Shahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Fracture prediction of key-hole notched graphite plates by using the strain energy density based on the equivalent factor conceptFracture prediction of key-hole notched graphite plates by using the strain energy density based on the equivalent factor concept115101810.22044/jsfm.2017.5011.2253FAA.R.TorabiAssoc. Prof., Faculty of New Sciences & Technologies, University of Tehran, Tehran, IranH.R.MajidiM.Sc. Graduated, Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.M.R.AyatollahiJournal Article20161109In this research, the strain energy density criterion is modified to predict the fracture load in engineering components weakened by key-hole notches under tensile-shear mixed mode loading. This new approach is based on the equivalent mode І factor concept as presented in a new closed-form solution. In fact, the new proposed method is the governing idea of the equivalent local mode I concept, which has been formerly applied to U- and V-notches; but in this investigation the new equivalent factor is introduced in order to reduce the numerical analyses. Therefore, by applying the equivalent mode І factor, one can eliminate the large part of the energy section calculation to predict the fracture load of the notched specimens. To verify the validity of the presented new method, the theoretical predictions are compared with a large bulk of experimental data reported in the literature which obtained from the fracture tests on the key-hole notched graphite specimens. Finally, it is shown that new proposed model with a total discrepancy of about 6 % is an appropriate failure criterion.In this research, the strain energy density criterion is modified to predict the fracture load in engineering components weakened by key-hole notches under tensile-shear mixed mode loading. This new approach is based on the equivalent mode І factor concept as presented in a new closed-form solution. In fact, the new proposed method is the governing idea of the equivalent local mode I concept, which has been formerly applied to U- and V-notches; but in this investigation the new equivalent factor is introduced in order to reduce the numerical analyses. Therefore, by applying the equivalent mode І factor, one can eliminate the large part of the energy section calculation to predict the fracture load of the notched specimens. To verify the validity of the presented new method, the theoretical predictions are compared with a large bulk of experimental data reported in the literature which obtained from the fracture tests on the key-hole notched graphite specimens. Finally, it is shown that new proposed model with a total discrepancy of about 6 % is an appropriate failure criterion.https://jsfm.shahroodut.ac.ir/article_1018_0bbcffe85a3691819bfd6cbb6487de5a.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Analysis of torsional and bending stiffness of a sedan vehicle using simplified Finite element modelAnalysis of torsional and bending stiffness of a sedan vehicle using simplified Finite element model1726101910.22044/jsfm.2017.5508.2352FAM.IzanlooM.s, Automotive Simulation and Optimal Design Research labratory, Iran University of Science and Technology, Tehran.A.KhalkhaliAssistant professor, Automotive Simulation and Optimal Design Research labratory, Iran University of Science and Technology, Tehran.Journal Article20170323Simplified models of vehicle body are suitable tools for optimization of main structures of a vehicle in the early phase of design. In this paper, a simplified finite element model for a sedan vehicle is provided. In this model, main load-carrying members such as pillars, rails, rockers and Main floor members with equivalent one dimension beam and panels with coarsening element are replaced. In order to validate the static accuracy of the provided model, the torsional and bending stiffness for Full Finite element model of the vehicle and simplified finite element model are calculated. The result is shown that the simplified model for calculating a torsional and bending stiffness are highly accurate The strong influence of B-pillar on the strength of the structure is obvious in the strain energy, torsional and bending tests. In these tests, after removing the B-Pillar bending and torsional stiffness decrease by 44% and 15%, respectively.Simplified models of vehicle body are suitable tools for optimization of main structures of a vehicle in the early phase of design. In this paper, a simplified finite element model for a sedan vehicle is provided. In this model, main load-carrying members such as pillars, rails, rockers and Main floor members with equivalent one dimension beam and panels with coarsening element are replaced. In order to validate the static accuracy of the provided model, the torsional and bending stiffness for Full Finite element model of the vehicle and simplified finite element model are calculated. The result is shown that the simplified model for calculating a torsional and bending stiffness are highly accurate The strong influence of B-pillar on the strength of the structure is obvious in the strain energy, torsional and bending tests. In these tests, after removing the B-Pillar bending and torsional stiffness decrease by 44% and 15%, respectively.https://jsfm.shahroodut.ac.ir/article_1019_0f7bc0ad8e8a0c4c60aeb5f9f50794d5.