Range Of Internal Pressures Research Articles

Using J-integral analysis to predict the failure of HDPE pipes under crack face load and internal pressure

Cracks in pipes used for water transfer have been identified as a significant contributor to water loss and potential failures. To assess fracture behavior, the J-integral was computed for 3D finite element HDPE pipes (DN 355) with axial internal and external cracks (with a/ c and a/ t ratios of 0.5) subjected to a range of internal pressure (16–30 bar) and crack face load condition. Four ratios of a/ c ranging from 0.3 to 0.9 (with an increment of 0.2) were examined with the internal crack. Results indicate that under face crack loading, the external axial crack exhibits a higher J-integral intensity than the internal axial crack. J-integral values greater than 8.4 kJ/m2 were found to lead to pipe failure, with higher internal pressures (25–30 bar for external crack, and 30 bar for internal pressure). Moreover, the a/ c ratio plays a significant role in influencing the distribution of J-integral along internal crack arc length. For pipes of DN 355 size with axial cracks, internal pressure exceeding 20 bar is not recommended. These findings underscore the importance of considering J-integral values in pipe design to prevent failure.

Analysis of pressure interval/injection and production frequency on stability of large-scale supercritical CO2 storage in salt caverns

Carbon dioxide (CO2) is the primary greenhouse gas, with annual emissions reaching up to 54 billion tons globally, leading to an unprecedented acceleration of global warming. In conjunction with carbon capture, utilization, and storage (CCUS), which represents the most advanced and efficient technology for energy conservation and emission reduction, as well as the innovative concept of CO2 storage in salt caverns, this paper investigates the industrial application potential of supercritical CO2. Herein the feasibility of large-scale storage of supercritical CO2 in salt caverns was investigated, focusing on the stability aspect associated with such storage. Specifically concentrating on the impact of upper and lower injection/production pressures and frequencies on the stability of carbon storage in salt caverns, this study utilizes numerical simulation methods to simulate the creep process that occurs in China's bedded salt formations. Numerical simulation results showed that: 1) From the perspective of salt cavern stability, the volume shrinkage, creep and damage degree of surrounding rock during operation all fall within an acceptable range. Consequently, it is feasible to implement carbon storage in these salt caverns for a during of 100 years. 2) Shortening the range of internal pressure will enhance the stability of salt cavern for carbon storage. Furthermore, different pressure intervals have an impact on the creep concentration position within the cavern, primarily resulting in a transformation between internal contraction of surrounding rock and sediment accumulation caused by floor creep by altering the lower pressure limit. 3) The injection and production frequency of salt cavern carbon storage (SCCS) is characterized by a low occurrence rate (<10 cycles). The stability of the cavern can be enhanced by increasing the injection and production frequency, nevertheless, it is important to note that internal pressure remains the primary factor influencing cavern stability compared to the injection and production frequency.

A Deep Neural Network to Identify Vacuum Degrees in Vacuum Interrupter Based on Partial Discharge Diagnosis

One of the most crucial parameters in operating a vacuum interrupter (VI) is internal pressure. The failure of switching or insulation occurs when the pressure rises above a specific level. Characteristics of partial discharge (PD) in VI can be used to measure the internal pressures of VI. This paper defines a classification problem for the degree of internal pressure in VI using PDs, which were measured using a capacitive PD coupler. Then, we propose a deep neural network to monitor the internal pressure of VI by analyzing PDs. Experimental results show that the proposed deep neural network monitors the internal pressure range, from 1.0 &#x00D7;10^-2 torr to 10 torr in VI. The classification performance of the proposed method is significantly better than those of machine learning algorithms such as support vector machines and <i>k</i>-nearest neighbor algorithm and the proposed method achieves an 100% classification accuracy.

