Hydrostatic Behavior Research Articles

Density dependent constitutive model for Bi-2212 powder compression deformation

Bi-2212 HTS materials are fabricated into multi-filamentary wires via powder-in-tube (PIT) method followed by proper heat treatment to obtain superconductivity, but how to predict the large compression deformation behaviors of the Bi-2212 powder is critical to design the processing of the Bi-2212 HTS wire. Drucker Prager/Cap (DPC) model was the most commonly used model for powders including Bi-2212 with soil-like mechanical behavior to consider its shear failure as well as hydrostatic compression. However, the parameters for DPC Cap evolve with densities change and the original model is inadequate to precisely describe the densification process of Bi-2212 powder with large strain. In this study, the modified DPC model with density dependent parameters was introduced for Bi-2212 powder compressions by measuring the failure strength and hydrostatic compressive behavior under different density states. The DPC yield surface was plotted with an evolution trend of non-linear outward expansion with density increased. FEM model of uniaxial compression based on the as-introduced model was built with subroutine VUSDFLD applied. The distribution of Mises stress and relative density were analyzed. The axial stress-density curve for FEM and experimental results were normalized and quantitively evaluated by Mean Square Error (MSE). The introduced model shows good convergence and could match the experimental results well with normalized MSE of 0.000207 and Root Mean Square Error (RMSE) of 0.0144, indicating the mean error percentage of 1.44%. The model introduced in this article provides supports toward large strain deformation simulation of Bi-2212 powder.

Experimental Investigation of Sand Subjected to High Stress Levels in Wet and Dry Conditions.

This work aimed to understand the mechanical behavior of siliceous and calcareous sand materials under uniaxial confined compression loading at high stress levels. For this purpose, a series of quasi-oedometric compression tests were conducted on sand materials, to examine the effects of grain size, nature, and moisture contents on the soil crushability and the compression behavior, using an upgraded thick pressure vessel device that can reach mean stress up to 500 MPa. All samples were prepared using an aspect ratio of 1:1 (diameter: height), placed inside a high strength steel vessel, and compressed at a uniform axial displacement rate of 5 µm/s. The vessel is instrumented with multiple strain gauges allowing for the characterization of the hydrostatic and deviatoric behavior of each test. The results of quasi-oedometric tests, conducted on these types of sand, up to a passive confinement of 500 MPa, show that particle breakage is enhanced by the presence of water. It was noticed that, for siliceous sand, smaller particles break more than larger particles, and that the calcareous grains manifest a rapid response to axial stress compared to siliceous sand. Testing various soil properties shows a great potential to better characterize the sensitivity to breakage of soils. Lastly, a post-mortem analysis of samples before and after testing, using the X-ray micro-tomography technique, was applied to study the mechanical damage of sand specimens.

New Triaxial Connection Safety Factor for Tubular Design

Summary The American Petroleum Institute (API) equation for internal leak of API connections is uniaxial because it ignores axial force and external backup pressure. The ISO 13679 (2002) standard for qualification of premium connections is biaxial at best. It includes tension/compression but ignores backup pressure for both internal and external leak tests. For tubular design, this paper introduces a new fully triaxial safety factor for threaded connections with dependence on thread shear and hydrostatic pressure. Triaxial hydrostatic behavior is modeled with the mean normal stress, and thread shear behavior is modeled with the shear component of the von Mises stress. A leak line for use like the pipe body ellipse is proposed for quick leak assessment. Leak ratings and correlation with finite element analysis (FEA) results are presented for an example case of a 7-in. 35-ppf N80 long-thread-casing (LTC) connection. The new triaxial safety factor with two connection constants applies to all types of threaded connections, including tubing, casing, and drillpipe, so long as the two constants are evaluated with appropriate but simple physical tests.

Experiments in measuring dynamic hydrostatic constitutive properties of soft materials

An experimental investigation is conducted to develop, analytically model, and test a novel facility to obtain the dynamic hydrostatic constitutive properties and behavior of soft materials. The novel facility is an underwater shock tube consisting of two aluminum sections and an optically-clear acrylic section in between, all filled with water. A striker-piston configuration is used to provide an axial shock loading to one end of the assembly. Dynamic pressure sensors provide pressure data along the entire length of the assembly, including at the specimen location in the acrylic section. 3D Digital Image Correlation (DIC) is used in conjunction with high-speed photography to provide full-field deformation data of the specimen to obtain volumetric strain. The mismatch in acoustic impedance between the aluminum and the acrylic sections causes a reduction in the amplitude of the pressure pulse by 33%. The pressure pulse also undergoes appreciable dispersion in the acrylic section. Fluid-structure interaction (FSI) models are considered and applied to understand the dispersion characteristics of the axially propagating pressure pulse. The dynamic hydrostatic constitutive response of closed-cell polyvinyl chloride (PVC) foam is obtained at a volumetric strain rate of 100s−1. The bulk modulus at this strain rate for H130 PVC foam is measured to be 106.97 ± 3.11MPa. This is more than double that of the quasi-static (0.001s−1) value of 46.71 ± 1.91MPa, indicating a strong effect of strain rate on the material's response. The buckling pressure is also found to be strain rate dependent, with the dynamic buckling occurring at 3.09 ± 0.12MPa and quasi-static buckling occurring at 1.39 ± 0.17MPa.