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Study on the influences of effective parameters on the fatigue life of welded joint between locomotive gearbox baracket and bogie using FE model verified by experimental resultsStudy on the influences of effective parameters on the fatigue life of welded joint between locomotive gearbox baracket and bogie using FE model verified by experimental results2743102010.22044/jsfm.2017.5369.2314FAA.RajaeeM.S. Student, Engineering and High Tech. Department, Iran University of Industries and Mines, Tehran, Iran.A.Jalali AghchaiAssistant Prof., Faculty of Mech. Eng., K.N.Toosi University Technology, Tehran, Iran.Journal Article20170129In the driving system of trains locomotives, Gearbox bracket connects gearbox to the bogie frame. This baracket is a casting part which welded to the bogie frame and is connected to the gearbox. This part suffers the fluctuating stresses during the train paths in both go and return paths. In this paper, influences of effective parameters on fatigue life of this baracket were investigated. The length of welded lines, material and thickness of baracket are the effective parameters. The FE model in FE Safe software was developed to predict the fatigue life. Factorial design was used to design of experiments. Experiments were done according to designed procedure. Results showed that, weld length, thickness of baracket and material of baracket has greater effect on fatigue life respectively. Also, in the fair choice of parameters, fatigue life became 330440 cycles which is 30.45% more than the fatigue life for initial model of baracket.In the driving system of trains locomotives, Gearbox bracket connects gearbox to the bogie frame. This baracket is a casting part which welded to the bogie frame and is connected to the gearbox. This part suffers the fluctuating stresses during the train paths in both go and return paths. In this paper, influences of effective parameters on fatigue life of this baracket were investigated. The length of welded lines, material and thickness of baracket are the effective parameters. The FE model in FE Safe software was developed to predict the fatigue life. Factorial design was used to design of experiments. Experiments were done according to designed procedure. Results showed that, weld length, thickness of baracket and material of baracket has greater effect on fatigue life respectively. Also, in the fair choice of parameters, fatigue life became 330440 cycles which is 30.45% more than the fatigue life for initial model of baracket.https://jsfm.shahroodut.ac.ir/article_1020_9f3ad6bae0e4bf5fd0b911cc3b9400f1.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Experimental Investigation and Optimization of Bi-Layered Tube Hydroforming Process Parameters with Particle Swarm Optimization AlgorithmExperimental Investigation and Optimization of Bi-Layered Tube Hydroforming Process Parameters with Particle Swarm Optimization Algorithm455393710.22044/jsfm.2017.937FAJ.Shahbazi KaramiPh.D, Mech. Eng., Shahid Rajaee Teacher Training University, Tehran, Iran.M.SheikhiAssis. Prof., Mech. Eng., Shahid Rajaee Teacher Training University, Tehran, Iran.K.Malekzadeh FardProf., Mech. Eng., Maleke Ashtar University of Technology, Tehran, Iran.D.ManafiPh.D. Student, Mech. Eng., Tarbiat Modares University, Tehran, Iran.Journal Article20160811Determining of exact loading paths for bi-layered hydroforming are very neseccery to produce good products that confirmed design specifications. Unfortunately, theoretical formulas don’t exist to determine the process parameters. The process parameters were determined by trial-and-error and experiences of process planner. Therefore, a hybrid method of finite element and particle swarm optimization (PSO) was proposed for determining of the bi-layered hydroforming parameters. First, this process was simulated and verified by experimental data. Then, finite element and optimization algorithm were linked and used to determine of exact process parameters. Two constraints, thickness variations and maximum stress, were considered in the optimization process. Also, conformation of the geometrical dimension of the product with the design dimension was considered as a goal function. Pressure and feed loading paths were optimized in this research and both loading paths were assumed to be linear. Also, external and internal tubes materials are aluminium and copper, respectively. Python programming and ABAQUS software are used for hydroforming process simulation and linking the FE model and particle swarm optimization algorithm.Determining of exact loading paths for bi-layered hydroforming are very neseccery to produce good products that confirmed design specifications. Unfortunately, theoretical formulas don’t exist to determine the process parameters. The process parameters were determined by trial-and-error and experiences of process planner. Therefore, a hybrid method of finite element and particle swarm optimization (PSO) was proposed for determining of the bi-layered hydroforming parameters. First, this process was simulated and verified by experimental data. Then, finite element and optimization algorithm were linked and used to determine of exact process parameters. Two constraints, thickness variations and maximum stress, were considered in the optimization process. Also, conformation of the geometrical dimension of the product with the design dimension was considered as a goal function. Pressure and feed loading paths were optimized in this research and both loading paths were assumed to be linear. Also, external and internal tubes materials are aluminium and copper, respectively. Python programming and ABAQUS software are used for hydroforming process simulation and linking the FE model and particle swarm optimization algorithm.https://jsfm.shahroodut.ac.ir/article_937_571713eb78099111385e4c6e419db38c.