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Results in Journal Modeling and Numerical Simulation of Material Science: 102

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Abu Bakar Siddique, Tariq Khraishi
Modeling and Numerical Simulation of Material Science, Volume 11, pp 1-18; doi:10.4236/mnsms.2021.111001

Simulation of dislocation dynamics opens the opportunity for researchers and scientists to observe in-depth many plastic deformation phenomena. In 2D or 3D media, modeling of physical boundary conditions accurately is one of the keys to the success of dislocation dynamics (DD) simulations. The scope of analytical solutions is restricted and applies to specific configurations only. But in dynamics simulations, the dislocations’ shape and orientation change over time thus limiting the use of analytical solutions. The authors of this article present a mesh-based generalized numerical approach based on the collocation point method. The method is applicable to any number of dislocations of any shape/orientation and to different computational domain shapes. Several verifications of the method are provided and successful implementation of the method in 3D DD simulations have been incorporated. Also, the effect of free surfaces on the Peach-Koehler force has been computed. Lastly, the effect of free surfaces on the flow stress of the material has been studied. The results clearly showed a higher force with increased closeness to the free surface and with increased dislocation segment length. The simulations’ results also show a softening effect on the flow stress results due to the effect of the free surfaces.
Pierre Marcel Anicet Noah, Fabien Betene Ebanda, Louis-Max Ayina Ohandja, Ateba Atangana
Modeling and Numerical Simulation of Material Science, Volume 11, pp 19-33; doi:10.4236/mnsms.2021.111002

The objective of this paper is to investigate the relative variations of the constants of the thermal properties and the degree of crystallinity of the mixtures (PP/EPR)/Calcium carbonates elaborated with the Micro Bivis. We have strengthened the basic copolymer PP/EPR of a low level (5%) by three calcium carbonates models socal312, socal322v, Winnofil spm. We then subjected the different mixtures obtained, two cycles of a thermal loading under differential scanning calorimetry DSC. We finally focused on the thermal properties of isotactic polypropylene (TfP, TcP, ΔHfP, ΔHcP) and we calculated the degree of crystallinity of the mixtures. Reducing the energy cost of implementing mixtures is one of the objectives of this work. We quantified the relative variations of the above properties with those of the base copolymer. It shows that at a low loading rate of calcium carbonate, there is a decrease in the enthalpies of crystallization during the second exothermic cycle, with values that can reach 5.53 J/gPP for the basic copolymer PP/EPR. During the second endothermic cycle, there is an overall increase in isotactic polypropylene melting temperature values for all the blends as well as for the basic copolymer PP/EPR. There is evidence that calcium carbonates are useful for lowering the melting energy of isotactic polypropylene, even at a low loading rate for the majority. The number of endothermic cycles accentuates this phenomenon which is linked to the presence in our composites, of a so-called confined amorphous phase.
Matteo Villa, Jeffery W. Brooks, Richard P. Turner, Mark Ward
Modeling and Numerical Simulation of Material Science, Volume 10, pp 55-73; doi:10.4236/mnsms.2020.103004

The microstructural kinetics of β grain growth in the β field of a Ti-6Al-4V alloy was studied by a series of controlled heat treatments at constant temperature rates. Heating rates of 5°C/s, 50°C/s and 500°C/s were considered, stopping at different peak temperatures. The thickness evolution of martensitic needles and lamellar α laths, formed on cooling, was also investigated, by soaking the material above its β-transus temperature and cooling down at 5°C/s, 50°C/s, 100°C/s and 300°C/s till ambient temperature. Quantitative microstructural analyses were used to measure the particle dimensions. The β grain growth kinetics was reasonably well described by a modified Avrami equation. The thickness of α lamellae was a function of the cooling rate and the β grain dimension in which they nucleated. The martensite needle thickness was shown to be a function of the cooling rate to which the material was subjected.
Drissa Ouedraogo, Serge Wendsida Igo, Gaël Lassina Sawadogo, Abdoulaye Compaore, Belkacem Zeghmati, Xavier Chesneau
Modeling and Numerical Simulation of Material Science, Volume 10, pp 15-30; doi:10.4236/mnsms.2020.102002

In this work, a numerical study of heat transfers in a metallic pressure cooker isolated with kapok wool was carried out. This equipment works like a thermos, allowing finishing cooking meals only thanks to the heat stored at the beginning of cooking, which generates energy savings. Cooked meals are also kept hot for long hours. In our previous work, we have highlighted the performances of the pressure cooker when making common dishes in Burkina Faso. Also, the parameters (thickness and density) of the insulating matrix allowing having such performances as well as the influence of the climatic conditions on the pressure cooker operation were analyzed in detail in this present work. The numerical methodology is based on the nodal method and the transfer equations obtained by making an energy balance on each node have been discretized using an implicit scheme with finite differences and resolved by the Gauss algorithm. Numerical results validated experimentally show that the thickness of the kapok wool as well as its density play an important role in the pressure cooker operation. In addition, equipment performances are very little influenced by the weather conditions of the city of Ouagadougou (Burkina Faso).
Baha Tarchoun, Abderrazak El Ouafi, Ahmed Chebak
Modeling and Numerical Simulation of Material Science, Volume 10, pp 31-54; doi:10.4236/mnsms.2020.103003