Triaxial mechanical behaviour of hybrid basalt\u2013polypropylene fibre-reinforced concrete: The effect of micro-fibres at multi scale levels

The triaxial mechanical properties of hybrid basalt–polypropylene fibre-reinforced concrete (HBPRC) were investigated in detail. The different effects of micro-basalt fibre (BF) and micro-polypropylene fibre (PF) on the triaxial properties of concrete were revealed. The strength criterion for HBPRC was established. The results showed that the hydrostatic behaviour, volumetric strain, peak deviatoric stress, elastic modulus, and Poisson’s ratio of HBPRC are affected by not only the confining pressure but also the BF and PF. The confining pressure gradually changes the failure mode of HBPRC from split failure to shear failure and extrusion plastic flow failure. The BF and PF mainly improve the strength and deformation performance of concrete, respectively. A nonlinear Mohr–Coulomb (M–C) strength criterion for HBPRC, which takes into account the fibre effect, is established. The calculated results performed using the proposed criterion agree well with the experimental results.

Numerical and experimental study of mechanical properties and hydrostatic behavior of PVC-O material for drinking water pipes

     This study investigates the mechanical properties for oriented polyvinyl chloride PVC-O material from three different directions of stress application.  A PVC-O 500 pipe material has been studied in terms of mechanical properties in three different directions (0o, 45o, 90o). Tensile strength at yield and percent elongation at fracture has been determined in all three directions. Two types of end caps (A and B) have been used to evaluate the pipe's hydrostatic strength. Results showed that molecular orientation has a significant impact on the pipe strength and ductility in different directions. Increasing the molecular orientation in the direction of the hoop (90o direction), the strength increased to 91 MPa compared with 0o and 45o direction, which were 49 MPa and 61 MPa, respectively. Results showed that the percentage of elongations was 200%, 76 %, and 61% for 0o, 45o, and 90o directions, respectively. The burst pressure for type A and B end caps was 6.22 MPa. Finite element analysis by SolidWorks 2018 simulation has been employed; the FEA has showed a good agreement with experimental results with a maximum difference of 5.16%. The FE results also showed that end caps affect stress distribution around the pipe during the hydrostatic test specially when using type B end caps. It's also concluded that both types of end caps cause stress concentration near the edges of the caps.

Parameterization of hydrostatic behavior of deployable hypar umbrellas as flood barriers

Deployable four-sided hyperbolic paraboloid (hypar) umbrellas inspired by the architecture of Félix Candela have been conceptualized as a feasible countermeasure against surge-induced coastal inundation. Referred as Kinetic Umbrellas, such structures may readily deploy from an open canopy to form a physical barrier prior to imminent coastal hazard scenarios. This paper presents a parametric investigation into the structural behavior of Kinetic Umbrellas exhibiting rise/area (r∕A) ratios from 0 to 0.045 m−1 subject to hydrostatic inundation ranging from 50% to 100% of the total deployed height. An analytical method for the discretization of hydrostatic forces on tilted hypar manifolds was developed and validated, enabling the determination of internal forces and deformations within the umbrella and supporting column via finite element modeling. All critical demands were highly influenced by the lateral column rigidity for any given r∕A, to which a ratio of 0.03 m−1 was revealed as optimal for the minimization of shell stresses. Longitudinally asymmetric umbrellas were also analyzed and were discovered to exhibit inferior structural performance relative to their doubly-symmetric counterparts. Finally, concrete reinforced with glass fiber polymers was demonstrated as a feasible material for such structures even at the maximum level of inundation. This work ultimately provides insight into the holistic response of Kinetic Umbrellas to aid their prototyping and design for practical engineering applications.

Hydrostatic limit for the symmetric exclusion process with long jumps: supper-diffusive case

Hydrostatic behavior for the one dimensional exclusion process with long jumps in contact with infinite reservoirs at different densities are derived. The jump rate is described by a transition probability p which is proportional to | · |−(γ+1) for 1 < γ < 2 (supper-diffusive case). The reservoirs add or remove particles with rate proportional to κ > 0.

