scholarly journals Discrete Element Framework for Determination of Sintering and Postsintering Residual Stresses of Particle Reinforced Composites

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4015
Author(s):  
Szymon Nosewicz ◽  
Jerzy Rojek ◽  
Marcin Chmielewski
Keyword(s):  
Viscoelastic Model ◽  
Discrete Element ◽  
Homogenization Method ◽  
The Body ◽  
Two Phase ◽  
Particle Assembly ◽  
Thermal Expansion Coefficients ◽  
Intermetallic Matrix ◽  
Powder Metallurgy Process ◽  
Cooling Mechanism

In this paper, the discrete element method framework is employed to determine and analyze the stresses induced during and after the powder metallurgy process of particle-reinforced composite. Applied mechanical loading and the differences in the thermal expansion coefficients of metal/intermetallic matrix and ceramic reinforcing particles during cooling produce the complex state of stresses in and between the particles, leading to the occurrence of material defects, such as cracks, and in consequence the composite degradation. Therefore, the viscoelastic model of pressure-assisted sintering of a two-phase powder mixture is applied in order to study the stress field of particle assembly of intermetallic-ceramic composite NiAl/Al2O3. The stress evaluation is performed at two levels: macroscopic and microscopic. Macroscopic averaged stress is determined using the homogenization method using the representative volume element. Microscopic stresses are calculated both in the body of particles and in the contact interface (necks) between particles. Obtained results are in line with the cooling mechanism of the two-phase materials.

A Developed Numerical Method for Turbulent Unsteady Fluid Flow in Two-Phase Systems with Moving Interface

2017 ◽  
Vol 14 (06) ◽  
pp. 1750063 ◽  
Author(s):  
A. M. Hegab ◽  
S. A. Gutub ◽  
A. Balabel
Keyword(s):  
Numerical Model ◽  
Gas Phase ◽  
Level Set ◽  
The Body ◽  
Phase System ◽  
Computational Domain ◽  
Two Phase ◽  
Moving Interface ◽  
Level Set Function ◽  
Gas System

This paper presents the development of an accurate and robust numerical modeling of instability of an interface separating two-phase system, such as liquid–gas and/or solid–gas systems. The instability of the interface can be refereed to the buoyancy and capillary effects in liquid–gas system. The governing unsteady Navier–Stokes along with the stress balance and kinematic conditions at the interface are solved separately in each fluid using the finite-volume approach for the liquid–gas system and the Hamilton–Jacobi equation for the solid–gas phase. The developed numerical model represents the surface and the body forces as boundary value conditions on the interface. The adapted approaches enable accurate modeling of fluid flows driven by either body or surface forces. The moving interface is tracked and captured using the level set function that initially defined for both fluids in the computational domain. To asses the developed numerical model and its versatility, a selection of different unsteady test cases including oscillation of a capillary wave, sloshing in a rectangular tank, the broken-dam problem involving different density fluids, simulation of air/water flow, and finally the moving interface between the solid and gas phases of solid rocket propellant combustion were examined. The latter case model allowed for the complete coupling between the gas-phase physics, the condensed-phase physics, and the unsteady nonuniform regression of either liquid or the propellant solid surfaces. The propagation of the unsteady nonplanar regression surface is described, using the Essentially-Non-Oscillatory (ENO) scheme with the aid of the level set strategy. The computational results demonstrate a remarkable capability of the developed numerical model to predict the dynamical characteristics of the liquid–gas and solid–gas flows, which is of great importance in many civilian and military industrial and engineering applications.