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622A survey on processing map for the hot deformation of Copper - Alumina nanocomposites using artificial neural networkA survey on processing map for the hot deformation of Copper - Alumina nanocomposites using artificial neural network5562102110.22044/jsfm.2017.4043.2081FAA.R.PustforushanM.Sc. Student, Mech. Eng., Ferdowsi University of Mashhad, Mashhad, IranP.ZamaniPh.D. Student, Mech. Eng., Ferdowsi University of Mashhad, Mashhad, Iran.R.Masoudi NejadPh.D. Student, Mech. Eng., Ferdowsi University of Mashhad, Mashhad, Iran.M.KadkhodayanProf., Mech. Eng., Ferdowsi University of Mashhad, Mashhad, Iran.Journal Article20160310Based on the mechanic of nanoparticles, the present research studies the deformation of cu-alumina nanocomposite experimentally and also by modeling. To optimize the deformation parameters and to control the microstructure in hot deformation process for copper-alumina nano-composites, cylindrical alumina nanoparticles samples in different percentages has been heat pressure tested. Distributions of alumina nanoparticles in copper, as well as the effects of nanoparticles on deformation have been investigated by transmission electron microscopy (TEM). To study the parameters affecting the deformation of material, the test temperatures of 350, 400, 450, 500° C and strain rates of 0.3, 0.03, 0.003 1/s have been selected. By the results of 48 experiments of stress-strain curves and to optimize the process parameters in the hot deformation, processing map is obtained for different strains. Also the hot deformation behaviors of nano-composites modeling of neural network with 4 input and one output parameters have been used. The modeling and experimental results are compared and the most optimal conditions for hot deformation of nanocomposite materials have been presented.Based on the mechanic of nanoparticles, the present research studies the deformation of cu-alumina nanocomposite experimentally and also by modeling. To optimize the deformation parameters and to control the microstructure in hot deformation process for copper-alumina nano-composites, cylindrical alumina nanoparticles samples in different percentages has been heat pressure tested. Distributions of alumina nanoparticles in copper, as well as the effects of nanoparticles on deformation have been investigated by transmission electron microscopy (TEM). To study the parameters affecting the deformation of material, the test temperatures of 350, 400, 450, 500° C and strain rates of 0.3, 0.03, 0.003 1/s have been selected. By the results of 48 experiments of stress-strain curves and to optimize the process parameters in the hot deformation, processing map is obtained for different strains. Also the hot deformation behaviors of nano-composites modeling of neural network with 4 input and one output parameters have been used. The modeling and experimental results are compared and the most optimal conditions for hot deformation of nanocomposite materials have been presented.https://jsfm.shahroodut.ac.ir/article_1021_c1157677b47ded8d180e7a579554f92b.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Experimental study of the influence of mixing method of nanoclay on mechanical properties of polymer composites and fiber metal laminatesExperimental study of the influence of mixing method of nanoclay on mechanical properties of polymer composites and fiber metal laminates6380102210.22044/jsfm.2017.4885.2227FAM.NajafiPh.D. Student, Mech. Eng., Univ. Campus 2, Guilan Univ., Rasht, IranR.AnsariAssoc. Professor, Mech. Eng., Guilan Univ., Rasht, IranA.DarvizehProfessor, Mech. Eng., Guilan Univ., Rasht, IranJournal Article20161009In this paper, the effect of different types of mixing processes of nanoclay on the mechanical properties of glass fiber/epoxy and fiber metal laminates is studied. For this purpose, the nanoclay was added to pure epoxy resin under mixing process by mechanical mixer, high-speed mechanical homogenizer, and ultrasonic homogenizer. Then, glass fiber/epoxy and fiber metal laminates were fabricated by pure resin and modified resin with nanoclay. In order to achieve high quality in the fabrication of laminate sheets, vacuum operation and post-curing in an autoclave were used under certain temperature and pressure. The effect of two parameters of the nanoclay percent and mixing process on the mechanical properties of the specimens was investigated using Taguchi design of experiments. The results obtained suggest that the nanoclay addition at lower percentages has a more effective role in increasing the flexural strength of the specimens. While by adding nanoclay particles in both material types, the flexural modulus show an increasing trend. Additionally, the result of signal to noise ratio showed that in determining mechanical properties of both material types containing nanoclay, the role of mixing process is more effective than nanoparticle loading.In this paper, the effect of different types of mixing processes of nanoclay on the mechanical properties of glass fiber/epoxy and fiber metal laminates is studied. For this purpose, the nanoclay was added to pure epoxy resin under mixing process by mechanical mixer, high-speed mechanical homogenizer, and ultrasonic homogenizer. Then, glass fiber/epoxy and fiber metal laminates were fabricated by pure resin and modified resin with nanoclay. In order to achieve high quality in the fabrication of laminate sheets, vacuum operation and post-curing in an autoclave were used under certain temperature and pressure. The effect of two parameters of the nanoclay percent and mixing process on the mechanical properties of the specimens was investigated using Taguchi design of experiments. The results obtained suggest that the nanoclay addition at lower percentages has a more effective role in increasing the flexural strength of the specimens. While by adding nanoclay particles in both material types, the flexural modulus show an increasing trend. Additionally, the result of signal to noise ratio showed that in determining mechanical properties of both material types containing nanoclay, the role of mixing process is more effective than nanoparticle loading.https://jsfm.shahroodut.ac.ir/article_1022_0633bce1f914e9df32bfe3e9d4057a55.