Laser surface hardening is becoming one of the most successful heat treatment processes for improving wear and fatigue properties of steel parts. In this process, the heating system parameters and the material properties have important effects on the achieved hardened surface characteristics. The control of these variables using predictive modeling strategies leads to the desired surface properties without following the fastidious trial and error method. However, when the dimensions of the surface to be treated are larger than the cross section of the laser beam, various laser scanning patterns can be used. Due to their effects on the hardened surface properties, the attributes of the selected scanning patterns become significant variables in the process. This paper presents numerical and experimental investigations of four scanning patterns for laser surface hardening of AISI 4340 steel. The investigations are based on exhaustive modelling and simulation efforts carried out using a 3D finite element thermal analysis and structured experimental study according to Taguchi method. The temperature distribution and the hardness profile attributes are used to evaluate the effects of heating parameters and patterns design parameters on the hardened surface characteristics. This is very useful for integrating the scanning patterns’ features in an efficient predictive modeling approach. A structured experimental design combined to improved statistical analysis tools is used to assess the 3D model performance. The experiments are performed on a 3 kW Nd:Yag laser system. The modeling results exhibit a great agreement between the predicted and measured values for the hardened surface characteristics. The model evaluation reveals also its ability to provide not only accurate and robust predictions of the temperature distribution and the hardness profile as well an in-depth analysis of the effects of the process parameters.
Tomas De La Mora Ramírez, Isaías Hilerio Cruz, Marco Antonio Doñu Ruiz, Noé López Perrusquia, David García Bustos, Martín Flores Martínez, De La Mora Ramírez Tomas, Hilerio Cruz Isaías, Antonio Doñu Ruiz Marco, López Perrusquia Noé, et al.
Modeling and Numerical Simulation of Material Science, Volume 10, pp 1-14; doi:10.4236/mnsms.2020.101001

Ultra-high molecular weight polyethylene (UHMWPE) has been used in orthopedics as one of the materials for artificial joints in knee, hip and spine prostheses, most of the implanted joints are designed so that the metal of the prosthesis is articulate against a polymeric material, however the main problems is the average life time of the UHMWPE due to wear, and the particles generated by the friction of the metal on the articulation of the polymer are the most common inducer of osteolysis, generating a loosening of the implant leading to an imminent failure resulting in the total replacement of the prosthesis. In this investigation a numerical model of abrasive wear was made using the classic Archard wear equation applied to dynamic simulation of finite element analysis (FEA) of the micro-abrasion test using a subroutine written in Fortran language linked to the finite element software to predict the rate of wear. The results of the numerical model were compared with tests of abrasive wear in the laboratory, obtaining a margin of error below 5%,concluding that the numerical model is feasible for the prediction of the rate of wear and could be applied in knowing the life cycle of joint prostheses or for the tribological analysis in industrial machinery or cutting tools. The wear coefficient (K) was obtained from the grinding tests depending on the depth of stroke of the crater, which was analyzed by 3D profilometry to obtain the wear rate and the wear constant.
Christopher E. Ozigagu, Anthony J. Duben
Modeling and Numerical Simulation of Material Science, Volume 9, pp 1-15; doi:10.4236/mnsms.2019.91001

The Soave-Redlich-Kwong (SRK-EOS) and Peng-Robinson (PR-EOS) equations of state are used often to describe the behavior of pure substances and mixtures despite difficulties in handling substances, like water, with high polarity and hydrogen bonding. They were employed in studying the binary vapor-liquid equilibria (VLE) of methane + methanol, monoethylene glycol (MEG), and triethylene glycol (TEG). These liquids are used to inhibit the formation of gas hydrates. The investigation focused on the conditions at which methane-water clathrates can form 283.89 K to 323.56 K and 5.01 MPa to 18.48 MPa. The pressure of methane in methanol is overestimated by a factor of two by either the SRK-EOS or the PR-EOS. In the methane + MEG system, the predicted pressures for both equations of state are generally less than experimental pressure except for the highest concentration of methane in MEG calculated by the SRK-EOS. In the methane + TEG system, the predictions of both models are close and trend similarly. Because of the comparative lack of extensive experimental methane + TEG data, the similarity of the methane + TEG computed results can be used as a basis for further study of this system experimentally.
Claude Lincourt, Jacques Lanteigne, Madhavarao Krishnadev, Carl Blais
Modeling and Numerical Simulation of Material Science, Volume 9, pp 17-28; doi:10.4236/mnsms.2019.92002

Isa Ibrahim Mohammed, Ibrahim Isa Adamu, Seni James Barka
Modeling and Numerical Simulation of Material Science, Volume 9, pp 71-96; doi:10.4236/mnsms.2019.94005

In this work, we presented a mathematical model for the dynamics of glucose, insulin and beta-cell mass under the influence of trauma, excitement and/or stress, the model is an improvement on the work by [1]. We defined and incorporated a parameter to represent the effectiveness of epinephrine in suppressing insulin secretion and a parameter Ge representing epinephrine induced glucose increase as the factors that affect glucose and insulin homeostasis. The model which consists of a system of three nonlinear ordinary differential equations was used to investigate the effect of epinephrine on glucose, insulin and beta-cell mass dynamics. The result of the study showed that; In the presence of epinephrine, the blood glucose increased and the blood insulin decreased due to suppression by the hormone, despite the fact that there is an increase in beta-cell mass the system remained extremely hyperglycemic. Furthermore, the result of the numerical experiment carried out indicated that frequent epinephrine secretion into the blood induced prolong and extreme hyperglycemia. Frequent epinephrine secretion increases the risk of diabetes in humans. In view of the findings of this study, we recommend that there should be massive and continuous health education, especially for communities living in the areas where the stated agents (trauma, excitement and stress) of epinephrine secretion are common.
Abou Bakary Coulibaly, Sampson Oladapo Oyedele, N’Guessan Raymond Kre, Boko Aka
Modeling and Numerical Simulation of Material Science, Volume 9, pp 97-107; doi:10.4236/mnsms.2019.94006