Hydrodynamics for SSEP with Non-reversible Slow Boundary Dynamics: Part I, the Critical Regime and Beyond

The purpose of this article is to provide a simple proof of the hydrodynamic and hydrostatic behavior of the SSEP in contact with slowed reservoirs which inject and remove particles in a finite size windows at the extremities of the bulk. More precisely, the reservoirs inject/remove particles at/from any point of a window of size K placed at each extremity of the bulk and particles are injected/removed to the first open/occupied position in that window. The hydrodynamic limit is given by the heat equation with non-linear Robin boundary conditions or Neumann boundary conditions, the latter being in the case when the reservoirs are too slow. The proof goes through the entropy method of Guo, Papanicolaou and Varadhan. We also derive the hydrostatic limit for this model, whose proof is based on the method developed by Landim and Tsunoda. We observe that we do not make use of correlation estimates in none of our results.

Hydrodynamics for SSEP with non-reversible slow boundary dynamics: Part II, below the critical regime

The purpose of this article is to provide a simple proof of the hydrodynamic and hydrostatic behavior of the SSEP in contact with reservoirs which inject and remove particles in a finite size windows at the extremities of the bulk. More precisely, the reservoirs inject/remove particles at/from any point of a window of size $K$ placed at each extremity of the bulk and particles are injected/removed to the first open/occupied position in that window. The reservoirs have slow dynamics, in the sense that they intervene at speed $N^{-\theta}$ w.r.t. the bulk dynamics. In the first part of this article, we treated the case $\theta>1$ for which the entropy method can be adapted. We treat here the case where the boundary dynamics is too fast for the Entropy Method to apply. We prove, using duality estimates inspired by previous work by Erignoux, Landim and Xu, that the hydrodynamic limit is given by the heat equation with Dirichlet boundary conditions, where the density at the boundaries is fixed by the parameters of the model.

Novel test method for the hydrostatic properties of syntactic foams

Hydrostatic properties are important in characterizing the syntactic foams in subsea applications. But they are rarely studied due to the lack of standard test methods and instruments. A novel method of characterizing the hydrostatic properties of syntactic foams based on the pressure build-up and the water input has been developed. A test system has been built with standard and easily accessible parts and components. A demonstration experiment has been carried out on two types of syntactic foams. The effect of the preliminary pressure cycles on the bulk modulus has been studied. The distinct hydrostatic yield and crush behaviors of the two types of syntactic foams are revealed in the test results. The Type I syntactic foam, which is composed of a lighter but weaker type of glass bubble, exhibits a hydrostatic compressive behavior dominated by the properties of the filler. The Type II syntactic foam, which is composed of a stronger but heavier type of glass bubble, exhibits a catastrophic failure mechanism involving both the crushing of the glass bubbles and the failure of the matrix material. With the developed test method, further investigations into the hydrostatic behaviors of the syntactic foams are possible.

Elastic and hydrostatic behaviour of a zinc dietary supplement, zinc glycinate hydrate.

Coordination polymer based dietary supplement tablets are commonly consumed in our daily life and play an important role in the pharmaceutical industry. To fully understand their tableting process, their mechanical properties need to be comprehensively studied. In this work, the elastic and hydrostatic behaviour of a zinc supplement, zinc glycinate hydrate (Zn[O2CCH2NH2]2·H2O), have been studied via density functional theory (DFT) calculations and high-pressure synchrotron powder X-ray diffraction. This material has a pseudo-layered structure and can be successfully exfoliated into nanosheets. The DFT calculated elastic moduli along the principal axes (13.84–36.11 GPa) indicate a significant elastic anisotropy of ZnG as expected for a layered system, and the directional dependent elastic modulus can be corroborated with the underlying atomic structure. In addition, the calculated B/G ratios (1.30–3.83) according to Pugh's criterion reveal that ZnG could be brittle under uniaxial stress (B and G are bulk modulus and shear modulus, respectively). Furthermore, the measured B is ∼31 GPa, which lies in the middle of the values between inorganic dietary supplements and small organic drug crystals. These results provide some quantitative information about the tableting process of the hybrid dietary supplement which could be different from their inorganic and organic pharmaceutical counterparts.

