Showing 19 results for Simulation
Babaei R., Varahram N., Davami P., Sabzevarzadeh A.,
Volume 1, Issue 2 (6-2004)
Abstract
In this investigation, α 2-D Finite Volume Method (FVM) with unstructured triangular mesh is developed to simulate the mould filling process. The simulation of fluid flow and track of free surface is based on the Marker And Cell (MAC) technique. This technique has capability ofhandling the arbitrary curved solid boundaries in the casting processes. In order to verify the computational results of the simulation, a thin disk plate with transparent mould was tested. The mould filling process was recorded using a 16mm high-speed camera. Images were analyzed frame by frame, in order to tracking of free surface and filling rate during mould filling. Comparison between the experimental method and the simulation results has shown a good agreement.
Mirbagheri S.m.h., Ashouri H., Varahram N., Davami P.,
Volume 1, Issue 2 (6-2004)
Abstract
In this investigation a new model was developed to calculate gas pressure at the melt/foam interface (Gap) resulting from foam degradation during mould filling in the Lost Foam Casting (LFC) process. Different aspects of the process, such as foam degradation, gas elimination, transient mass, heat transfer, and permeability of the refractory coating were incorporated into this model. A Computational Fluid Dynamic (CFD) code was developed based on the numerical technique of the SOLution Algorithm- Volume Of Fluid (SOLA- VOF) utilizing model, for the simulation and prediction of the fluid flow in the LFC process. In order to verify the computational results of the simulation, a thin plate of gray iron was poured into a transparentfoam mould. The mould filling process was recorded using a 16mm high-speed camera. Images were analysed frame by frame, in order to measuring foam depolymerization rate and the gap volume during mould filling. Comparison between the experimental method and the simulation results, for the LFC filling sequence, has shown a good agreement.
Attar E., Babaei R., Homayonifar P., Asgary K., Davami P.,
Volume 1, Issue 4 (12-2004)
Abstract
During mold filling, molten metal can only advance as quickly as the air inside thecavity is expelled. In this work an analytical model describing air flow is developed based on aincompressible flow theory. Air pressure has serious effects upon the filling behaviour such assurface profile and filling time. In this work a new mathematical model is proposed for calculationthe air pressure during the mold filling. A single phase computational fluid dynamic code based onthe SOLA-VOF algorithm used for prediction the fluid flow. Air discharged through the vents ismodelled by ideal gas assumption, conservation of mass equation and Bernoulli law. A newalgorithm was developed to interpolates the air pressure on the surface cell. The creation of airback pressure was correlated with sizes of vents and pouring basin height. In order to verify thecomputational results a series of experimental test was conducted. Comparison between theexperimental data and simulation results has shown a good agreement.
Yahosseini M.r.s., Simchi A., Varahram N., Davami P.,
Volume 2, Issue 1 (3-2005)
Abstract
In the present work, a model was proposed to predict the thermal history during rapid solidification (RS) of metal droplets in the gas atomization process. The classical theory of heterogeneous nucleation was based on Newtonian heat flow and enthalpy method. Solving the governing numerical equations by the finite difference method (FDM) gave up the opportunity of analyzing the temperature-time history of the droplets during cooling in the RS process. Here, cooling in the liquid state, nucleation and recalescence, segregated solidification, eutectic solidification and cooling in the solid state were considered. To verify the model, the gas atomization of Al-4.5% Cu alloy was studied and the results were compared with the Shukla's model [1]. Convincing agreement was obtained between the predicted undercoolings and the experimental results reported previously.
Mirbagheri S.m.h., Chirazi A.,
Volume 2, Issue 3 (9-2005)
Abstract
A numerical model has been developed for the determination of liquid flow permeability through columnar dendrite during growth. The model is inclusive two stages, first numerical evolution of the dendrite shape during growth, and second numerical determination of the interdendritic liquid permeability. Simulation results shown which solute concentration by evolution of dendrite shape could result to reduction of the permeability during solidification time. Comparison between the experimental data from other authors and the present numerical model data, for the low and high solid fractions, has shown a good agreement rather than current numerical models. Therefore present permeability model, in this investigation, could be used for all of the micro solidification codes by coupling on the segregation and the Fick's equations in domain of the inter-dendritic liquid for mushy alloys.
N. Hatami,, R. Babaei, P. Davami,
Volume 5, Issue 2 (6-2008)
Abstract
Abstract: In this study an algorithm for mold-filling simulation with consideration of surface
tension has been developed based on a SOLA VOF scheme. As the governing equations, the
Navier-Stokes equations for incompressible and laminar flows were used. We proposed a way of
considering surface tension in mold-filling simulation. The proposed scheme for surface tension
was based on the continuum surface force (CSF) model we could confirm the remarkable
effectiveness of the surface tension by experiment which concluded in very positive outcome.