In recent years, there has been an unprecedented rise in the performance of metal halide perovskite solar cells. The lead-free perovskite solar cells (PSCs) have drawn much research interest due to the Pb toxicity of the lead halide perovskite. CH3NH3SnI3 is a viable alternative to CH3NH3PbX3. In this work, we designed a tin-based perovskite simulated model with the novel architecture of (TCO)/buffer (TiO2)/absorber (Perovskite)/hole transport material (HTM) and analyzed using the solar cell capacitance simulator (SCAPS-1D), which is well adapted to study the photovoltaic architectures. In the paper, we studied the influences of perovskite thickness and the doping concentration on the solar cell performance through theoretical analysis and device simulation. The results are indicating that the lead-free CH3NH3SnI3 is having the greatpotential to be an absorber layer with suitable inorganic hole transport materials like CuI (PCE: 23.25%), Cu2O (PCE: 19.17%), organic hole transport materials like spiro-OMETAD (PCE: 23.76%) and PTAA (PCE: 23.74%) to achieve high efficiency. This simulation model will become a good guide for the fabrication of high efficiency tin-based perovskite solar. The results show that the lead-free CH3NH3SnI3 is a potential environmentally friendly solar cells with high efficiency.
Lina Wang, Yongqiang Pan, Linjiao Yang, Yitong Wang, Fulin Li, Jiaqi Wang, Shanwei Wang, Na Zuo
Modeling and Numerical Simulation of Material Science, Volume 9, pp 29-40; doi:10.4236/mnsms.2019.92003

Ahmadreza Ejraei Bakyani, Samira Heidari, Alireza Rasti, Azadeh Namdarpoor
Modeling and Numerical Simulation of Material Science, Volume 8, pp 1-19; doi:10.4236/mnsms.2018.81001

Separator design in petroleum engineering is so important because of its important role in the evaluation of optimum parameters and also to achieve to maximum stock tank liquid. However, no simulator exists that simultaneously and directly optimizes the parameters “pressure”, “temperature”, and so on. On the other hands, Commercial simulators fix one parameter and vary another parameter to achieve the optimum conditions. So, they need long-time simulation. Moreover, gas condensate reservoirs, like another reservoirs, have this problem as well. In present paper, a self-developed simulator applied in the optimized design of gas condensate reservoir’s separators by determining optimized pressure, temperature, and number of separators in order to obtain maximized tank liquid volume and minimized tank liquid density utilizing Matlab software and other commercial simulators such as Aspen-Plus, Aspen-Hysys, and PVTi to do a comparison. Also, each software was separately tested with one, two, and three separators to obtain the optimum number of separators. Additionally, Peng-Robinson equation of state (PR EOS) has been applied in the simulation. For simulation input, a set of field data of gas condensate reservoir has been utilized, as well. The results show a good compatibility of this simulator with other simulators but in so little runtime (this simulator calculates the optimum pressure and temperature in a wide range of pressures and temperatures with the help of a simultaneous optimization algorithm in one stage) and the highest stock tank liquid is calculated with this simulator in comparison to other simulators. Also, with the help of this simulator, we are able to obtain the optimum pressure, temperature, and the number of separators in the gas condensate reservoir’s separators with any desired properties. Finally, this simulator optimizes the temperatures for each separator and obtains very good results despite the other simulators that fix temperatures for all separators in most times.
Samira Heidari, Jafar Saberi Doust,
Modeling and Numerical Simulation of Material Science, Volume 8, pp 65-78; doi:10.4236/mnsms.2018.84004

Unwanted water production together with oil and gas production is a striking problem in oil and gas industries, and many approaches have been examined to overcome this major problem. Preformed particle gels (PPGs) showed dramatically good properties for this purpose in mature oil and gas reservoirs. In this study, we carefully synthesized an efficient series of PPGs with using a design of experiments (DOE) software. Acrylamide (AAm)/Acrylic acid (AA) mole ratio, N,N’-methylenebisacrylamide (MBA) mole percentage and swelling time were considered as key parameters to examine PPG swelling behavior. Our results presented a detailed empirical correlation, which could significantly predict the swelling capacity of PPGs in CaCl2 salt solution (200,000 ppm).
Modeling and Numerical Simulation of Material Science, Volume 8, pp 21-46; doi:10.4236/mnsms.2018.82002

Electron density differences resulting from atom displacement patterns aligned with phonon modes in MgB2 have been calculated using density functional theory (DFT). The extent of phonon anomalies, identified as indicators of the superconducting transition temperature, Tc, under a range of conditions in AlB2-type structures, reduce as boron atoms are displaced from their equilibrium positions along E2g mode directions. The Fermi energy for displacements along the directions of the E2g phonon mode accounts for changes in the covalent B-B bond electronic charge density. We applied differential atom displacements to show that the shifted σ band structure associated with the light effective mass became tangential to the Fermi level and that the Fermi surface undergoes a topological transition at a critical relative displacement of ~0.6% of the boron atoms from equilibrium. The difference in Fermi energies at this critical displacement and at the equilibrium position correspond to the superconducting energy gap. The net volume between tubular σ surfaces in reciprocal space correlated with the depth of the phonon anomaly and, by inference, it is a key to an understanding of superconductivity. This ab initioapproach offers a phenomenological understanding of the factors that determine Tc based on knowledge of the crystal structure.
Abolfazl Ezadi Sharif Abad, Ahmad Adib
Modeling and Numerical Simulation of Material Science, Volume 8, pp 47-63; doi:10.4236/mnsms.2018.83003

