folded airbag cases, however neck normal forces were higher compared to zig-zag folded airbag. The internal pressure in the early stage of deployment was 33% higher for the top-roll folded airbags.