S. Kianfar,, S. H. Seyedein, M. R.aboutalebi,
Volume 5, Issue 4 (12-2008)
Abstract
Abstract: The horizontal continuous casting process has received a significant attention for near net shape casting of
non ferrous metals and alloys. Numerical Simulation has been widely used for process design and optimization of
continuous casting process.
In the present study, a 3-dimensional heat flow model was developed to simulate the heat transfer and solidification in
a horizontal billet continuous casting system in which the air gap formation and its effect on heat extraction rate from
solidifying billet was also considered. In order to test the developed model, it was run to simulate the heat transfer
and solidification for an industrial billet caster. The predicted temperature distribution within the mold and billet was
compared with those measured on the industrial caster in which a good agreement was obtained.
Finally, parametric studies were carried out by validated model to evaluate the effects of different parameters on
solidification profile and temperature distribution within the model brass billet. The microstructure of cast billet was
analyzed to determine the secondary dendrite arm spacing (SDAS) under different cooling conditions. Based on
measured SDAS and predicted solidification rate a correlation between SDAS and cooling rate was proposed for
continuously cast brass billet.
B. Mirzakhani,mohammadi, H. Arabi,s. H. Seyedein, M. R. Aboutalebi, M. T. Saleh, Sh. Khoddam,
Volume 6, Issue 3 (9-2009)
Abstract
Abstract:Optimization of specimen geometry before subjecting it to hot torsion test (HTT) is essential for minimizingnon-uniform temperature distribution and obtaining uniform microstructure thought the specimen.In the present study, a nonlinear transient analysis was performed for a number of different geometries andtemperatures using the commercial finite element (FE) package ANSYSTM. FE thermal results then were applied tooptimize HTTspecimen produced from API-X 70 microalloyed steel taking into account the microstructurehomogeneity. The thermodynamic software Thermo-calcTM was also used to analysis solubility of microalloyingelements and their precipitates that may exist at different equilibrium conditions. In addition the behavior of austenitegrain size during reheating was investigated. The results show high temperature gradient occurred in long specimens.This could lead to non homogeneous initial austenite grain size and alloying element or precipitates within the gaugesection of the specimen. The proposed optimization procedure can in general be used for other materials and reheatingscenarios to reduce temperature. This then creates more homogeneous initial microstructure prior to deformation andreduces errors in post processing of the HTTresults
Karmous Mohamed Salah,
Volume 9, Issue 2 (6-2012)
Abstract
Atomistic simulations are carried out for zeolite with ABW framework. The structure is modeled and force field simulations are preformed to investigate its elastic properties, bulk, shear modulus and auxeticity. Bulk moduli (Ks), Shear moduli (G), and Poissons ratios (ν) were found to be Ks=79.71725 GPa, G=16.93265 GPa, νxy = -0.2207, νxz= -0.5730, νyx= -0.71717, νyz=0.87013, νzx= -0.33097 and νzy=1.54568 for ABW the negative value of Poisson’s ratios reflects an auxetic behavior of material. An evaluation of the directional young’s moduli shows that the compressibility of ABW is not uniform along [100], [010] and [001] axes. All calculations were performed using GULP program.
M. Ghanbari, M. R. Aboutalebi, S. G. Shabestari,
Volume 11, Issue 2 (6-2014)
Abstract
Geometrical design of the spiral crystal selector can affect crystal orientation in the final single crystal
structure. To achieve a better understanding of conditions associated with the onset of crystal orientation in a spiral
crystal selector, temperature field was investigated using three-dimensional finite element method during the process.
Different geometries of spiral crystal selector were used to produce Al- 3 wt. % Cu alloy single crystal using a
Bridgman type furnace. The Crystal orientation of the samples was determined using electron backscattered
diffraction (EBSD) and optical microscopy. Analysing the temperature field in the crystal selector revealed that, the
orientation of growing dendrites against liquidus isotherm in the spiral selector was the reason for crystal
misorientation which differs in various selector geometries. Increasing the take-off angle from 35° up to 45° increases
the misorientation with respect to <001> direction. Further increase of take-off angle greater than 45° will decrease
the crystal misorientation again and the efficiency of the selector to produce a single grain is decreased.