Accurate characterization of seismic properties in the prediction of P-wave and S-wave velocities through carbonate reservoirs is necessary due to their intrinsic heterogeneity. Moreover, both the waves velocities mentioned above are applied to the uncertainty analysis as well as the complexity investigation presented in the carbonate reservoirs. In this study, three wells of an Iranian oil field which its formation is the upper part of the Sarvak (Mishrif) has been studied. In accordance with the petrophysical interpretation of this oil field using Geo-log software, a rock physics model has been constructed based on Xu-Payne model (2009) using Hampson-Russel software to predict the elastic properties like P-wave and S-wave velocities as well as density. In the following, some synthetic seismic traces have been created based on the rock physics model using Hampson-Russel software to obtain the correlation coefficients of the seismic data with both the predicted and measured elastic properties. As results, the obtained correlation coefficients show that the predicted elastic properties by the rock physics model have higher quality than the measured elastic properties. In addition, the correlation coefficients of the predicted elastic properties in the well number 1, 2, and 3 have approximately increased by 19.6, 21.3, and 18.2 percent, respectively, in comparison to the correlation coefficients of the measured elastic properties. Therefore, the predicted elastic properties can be replaced with the low-quality measured elastic properties. Eventually, some templates have been created to accurate characterization the carbonate reservoir based on the rock physics model and also show the high-quality correlations between the rock physics model and the measured data.
Joel Hemanth
Modeling and Numerical Simulation of Material Science, Volume 7, pp 1-18; doi:10.4236/mnsms.2017.71001

This paper presents the results obtained, deductions made from solidification behaviour and a series of micro structural studies such as pearlite content, eu-tectic cell count and grain size of hypoeutectic gray cast iron which was sand cast (CO2 moulding) using metallic, nonmetallic, water cooled and subzero (cryogenic) end chills. Hypo-eutectic cast irons containing C 3.42, Si 2.4 and Ni 1.5 with impurity contents (S, P, Mn etc.) were solidified unidirectionally in an American Foundrymen Society (AFS) standard mould, the end of which was provided with different end chills to study the effect of chilling during solidifi-cation. The melts were inoculated with 0.3% Fe-Si to promote graphitization. It was observed that the transition from one structure to another is more gradual than normally obtained in the structure of cast irons solidified mul-ti-directionally in a sand mould at room temperature. Austenite dendrite interactions were shown to be a major factor in determining the microstructure, in which the higher dendrite reaction leads to changes in DAS, ECC and GS. It is observed that, the number of eutectic cells is an index of graphite nucleation and the effect of these on structure, since the eutectic cells are developed on the graphite nuclei during solidification.
Joel Hemanth
Modeling and Numerical Simulation of Material Science, Volume 7, pp 19-32; doi:10.4236/mnsms.2017.72002

Fins are the extended surfaces through which heat transfer takes place to keep the surface cool. Fins of various configurations are presently used ranging from automobile engine cooling to cooling of computer parts. Note that in a fin majority of the heat transfer to atmosphere is by convection and therefore in the present research, and importance is given to variation of temperature along the length of the fin which in turn gives rate of heat transfer. In the present research a solid rectangular aluminum fin and the same rectangular fin with different perforations (2, 4, 8 and 10) were compared analytically, experimentally and its validity through finite element analysis for its temperature distribution along the length. From the present research it is observed that the mathematical and FEA for a solid rectangular fin without perforations are converging within ±1°C and rectangular fin with 10 perforations are converging within ±2°C and hence the validity.
Yuze Peng, Yuxiang Wu, Linlin Tang, Juan Li, Jian Xu, Yangyang Du, , , Jian Ni, Jianjun Zhang
Modeling and Numerical Simulation of Material Science, Volume 7, pp 47-57; doi:10.4236/mnsms.2017.74004

Organic-inorganic hybrid perovskite materials have attracted significant research efforts because of their outstanding properties. Meanwhile the crystallization of organic-inorganic hybrid perovskite materials can significantly influence the films quality. Here, we research the influence of the characteristics of PbI2 thin film on final perovskite films and the mechanisms of film formation based on the two-step sequential deposition method. We found that the characteristics of PbI2 thin film, such as the grain size, the grain shape, the surface roughness and the film densification, have significant effects on the final perovskite films due to different film crystallization process. According to the analysis on the characteristics of the perovskite films obtained from different PbI2precursor, we suggested that the formation of perovskite film begins from the PbI2 crystals expanding when they are converted to MAPbI3 perovskite by migration of MA+ cations from the grain boundaries.
Sampson Oladapo Oyedele, Boko Aka
Modeling and Numerical Simulation of Material Science, Volume 7, pp 33-45; doi:10.4236/mnsms.2017.73003

Numerical simulation has been used to investigate the effect of different buffer layer components on the performance of CuInGaSe2 solar cells with SCAPS-1D software. The main photovoltaic parameters of simulated devices: open-circuit voltage (Voc), short-circuit current (Jsc), fill factor (FF), and conversion efficiency (h), areanalysed as a function of thickness and temperature in the different buffer layers used. According to numerical simulation the highest conversion efficiency (23%) of CIGS solar cell is reached for the CdS buffer layer. This result is validated by experimental results (20%). At 300 K, when the thickness of the buffer layer (CdS, ZnS, ZnSe, InSe2) increases from 100 nm to 500 nm, with the other parameters maintained constant, the efficiency decreases. When the temperature increases from 300 K to 400 K, with the other parameters maintained constant, both open circuit voltage and conversion efficiency also decrease. The effect of dual buffer layers of ZnS/CdS has also been analysed and his efficiency increases of 3% than a single buffer CdS.
, Bernhard Quatember
Modeling and Numerical Simulation of Material Science, Volume 6, pp 41-57; doi:10.4236/mnsms.2016.63005