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Optimization of End milling process for minimizing surface roughness with combined artificial Neural Network and Genetic AlgorithmOptimization of End milling process for minimizing surface roughness with combined artificial Neural Network and Genetic Algorithm8191102710.22044/jsfm.2017.4559.2174FAA.NegarestaniM.Sc., Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.M. H.AbolbashariProf., Department of Mechanical Engineering, Lean Production Engineering Research Center,
Ferdowsi University of Mashhad, Mashhad, Iran.Journal Article20160710Through enormous development of machining methods, applying optimization method in machining process to improve quality seems to be important. One of the most important parameter of a work piece is its surface roughness. As surface roughness decrease, the quality of work piece increase. In this study, optimization of input parameter of end mill machining to reach minimum surface roughness is investigated. Among these parameters five of them selected and Taguchi method is used for the design of experiments. The process is modeled with neural network method and using try and error test 5-8-6-1 architecture. Genetic algorithm is used for process optimizing and neural network model is selected as the target function. For three different tool path strategies, optimization has been conducted and results are discussed. Using genetic algorithm decrease surface roughness to 0.85 μm. Finally selected level of Taguchi method is analyzed and levels with maximum signal to noise ratio are introduced as optimized level that have minimum surface roughness.Through enormous development of machining methods, applying optimization method in machining process to improve quality seems to be important. One of the most important parameter of a work piece is its surface roughness. As surface roughness decrease, the quality of work piece increase. In this study, optimization of input parameter of end mill machining to reach minimum surface roughness is investigated. Among these parameters five of them selected and Taguchi method is used for the design of experiments. The process is modeled with neural network method and using try and error test 5-8-6-1 architecture. Genetic algorithm is used for process optimizing and neural network model is selected as the target function. For three different tool path strategies, optimization has been conducted and results are discussed. Using genetic algorithm decrease surface roughness to 0.85 μm. Finally selected level of Taguchi method is analyzed and levels with maximum signal to noise ratio are introduced as optimized level that have minimum surface roughness.https://jsfm.shahroodut.ac.ir/article_1027_d3f5d616ee9089531317e52a49401556.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Investigation of free and forced vibration of a composite circular cylindrical shell with internal fluidInvestigation of free and forced vibration of a composite circular cylindrical shell with internal fluid93109102810.22044/jsfm.2017.3445.1952FAY.AnsaryanMS.c, Mech. Eng., K. N. Toosi University of Technology, Tehran, Iran.A.AJafariProf., Mech. Eng., K. N. Toosi University of Technology, Tehran, Iran.Journal Article20151007The present study was aimed at investigating the vibration of composite cylindrical shell filled with internal liquid with simple two-headed boundary conditions. The shell was composed of multilayer composite. First-order shear theory was employed to solve the governing equations of the shell. First loves approximation theory was utilized to write strain-displacement and curvature-displacement equations. Natural frequencies of the composite cylindrical shell filled with fluid were calculated using minimum potential energy principle. The fluid was supposed to be ideal. According to the equations that were obtained through analytical solution, a computerized code was written using MATLAB software in order to achieve an answer for analyzing the vibrations of the shell. In order to make sure about the precision of the results, the composite cylindrical shell was modelled in Abacus Software, and modal analysis was carried out for it. Moreover, the effect of different parameters such as presence of fluid, the density and height of the fluid, the orientation of the fibers, and some geometrical parameters on the natural frequencies of the shell were investigated in empty and filled states of the shell. The transient dynamic response of the composite cylindrical shells filled with internal liquid that was under lateral impulse load was calculated through the principle of mode superposition. Finally, the effect of stable load and motivation frequency on the vibrations of the composite