Coefficients of thermal expansion of unidirectional fiber-reinforced composites using unit-cell model

2018 ◽  
Vol 53 (11) ◽  
pp. 1425-1436
Author(s):  
PC Upadhyay ◽  
JP Dwivedi ◽  
VP Singh
Keyword(s):  
Thermal Expansion ◽  
Cell Model ◽  
Unit Cell ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Unit Cell Model ◽  
Fiber Reinforced ◽  
Two Phase ◽  
Thermal Expansion Coefficients ◽  
Three Phase

Coefficients of thermal expansion of some uniaxially fiber-reinforced composites have been evaluated using three-phase unit-cell model. Results have been compared with the values predicted by two other models based on composite cylinders assembly (CCA), and also with some earlier reported experimental values. An extension of the two-phase unit-cell model has also been presented for the evaluation of thermal expansion coefficients of three-phase composites. The formulation has been used to evaluate the overall coefficients of thermal expansion of AS-graphite/epoxy system with a low modulus coating on the fibers. The results have been compared with the results obtained from the Sutcu's recursive concentric cylinders model for composites containing coated fibers. From the comparison of results of the unit-cell models (both, two-phase and three-phase) with the results obtained from some other models available in the literature, it is concluded that the overall thermal properties of fiber-reinforced composites evaluated by the unit-cell model can be used as effectively as by any other model.

Textures of the Hot-Forged Ti6Al4V Alloy

2013 ◽  
Vol 203-204 ◽  
pp. 111-114
Author(s):  
Adam Bunsch ◽  
Wiktoria Ratuszek ◽  
Małgorzata Witkowska ◽  
Joanna Kowalska ◽  
Aneta Łukaszek-Sołek
Keyword(s):  
Deformation Temperature ◽  
Phase State ◽  
Hexagonal Phase ◽  
Ti6al4v Alloy ◽  
The Body ◽  
Cubic Phase ◽  
Body Centered Cubic ◽  
Two Phase ◽  
Different Temperatures

This paper presents the results of the texture investigation in the hexagonal phase and the body-centered cubic  phase of the Ti6Al4V alloy hot-deformed by forging. Forging was performed at two different temperatures on the occurrence of the single  and in the two-phase  +  state. It was found that after deformation both  and  phases are textured and their textures strongly depends on deformation temperature.

scholarly journals Modeling of Interior Ballistic Gas-Solid Flow Using a Coupled Computational Fluid Dynamics-Discrete Element Method

2013 ◽  
Vol 80 (3) ◽  
Author(s):  
Cheng Cheng ◽  
Xiaobing Zhang
Keyword(s):  
Discrete Element Method ◽  
Gas Phase ◽  
Two Phase Flow ◽  
Discrete Element ◽  
Particle Collision ◽  
Contact Detection ◽  
Reconstruction Method ◽  
Phase Flow ◽  
Two Phase ◽  
Element Method

In conventional models for two-phase reactive flow of interior ballistic, the dynamic collision phenomenon of particles is neglected or empirically simplified. However, the particle collision between particles may play an important role in dilute two-phase flow because the distribution of particles is extremely nonuniform. The collision force may be one of the key factors to influence the particle movement. This paper presents the CFD-DEM approach for simulation of interior ballistic two-phase flow considering the dynamic collision process. The gas phase is treated as a Eulerian continuum and described by a computational fluid dynamic method (CFD). The solid phase is modeled by discrete element method (DEM) using a soft sphere approach for the particle collision dynamic. The model takes into account grain combustion, particle-particle collisions, particle-wall collisions, interphase drag and heat transfer between gas and solid phases. The continuous gas phase equations are discretized in finite volume form and solved by the AUSM+-up scheme with the higher order accurate reconstruction method. Translational and rotational motions of discrete particles are solved by explicit time integrations. The direct mapping contact detection algorithm is used. The multigrid method is applied in the void fraction calculation, the contact detection procedure, and CFD solving procedure. Several verification tests demonstrate the accuracy and reliability of this approach. The simulation of an experimental igniter device in open air shows good agreement between the model and experimental measurements. This paper has implications for improving the ability to capture the complex physics phenomena of two-phase flow during the interior ballistic cycle and to predict dynamic collision phenomena at the individual particle scale.

scholarly journals An investigation on effect of EDL on heat transfer of micro heat pipe with square and triangular cross section