The treatment with a mechanical ventilator is required whenever a patient’s respiratory system becomes unable to keep the concentrations of O2 and CO2 in blood at tolerable levels. However, in particular cases, the thoracic artificial lung (TAL) can be regarded as a viable alternative to mechanical ventilation (MV). We aim at studying the effects of mechanical ventilators and thoracic artificial lungs devices will have on the cardiovascular system. We will give careful consideration to cardiovascular energetic parameters, such as left and right ventricular external work, pressure-volume area, and cardiac mechanical efficiency. We simulated both, mechanically ventilated patients who are not subject to the application of an artificial lung and patients who are provided with a thoracic artificial lung (TAL). In the case of a thoracic artificial lung, we involved in our simulation studies all the usual operating modes of a TAL, viz. series mode, parallel mode, and hybrid mode of the TAL with regard to the native lung. In particular, the presented simulation results will contribute to elucidate the specific characteristics of each of the aforementioned operating modes. Generally, the energetic variables are influenced by different values of input TAL resistance in both modes: parallel and in series. In this paper, we concentrated on simulation studies of the effects evoked by TAL assistance on cardiac energetic and some other important circulatory parameters. The simulation results presented show that at all modes of TAL assistance exists a strong dependency on the TAL input variables and on the value of the mean intrathoracic pressure which has been assumed for a given situation.
Maharavo Randrianarivony
Modeling and Numerical Simulation of Material Science, Volume 6, pp 69-93; doi:10.4236/mnsms.2016.64007

We consider the modeling and simulation by means of multiwavelets on many patches. Our focus is on molecular surfaces which are represented in the form of Solvent Excluded Surfaces that are featured by smooth blendings between the constituting atoms. The wavelet bases are constructed on the unit square which maps bijectively onto the patches embedded in the space. The cavity which designates the surface bounding a molecular model is acquired from the nuclei coordinates and the Van-der-Waals radii. We use multi-wavelets for which the wavelet basis functions are organized hierarchically on several levels. Our assembly of the linear system is accomplished by using a hierarchical tree which enables the treatment of large molecules admitting thousands of patches. Along with the patch construction, some wavelet simulation outcomes which are applied to realistic patches are reported.
Victor G. Zavodinsky, Olga A. Gorkusha
Modeling and Numerical Simulation of Material Science, Volume 6, pp 11-16; doi:10.4236/mnsms.2016.62002

The Paulie’s principle is used for development of the orbital-free (OF) version of the density functional theory. On the example of the three-atomic clusters, Al3, Si3, and C3, it is shown that the OF approach may lead to equilibrium configurations of atomic systems with both the metallic and covalent bonding. The equilibrium interatomic distances, interbonding angles and binding energies are found in good accordance with the known data. Results will be useful for developing of theoretical study of huge molecules and nanoparticles.
Moeiz Rouis, Khaled Omrani
Modeling and Numerical Simulation of Material Science, Volume 6, pp 1-9; doi:10.4236/mnsms.2016.61001

Ismail J. Abubakar, Peter Myler, Erping Zhou
Modeling and Numerical Simulation of Material Science, Volume 6, pp 28-40; doi:10.4236/mnsms.2016.62004

Elastomers are used in numerous engineering applications such as sealing components, it is therefore important to devise a method that can accurately predict elastomers’ response to load. Many applications that employ the use of these materials subject them to a nonlinear large strain; therefore the simple Hooke’s law is not sufficient to describe their material behaviour. This paper presents an approach to obtain material properties of elastomer under compression loading, based on hyperelastic strain formulation, through experimental test and finite element modelling. The paper focuses on the isotropic incompressible behaviour exhibited by elastomers, and obtains strain energy functions that satisfy the characteristic properties of a hyperelastic model. Data obtained from compression test on a nitrile rubber (NBR) specimen were used as material input into ABAQUS®—a finite element analysis software. A least square fitting technique was used to determine the coefficients of various stable hyperelastic models, based on Drucker’s stability criteria within the software. The strain energy functions obtained concentrate on material parameters which are related to physical quantities of the material molecular network they are subjected to in practical application. The approach benefits from mathematical simplicity, and possesses the property of the deformation mode dependency. Furthermore, a model validation procedure using a step-by-step method for parameters estimation is explained. The work herein is a nonlinear finite element modelling process that leads to an optimal solution and can be employed not only for elastomeric seals, but also for similar engineering assets.
Ahmed Ghazi Jerniti, Abderazzak El Ouafi, Noureddine Barka
Modeling and Numerical Simulation of Material Science, Volume 6, pp 17-27; doi:10.4236/mnsms.2016.62003

Laser surface hardening becomes one of the most effective techniques used to enhance wear and fatigue resistance of mechanical parts. The characteristics of the hardened surface depend on the physicochemical properties of the material as well as the heating system parameters. To adequately exploit the benefits presented by the laser heating method, it is necessary to develop a comprehensive strategy to control the process parameters in order to produce desired hardened surface attributes without being forced to use the traditional and fastidious trial and error procedures. This study presents a comprehensive approach used to build a simplified model for predicting the hardness profile. A finite element method based prediction model for AISI 4340 steel is investigated. A circular shape with a Gaussian distribution is used for modeling the laser heat source. COMSOL MULTIPHYSICS software is used to solve the heat transfer equations, estimate the temperature distribution in the part and consequently predict the hardness profile. A commercial 3 kW Nd:Yag laser system is combined to a structured experimental design and confirmed statistical analysis tools for conducting the experimental calibration and validation of the model. The results reveal that the model can effectively lead to a consistent and accurate prediction of the hardness profile characteristics under variable hardening parameters and conditions. The results show great concordance between predicted and measured values for the dimensions of hardened and melted zones.
Raul Miranda, Miguel A. Barron, Carlos A. Hernandez
Modeling and Numerical Simulation of Material Science, Volume 6, pp 59-68; doi:10.4236/mnsms.2016.64006