A. M. Behagh, A. Fadaei Tehrani, H. R. Salimi Jazi, O. Behagh,
Volume 12, Issue 1 (3-2015)
Abstract
n this paper a finite element model has been proposed for evaluation of primary and secondary current
density values on the cathode surface in nickel electroplating operation of a revolving part. In addition, the capability
of presented electroplating simulation has been investigated in order to describe the electroplated thickness of the
nickel sulfate solution. Nickel electroplating experiments have been carried out. A good agreement between the
simulated and experimental results was found. Also the results showed that primary current density can describe the
general form of thickness distribution but the relative value of current density using secondary current density can
present better description of thickness distribution
A. Salimi, A. Özdemir, A. Erdem,
Volume 12, Issue 3 (9-2015)
Abstract
On time replacement of a cutting tool with a new one is an important task in Flexible Manufacturing Systems
(FMS). A fuzzy logic-based approach was used in the present study to predict and simulate the tool wear progress in
turning operation. Cutting parameters and cutting forces were considered as the input and the wear rate was regarded
as the output data in the fuzzy logic for constructing the system. Flank wear was used as the tool life criterion and the
wear ranges were selected between 0 and 0, 3 based on ISO 3685 standard for new and worn tool respectively. For
conducting the tests, Taghuchi method was used to design an experimental table. The results of the measurements and
estimates confirmed the reliability of the fuzzy logic method for estimating tool wear. One significant feature of the
proposed system is that it can predict the wear rate on-line by transferring the cutting force signals from the sensor to
the fuzzy logic simulation box.
E. Barati, Kh. Farmanesh,
Volume 12, Issue 4 (12-2015)
Abstract
The purpose of this research is to achieve the optimal parameters for producing forged aluminium alloy 7075 aircraft door bracket by using finite element modelling (FEM) with commercial DEFORM-3D V6.1 and physical simulations with plasticine and Plexiglas dies. Also, forging speed has been examined as the main factor for controlling to produce a part without any defects. The results of Physical Simulation showed that the flow pattern has good agreement with the results of FEM that based on the use of hydraulic presses with initial billet and dies temperatures 410 and 400 ° C, respectively, and different forging speeds 5, 10 and 15 mm/sec. Distribution of effective strain rate, effective strain, effective stress, temperature , forging force and dies wear showed improvement the results in forging speed of 5 mm/sec. Processing map of Aluminium alloy 7075 also checked out at constant strain 0.5, indicated that the specified area of the forged part is located in a safe area. Forging force in optimized forging speed 5 mm/sec showed that the forging process using a 1000-ton press can be done easily
M. Shahraki, S. M. Habibi-Khorassani, M. Noroozifar, Z. Yavari, M. Darijani, M. Dehdab,
Volume 14, Issue 4 (12-2017)
Abstract
The inhibition performances of nafcillin (III), methicillin (II) and penicillin G (I) on the corrosion of copper in HCl was studied and tested by weight loss, Tafel polarization, SEM, UV-vis spectrophotometry, molecular dynamics method and quantum chemical calculations. Polarization curves indicated that the studied inhibitors act as mixed-type inhibitors. The values of inhibition efficiency and surface coverage were found to follow the order: Blank
ads, indicated that the adsorption of three inhibitors was a spontaneous process. The SEM micrographs confirmed the protection of copper in a 1 M HCl solution by penicillin G, nafcillin, and methicillin. The shape of the UV/vis spectra of inhibitors in the presence of the immersion of Cu showed a strong support to the possibility of the chemisorbed layer formation on Cu surface by nafcillin (between nafcillin and Copper) and physisorption between penicillin and methicillin with copper. DFT calculations were performed to provide further insight into the inhibition efficiencies which were determined experimentally. Molecular dynamics (MD) simulations were applied to find the most stable configuration and adsorption energies of penicillin G, nafcillin and methicillin molecules on Cu (110) surface. The interaction energy followed the order: nafcillin (III)> methicillin (II)> penicillin G (I), which confirmed that nafcillin has the strongest interaction with the metal surface. The obtained results from experimental and theoretical methods were in reasonable agreement.
A. Kermanpur, H. Ebrahimiyan, A. Heydari, D. Heydari, M. Bahmani,
Volume 14, Issue 4 (12-2017)
Abstract
Formation of stray grain defects particularly around re-entrant features of the turbine blade airfoils is one of the major problems in directional and single crystal solidification processes. In this work, directional solidification tests of the GTD-111 Ni-based superalloy were conducted at different withdrawal velocities of 3, 6 and 9 mm.min-1 using various stepped cylindrical and cubic designs. The process was also simulated using ProCAST finite element solver to characterize the crystal orientations. The phase transformation temperatures of the superalloy were estimated by the differential scanning calorimetry test. A process map was developed to predict the formation of stray grains in the platform regions of the stepped cylindrical and cubic specimens using the experimentally-validated simulation model. The process map shows critical values of the platform size, withdrawal velocity and initial sample size for the stray grain formation. The withdrawal velocity, platform size and initial sample size all had an inverse effect on the formation of stray grains.