cylindrical shell was examined.The present study was aimed at investigating the vibration of composite cylindrical shell filled with internal liquid with simple two-headed boundary conditions. The shell was composed of multilayer composite. First-order shear theory was employed to solve the governing equations of the shell. First loves approximation theory was utilized to write strain-displacement and curvature-displacement equations. Natural frequencies of the composite cylindrical shell filled with fluid were calculated using minimum potential energy principle. The fluid was supposed to be ideal. According to the equations that were obtained through analytical solution, a computerized code was written using MATLAB software in order to achieve an answer for analyzing the vibrations of the shell. In order to make sure about the precision of the results, the composite cylindrical shell was modelled in Abacus Software, and modal analysis was carried out for it. Moreover, the effect of different parameters such as presence of fluid, the density and height of the fluid, the orientation of the fibers, and some geometrical parameters on the natural frequencies of the shell were investigated in empty and filled states of the shell. The transient dynamic response of the composite cylindrical shells filled with internal liquid that was under lateral impulse load was calculated through the principle of mode superposition. Finally, the effect of stable load and motivation frequency on the vibrations of the composite cylindrical shell was examined.https://jsfm.shahroodut.ac.ir/article_1028_e79fba5071ea3506985f80ff277c5cba.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Study on the collapse behavior of multi-cell conical structures and their optimization using artificial neural networksStudy on the collapse behavior of multi-cell conical structures and their optimization using artificial neural networks111127102910.22044/jsfm.2017.5577.2363FAS.PirmohammadAssist. Prof., Mech. Eng., Mohaghegh Ardabili Univ., Ardabil, Iran.S.Esmaeili MarzdashtiM.Sc. Student, Mech. Eng., Mohaghegh Ardabili Univ., Ardabil, Iran.Journal Article20170407In the present research, the collapse behavior of multi-cell conical structures has been studied under axial dynamic loading. These conical structures consisted of two inner and outer walls which have been connected together by several plates as stiffeners. These structures were assumed to have five different cross-sections of square, hexagonal, octagonal, decagonal and circular. Before performing the numerical simulations using LS-DYNA, the numerical results were validated by experimental results. After ensuring correctness of the created finite element models, indicators of SEA and F_max were then computed for all the structures to find the best structure from the crashworthiness point of view. The artificial neural networks and genetic algorithm methods were used to obtain the optimized dimentions of the mentioned structures including θ (cone angle) and S (ratio of the inner wall size to the outer wall one). Among the optimized structures, the best structure was selected using the decision making method called TOPSIS. The multi-cell conical structure with circular cross-section having dimensions of S=0.578 and θ=3.94°, was found to perform the best in terms of crashworthiness capability. Effect of triggers (inner wall and stiffeners) was finally studied, and the results revealed that the triggering by inner wall had a suitable result.In the present research, the collapse behavior of multi-cell conical structures has been studied under axial dynamic loading. These conical structures consisted of two inner and outer walls which have been connected together by several plates as stiffeners. These structures were assumed to have five different cross-sections of square, hexagonal, octagonal, decagonal and circular. Before performing the numerical simulations using LS-DYNA, the numerical results were validated by experimental results. After ensuring correctness of the created finite element models, indicators of SEA and F_max were then computed for all the structures to find the best structure from the crashworthiness point of view. The artificial neural networks and genetic algorithm methods were used to obtain the optimized dimentions of the mentioned structures including θ (cone angle) and S (ratio of the inner wall size to the outer wall one). Among the optimized structures, the best structure was selected using the decision making method called TOPSIS. The multi-cell conical structure with circular cross-section having dimensions of S=0.578 and θ=3.94°, was found to perform the best in terms of crashworthiness capability. Effect of triggers (inner wall and stiffeners) was finally studied, and the results revealed that the triggering by inner wall had a suitable result.https://jsfm.shahroodut.ac.ir/article_1029_f64db546552e2309100495383efab8ce.