The horizontal and vertical velocity components of molten steel in a slab continuous casting mold produced by three different two-port Submerged Entry Nozzle (SEN) designs are monitored and compared using Computational Fluid Dynamics (CFD) simulations. These two ports designs correspond to a conventional cylindrical SEN, a plate SEN and an anchor-shaped SEN. Four monitoring points at the molten steel in the centered vertical plane were selected to track the horizontal and the vertical component of the velocity vector. Two of them are located near the free surface and the remaining two are located in the vicinity of the SEN discharge nozzles. Some statistical values of the time series of above the velocity components are analyzed and correlated with the Kelvin-Helmholtz instability and the Karman vortex streets, which cause mold powder entrapment in the molten steel.
Modeling and Numerical Simulation of Material Science, Volume 5, pp 55-62; doi:10.4236/mnsms.2015.54006

This work is dealing with two-temperature generalized thermoelasticity without energy dissipation infinite medium with spherical cavity when the surface of this cavity is subjected to laser heating pulse. The closed form solutions for the two types of temperature, strain, and the stress distribution due to time exponentially decaying laser pulse are constructed. The Laplace transformation method is employed when deriving the governing equations. The inversion of Laplace transform will be obtained numerically by using the Riemann-sum approximation method. The results have been presented in figures to show the effect of the time exponentially decaying laser pulse and the two temperature parameter on all the studied fields.
Modeling and Numerical Simulation of Material Science, Volume 5, pp 49-53; doi:10.4236/mnsms.2015.53005

The equation of state and the shear modulus data of sintered Nd2Fe14B were investigated up to 140 GPa by the Gruneisen’s model, the volume superposition principle and the Hugoniot’s relations. Then, the results were compared to the prior experiments with a standard deviation of 0.125% from 18 GPa to 78 GP; and then, the loading pressure was extended to higher. Meanwhile, the softening feature has not been observed both in adiabat and shear modulus throughout the interested range.
Victor G Zavodinsky, Olga A Gorkusha
Modeling and Numerical Simulation of Material Science, Volume 5, pp 39-47; doi:10.4236/mnsms.2015.52004

Development of the orbital-free (OF) approach of the density functional theory (DFT) may result in a power instrument for modeling of complicated nanosystems with a huge number of atoms. A key problem on this way is calculation of the kinetic energy. We demonstrate how it is possible to create the OF kinetic energy functionals using results of Kohn-Sham calculations for single atoms. Calculations provided with these functionals for dimers of sp-elements of the C, Si, and Ge periodic table rows show a good accordance with the Kohn-Sham DFT results.
Hamid Reza Rezaei Ashtiani, Peyman Karami
Modeling and Numerical Simulation of Material Science, Volume 5, pp 1-14; doi:10.4236/mnsms.2015.51001

The mechanical properties such as hardness and ultimate tensile strength of metals depend on the grain size, which have to be properly controlled and optimized to ensure the better economy and desirable mechanical characteristics of the metals. In order to study the microstructure evolution of AA1070, many experimental tests were conducted at different cold working and annealing conditions. Utilizing the experimental results, the static recrystallization and grain growth behavior of AA1070 have been investigated and the developed equations that can be used to the FEM of the annealing process have been obtained. The agreement between numerical modeling and experimental results is reasonably good for this material. The results showed that the recrystallization and grain growth behavior of AA1070 was evidently affected by both the annealing temperature and plastic strain.
Oscar Andersson, Arne Melander
Modeling and Numerical Simulation of Material Science, Volume 5, pp 26-37; doi:10.4236/mnsms.2015.51003

Resistance spot welding (RSW) is the most common welding method in automotive engineering due to its low cost and high ability of automation. However, physical weldability testing is costly, time consuming and dependent of supplies of material and equipment. Finite Element (FE) simulations have been utilized to understand, verify and optimize manufacturing processes more efficiently. The present work aims to verify the capability of FE models for the RSW process by comparing simulation results to physical experiments for materials used in automotive production, with yield strengths from approximately 280 MPa to more than 1500 MPa. Previous research has mainly focused on lower strength materials. The physical weld results were assessed using destructive testing and an analysis of expulsion limits was also carried out. Extensive new determination of material data was carried out. The material data analysis was based on physical testing of material specimens, material simulation and comparison to data from literature. The study showed good agreement between simulations and physical testing. The mean absolute error of weld nugget size was 0.68 mm and the mean absolute error of expulsion limit was 1.10 kA.
Modeling and Numerical Simulation of Material Science, Volume 5, pp 15-25; doi:10.4236/mnsms.2015.51002

The location and nature of the moisture leakages are sometimes difficult to detect. Moreover, the relation between observed inside surface moisture patterns and where the moisture enters the construction is often not clear. The objective of this paper is to investigate inverse modeling techniques as a tool for the detection of moisture leakage locations in building constructions from inside surface moisture patterns. It is concluded that although the presented methodology is promising, more research is needed to confirm its usability.
Minghu Yuan, Leilei Cao, Yaozeng Xu, Xuding Song
Modeling and Numerical Simulation of Material Science, Volume 4, pp 20-24; doi:10.4236/mnsms.2014.41004

A three-dimensional mathematical and physical model coupling with the heat transfer and the flow of molten metal in the centrifugal casting of the high speed steel roll was established by using CFD software FLUENT. It can be used to analyze the distribution of the temperature filed and the flow filed in the centrifugal casting under the gravity, the electromagnetic stirring force and the centrifugal force. Some experiments were carried out to verify the above analysis results. The effects of the electromagnetic force on the centrifugal casting process are discussed. The results showed that under the 0.15 T electromagnetic field intensity, both the absolute pressure of metal flow to mold wall and the metal flow velocity on the same location have some differences between the electromagnetic centrifugal casting and the centrifugal casting. Numerical results for understanding the electromagnetic stirring of the centrifugal casting process have a guiding significance.
, Akbar Vajd
Modeling and Numerical Simulation of Material Science, Volume 4, pp 32-36; doi:10.4236/mnsms.2014.41006