Effects of mechanical property parameters on wrinkling behavior of thin-walled tubes in hydroforming process

In tube hydroforming, some controllable wrinkles can be used to improve the formability of tubes, so as to obtain the tubular parts with large expansion ratio and relatively uniform wall thickness. In this paper, finite element analysis and experimental research with 5052 aluminum alloy and 304 stainless steel tubes are used to investigate the effects of mechanical property parameters on wrinkling behavior of thin-walled tubes for hydroforming application. The numerical simulation results show that the effect of elastic modulus is very small and ignorable, but the initial yield stress and tangent modulus of tubes have an obvious effect on their wrinkling behavior. Tubes with higher initial yield stress and lower tangent modulus tend to possess three axisymmetric wrinkles within the lower internal pressure range. Moreover, it is found that the ratio of initial yield stress to flow stress of the tubes, σs/σf, is a significant factor to their wrinkling behavior. Three axisymmetric wrinkles could be produced on the tubes with higher σs/σf under a lower internal pressure. All of these were verified by the experimental results of 5052 aluminum alloy and 304 stainless steel tubes, whose wrinkles obtained under wrinkling internal pressure of 1.8 ps and 1.2 ps can be flattened completely in the calibration stage. These research findings are extremely meaningful to get controllable wrinkles for different kinds of tubes.

Correlation between the Thermo-physical Properties and Core Material Structure of Vacuum Insulation Panel: Role of Fiber Types

Vacuum insulation panel (VIP), which is composed of an evacuated core material encapsulated in an envelope and supplemented with a desiccant, is a high performance thermal insulation material. In this paper, thermos-physical properties of chopped fiber, centrifugal-spinneret-blow (CSB) fiber, flame-spinneret-blow (FSB) fiber and hybrid (CSB: FSB=1:1) fiber as fillers of vacuum insulation panel are explored. The results show that the increase of pore size can improve thermal insulation property; fibers distribute in 2-D structure, which can reduce the heat conduction, leads to reduce the thermal conductivity. VIP with chopped fiber has the best thermal insulation, and thermal conductivity is 1.4 mW/m.K. Due to difference of core materials, thermal insulation characteristics of VIP can be divided into three distinct regions based on the internal pressure range, i.e., (I) ≥12000 Pa region, (II) 80-12000 Pa region, (III) ≤ 80 Pa region. It also finds that service life of VIP can be improved by the reducing the pore size of core materials. VIP with different core materials shows different degradation and the degradation rate of VIP with FSB core material is minimum.

Phase-dependent space weathering effects and spectroscopic identification of retained helium in a lunar soil grain

The solar wind is an important driver of space weathering on airless bodies. Over time, solar wind exposure alters the physical, chemical, and optical properties of exposed materials and can also impart a significant amount of helium into the surfaces of these bodies. However, common materials on the surface of the Moon, such as glass, crystalline silicates, and oxides, have highly variable responses to solar wind irradiation. We used scanning transmission electron microscopy (STEM) with electron energy loss spectroscopy (EELS) to examine the morphology and chemistry of a single grain of lunar soil that includes silicate glass, chromite and ilmenite, all present and exposed along the same surface. The exposure of the silicate glass and oxides to the same space weathering conditions allows for direct comparisons of the responses of natural materials to the complex lunar surface environment. The silicate glass shows minimal effects of solar wind irradiation, whereas both the chromite and ilmenite exhibit defect-rich rims that currently contain trapped helium. Only the weathered rim in ilmenite is rich in nanophase metallic iron (npFe0) and larger vesicles that retain helium at a range of internal pressures. The multiple exposed surfaces of the single grain of ilmenite demonstrate strong crystallographic controls of planar defects and non-spherical npFe0. The direct spectroscopic identification of helium in the vesicles and planar defects in the oxides provides additional evidence of the central role of solar wind irradiation in the formation of some common space weathering features.

수치 해석을 통한 비행체 내부 압력 예측과 실험적 검증

In this study, a numerical analysis for predicting the internal pressure of the flight vehicle system with relief valve and N2-injection type cooler was conducted to operate the system safely in an unsteady-state condition. By adopting an incompressible ideal gas equation to computational domain at each time step, internal pressure was calculated without iteration. To increase the accuracy of the numerical analysis results, numerical model was correlated by modifying the volume of the computational domain. To modify the volume of computational domain, internal pressure along time was compared with experimental results. It showed good agreement within system operating time. Air mass flow rate at the relief valve is calculated by interpolating the performance curve data. For accurate and rapid calculation of the internal pressure in an unsteady-state condition, time step size convergence study was conducted additionally. By using a correlated numerical model, Pcr of the relief valve is conducted to remain the flight vehicle system within an internal pressure range of 0.6-2.0 atm, in each flight profile. Finally, specific Pcr of relief valve was applied to the system and the experimental results showed that the internal pressure remained in a safe range.