2020 ◽  
Vol 21 (3) ◽  
pp. 309
Author(s):  
Maryam Fallah Abbasi ◽  
Hossein Shokouhmand ◽  
Morteza Khayat
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Double Layer ◽  
Electric Double Layer ◽  
Heat Pipes ◽  
The Body ◽  
Working Fluid ◽  
Two Phase ◽  
Micro Heat Pipe ◽  
Micro Heat Pipes

Electronic industries have always been trying to improve the efficiency of electronic devices with small dimensions through thermal management of this equipment, thus increasing the use of small thermal sinks. In this study micro heat pipes with triangular and square cross sections have been manufactured and tested. One of the main objectives is to obtain an understanding of micro heat pipes and their role in energy transmission with electrical double layer (EDL). Micro heat pipes are highly efficient heat transfer devices, which use the continuous evaporation/condensation of a suitable working fluid for two-phase heat transport in a closed system. Since the latent heat of vaporization is very large, heat pipes transport heat at small temperature difference, with high rates. Because of variety of advantage features these devices have found a number of applications both in space and terrestrial technologies. The theory of operation micro heat pipes with EDL is described and the micro heat pipe has been studied. The temperature distribution have achieved through five thermocouples installed on the body. Water and different solution mixture of water and ethanol have used to investigate effect of the electric double layer heat transfer. It was noticed that the electric double layer of ionized fluid has caused reduction of heat transfer.

scholarly journals Advances in Biosynthesis, Pharmacology, and Pharmacokinetics of Pinocembrin, a Promising Natural Small-Molecule Drug

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2323 ◽  
Author(s):  
Xiaoling Shen ◽  
Yeju Liu ◽  
Xiaoya Luo ◽  
Zhihong Yang
Keyword(s):  
Ischemic Stroke ◽  
Mechanisms Of Action ◽  
The Body ◽  
Pharmacological Activities ◽  
Two Phase ◽  
Phase Ii Clinical Trials ◽  
Significant Efficacy ◽  
Engineering Strategy ◽  
Fermentation Strategy ◽  
New Treatment

Pinocembrin is one of the most abundant flavonoids in propolis, and it may also be widely found in a variety of plants. In addition to natural extraction, pinocembrin can be obtained by biosynthesis. Biosynthesis efficiency can be improved by a metabolic engineering strategy and a two-phase pH fermentation strategy. Pinocembrin poses an interest for its remarkable pharmacological activities, such as neuroprotection, anti-oxidation, and anti-inflammation. Studies have shown that pinocembrin works excellently in treating ischemic stroke. Pinocembrin can reduce nerve damage in the ischemic area and reduce mitochondrial dysfunction and the degree of oxidative stress. Given its significant efficacy in cerebral ischemia, pinocembrin has been approved by China Food and Drug Administration (CFDA) as a new treatment drug for ischemic stroke and is currently in progress in phase II clinical trials. Research has shown that pinocembrin can be absorbed rapidly in the body and easily cross the blood–brain barrier. In addition, the absorption/elimination process of pinocembrin occurs rapidly and shows no serious accumulation in the body. Pinocembrin has also been found to play a role in Parkinson’s disease, Alzheimer’s disease, and specific solid tumors, but its mechanisms of action require in-depth studies. In this review, we summarized the latest 10 years of studies on the biosynthesis, pharmacological activities, and pharmacokinetics of pinocembrin, focusing on its effects on certain diseases, aiming to explore its targets, explaining possible mechanisms of action, and finding potential therapeutic applications.

scholarly journals Discrete Element Modeling of Intermetallic Matrix Composite Manufacturing by Powder Metallurgy

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 281 ◽  
Author(s):  
Szymon Nosewicz ◽  
Jerzy Rojek ◽  
Marcin Chmielewski ◽  
Katarzyna Pietrzak
Keyword(s):  
Powder Metallurgy ◽  
Numerical Model ◽  
Sintered Sample ◽  
Discrete Element ◽  
Adhesive Contact ◽  
Ceramic Composites ◽  
Numerical Representation ◽  
Discrete Element Modeling ◽  
Two Phase ◽  
Neck Size