In this paper, the finite element method was applied to analyze the deformation behavior of Al-1%Mg alloy during constrained groove pressing (CGP). Deformation inhomogeneity was studied in term of plastic strain distribution during deformation. It was found that after first pressing and flattening steps, the plastic strain is inhomogeneous but second pressing and flattening improve deformation distribution considerably. Also the regions between flat and inclined parts of sample receive less shear strain and consequently after four passes the deformation distribution is still inhomogeneous and doesn’t improve remarkably with more deformation steps.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 53-69; doi:10.4236/mnsms.2014.42008

Density functional calculations of the electronic band structure for superconducting and semiconducting metal hexaborides are compared using a consistent suite of assumptions and with emphasis on the physical implications of computed models. Spin polarization enhances mathematical accuracy of the functional approximations and adds significant physical meaning to model interpretation. For YB6 and LaB6, differences in alpha and beta projections occur near the Fermi energy. These differences are pronounced for superconducting hexaborides but do not occur for other metal hexaborides.
, Kamran Dehghani, Ghader Faraji
Modeling and Numerical Simulation of Material Science, Volume 4, pp 128-135; doi:10.4236/mnsms.2014.43014

In this paper, fatigue life circular cross-section elastic bar under pure fatigue axial loading is studied through principles of linear elastic fracture mechanics (LEFM) coupled with the three-dimensional finite element technique for determination of critical crack size and residual lifetime. Three different initial notch depths are discussed. The relations between aspect ratio (b/c) and relative crack depth (b/D) are obtained, and it is shown that there is great difference in the growth of cracks with different front shapes and initial notch depths.
, Sankar Jayaram, Uma Jayaram, Hussein M. Zbib,
Modeling and Numerical Simulation of Material Science, Volume 4, pp 79-93; doi:10.4236/mnsms.2014.43010

In this article, we present a three-dimensional visualization technique that has been developed in order to establish an interactive immersive environment to visualize the particles in granular materials and dislocations in crystals. Simple elementary objects often exhibit complex collective behavior. Understanding of such behaviors and developments of coarse-scale theories, often requires insight into collective behavior that can only be obtained through immersive visualization. By displaying the computational results in a virtual environment with three-dimensional perception, one can immerse inside the model and analyze the intricate and very complex behavior of individual particles and dislocations. We built the stereographic images of the models using OpenGL rendering technique and then combine with the Virtual Reality technology in order to immerse in the three-dimensional model. A head mounted display has been used to allow the user to immerse inside the models and a flock of birds tracking device that allows the movements around and within the immersive environment.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 153-162; doi:10.4236/mnsms.2014.44017

Surface roughness is a commonly used criterion for characterization of surface quality in a machining operation. In the study of micro-scale mechanical properties of machined surface and cutting tool using nanoindentation method, perfect surface finish on the specimen is often required for the reliable indentation result. However, the perfect surface finish is often difficult to obtain from the machining operation due to the dynamic behavior of the machining and the limitation of the cutting tool geometry. In the presented paper, the effect of surface roughness on the nanoindentation measurements is investigated by using finite element method. A 3D finite element model with seven levels of surface roughness is developed to simulate the load-displacement behavior in an indentation process with a Berkovich indenter. The material used in the simulation is AISI 316 L stainless steel, modeled as an elastic-plastic material. The mechanical properties were calculated by combining simulations with the Oliver-Pharr method. The hardness and reduced modulus from the simulation were found to decrease with an increase of roughness. The study showed that the scatter of the load-depth curves and the deviation of the hardness and the reduced modulus are significant affected by the variation of roughness. It was also found that the height of pile-up was little affected by the surface roughness from the simulation. The combined effect of indenter tip radius and surface roughness was also investigated. The study was complemented with experimental tests and the results from these tests support the results from the simulation.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 14-19; doi:10.4236/mnsms.2014.41003

An analytical model describing the physical relations of a UV-based process for halogenation of polymeric surfaces is presented. The process allows, depending on the parameters, a local halogenation with sharp edges at the interfaces to areas where no halogenation is desired. This is achieved via a nonreactive halogen-containing gaseous precursor and a UV source providing photons which dissociate the precursor photolytically. Thus, only where the UV photons affect the precursor, halogens are generated and the polymer is being halogenated.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 37-52; doi:10.4236/mnsms.2014.41007

In this paper, a p-i-n heterojunction based on strain-compensated Si/Si1-xGex/Si multiple quantum wells on relaxed Si1-yGey is proposed for photodetection applications. The Si1-yGey/Si/Si1-xGex/Si/Si1-yGey stack consists in a W-like potential profile strain-compensated in the two low absorption windows of silica fibers infrared (IR) photodetectors. These computations have been used for the study of p-i-n infrared photodetectors operating at room temperature (RT) in the range 1.3 - 1.55 μm. The electron transport in the Si/Si1-xGex/Si multi-quantum wells-based p-i-n structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. These processes were modeled with a system of Schrodinger and kinetic equations self-consistently resolved with the Poisson equation. Temperature dependence of zero-bias resistance area product (RoA) and bias-dependent dynamic resistance of the diode have been analyzed in details to investigate the contribution of dark current mechanisms which reduce the electrical performances of the diode.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 1-7; doi:10.4236/mnsms.2014.41001

In controlled solidification, one of the important factors that affects heat transfer from the solidifying casting is the resistance offered at the casting/chill interface. In the present investigation, heat transfer analysis during solidification of Al-12%Si (LM 13) alloy is carried out by collecting temperature history of the solidifying casting. The temperature distribution during solidification in the present investigation is obtained using ANSYS multiphysics software and further for comparison. The temperature profiles are also obtained by FE (Finite Element) modelling using the same software. By using a temperature data logger and lab view based software, the temperature data is acquired and processed at every second. The cooling curves obtained are analysed to know the effect of chilling on solidification behaviour of Al-12%Si alloy castings. Finally, it is concluded from the above research that the cooling curves and temperature distribution obtained by FE analysis do not so closely converge with the experimental data due to modelling limitations.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 8-13; doi:10.4236/mnsms.2014.41002