Effects of diabetes mellitus on biomechanical properties of the rabbit cornea

To investigate the effects of diabetes on the biomechanical behavior of cornea in alloxan-induced diabetic rabbits. Diabetes mellitus (DM) was induced in 20 rabbits using alloxan, while another 20 age- and weight-matched non-diabetic rabbits served as controls. Eyes were enucleated after 8 weeks of inducing diabetes and the whole cornea was removed with a 3 mm wide scleral ring and tested under inflation conditions with an internal pressure range of 2.0–30.0 mmHg to determine their stress-strain behavior using an inverse analysis process. The blood glucose level (BG), advanced glycosylation end products (AGEs), central corneal thickness (CCT) and intraocular pressure (IOP) increased significantly in the DM group. There were statistically significant correlations between BG and AGEs (r = 0.768, p = 0.00), and between AGEs and CCT variation upon induction of DM (r = 0.594, p = 0.00). The tangent modulus (Et) of the cornea at four stress levels (1–4 kPa, equivalent to approximately IOP of 7.5, 15, 22.5 and 30 mmHg, respectively) was significantly higher in diabetic rabbits than in the control group (p < 0.05). Further, Et at stress of 2 kPa (which corresponded to the average IOP for the control group) was significantly correlated with BG (r = 0.378, p < 0.05), AGEs (r = 0.496, p < 0.05) and CCT variation upon induction of DM (r = 0.439, p < 0.05). IOP, as measured by contact tonometry, was also significantly correlated with both CCT (r = 0.315, p < 0.05) and Et at 2 kPa (r = 0.329, p < 0.05), and even after correcting for the effects of CCT and Et, IOP still significantly increased with both AGEs (r = 0.772, p = 0.00) and BG (r = 0.762, p = 0.00). The cornea of diabetic rabbits showed a significant increase in mechanical stiffness as evidenced by increases in corneal thickness and tangent modulus. The Et increase may be explained by a non-enzymatic cross-linking of collagen fibrils mediated by AGEs due to the high blood glucose levels in diabetes. The study also found significant IOP increases with higher blood glucose level even after controlling the effects of both corneal thickness and tangent modulus.

Research on flattening behavior of wrinkled 5A02 aluminum alloy tubes under internal pressure

Control of wrinkle for its utilization in tube hydroforming process is a challengeable subject up to now, because wrinkle was always considered as one of the tube’s defects from the traditional view. In order to investigate the flattening behavior of wrinkles in the calibration stage, the wrinkled 5A02 aluminum alloy tubes, obtained under different internal pressures with same amount of axial feeding, were used as the preformed samples for the hydroforming under higher internal pressure of 15 ps (ps represents the initial yield pressure of tube). The effect of internal pressure during wrinkling process, as well as the axial feeding, on the flattening behavior of wrinkles was investigated and discussed. It has been found that the wrinkles can be flattened completely when the wrinkling internal pressure is 1.8 ps. Furthermore, when the axial feeding ratio is reduced from 80 to 75 %, the wrinkling internal pressure range for fractured wrinkles in calibration stage will be enlarged backward to 1.2 ps, but the pressure range for useful wrinkles can be improved forward to 1.6 ps. In addition, the fitted Gauss function for every wrinkle was integrated in order to compare its area with the corresponding area of die cavity, so as to reveal the flattening behavior of the wrinkles. It is shown that the wrinkles are easier to be flattened completely without any dead wrinkles when the surface areas of left and right wrinkles are smaller than their die cavity, and the surface area of middle wrinkle is bigger than its die cavity.