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Low-velocity impact response of A356/SiCp composite foamLow-velocity impact response of A356/SiCp composite foam129147103010.22044/jsfm.2017.4742.2206FAH.FarahatDepartment of Mechanical Engineering, Birjand Branch, Islamic Azad University, Birjand, Iran.S.Y.Ahmadi BrooghaniDepartment of Mechanical Engineering, University of Birjand, Birjand, Iran.Journal Article20160901Metallic foams are used widely in the automotive and aerospace industries due to high strength to weight ratio and high energy absorption capacity. Knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. In this paper, the impact response of A356 aluminum foams reinforced by SiC particles was studied. Predicted numerically results, which are obtained from the simulation of impact behavior at the foam material, were compared and validated with the experimental measurements. For determination of the material parameters in Deshpande-Fleck constitutive model, the uniaxial compression test data have been used. The FEM results showed that the changes in load with time are in a good agreement with the impact experiment. The numerical model can predict accurately the plateau load, the impact time, the energy absorbed by foam and the failure mode of the material. The energy balance diagram and convergence test confirm the simulation. Considering that the simulation of porous and composite material behavior is faced with numerous challenges, this work presents effective ways to solve them. Regarding the lack of numerical and experimental results on the impact behavior of A356/SiCp foam, the obtained results can be used to develop advanced composite materials.Metallic foams are used widely in the automotive and aerospace industries due to high strength to weight ratio and high energy absorption capacity. Knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. In this paper, the impact response of A356 aluminum foams reinforced by SiC particles was studied. Predicted numerically results, which are obtained from the simulation of impact behavior at the foam material, were compared and validated with the experimental measurements. For determination of the material parameters in Deshpande-Fleck constitutive model, the uniaxial compression test data have been used. The FEM results showed that the changes in load with time are in a good agreement with the impact experiment. The numerical model can predict accurately the plateau load, the impact time, the energy absorbed by foam and the failure mode of the material. The energy balance diagram and convergence test confirm the simulation. Considering that the simulation of porous and composite material behavior is faced with numerous challenges, this work presents effective ways to solve them. Regarding the lack of numerical and experimental results on the impact behavior of A356/SiCp foam, the obtained results can be used to develop advanced composite materials.https://jsfm.shahroodut.ac.ir/article_1030_ee36e51482d3ad160790fc3c9ee00e3b.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Experimental Investigation of wake on an elliptic cylinder in the presence of tripping wireExperimental Investigation of wake on an elliptic cylinder in the presence of tripping wire149163103110.22044/jsfm.2017.3999.2067FAA.Bak KhoshnevisAssoc. Prof., Mech. Eng., Hakim Sabzevari Univ., Sebzevar, Iran.S.NazariM.S.C., Mech. Eng., Hakim Sabzevari Univ., Sabzevar, Iran.M. J.Ezadi YazdiM.S.C., Mech. Eng., Hakim Sabzevari Univ., Sabzevar, Iran.Journal Article20160221In this research, the behavior and characteristics of the wake of flow around an elliptic cylinder at zero angle of attack in the presence of a tripping wire were investigated experimentally. An aluminum elliptic cylinder with major axis, minor axis and height of 42.4 mm, 21.2 mm and 390 mm respectively, was used for this purpose. The cylinder model was examined in the test section of a blower type wind tunnel. The Reynolds numbers of the experiment based on major axis are 25700 and 51400 for 10 m/s and 20 m/s speeds, respectively. Tripping wires with the diameter of 0.5 mm, 1 mm, and 1.5 mm are placed symmetrically at both sides of the cylinder, and each are tested at angles of zero, 23.7, and 40.9 degrees with respect to the stagnation point. The drag coefficient of the smooth cylinder for both of the Reynolds numbers is about 0.6. The results indicate that in the best possible case, the drag coefficient for the 0.5 mm wire decreases by 75%. In the best cases, it is also reduced by 56.9% and 65.5% for the 1 mm and the 1.5 mm wires, respectively.In this research, the behavior and characteristics of the wake of flow around an elliptic cylinder at zero angle of attack in the presence of a tripping wire were investigated experimentally. An aluminum elliptic cylinder with major axis, minor axis and height of 42.4 mm, 21.2 mm and 390 mm respectively, was used for this purpose. The cylinder model was examined in the test section of a blower type wind tunnel. The Reynolds numbers of the experiment based on major axis are 25700 and 51400 for 10 m/s and 20 m/s speeds, respectively. Tripping wires with the diameter of 0.5 mm, 1 mm, and 1.5 mm are placed symmetrically at both sides of the cylinder, and each are tested at angles of zero, 23.7, and 40.9 degrees with respect to the stagnation point. The drag coefficient of the smooth cylinder for both of the Reynolds numbers is about 0.6. The results indicate that in the best possible case, the drag coefficient for the 0.5 mm wire decreases by 75%. In the best cases, it is also reduced by 56.9% and 65.5% for the 1 mm and the 1.5 mm wires, respectively.https://jsfm.shahroodut.ac.ir/article_1031_e3e234281454d7cbc29e12d5724ce4d4.