scholarly journals Modeling solvent dynamics in polymers with solvent-filled cavities

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Michele Curatolo ◽  
Paola Nardinocchi ◽  
Luciano Teresi
Keyword(s):  
Hollow Spheres ◽  
Polymer Gels ◽  
Finite Element Code ◽  
Cavity Volume ◽  
Solvent Dynamics ◽  
Stress Diffusion ◽  
External Conditions ◽  
Stress States ◽  
As Stress ◽  
The Mathematical Model

AbstractDynamics of solvent release from polymer gels with small solvent-filled cavities is investigated starting from a thermodynamically consistent and enriched multiphysics stress-diffusion model. Indeed, the modeling also accounts for a new global volumetric constraint which makes the volume of the solvent in the cavity and the cavity volume equal at all times. This induces a characteristic suction effect into the model through a negative pressure acting on the cavity walls. The problem is solved for gel-based spherical microcapsules and microtubules. The implementation of the mathematical model into a finite element code allows to quantitatively describe and compare the dynamics of solvent release from full spheres, hollow spheres, and tubules in terms of a few key quantities such as stress states and amount of released solvent under the same external conditions.

Deformation Analysis for Coal and Gas Outburst Cavity

2011 ◽  
Vol 121-126 ◽  
pp. 2607-2613
Author(s):  
Qian Ting Hu ◽  
Wen Bin Wu ◽  
Guo Qiang Cheng
Keyword(s):  
Damage Zone ◽  
Coal And Gas Outburst ◽  
Gas Content ◽  
Combination Method ◽  
Deformation Analysis ◽  
Failure Zone ◽  
Finite Element Code ◽  
Cavity Volume ◽  
Gas Emission ◽  
Gas Outburst

Outburst cavity formed during coal and gas outburst can be pear shaped, elliptical, or just like an irregularly elongated ellipsoid, its capacity is always smaller than the volume of ejected coal. And the gas emission quantity is almost 4 to 10 times as gas content in ejected coal. These are two different expressions of the same problem. To find the reasons for the decrease of outburst cavity volume and the increase of gas emission quantity per ton, by using the finite element code ANSYS, the damage zone and the failure zone of the outburst cavity were determined based on the static and dynamic combination method. In this paper, the reason for the decrease of the outburst volume was explained.

A Mechano-Chemical Coupling for Hydrogen Diffusion in Metals Based on a Thermodynamic Approach

2014 ◽  
Vol 353 ◽  
pp. 286-291 ◽  
Author(s):  
Nicolas Creton ◽  
Steeve Dejardin ◽  
B. Grysakowski ◽  
Virgil Optasanu ◽  
Tony Montesin
Keyword(s):  
Hydrogen Diffusion ◽  
Thermodynamic Approach ◽  
Finite Element Code ◽  
Diffusion Mode ◽  
Significant Progress ◽  
Diffusion Coupling ◽  
Metal Parts ◽  
Stress Diffusion ◽  
Steel Tank ◽  
Chemical Coupling

Hydrogen diffusion in metals is still an ongoing topic of research due to its technical relevance (hydrogen embrittlement, hydrogen storage...). In the last decades, significant progress in understanding the time evolution of the hydrogen concentration in solids was completed. This paper presents a modeling of hydrogen diffusion with a general and thermodynamically based diffusion concept coupled with mechanical and chemical aspects. This model was previously used to simulate the oxidation of a metal [1][2]. This concept has been upgraded to offer a thoroughly macroscopic behavior law used to simulate hydrogen diffusion in metal parts under mechanical loadings. The thermodynamic approach of the stress-diffusion coupling was implemented in a finite element code in order to study the hydrogen diffusion mode into a strained metal. Simulations were performed on a cylindrical austenitic steel tank under important internal pressure. The results of this study allow us to understand how hydrogen diffusion and mechanical stresses are mutually induced and modified.

scholarly journals IN SILICO MODELING OF THE REDOX METABOLISM IN HUMAN ERYTHROCYTES

2016 ◽  
Vol 1 ◽  
pp. 39-46
Author(s):  
Olga Dotsenko
Keyword(s):  
Redox State ◽  
Physiological State ◽  
Pentose Phosphate ◽  
Human Erythrocytes ◽  
Final Model ◽  
In Silico Modeling ◽  
Long Time ◽  
External Conditions ◽  
The Many ◽  
The Mathematical Model