A Finite Element Analysis of the Cyclic Plasticity Behavior of Circumferential Weld of Coke Drum under Moving Axial Temperature Gradient

Coke drums undergo cyclic thermal and mechanical loading during operation, which tend to cause damage like bulging and cracking near circumferential welds in coke drums. In this paper, considering the existence of the overmatch welds and uneven temperature field during oil-feeding and water quenching as well as quenching conditions, the bulging behavior of the coke drum is investigated. Firstly, the uniaxial tension and ratchetting experiments of parent metal and weld of coke drum are carried out at 20 oC, 200 oC, 300 oC, and 400 oC. Secondly, the ratchetting strains are predicted by OW-II kinematic hardening model and the predicted ratchetting strain rates of steady stage are in qualitative agreement with the experimental results. By comparison, weld has significantly smaller ratchetting strain rate than parent metal under the same loading conditions, which shows that the anti-ratchetting ability of weld is better than that of parent metal. Thirdly, the transient temperature field during oil-feeding and water quenching are numerically simulated with the help of dynamic coordinate system method, which yields the axial temperature difference and its characteristic value for the simplified characteristic load to be used in the cyclic plastic analysis of coke drum cycled between oil-feeding and water quenching. Fourthly, the ratchet boundaries are determined under moving axial temperature gradient by cyclic plasticity analysis for the parent metal. It is found that, when temperature difference range of water quenching is smaller, the ratchet boundaries are heavily influenced by the cyclic internal pressure. Finally, considering the strength differences between parent metal and weld, cyclic plasticity analysis is done for the circumferential weld connection region of coke drum. The results indicate that the bulging is preferentially near and about 10mm above the weld under given loading conditions. It is also observed that, for cylinder with or without the circumferential weld, the co-existence of cyclic internal pressure can increase the ratchetting strain of the structure and the ratchetting strain rate of structure also increases with the cyclic internal pressure range.

Creation of an in vitro biomechanical model of the trachea using rapid prototyping

Previous in vitro models of the airways are either rigid or, if flexible, have not matched in vivo compliance characteristics. Rapid prototyping provides a quickly evolving approach that can be used to directly produce in vitro airway models using either rigid or flexible polymers. The objective of this study was to use rapid prototyping to directly produce a flexible hollow model that matches the biomechanical compliance of the trachea. The airway model consisted of a previously developed characteristic mouth–throat region, the trachea, and a portion of the main bronchi. Compliance of the tracheal region was known from a previous in vivo imaging study that reported cross-sectional areas over a range of internal pressures. The compliance of the tracheal region was matched to the in vivo data for a specific flexible resin by iteratively selecting the thicknesses and other dimensions of tracheal wall components. Seven iterative models were produced and illustrated highly non-linear expansion consisting of initial rapid size increase, a transition region, and continued slower size increase as pressure was increased. Thickness of the esophageal interface membrane and initial trachea indention were identified as key parameters with the final model correctly predicting all phases of expansion within a value of 5% of the in vivo data. Applications of the current biomechanical model are related to endotracheal intubation and include determination of effective mucus suctioning and evaluation of cuff sealing with respect to gases and secretions.

A Method to Monitor Vacuum Degree Using Capacitive Partial Discharge Coupler

Internal pressure of vacuum interrupter (VI) is one of the most important parameters in VI operation and may increase due to the outgassing from the materials inside VI or gas permeation through metal flange or ceramic vessel. The increase of the pressure above a certain level leads to the failures of switching or insulation. Therefore, an effective pressure check of VI is essential and an analysis of partial discharge (PD) characteristics is an effective monitoring method to identify the degree of the internal pressure of VI. This paper introduces a research work on monitoring the internal pressure of VI by analyzing PDs which were measured using a capacitive PD coupler. The authors have developed cost effective capacitive coupler based on the ceramic material that has an excellent insulation properties and the main component of the capacitive coupler is made by SrTiO3. Detectable internal pressure range and distinguishability of the internal pressure of VI were investigated. From the PD tests results, the internal pressure range, from <TEX>$10^{-2}$</TEX> torr to 500 torr, can be monitored by PD measurements using the capacitive coupler and PD inception voltage (PDIV) follows the Paschen's law. In addition, rise time of PD pulse at 13.2kV decreases with the increase of the internal pressure of VI.