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Investigation of Stability of Noncircular Lobed Journal Bearings Lubricated by FerrofluidInvestigation of Stability of Noncircular Lobed Journal Bearings Lubricated by Ferrofluid165177103210.22044/jsfm.2017.4256.2125FAR.Rashidi MeybodiAssis. Prof., Mech. Eng., Payame Noor Univ., Tehran, Iran.N.FarehyfarM. Sc. Student, Mech. Eng., Yazd Univ., Yazd, Iran.A.Dashti RahmatabadiAssoc. Prof., Mech. Eng., Yazd Univ., Yazd, Iran.M.Zare MehrjardiAssis. Prof., Mech. Eng., Ardakan Univ., Ardakan, Iran.Journal Article20160425Nowadays, the demand for journal bearings operating at high speeds and also the importance of their stability in practical usage has caused a need for noncircular lobed bearings instead of circular bearings. This makes the extreme effects of lubrication kind in bearing performance more important. For this reason, choosing appropriate lubricant is of great significance. Ferrofluids as a result of having unique features can be considered as one of the choices. The aim of this paper is to study the stability of two, three and four lobe noncircular journal bearings lubricated with ferrofluids considering parameters such as eccentricity ratio, the ratio of length to diameter and also the magnetic force coefficient. In this work, the numerical method of finite elements is used to solve the equations. The results show that by increasing the eccentricity ratio and the length to diameter ratio and also by decreasing the magnetic force coefficient, bearing stability increases. As well as, by increasing the number of lobes in noncircular lobed bearings, it is possible to get more stability range.Nowadays, the demand for journal bearings operating at high speeds and also the importance of their stability in practical usage has caused a need for noncircular lobed bearings instead of circular bearings. This makes the extreme effects of lubrication kind in bearing performance more important. For this reason, choosing appropriate lubricant is of great significance. Ferrofluids as a result of having unique features can be considered as one of the choices. The aim of this paper is to study the stability of two, three and four lobe noncircular journal bearings lubricated with ferrofluids considering parameters such as eccentricity ratio, the ratio of length to diameter and also the magnetic force coefficient. In this work, the numerical method of finite elements is used to solve the equations. The results show that by increasing the eccentricity ratio and the length to diameter ratio and also by decreasing the magnetic force coefficient, bearing stability increases. As well as, by increasing the number of lobes in noncircular lobed bearings, it is possible to get more stability range.https://jsfm.shahroodut.ac.ir/article_1032_8dc4e18fdf8f766080690d713d285b4d.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Volume fraction measurement in gas-liquid two phase flow using gamma radiation scatteringVolume fraction measurement in gas-liquid two phase flow using gamma radiation scattering179187103310.22044/jsfm.2017.4896.2229FAA.FatehiShahid Beheshti University, Department of Radiation Application, Tehran, Iran.Gh. H.RoshaniElectrical Engineering Department, Kermanshah University of Technology, Kermanshah, Iran.S.A.H.FeghhiShahid Beheshti University, Department of Radiation Application, Tehran, Iran.Journal Article20161010During the last three decades, development, evaluation, and use of multiphase-flow- measurement systems have been a major focus for the oil and gas industry worldwide. Volume fraction measurement of the multi phase flows, especially gas - liquid two phase flows is so important issue in the oil and petroleum industry. Volume fractions are key parameters in multi phase flow rate metering. In this study, volume fraction of each phase was measured using gamma ray scattering and artificial neural network. The density of two phase flow is related to the volume fractions and number of the scattered gamma can be changed with this density. 137Cs single energy source and one 3-inch NaI (Tl) scintillation detector were used and the registered counts in the detector were applied to the multi layer neural network. The output of the network was gas volume fraction which was predicted with the mean relative error of less than 2.5%.During the last three decades, development, evaluation, and use of multiphase-flow- measurement systems have been a major focus for the oil and gas industry worldwide. Volume fraction measurement of the multi phase flows, especially gas - liquid two phase flows is so important issue in the oil and petroleum industry. Volume fractions are key parameters in multi phase flow rate metering. In this study, volume fraction of each phase was measured using gamma ray scattering and artificial neural network. The density of two phase flow is related to the volume fractions and number of the scattered gamma can be changed with this density. 137Cs single energy source and one 3-inch NaI (Tl) scintillation detector were used and the registered counts in the detector were applied to the multi layer neural network. The output of the network was gas volume fraction which was predicted with the mean relative error of less than 2.5%.https://jsfm.shahroodut.ac.ir/article_1033_b1ea6c9edd61c2954274eee6b23f9691.