H. Esfandiar, S. M. Hashemianzadeh, S. Saffary, S. Ketabi,
Volume 15, Issue 3 (9-2018)
Abstract
Gold nanoparticles have become common in many applications of biotechnology due to their specific properties. Shape and size are important attributes which affect their solubility in water. In this study, the outcomes of Monte Carlo Simulation for the solvation of gold nanorods in aqueous solution with the different radii, in terms of solvation free energy, are discussed. Simulation results show a negative solvation free energy for all the samples with radii of 4 to 9Å. The results show that the absolute values of solvation free energy for gold nanorods with smaller radius are larger, which indicate the dependency between the gold nanorods solvation and their radius.
M. Imran, R. Khan, S. Badshah,
Volume 16, Issue 1 (3-2019)
Abstract
Composite structures are widely used in many applications ranging from, but not limited to, aerospace industry, automotive, and marine structures due to their attractive mechanical properties like high strength to weight ratios. However composite structures needs utmost care during structures manufacturing and working conditions should be assessed prior to installation. One of the important defect in composite structures is delamination. Present work is focused on investigation of delamination effects on the natural frequencies of composite plate using commercial finite element software, ABAQUS. Analytical results were also analyzed using MATLAB code. Different stacking sequences and boundary conditions are considered for study in both analytical formulation and finite element analysis. Finite element results are compared with analytical results to validate the perfect composite plate. The natural frequency of the composite plate reduced with an increase in delamination size. Additionally, all-sides clamped composite plate showed higher values of natural frequency than other constraints in lower modes for symmetrical laminates. Natural frequency in cross ply laminates are higher for the simply supported composite plates. On comparison, results from both the techniques, finite element analysis and analytical analysis, were in good agreement.
Mohammad Ali Maghsoudlou, Reza Barbaz Isfahani, Saeed Saber-Samandari, Mojtaba Sadighi,
Volume 18, Issue 2 (6-2021)
Abstract
The low velocity impact (LVI) response of pure and glass fiber reinforced polymer composites (GFRP) with 0.1, 0.3 and 0.5 wt% of functionalized single-walled carbon nanotubes (SWCNTs) was experimentally investigated. LS-DYNA simulation was used to model the impact test of pure and incorporated GFRP with 0.3 wt% of SWCNT in order to compare experimental and numerical results of LVI tests. All tests were performed in two different levels of energy. In 30J energy, the specimen containing 0.5 wt% SWCNT was completely destructed. The results showed that the incorporated GFRP with 0.3 wt% SWCNT has the highest energy absorption and the back-face damage area of this sample was smaller than other specimens. TEM images from specimens were also analyzed and showed the incorporation of well-dispersed 0.1 and 0.3 wt% of SWCNT, while in specimens containing 0.5 wt% of CNT, tubes tended to be agglomerated which caused a drop in LVI response of the specimen. The contact time of impactor in numerical and experimental results was approximately equal; however, the maximum contact forces in LS DYNA simulation results were higher than the experimental results which could be due to the fact that in the numerical modeling, properties are considered ideal, unlike in experimental conditions.
Assist. Prof. Dr. Saad Mahmood Ali,
Volume 20, Issue 4 (12-2023)
Abstract
In the present work, development models of a new artificial human soft heart and artificial heart valves using nanocomposite materials and synthetics were designed, manufactured, and tested. The fabricated mechanical artificial heart valves were examined to determine the best service life for each type. The fatigue life results were implemented by using the transient repeated and continuously applied blood pressure on each produced value to simulate diastolic and systolic that occur in the natural heart at each pulse cycle. The obtained results showed that a 3D printing of a new generation soft artificial heart for a permanent replacement was implemented as an alternative to the high-cost available temporary implant mechanical hearts, which may exceed the price by tens and hundreds of thousands of dollars, with a working life of not more than five years. The obtained fatigue safety factors for the produced artificial valves using different materials and designs were decreased with the complexity of the movement of the moving parts of the valve. The highest rates were obtained when using the valves with flat, simple movement in one direction like the single-leaflet type valve, where all the used materials are suitable for the production of this type of valve. The highest obtained safety factor was reached (15). The lowest rates were recorded when using the highly flexible and strong PSN4 nanocomposite material for fabricating the mitral tri-leaflet valve (thick. = 1.0 mm) reached 1.91. This value decreases to 0.99 when using the same type and material of valve but with a thickness equal to 0.5 mm. It can be noted here that the only suitable for the manufacture of this artificial valve type is the nanocomposite polyetherimide/ silicone rubber with nano silica (PSN4), whereas the other used materials failed because the fatigue factor values are less than 1. The service life span of this material is about 9200 x 106 cycles, which is equivalent to about 290 years, followed by SIBSTAR 103 with a default age of 209.6 x 106 cycles or 9 years.