Constitutive function, residual stress, and state of uniform stress in arteries

Fung (1983) has conjectured that the residual stress in an artery distributes itself in such a way to assure that the circumferential stress is uniform across the artery wall under physiological conditions. In this work, we identify the entire class of constitutive functions for which the circumferential stress is uniform across the artery wall when it is subjected to an internal pressure. It is found that these constitutive functions do not necessarily endow residual stresses. Furthermore, a subset of the class of the constitutive functions is identified for which the circumferential stresses are uniform for the entire range of internal pressures. The constitutive functions in this sub-class are found to have zero residual stress. It is the inhomogeneity, rather than residual stress, that assures uniform circumferential stresses. We also examine the possibility of utilizing these constitutive functions in the design and fabrication of an engineered blood vessel with optimal mechanical properties.

Structural analysis of a power plant component using a stress-range-dependent creep-damage constitutive model

Structural analysis and design of power plant components requires us to take into account inelastic deformation and material damage processes for wide stress and temperature ranges. The aim of this paper is to discuss a stress-range-dependent model of creep and damage for advanced heat resistant steels under stationary loading conditions. An emphasis is placed on the transition from the power law to the viscous creep as well as the ductile–brittle transition of the damage mode. The creep constitutive equation is proposed which includes both the linear and power-law response functions of stress. Two internal state variables are introduced to account for the material softening and brittle damage, respectively. The corresponding evolution equations are developed to fit the stress-range dependence of the creep rupture strength. To evaluate the response functions of stress and the material constants, recently published experimental data for a 9% Cr steel are applied. Examples are presented to illustrate basic features of the stress redistribution and the damage evolution in pressurized thick-walled structures. The analysis shows that for a certain specified range of internal pressure the character of the stress distribution is essentially influenced by the change of the creep deformation mechanisms. The corresponding stress levels in the steady creep state suggest that the brittle damage processes should be taken into account for the life-time estimations.

Prediction of thermoplastic failure of a reactor pressure vessel under a postulated core melt accident

This paper presents the lower-head failure calculations performed for a postulated accident scenario in a commercial nuclear power plant. A postulated 1 inch break in the primary coolant circuit leads to dry-out and subsequent meltdown of the core. The reference plant is a pressurized-water reactor without penetrations in the reactor vessel lower head. The molten core material accumulates in the lower head, eventually causing failure of the vessel. The analysis investigates flow conditions in the melt pool, temperature evolution in the reactor vessel wall and structure mechanical evaluation of the vessel under strong thermal loads and a range of internal pressures. The calculations were performed using the ADINA finite-element codes. The analysis focusses on the failure processes, and time and mode of failure. The most likely mode of failure at low pressure is global rupture due to gradual accumulation of creep strain over a large part of the heated area. In contrast, thermoplasticity becomes important at high pressure or following a pressure spike and can lead to earlier local failure. In situations in which part of the heat load is concentrated over a small area, resulting in a hot spot, local failure occurs, but not until the temperatures are close to the melting point. At low pressure in particular, the hot spot area remains intact until the structure is molten across more than half of the thickness.

Calculating the performance of sprinkler pipe exposed to fire conditions

A computer model for predicting the onset of yielding in pressurized plastic pipe exposed to fire conditions has been developed. The model couples the aspects of solid mechanics and heat transfer to simulate the pipe performance. The von Mises yield criterion from solid mechanics is applied to predict yielding resulting from the plane stress induced in the pipe wall from the internal water pressure. The heat transfer analysis is performed via a finite difference approach to estimate the temperature profile in the pipe wall resulting from exposure to a heated ceiling jet. Results are reported of estimates for the time to yielding for 1 and 1 1/4 in. (25 and 32 mm) SDR-11 polybutylene pipe at three selected locations relative to the fire considering a range of internal pressures and water flow rates inside the pipe.