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1.
A. Ghorbanpour Arani S. Golabi A. Loghman H. Daneshi 《Journal of Mechanical Science and Technology》2007,21(7):983-996
In this paper, the elastic axisymmetric buckling of a thin, isotropic and simply supported cylindrical shell with an elastic
core under axial compression has been analyzed using energy method. The nonlinear strain-displacement relations in general
cylindrical coordinates are simplified using Sanders kinematic relations (Sanders, 1963) for axial compression. Equilibrium
equations are obtained by using minimum potential energy together with Euler equations applied for potential energy function
in cylindrical shell. To acquire stability equation of cylindrical shell with an elastic core, minimum potential energy theory
and Trefftz criteria are implemented. Stability and compatibility equations for an imperfect cylindrical shell with an elastic
core are also obtained by the energy method, and the buckling analysis of shell is carried out using Galerkin method. Critical
load curves versus the aspect ratio are obtained and analyzed for a cylindrical shell with an elastic core. It is concluded
that the application of an elastic core increases elastic stability and significantly reduces the weight of cylindrical shells. 相似文献
2.
This paper describes a numerical model developed for the computation of creep damages in a thick-walled sphere subjected to
an internal pressure and a thermal gradient. The model predicts the creep damage histories during the life of the sphere,
owing to variations in stresses with time and through-thickness variations. The creep damage fraction is based on the Robinson’s
linear life fraction damage rule, which has been incorporated in a nonlinear time-dependent stress analysis. Following the
stress histories, the effective stress histories are obtained and the creep damages are calculated and summed during the life
of the sphere. The material long-term creep properties up to the rupture and creep rupture data are defined by the Θ projection
concept [1]. The damage histories up to 38 years are calculated and the results show that the maximum damages are always located
at the inner surface of the sphere, while the outer surface of the vessel sustains minimum damages. 相似文献
3.
This research aims to create the durable self-cleaning property on cotton fabric using nano titanium dioxide and corona treatment as a dry and environmentally friendly process. In this regard, cotton fabrics were investigated under corona treatment with intensities of 2 and 3 A for 1, 3, and 5?min of irradiation. The treated samples with 0.1, 0.5, 1, and 1.5 on weight of bath percent were cured by nano titanium dioxide to obtain the highest self-cleaning property. The treated cotton fabrics, which were stained with direct green 6, were exposed to 20 and 400?W of UV radiation and their self-cleaning property was examined, and the results were reported. In addition, using corona treatment helped to stabilize the nano titanium dioxide on the cotton fabric surface even after 50 washing cycles. Through SEM images, Thermo Gravimetric Analysis plots, and XRD patterns, the presence of nano titanium dioxide on the surface of the treated cotton samples after washing was verified. Also, the tensile strengths of TiO2-coated cotton fabrics were measured. 相似文献
4.
Masoumeh shahriari KallehMasihi Mohammad Reza Loghman Estarki Hojjatollah Mansouri Hossein Jamali Mehran Sardarian Gholam Reza Gordani 《International Journal of Applied Ceramic Technology》2022,19(5):2500-2513
The purpose of this work is to optimize the feed containing alumina-binder nanoparticles for ceramics injection molding to create transparent alumina parts. In this research, two Alumina with and without MgO as sintering aid fabricated via the spark plasma sintering method. Feed fluidity, fracture toughness, density, IR, and visible transmission of SPSed bodies of the sintered pieces were measured. Furthermore, a pin on the disc test was used on the disk to examine the alumina friction coefficient. The results of feed rheology showed that the sample prepared at 90°C had the best conditions as a pseudoplastic fluid for the ceramic injection molding (CIM) method. The results showed that a combination of CIM and spark plasma sintering (SPS) methods cause more visible transmission than conventional SPS of alumina nanopowder. Also, the fracture toughness and hardness of as-obtained transparent alumina were in the range of 3.6 MPa m0.5 and 20.1 MPa, respectively. The wear rate of the as-obtained transparent sample (4.5 × 10−7 mm3/N m) was proportional to the alumina grain size (1–4 μm). 相似文献
5.
Bastani Parnia Mohseni Seyed Majid Jamilpanah Loghman Azizi Behnam Gharehbagh Javad Shoa e 《Journal of Materials Science: Materials in Electronics》2022,33(9):6403-6410
Journal of Materials Science: Materials in Electronics - Heterostructures of materials can possess the prominent characteristics of their individual layers or gain newly emerged interface effects... 相似文献
6.
Namdari Tahereh Manouchehri Sohrab Loghman Estarki Mohammad Reza 《Journal of Materials Science: Materials in Electronics》2022,33(24):19434-19446
Journal of Materials Science: Materials in Electronics - In this work, the cubic structure of Yttria-stabilized Zirconia (8YSZ) and Indium and Erbium co-doped 8YSZ nanopowders have been prepared by... 相似文献
7.
A. Ghorbanpour Arani A.A. Mosallaie Barzoki R. Kolahchi M.R. Mozdianfard A. Loghman 《Computers & Structures》2011,89(15-16):1494-1502
History of strains, stresses, deformations and electric potentials of hollow cylinders made from PZT_5 have been investigated using successive elastic solution method. A differential equation containing creep strains for displacement is obtained. Since creep strains are time, temperature and stress dependent, the closed form solution cannot be found for this constitutive differential equation. Hence, a semi-analytical method is proposed. Electric potentials increase with time (similar to the radial stress histories), since it is induced by the radial stress histories during creep deformation of the cylinder, justifying industrial application of such a material as efficient actuators and sensors. 相似文献
8.
Time-dependent creep response of a smart sphere made of functionally graded piezoelectric material (FGPM) is investigated. The vessel is subjected to an internal pressure, a uniform temperature field, an electric potential and a uniform magnetic field. Under such a loading condition initial elastic stresses are locked in the vessel at zero time. Due to high temperature, creep evolution causes stress redistribution in the sphere which is followed by electric potential redistribution across the thickness of the sphere. History of radial stresses is always reflected by history of electric potential which can be used for condition monitoring of the smart sphere. From the initial elastic stresses it has been found that imposing an electric potential decreases effective stresses. It has also been concluded from history of electric potential that electric potential redistribution is decreasing due to creep evolution and therefore this is followed by increasing effective stresses. 相似文献
9.
A. Ghorbanpour Arani A. Loghman A. R. Shajari S. Amir 《Journal of Mechanical Science and Technology》2010,24(10):2107-2118
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. 相似文献
10.
A. Loghman A. Ghorbanpour Arani S. M. A. Aleayoub 《Mechanics of Time-Dependent Materials》2011,15(4):353-365
Time-dependent creep stress redistribution analysis of thick-walled spheres made of functionally graded material (FGM) subjected
to an internal pressure and a uniform temperature field is performed using the method of successive elastic solution. The
material creep and mechanical properties through the radial graded direction are assumed to obey a simple power-law variation.
Total strains are assumed to be the sum of elastic, thermal and creep strains. Creep strains are time, temperature and stress
dependent. Using the equations of equilibrium, compatibility and stress–strain relations a differential equation, containing
creep strains, for radial stress are obtained. Ignoring creep strains, a closed-form solution for initial thermoelastic stresses
at zero time is presented. It has been found that the material in-homogeneity parameterβ has a substantial effect on thermoelastic stresses. From thermoelastic analysis the material identified by β=2 in which a more uniform shear stress distribution occurs throughout the thickness of the FGM sphere is selected for time-dependent
stress redistribution analysis. Using the Prandtl–Reuss relations and Norton’s creep constitutive model, history of stresses
and strains are obtained. It has been found that radial stress redistributions are not significant, however, major redistributions
occur for circumferential and effective stresses. It has also been concluded that stresses and strains are changing with time
at a decreasing rate so that there is a saturation condition beyond which not much change occurs. Indeed after 50 years the
solution approaches the steady-state condition. 相似文献