Theoretically based hydrostatic stress analysis in short fiber composites for second stage creep using Legendre polynomials by micromechanics model and golden functions

In this research work, hydrostatic stress behavior of creeping composite is predicted using Legendre polynomials (special functions), governing and basic equations, micromechanics model and golden functions. Prediction of the creep hydrostatic stress behavior is experimentally complicated and intricate and sometimes is impossible. Significant applications of the present model are in the fields of plasticity and elasticity analyses, nanocomposites, turbine blades and disks design. The present analytical method can prevent from difficulties arising from the experimental and finite element methods. Also, the regions under the creep rupture and debonding are predicted by finite element method. Finally, because of using the analytic, controller and golden functions, good and reasonable agreements are found among FEM, experimental method and present analytical method results.

A first principle study of the perovskite lanthanum aluminate

A self-consistent first-principles calculation with a precise hybrid PBEsol functional, Density Functional Theory (DFT) have been used to investigate the stability, elastic, mechanical, electronic, acoustic and thermodynamic properties of the cubic perovskite Lithium Aluminate (LaAlO3). An investigation of the stability showed that the computed lattice parameter LaAlO3 is stable, results also show that the lattice of LaAlO3 becomes more distorted and deviates from the hydrostatic behavior as pressure is increased up to 11 GPa, after this limit, the structure encounter a phase shift, which is seen from the nature of the thermal properties of heat capacity. LaAlO3 is thermos conversion-efficient cubic perovskite with its strong phonon scattering interactions resides mostly unclear. The energy band structure appears to display an indirect band gap insulator, with Γ−R separating the valence and conduction bands. Pressure dependence of cubic elastic Moduli, elastic wave velocities, Debye temperature and the density of states of LaAlO3 were calculated, our results appear to converge with available experimental data. The elastic constants reveal the fact that the crystal is stable and show nature of crispness. The thermal characteristics were computed within the hybrid functional PBEsol using the Debye-Waller model and response functions. Lattice dynamics investigation of the perovskite thermoelectric LaAlO3 are investigated with the single-crystal first-principles simulations and compared against inelastic neutron scattering (INS) at 100 K. Our ab-initio calculations of LaAlO3 show a free asymmetry in the first nearest-neighbor peak. In addition, our first principles calculations data reveal stiffer bonding at the anion sites, which is in good agreement with the partial phonon densities of states from INS. The 4-dimensional phonon-dispersion surfaces of LaAlO3, have been mapped and it is found that the origins of the ionic potential an-harmonicity being responsible for the unique behavior and phonon properties of LaAlO3. The latter results provide clear evidence for the anharmonicity phonon distribution associated with the resonant bonding leading to a ferroelectric nature.

Hydrostatic pressure–dependent wear behavior of thermoplastic polymers in deep sea

It is generally acknowledged that wear behavior of approved water‐lubricated thermoplastic polymers are not susceptible to hydrostatic pressure in seawater environment. However, in our recent study reported in this letter, it has been shown that the wear behavior of thermoplastic polymers sliding in seawater is strongly dependent on the hydrostatic pressure. The correlation between hydrostatic pressure and wear rates of thermoplastic polymers can be expressed in an identical form of exponential function, which has been found to be susceptible to some factors, such as polymer property, seawater absorption, filler type, sliding condition, and counterpart material. Moreover, in this letter, a primary model has been proposed to illuminate the effect of hydrostatic pressure on the wear behavior of thermoplastic polymers sliding in deep sea.

A hydrostatic model of the Wirtz pump

The Wirtz pump is not only an excellent example of alternative technology, using as it does the kinetic energy of a stream to raise a proportion of its water, but its mathematical modelling also poses several intriguing problems. We give some history of the Wirtz pump and describe its operation. Taking a novel dynamical systems approach, we then derive a discrete mathematical model in the form of a mapping that describes its hydrostatic behaviour. Our model enables us to explain several aspects of the behaviour of the pump as well as to design one that gives approximately maximal, and maximally constant, output pressure.