There was elaborated the mathematical model of erythrocytes metabolism, including glycolysis (Embden-Meyerhof pathway), pentose phosphate pathway, metHb restoration pathway, Н2О2 metabolism reaction. The final model includes 50 reactions and 60 metabolites. Within the model was studied the change of activity of some enzymes and concentrations of metabolites in stationary state, that take part in the processes of utilization of oxygen active forms and restoration of metgemoglobin, depending on amount of exogenous and endogenous Н2О2. There was demonstrated the threshold character of changes of the many studied parameters, that testifies that the cells can be practically in physiological state at the change of external conditions for rather long time. There was carried out an assessment of redox-state of erythrocytes at oxidizing load: was demonstrated the change of EGSSG/2GSH, ENADP+/NADPH and ENAD+/NADH from the concentration of endogenous Н2О2. There was established that in the studied diapason of concentrations of endogenous Н2О2 was observed the high slope of the change of EGSSG/2GSH, that was not observed for ENADP+/NADPH and the other redox-pairs. The results of modeling coincide with existing views on the functioning of enzymes of antioxidant protection in human erythrocytes and testify to the possibility of practical use of the model

scholarly journals Dehydration-induced mechanical instabilities in active elastic spherical shells

2021 ◽  
Vol 477 (2254) ◽  
Author(s):  
M. Curatolo ◽  
G. Napoli ◽  
P. Nardinocchi ◽  
S. Turzi
Keyword(s):  
Analytical Model ◽  
Numerical Experiments ◽  
Water Concentration ◽  
Closed Shell ◽  
Natural World ◽  
Cavity Volume ◽  
Stress Diffusion ◽  
Elastic Instabilities ◽  
Simplifying Assumptions ◽  
Set Up

Active elastic instabilities are common phenomena in the natural world, where they have the character of sudden mechanical morphings. Frequently, the driving force of the instability mechanisms has a chemo-mechanical nature, which makes the instabilities very different from the standard elastic instabilities. In this paper, we describe and study the active elastic instability occurring in a swollen spherical closed shell, confining a water-filled cavity, during a dehydration process. We set up a few numerical experiments based on a stress-diffusion model to give an insight into the phenomenon. Then, we present a study that looks at the chemo-mechanical problem and, through a few simplifying assumptions, allows us to derive a semi-analytical model of the phenomenon. It takes into account both the stress state and the water concentration in the walls of the shell at the onset of the instability. Moreover, it considers the invariance of the cavity volume at the onset of instability, which is due to the impossibility of instantaneously changing the cavity volume filled with water. Eventually, it is shown that the semi-analytic model matches very well the outcomes of the numerical experiments far from the initial regime; the ranges of validity of the approximated analytical model are also discussed.

scholarly journals Investigation of robust ship course control based on auxiliary loop method

2021 ◽  
pp. 248-252
Author(s):  
Aliya Imangazieva
Keyword(s):  
Control Law ◽  
Sea Waves ◽  
Unknown Parameters ◽  
External Disturbances ◽  
Loop Method ◽  
Wind Gusts ◽  
Course Control ◽  
External Conditions ◽  
Yaw Angle ◽  
The Mathematical Model

A novel robust control law is investigated on the problem of ship stabilization on the trajectory, which allows one to compensate perturbations in the parameters of the mathematical model of ship dynamics in cases of their changes caused by external conditions, namely: sea waves, currents, wind gusts, etc. To implement the proposed control law, only measured adjustable values are required such as the yaw angle and the control action that is the angle of the rudder of the ship. The synthesized ship course control system was investigated in MATLAB. The law of controlling the ship’s course with unknown parameters and external disturbances in the power supply is proposed. The design of the control law is based on a robust auxiliary loop algorithm and Khalil observers. The simulations illustrate the efficiency of the proposed control law.

scholarly journals Swelling and shrinking in prestressed polymer gels: an incremental stress–diffusion analysis

2019 ◽  
Vol 475 (2230) ◽  
pp. 20190174 ◽  
Author(s):  
Marco Rossi ◽  
Paola Nardinocchi ◽  
Thomas Wallmersperger
Keyword(s):  
Chemical Potential ◽  
Polymer Gels ◽  
Mechanical Analysis ◽  
Test Case ◽  
Diffusion Analysis ◽  
Stress Diffusion ◽  
Nonlinear Stress ◽  
Deformation State ◽  
Poroelastic Theory ◽  
Elastic Constraint