The Cahn, Lücke and Stüwe theory remains the backbone of more complex analysis dealing with solute drag, however, the mathematical treatment is rather involved. A new approach based on solute pinning the boundary has therefore recently been suggested, which has the main advantage of a simpler mathematical treatment. In the present paper this approach has been generalized to take into account the influence of different types of solute atoms in the high solute content/low driving force regime.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 25-31; doi:10.4236/mnsms.2014.41005

Cold expansion is an efficient way to improve the fatigue life of an open hole. In this paper, three finite element models have been established to crack growth from an expanded hole is simulated. Expansion and its degree influence are studied using a numerical analysis. Stress intensity factors are determined and used to evaluate the fatigue life. The residual stress field is evaluated using a nonlinear analysis and superposed with the applied stress field in order to estimate fatigue crack growth. Experimental test is conducted under constant loading. The results of this investigation indicate expansion and its degree are a benefit of fatigue life and a good agreement was observed between FEM simulations and experimental results.
Miguel A. Barron, Dulce Y. Medina, Isaias Hilerio
Modeling and Numerical Simulation of Material Science, Volume 4, pp 94-103; doi:10.4236/mnsms.2014.43011

An improved mathematical model to describe the decarburization process in basic oxygen furnaces for steelmaking is presented in this work. This model takes into account those factors or parameters that determine the bath-oxygen impact area, such as the cavity depth, the lance height, the number of nozzles and the nozzles diameter. In the thermal issue, the model includes the targeted carbon content and temperature. The model is numerically solved, and is validated using reported data plant. The oxygen flow rate and the lance height are varied in the numerical simulations to study their effect on the carbon content and decarburization rate.
Modeling and Numerical Simulation of Material Science, Volume 4, pp 104-118; doi:10.4236/mnsms.2014.43012

Thermal expansion coefficients play an important role in the design and analysis of composite structures. A detailed analysis of thermo-mechanical distortion can be performed on microscopic level of a structure. However, for a design and analysis of large structures, the knowledge of effective material properties is essential. Thus, either a theoretical prediction or a numerical estimation of the effective properties is indispensable. In some simple cases, exact analytical solutions for the effective properties can be derived. Moreover, bounds on the effective values exist. However, in dealing with complex heterogeneous composites, numerical methods are becoming increasingly important and more widely used, because of the limiting applicability of the existing (semi-)analytical approaches. In this study, finite-element methods for the calculation of effective thermal expansion coefficients of composites with arbitrary geometrical inclusion configurations are discussed and applied to a heterogeneous lightning protection coating made from Dexmet® copper foil 3CU7-100FA and HexPly® epoxy resin M21. A short overview of some often used (semi-)analytical formulas for effective thermal expansion coefficients of heterogeneous composites is given in addition.
Jihen Chermiti, , , Mhamed Trabelsi, Abdelhamid Errachid
Modeling and Numerical Simulation of Material Science, Volume 4, pp 119-127; doi:10.4236/mnsms.2014.43013

Ions Sensitive Field Effect Transistors (ISFETs) are becoming the platform sensors for important chemical and biomedical applications. However, the accuracy of ISFET output measurement is greatly affected by the presences of low-frequency noise, drift and slow response of the device. This requires more safety in measured results and the tools of analysis. In this paper, we present fundamental limits on the sensitivity of ISFETs micro-sensors, arising from intrinsic and extrinsic noise sources. We developed an algorithm in MATLAB in order to model the frequency analysis of the 1/f noise in ISFET sensor using Hooge theory. We have shown that the 1/f noise of the ISFETs sensors is due to both the electrochemical system (pH solution) and the MOS component (canal size, insulator thickness). The temperature effect on the ISFET noise and the signal conditioning are also performed.
, Volodymyr Grimalsky
Modeling and Numerical Simulation of Material Science, Volume 4, pp 136-142; doi:10.4236/mnsms.2014.43015

Numerical simulations of nonlinear interaction of space charge waves in microwave and millimeter wave range in n-InN films have been carried out. A micro- and millimeter-waves frequency conversion using the negative differential conductivity phenomenon is carried out when the harmonics of the input signal are generated. An increment in the amplification is observed in n-InN films at essentially at high-frequencies f < 450 GHz, when compared with n-GaAs films f < 44 GHz. This work provides a way to achieve a frequency conversion and amplification of micro- and millimeter-waves.
P. P. Mashingo, G. R. John, C. F. Mhilu
Modeling and Numerical Simulation of Material Science, Volume 4, pp 70-77; doi:10.4236/mnsms.2014.42009

Modeling and Numerical Simulation of Material Science, Volume 4, pp 143-152; doi:10.4236/mnsms.2014.44016

Numerical simulations based on a conjugate heat transfer solver have been carried out to analyze various gas quenching configurations involving a helical gear streamed by an air flow at atmospheric pressure in a gas quenching chamber. In order to optimize the heat transfer coefficient distribution at key positions on the specimen, configurations involving layers of gears and flow ducts comprising single to multiple gears have been simulated and compared to standard batch configurations in gas quenching. Measurements have been performed covering the local heat transfer for single gears and batch of gears. The homogeneity of the heat transfer coefficient is improved when setting up a minimal distance between the gears (batch density) and when introducing flow ducts increasing the blocking grade around the gears. An offset between layers of the batch as well as flow channels around the gears plays a significant role in increasing the intensity and the homogeneity of the heat transfer in gas quenching process.
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