This paper presents a numerical and experimental analysis of manufacturing of intermetallic ceramic composites by powder metallurgy techniques. The scope of the paper includes the formulation and development of an original numerical model of powder metallurgy of two-phase material within the framework of the discrete element method, simulations of powder metallurgy processes for different combinations of process parameters, and a verification of the numerical model based on own experimental results. Intermetallic-based composite NiAl–Al 2 O 3 has been selected as representative material for experimental and numerical studies in this investigation. Special emphasis was given to the interactions between the intermetallic and ceramic particles by formulating the special model for adhesive contact bond. In order to properly represent a real microstructure of a two-phase sintered body, a discrete element specimen was generated using a special algorithm. Numerical validation showed the correct numerical representation of a sintered two-phase composite specimen. Finally, micromechanical analysis was performed to explain the macroscopic behavior of the sintered sample. The evolution of the coordination number, a number of equilibrium contacts, and the distribution of the cohesive neck size with respect to time are presented.

Numerical and Experimental Investigation of Bubble Dynamics via Electrowetting-on-Dielectric (EWOD)

2016 ◽  
Author(s):  
Sheng Wang ◽  
Junxiang Shi ◽  
Hsiu-Hung Chen ◽  
Tiancheng Xu ◽  
Chung-Lung (C. L.) Chen
Keyword(s):  
Thin Film ◽  
Contact Angle ◽  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Experimental System ◽  
Hydrophobic Surface ◽  
Numerical Results ◽  
The Body ◽  
Two Phase ◽  
Electrowetting On Dielectric

With the inspiration from electrowetting-controlled droplets, the potential advantages of electrowetting for bubble dynamics are investigated experimentally and numerically. In our experimental system, a 100 nanometer thin film gold metal was used as an electrode, and a 6.5 micrometer polydimethylsiloxane (PDMS) was spin-coated on the electrode acting both as an dielectric layer and hydrophobic surface. A two-phase model coupled with a electrostatics was used in our simulation work, where the body force due to the electric field acts as an external force. Our numerical results demonstrated that electrowetting can help the detachment of a small bubble by changing the apparent contact angle. Similar results were observed in our experiments that with electrowetting on dielectric, the contact angle of bubble on a hydrophobic surface will obviously decrease when a certain electrical field is applied either with a small size bubble (diameter around 1mm) or a relatively larger size bubble (diameter around 3 mm). When the applied voltage becomes high enough, both the experimental and numerical results demonstrate the characteristics of bubble detachment within a thin film liquid layer.

Modeling Separation and Cavitation Behind a Blunt Body

2016 ◽  
Author(s):  
Jingsen Ma ◽  
Chao-Tsung Hsiao ◽  
Xiongjun Wu ◽  
Georges L. Chahine
Keyword(s):  
Blunt Body ◽  
Ambient Pressure ◽  
Separated Flow ◽  
The Body ◽  
Large Cavity ◽  
Cavitation Flow ◽  
Two Phase ◽  
Free Surfaces ◽  
Number Flow ◽  
Transition Scheme

Cavitation flow behind a blunt body is modeled using a physics-based numerical model of cavitation initiation and transition to larger cavities. The calculations initiate from the dynamics of nuclei, then tracks the dispersed bubble phase with a two-phase viscous model. This solver includes a level set method to model coalescence of the nuclei into large cavities and to track the dynamics of the resulting free surfaces. A transition scheme enables collection of the bubbles into a large cavity and also enables breakup of a large cavity into a bubble cloud. Using this model, simulations are conducted for different flow velocities and corresponding cavitation regimes. When the velocity is relatively small (i.e., large cavitation number), flow separation behind the body results in the shedding of vortices, which capture nuclei in their cores to form elongated vortical cavities. As the flow velocity increases (or as the ambient pressure decreases) the flow evolves into a separated flow with a large cavity behind the body. A reentrant jet may form and move upstream into the cavity towards the body. This jet periodically shears off portions of the cavity volume, resulting in large amounts of bubble clouds. These results are in good qualitative agreements with experimental observations.

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