Research Paper
Heat and Mass Transfer
M. Gnaneswara Reddy
Abstract
This paper was concerned with studying the magnetohydrodynamic steady laminar free convection flow of a micropolar fluid past a continuously moving surface in the presence of heat generation and thermal radiation. Similarity transformation was employed to transform the governing partial differential ...
Read More
This paper was concerned with studying the magnetohydrodynamic steady laminar free convection flow of a micropolar fluid past a continuously moving surface in the presence of heat generation and thermal radiation. Similarity transformation was employed to transform the governing partial differential equations into ordinary ones, which were then solved numerically using the finite element method. Numerical results for the dimensionless velocity, microrotation and temperature profiles were obtained and displayed graphically for pertinent parameters to show interesting aspects of the solution. The skin friction and the rate of heat transfer were also computed and presented through tables. Favorable comparison with previously published work was performed.
Research Paper
Vibration
M. Shariati; H. Hatami; M. Damghani Nouri
Abstract
In this research, softening and ratcheting behaviors of Ck20 alloy steel cylindrical shells were studied under displacement-control and force-control cyclic axial loading and the behavior of hysteresis curves of specimens was also investigated. Experimental tests were performed by a servo-hydraulic INSTRON ...
Read More
In this research, softening and ratcheting behaviors of Ck20 alloy steel cylindrical shells were studied under displacement-control and force-control cyclic axial loading and the behavior of hysteresis curves of specimens was also investigated. Experimental tests were performed by a servo-hydraulic INSTRON 8802 machine. The mechanical properties of specimens were determined according to ASTM E8 standard. Under force-control loading with non-zero mean force, ratcheting behavior occurred on cylindrical shell and plastic strain accumulation continued up to the collapse point of cylindrical shell. The rate of ratcheting strain became higher using the higher force amplitude. Softening behavior was observed under displacement control loading and, due to the occurred buckling in compression zone, this behavior became more extreme. The behavior of hysteresis curves of this alloy was not symmetrical under tensile and compressive loads. Moreover, the influence of loading history was studied on the behavior of hysteresis curves of the specimens under various types of loadings.
Research Paper
Composite Materials
Y. Bayat; M. Alizadeh; A. Bayat
Abstract
In this paper, a general solution for torsion of hollow cylinders made of functionally graded materials (FGM) was investigated. The problem was formulated in terms of Prandtl’s stress and, in general, the shear stress and angle of twist were derived. Variations in the material properties such as ...
Read More
In this paper, a general solution for torsion of hollow cylinders made of functionally graded materials (FGM) was investigated. The problem was formulated in terms of Prandtl’s stress and, in general, the shear stress and angle of twist were derived. Variations in the material properties such as Young’s modulus and Poisson’s ratio might be arbitrary functions of the radial coordinate. Various material models from the literature were also used and the corresponding shear stress and angle of twist were individually computed. Moreover, by employing ABAQUS simulations, finite element results were compared with the analytical ones.
Research Paper
Thermodynamics and Cumbustion
A. H. Kakaee; J. Zareei
Abstract
Engine performance depends on two main factors of engine speed and ignition time. Ignition timing can affect engine life, fuel economy and engine power. In this paper, to study engine performance of Peugeot 206 TU3A with comparison ratio of 10.5:1 and displacement of 1361CC in MATLAB software, a two-zone ...
Read More
Engine performance depends on two main factors of engine speed and ignition time. Ignition timing can affect engine life, fuel economy and engine power. In this paper, to study engine performance of Peugeot 206 TU3A with comparison ratio of 10.5:1 and displacement of 1361CC in MATLAB software, a two-zone burned/unburned model with the fuel burning rate described by aWiebe function was used for modeling in-cylinder combustion. For studying this issue, thermodynamic models such as Woshni, Isentropic, etc. were used. Then, the experiments were carried out to validate the calculated data. The objective of the present work was to examine effect of ignition timing on the performance of an SI engine. For achieving this goal, at the speed of 3400 rpm, ignition timing was changed in the range of 41 degrees before the top dead centre to 10 degrees after TDC. By changing the ignition timing, the results of some characteristics such as power, torque, indicatory pressure, exhaust emission and efficiency were obtained and compared. The results demonstrated that optimal power and torque and the maximum efficiency were achieved at 31 degrees before the top dead centre and engine performance was improved by changing timing angle. It was also indicated that the maximum thermal efficiency could be accomplished while peak pressure occurred between 5 and 15 degrees of ATDC. The amounts of O2, CO2 and CO were almost constant but HC increased with increase of ignition timing.
Research Paper
Heat and Mass Transfer
Aminreza Noghrehabadi; Mohammad Ghalambaz; Amin Samimi
Abstract
In this paper, an integration of a symbolic power series method - Padé approximation technique (PS - Padé), was utilized to solve a system of nonlinear differential equations arising from the similarity solution of laminar thermal boundary layer over a flat plate subjected to a convective ...
Read More
In this paper, an integration of a symbolic power series method - Padé approximation technique (PS - Padé), was utilized to solve a system of nonlinear differential equations arising from the similarity solution of laminar thermal boundary layer over a flat plate subjected to a convective surface boundary condition. As both boundary conditions tended to infinity, the combination of series solutions with the Padé approximants was used for handling boundary conditions on the semi-infinite domain of solution. The combination of power series and Padé proposed an alternative approach of solution which did not require small parameters and avoided linearization and physically unrealistic assumptions. The results of the present approach were compared with numerical results as well as those of previous works reported in the literature. The obtained results represented remarkable accuracy in comparison with the numerical ones. Finally, reduced Nusselt number, as an important parameter in heat transfer, was calculated by the obtained analytical solution. The present power series-Padé technique was very simple and effective, which could develop a simple analytic solution for flow and heat transfer over the flat plate. The results of the present study could be easily used in practical applications.
Research Paper
Nonlinear Solution
M. Matinfar; M. Ghasemi
Abstract
Variational Iteration method using He's polynomials can be used to construct solitary solution and compacton-like solution for nonlinear dispersive equatioons. The chosen initial solution can be determined in compacton-like form or in solitary form with some compacton-like or solitary forms with ...
Read More
Variational Iteration method using He's polynomials can be used to construct solitary solution and compacton-like solution for nonlinear dispersive equatioons. The chosen initial solution can be determined in compacton-like form or in solitary form with some compacton-like or solitary forms with some unknown parameters, which can be determined in the solution procedure. The compacton-like solution and solitary solution can be converted into each other.
Research Paper
Forming
Gh. Payganeh; J. Shahbazi Karami; K. Malekzadeh Fard
Abstract
In this paper, single, bi-layered and three-layered tube hydroforming processes were numerically simulated using the finite element method. It was found that the final bulges heights resulted from the models were in good agreement with the experimental results. Three types of modeling were kept with ...
Read More
In this paper, single, bi-layered and three-layered tube hydroforming processes were numerically simulated using the finite element method. It was found that the final bulges heights resulted from the models were in good agreement with the experimental results. Three types of modeling were kept with the same geometry, tube material and process parameters to be compared between the obtained hydroformed products (branch height, thickness reduction and wrinkling) using different loading path types. The results were also discussed.