Polymer gels are porous fluid-saturated materials which can swell or shrink triggered by various stimuli. The swelling/shrinking-induced deformation can generate large stresses which may lead to the failure of the material. In the present research, a nonlinear stress–diffusion model is employed to investigate the stress and the deformation state arising in hydrated constrained polymer gels when subject to a varying chemical potential. Two different constraint configurations are taken into account: (i) elastic constraint along the thickness direction and (ii) plane elastic constraint. The first step entirely defines a compressed/tensed configuration. From there, an incremental chemo-mechanical analysis is presented. The derived model extends the classical linear poroelastic theory with respect to a prestressed configuration. Finally, the comparison between the analytical results obtained by the proposed model and a particular problem already discussed in literature for a stress-free gel membrane (one-dimensional test case) will highlight the relevance of the derived model.

The Use of Non-Dimensional Parameters to Study Stress in Lithium-Ion Battery Electrode Storage Particles

2012 ◽  
Author(s):  
Rajlakshmi T. Purkayastha ◽  
Robert M. McMeeking
Keyword(s):  
Stress Responses ◽  
Maximum Stress ◽  
Lithium Ion ◽  
Particle Morphology ◽  
Mechanical Degradation ◽  
Stress Diffusion ◽  
Battery Electrode ◽  
Dimensional Parameters ◽  
As Stress ◽  
Coupled Stress

Mechanical degradation is thought to be one of the causes of capacity fade within Lithium-Ion batteries. In this work we develop a coupled stress-diffusion model for idealized spherical storage particles, which is analogous to the development of thermal strains. We then non-dimensionalize the model and identify three important parameters that control the development of stress within these particles. We can therefore use a wide number of values for these parameters to make predictions about the stress responses of different materials. The maximum stress developed within the particle for different values of these parameters are plotted as stress maps. A two dimensional model of a battery was then developed, in order to study the effect of particle morphology.

Vacuum Induction Melting and Investment Casting Technologies Tailored to Near-Gamma TiAl Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 1463-1468 ◽  
Author(s):  
Antonín Dlouhý ◽  
Kateřina Dočekalová ◽  
Ladislav Zemčík
Keyword(s):  
Investment Casting ◽  
Cost Effective ◽  
Melting Process ◽  
Vacuum Induction Melting ◽  
Crucible Wall ◽  
Induction Melting ◽  
Ceramic Shell ◽  
Shell Mould ◽  
Stress States ◽  
As Stress

The present study focuses on vacuum induction melting and investment casting of neargamma TiAl intermetallic alloys. The attention is mainly given to a cost-effective melting process in which a primary alloy ingot is re-melted in a ceramic crucible and cast into a ceramic shell mould. Two types of crucibles (based on Al2O3 and Y2O3) are considered. The most detrimental reactions that govern the contamination of the molten alloy with ceramic particles were determined. Results suggest that the crucible wall attack can be considerably limited by using either the Y2O3 (with no SiO2-type binder) or Al2O3 crucibles with a suitable coating. After pouring, a mechanical interaction associated with different thermal expansions of TiAl casts and ceramic shell moulds can result in serious product damage. A simple 1D-1D model of the cooling process was formulated and the heat flow as well as stress states in the cast-mould system were numerically solved. Process parameters (melt superheat, initial mould temperature, cooling kinetics and mould composition) were optimized in order to reduce the stress in the casts. The optimized parameters delimited a processing window in which complex-shaped TiAl castings like turbocharger wheels can be fabricated.

Fluid Transport in Gels

2015 ◽  
Author(s):  
Masao Doi
Keyword(s):  
Continuum Model ◽  
Fluid Transport ◽  
Polymer Gels ◽  
Coupling Model ◽  
Mechanical Forces ◽  
Mechanical Coupling ◽  
Mechanical Responses ◽  
Solvent Dynamics ◽  
Solvent Flow ◽  
Gel Network

This article examines fluid transport and solvent dynamics in polymer gels, in equilibrium and under mechanical stress, and the effect of fluids on gel deformation. It also introduces a continuum model that describes the coupled phenomena of electric current, solvent flux, and deformation of gel network. This model is a generalization of the diffusio-mechanical coupling model of non-ionic gels. The discussion begins with an overview of the equilibrium state of non-ionic gels under the action of mechanical forces. This is followed by an analysis of the dynamics of non-ionic gels, especially the relaxation of mechanical responses caused by solvent flow. The article concludes with an assessment of the dynamics of ionic gels as well as the effect of electric field on solvent flow and the gel deformation.

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