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Numerical simulation of thermal storage using phase-change materialNumerical simulation of thermal storage using phase-change material189213103410.22044/jsfm.2017.5410.2333FAB.BarariM.A., Department of Mechanical Engneering, Mazandaran University of Science and Technology, Babol, Iran.A. A.RanjbarProfessor (PhD), Department of Mechanical Engineering, Babol University of Technology, Iran.Journal Article20170422This dissertation investigates the analysis of thermal energy storage system using phase change materials to improve. In this study for three different distances between tubes in heat exchangers, the effect of inner tubes arrangement on melting and solidification behavior of energy storage system is investigated. Then, in order to investigate the effect of adding tubes, a comparison have been done between heat exchangers with the least melting time. The results show that regardless of the number of tubes, their arrangement and the distance between them, the melting time decreases with respect to one tube heat exchanger. By increasing the number of tubes to five, changing the arrangement with the constant distance between tubes, does not affect melting time, however the distance between tubes is still effective. Comparing the heat exchangers with the least melting time with each other, it can be shown that variation in this distance, increases the melting time. Also increasing the tube numbers to more than four, does not affect the melting time any more. Except two tubes heat exchangers, the least solidification time happens in cases with the least melting time. By increasing the number of tubes from two to three, the time increasing is more than other cases in charging and discharging process.This dissertation investigates the analysis of thermal energy storage system using phase change materials to improve. In this study for three different distances between tubes in heat exchangers, the effect of inner tubes arrangement on melting and solidification behavior of energy storage system is investigated. Then, in order to investigate the effect of adding tubes, a comparison have been done between heat exchangers with the least melting time. The results show that regardless of the number of tubes, their arrangement and the distance between them, the melting time decreases with respect to one tube heat exchanger. By increasing the number of tubes to five, changing the arrangement with the constant distance between tubes, does not affect melting time, however the distance between tubes is still effective. Comparing the heat exchangers with the least melting time with each other, it can be shown that variation in this distance, increases the melting time. Also increasing the tube numbers to more than four, does not affect the melting time any more. Except two tubes heat exchangers, the least solidification time happens in cases with the least melting time. By increasing the number of tubes from two to three, the time increasing is more than other cases in charging and discharging process.https://jsfm.shahroodut.ac.ir/article_1034_437c0d3f76ab15d8dbff7ce2a67579e7.pdfShahrood University of TechnologyJournal of Solid and Fluid Mechanics2251-94757220170622Modification of k-e-v 2 Turbulence Model for Turbulent Accelerated Flows in PipesModification of k-e-v 2 Turbulence Model for Turbulent Accelerated Flows in Pipes21522894110.22044/jsfm.2017.941FAA.KhaleghiAssis. Prof., Mech. Eng., Shahrood University of Technology, Shahrood, Iran.M.PasandidehFardAssoc. Prof., Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.Journal Article20160829In this study k-e-v2 turbulence model has been considered and modified for pipe flows in accelerating condition. In order to determine the characteristics of the fluid under the non-periodic accelerating conditions and using water as the working fluid, k-e-v2 model has been under taken. This model imposes the wall effects into the flow field properly. However, most of turbulence models cannot predict this phenomenon appropriately for unsteady flows. Although, k-e-v2 model is the best among the same turbulence models, however, still it needs some modifications. First, the weight coefficient of various parameters effects available in this model have been considered thoroughly. Then the most effective parameter has been obtained. It has been found that the parameter and its differential equation must be modified to correlate the experimental data desirably. Considering the point that v2 has the same dimension of k-equation, its effect is imposed into this equation. Further, this modification has been examined for internal pipe flows with different periods of accelerations. It was found that the results of some characteristics of flow such as turbulence kinetic energy and wall shear stress for different accelerations of flow are improved desirably compared to the experimental data.In this study k-e-v2 turbulence model has been considered and modified for pipe flows in accelerating condition. In order to determine the characteristics of the fluid under the non-periodic accelerating conditions and using water as the working fluid, k-e-v2 model has been under taken. This model imposes the wall effects into the flow field properly. However, most of turbulence models cannot predict this phenomenon appropriately for unsteady flows. Although, k-e-v2 model is the best among the same turbulence models, however, still it needs some modifications. First, the weight coefficient of various parameters effects available in this model have been considered thoroughly. Then the most effective parameter has been obtained. It has been found that the parameter and its differential equation must be modified to correlate the experimental data desirably. Considering the point that v2 has the same dimension of k-equation, its effect is imposed into this equation. Further, this modification has been examined for internal pipe flows with different periods of accelerations. It was found that the results of some characteristics of flow such as turbulence kinetic energy and wall shear stress for different accelerations of flow are improved desirably compared to the experimental data.https://jsfm.shahroodut.ac.ir/article_941_412a2f1d082d277f461623f6caf67937.pdf