Mechanical Behavior of Metal under Hydrostatic Pressure and Low Temperature

The current work describes the behavior of metal under hydrostatic pressure and low temperature using finite element concept. This study was carried out in three stages: modelling, analysis and post processing. Structural steel and aluminum are tested at 600 bar pressure and 4°C temperature. Solid model of cylindrical shape having internal diameter 420 mm and thickness 25 mm was created and same was investigated for stress analysis using ANSYS 17.2 APDL emphasizing on hydrostatic behavior. Failure criterion is based on maximum stress to determine the onset of damage in material. In post processing phase, the material was checked for deformation and equivalent Von-Mises stresses developed around the material. The objective of this present paper is of two fold. Firstly the investigation of metal under high pressure through stress analysis is carried out followed by metallographic studies. The stress analysis results suggest that metals like steel which has BCC structure shows the remarkable decrease in ductility over the range of temperature. The maximum Von Mises stresses that the material can with stand were 65.14 MPa and 56.38 MPa for structural steel and aluminum respectively and revealed having high factor of safety for desired applications. It can be said that aluminum having FCC crystal structure are stiff and ductile even at low subzero temperature. The theoretical calculations are done and they are in agreement with the experimental results. It can be anticipated that influence of high pressure and low temperature can be criticized by two factors in terms of flow strength and fracture strength of metal. Ductile to Brittle Transition Temperature (DBTT) plays a vital role and can be considered as a measure of behavior of metal under high pressure and low temperature. So, it revels that the crystal structures of metals is the major factor which affects the behavior of metal which eventually affect the ductility and toughness of metal when subjected to high pressure and low temperature operations. However, in thick material the question of structural discontinuity and stress concentration is still regarded as open for further scope of study.

A molecular dynamics investigation of hydrostatic compression characteristics of mineral Jennite

This paper focuses on the study of mechanical behavior and deformation of mineral Jennite, under isothermal hydrostatic compression using Molecular Dynamics (MD) modeling. Atomistic structure of mineral Jennite is considered as a choice for representing calcium silicate hydrate (C-S-H), a key constituent in hydrated cement paste. The present work focuses and presents a molecular dynamics simulation approach to ascertain hydrostatic compression characteristics of mineral Jennite. The pressure–specific volume, and specific internal energy–specific volume relationships under isothermal hydrostatic compression conditions were determined. For the pressures ranging from 0.0001GPa to 5GPa, computational modeling results indicated that a linear relationship may be sufficient when describing the pressure–specific volume relationship. The results obtained in this study compared well with experimental and theoretical results recently published by other researchers. Additionally, a quadratic function was found to be appropriate to describe the specific energy–specific volume relationship, for the same pressure range used for studying the pressure–specific volume relationship. The pressure–specific volume, and specific internal energy-specific volume relationships reported in this paper are useful for further estimation of pressure–specific volume constitutive Hugoniot of the nanoscale mineral Jennite. Additionally, MD approach discussed and presented in this paper can be applied to understand hydrostatic compression behavior and deformation characteristics of other atomistic structures representing C-S-H. Further, the computational material modeling approach discussed in this paper provides an alternative methodology that can aid in the understanding of the deformation mechanisms and developing constitutive relationships from atomistic structures of materials.

Exclusion Process with Slow Boundary

We study the hydrodynamic and the hydrostatic behavior of the Simple Symmetric Exclusion Process with \emph{slow boundary}. The term \emph{slow boundary} means that particles can be born or die at the boundary sites, at a rate proportional to $N^{-\theta}$, where $\theta > 0$ and $N$ is the scaling parameter. In the bulk, the particles exchange rate is equal to $1$. In the hydrostatic scenario, we obtain three different linear profiles, depending on the value of the parameter $\theta$; in the hydrodynamic scenario, we obtain that the time evolution of the spatial density of particles, in the diffusive scaling, is given by the weak solution of the heat equation, with boundary conditions that depend on $ \theta $. If $\theta \in(0,1)$, we get Dirichlet boundary conditions, (which is the same behavior if $\theta=0$, see \cite{f}); if $\theta=1$, we get Robin boundary conditions; and, if $\theta\in(1,\infty)$, we get Neumann boundary conditions.

Changes in micromechanical properties of Na-montmorillonite caused by CO2/H2O sorption

CO2/H2O intercalation causes changes in the elastic mechanical properties of clay. This phenomenon is critical to geologic carbon sequestration (GCS) and enhancing oil rate (EOR) via CO2 adsorption. In this work, the elastic stiffness and hydrostatic mechanical behavior of Na-montmorillonite (MMT) exposure to variable component of CO2/H2O mixture are investigated using combinations of Monte Carlo and Molecular Dynamic methods. In the hydrostatic test simulation of 1W and 2W hydrated state, volume and basal spacing d001 linearly decrease with the increasing hydrostatic pressure. Moreover, gradients of 1W hydrated state are smaller than that of the gradients of 2W hydrated state. The linear gradient is related to the elastic modulus. Therefore higher hydrated state results in softer structure. Additionally, the yielding bulk modulus linearly decreases with the pressure. The decreasing gradient almost keeps at a constant of 1.0GPa/GPa with variable component of CO2/H2O. At the super critical condition of CO2 (P=0.01GPa, T=304.5K), the elastic stiffness fluctuates with the variable component of H2O/CO2. CO2 intercalation strongly affects the out-of-plane elastic stiffness while has little influence on the in-plane stiffness.