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A. Ghorbanpour Arani,A. Loghman,A. R. Shajari,S. Amir 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.10
In this paper, a semi-analytical solution for magneto-thermo-elastic problem in functionally graded (FG) hollow rotating disks with variable thickness placed in uniform magnetic and thermal fields is presented. Stresses and perturbation of magnetic field vector in FG rotating disks are determined using infinitesimal theory of magneto-thermo-elasticity under plane stress conditions. The material properties except Poisson’s ratio are modeled as power-law distribution of volume fraction. The profile of disk thickness is assumed to be a parabolic function of radius. The non-dimensional distribution of temperature, displacement, stresses and perturbation of magnetic field vector throughout radius are shown. Effects of material grading index, geometry of the disk and magnetic field on the stress and displacement fields are investigated. The results of stresses and radial displacements for two different boundary conditions with and without the effect of magnetic field are compared for a FG rotating disk with concave thickness profile. It has been found that imposing a magnetic field significantly decreases tensile circumferential stresses. Therefore the fatigue life of the disk will be significantly improved by applying the magnetic field. Results of this investigation could be applied for optimum design of FG hollow rotating disks with variable thickness.
A. Loghman,A. Askari Kashan,M. Younesi Bidgoli,A. R. Shajari,A. Ghorbanpour Arani 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.4
The effects of particle content, particle size, operating temperature and magnetic field on steady-state creep behavior of thick-walled rotating cylinders made of Al-SiC composites have been investigated. Loading is composed of a uniform magnetic field in axial direction,steady-state heat conduction in radial direction and an inertia body force due to rotation. The composite creep constitutive equation has been described by Norton's law in which the creep parameters are functions of particle size, temperature and particle content. The composite properties are radial dependent based on volume fraction of SiC reinforcement. It has been found that the minimum effective creep strain rate belongs to a composite identified by 25% SiC at the inner and 5% at the outer surfaces. Therefore this composite has been selected for the design of the cylinder. It has been concluded that increasing particle size and operating temperature significantly increases the effective creep strain rates. It has also been illustrated that magnetic field decreases the stresses and the effective creep strain rates.
A. Ghorbanpour Arani,A. A. Mosallaie Barzoki,R. Kolahchi,A. Loghman 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.9
The axial and torsional wave propagation in a double-walled carbon nanotube (DWCNT) embedded on elastic foundations are investigated using nonlocal continuum shell theory. The effects of the surrounding elastic medium are considered using the spring constant of the Winkler-type and the shear constant of the Pasternak-type. The van der Waals (vdW) forces between the inner and the outer nanotubes are taken into account. The dynamic response of the carbon nanotube is formulated on the basis of nonlocal elasticity shell theory. The cut-off frequencies are obtained and it has been concluded that the cut-off frequencies are independent of small scale coefficient and shear modulus of the elastic medium. It has been found that the phase velocity sharply decreases by increasing the axial half wave number and approaches a constant value. It has also been concluded that the maximum phase velocity predicted by nonlocal theory is located between 5 and 10 nanometers while for local theories the phase velocity sharply decreases in this interval and approaches a constant value. Results show that the effect of Pasternak-type on phase velocity is significant but the effect of Winkler-type is not really considerable.
The Overstrain of Thick-Walled Cylinders Considering the Bauschinger Effect Factor (BEF)
A. Ghorbanpour,A Loghman,H. Khademizadeh,M. Moradi 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.4
An independent kinematic hardening material model in which the reverse yielding point is defined by the Bauschinger effect factor (BEF), has been defined for stainless steel SUS 304. The material model and the BEF are obtained experimentally and represented mathematically as continuous functions of effective plastic strain. The material model has been incorporated in a non-linear stress analysis for the prediction of reverse yielding in thick-walled cylinders during the autofrettage process of these vessels. Residual stress distributions of the independent kinematic hardening material model at the onset of reverse yielding are compared with residual stresses of an isotropic hardening model showing the significant effect of the BEF on reverse yielding predictions. Critical pressures of direct and reverse yielding are obtained for the most commonly used cylinders and a range of permissible internal pressures for an efficient auto-frettaged process is recommended.
The Overstrain of Thick-Walled Cylinders Considering the Bauschinger Effect Facto. (BEF)
Ghorbanpour, A.,Loghman, A.,Khademizadeh, H.,Moradi, M. The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.4
An independent kinematic hardening material model in which the reverse yielding point is defined by the Bauschinger effect factor (BEF) , has been defined for stainless steel SUS 304. The material model and the BEF are obtained experimentally and represented mathematically as continuous functions of effective plastic strain. The material model has been incorporated in a non-linear stress analysis for the prediction of reverse yielding in thick-walled cylinders during the autofrettage process of these vessels. Residual stress distributions of the independent kinematic hardening material model at the onset of reverse yielding are compared with residual stresses of an isotropic hardening model showing the significant effect of the BEF on reverse yielding predictions. Critical pressures of direct and reverse yielding are obtained for the most commonly used cylinders and a range of permissible internal pressures for an efficient autofrettaged process is recommended.
S. Kheirkhah,A. Loghman 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6
In this study, the stresses and electric potential redistributions of a cylinder made from functionally graded piezoelectric material (FGPM) are investigated. All the mechanical, thermal and piezoelectric properties are modeled as power-law distribution of volume fraction. Using the coupled electro-thermo-mechanical relations, strain-displacement relations, Maxwell and equilibrium equations are obtained including the time dependent creep strains. Creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. A semianalytical method in conjunction with the Mendelson method of successive approximation is therefore proposed for this analysis. Similar to the radial stress histories, electric potentials increase with time, because the latter is induced by the former during creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors.
Kheirkhah, S.,Loghman, A. Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.6
In this study, the stresses and electric potential redistributions of a cylinder made from functionally graded piezoelectric material (FGPM) are investigated. All the mechanical, thermal and piezoelectric properties are modeled as power-law distribution of volume fraction. Using the coupled electro-thermo-mechanical relations, strain-displacement relations, Maxwell and equilibrium equations are obtained including the time dependent creep strains. Creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. A semi-analytical method in conjunction with the Mendelson method of successive approximation is therefore proposed for this analysis. Similar to the radial stress histories, electric potentials increase with time, because the latter is induced by the former during creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors.