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    Optimization of the Arrangement of Internal Rib Stiffeners for Columns of the Milling Machine to Achieve Maximum Stiffness and Maximum Working Frequency Range.

    , M.Sc. Thesis Sharif University of Technology Shokri, Aziz (Author) ; Akbari, Javad (Supervisor)
    Vertical milling machine is one of the most common machine tools for precision parts production. The static deflection of the machine tool and thus the displacement of the tool, is due to the high machining forces is the most important factor in reducing the dimensional Precision of the work piece. Also, the overlap of the frequency range of operation with the natural frequencies causes an undesirable resonance phenomenon. Reducing the strain energy of the column and thus the reducing the displacement of the tool, and increasing the first natural frequency of the milling machine, given that the frequency range of operating is below the first frequency, is a desirable change that can be... 

    Design of spherical vessels under steady-state thermal loading using thermo-elasto-plastic concept

    , Article International Journal of Pressure Vessels and Piping ; Volume 86, Issue 2-3 , 2009 , Pages 143-152 ; 03080161 (ISSN) Darijani, H ; Kargarnovin, M. H ; Naghdabadi, R ; Sharif University of Technology
    Governing equilibrium equations of thick-walled spherical vessels made of material following linear strain hardening and subjected to a steady-state radial temperature gradient using elasto-plastic analysis are derived. By considering a maximum plastic radius and using the concept of thermal autofrettage for the strengthening mechanism, the optimum wall thickness of the vessel for a given temperature gradient across the wall thickness is obtained. Finally, in the case of thermal loading on a vessel, the effect of convective heat transfer on the optimum thickness is studied and a general formula for the optimum wall thickness and design graphs for several different cases are presented. © 2008... 

    Shell-like instability of large diameter single-walled carbon nanotubes conveying fluid

    , Article Journal of Mechanical Science and Technology ; Volume 26, Issue 11 , 2012 , Pages 3389-3397 ; 1738494X (ISSN) Ali-Akbari, H. R ; Firouz Abadi, R. D ; Haddadpour, H ; Noorian, M. A ; Sharif University of Technology
    The instability of large diameter single-walled carbon nanotubes (SWCNTs) conveying fluid is investigated based on the molecular mechanics. Using the modal expansion for structural displacements, the governing equations of coupled fluid-structural dynamics of SWCNTs are derived. The natural frequencies and mode shape of the SWCNTs are obtained based on the molecular structural mechanics to account for the effect of chirality and discrete nature of SWCNTs. The results show that the vibrational behavior of large diameter SWCNTs conveying fluid is size dependent, but the effect of chirality is negligible. The obtained results are compared with the equivalent continuum-based model in the... 

    Synthesis and crystallization of lead-zirconium-titanate (PZT) nanotubes at the low temperature using carbon nanotubes (CNTs) as sacrificial templates

    , Article Advanced Powder Technology ; Volume 23, Issue 5 , September , 2012 , Pages 647-654 ; 09218831 (ISSN) Mohammadi, M. R ; Tabei, S. A ; Nemati, A ; Eder, D ; Pradeep, T ; Sharif University of Technology
    Elsevier  2012
    Pb(Zr 0.52Ti 0.48)O 3 (PZT) nanotubes with diameters of 80-100 nm and a wall thickness of 15-20 nm were prepared by sol-gel template technique and using multi-walled carbon nanotubes (MWCNT) as sacrificial templates. The coating process of MWCNT with PZT precursor sol and removal of the carbon nanotubes by an interrupt heat treatment were discussed and studied by Raman spectroscopy. Simultaneous thermal analysis (STA) revealed that PZT nanotube crystallized at the low temperature of 410°C by the significantly low activation energy of crystallization of 103.7 kJ/mol. Moreover, based on the X-ray diffraction (XRD) pattern and selected area electron diffraction pattern the crystal structure of... 

    Design of thick-walled cylindrical vessels under internal pressure based on elasto-plastic approach

    , Article Materials and Design ; Volume 30, Issue 9 , 2009 , Pages 3537-3544 ; 02641275 (ISSN) Darijani, H ; Kargarnovin, M. H ; Naghdabadi, R ; Sharif University of Technology
    By considering the Bauschinger effect and the yield criterion of Tresca, an exact elasto-plastic analytical solution for a thick-walled cylindrical vessel made of elastic linear-hardening material is derived. Having the working pressure and geometric dimensions of the vessel, the distribution of the hoop and equivalent stresses are optimized in the way that the distribution of stresses becomes smooth in the vessel wall. Based on two optimizing methods of the hoop and equivalent stresses, the best autofrettage pressure is determined. It is shown that this pressure is more than the working pressure and depends on the three following variables: Bauschinger effect, working pressure and geometric... 

    Simulation of low density lipoprotein (LDL) permeation into multilayer coronary arterial wall: interactive effects of wall shear stress and fluid-structure interaction in hypertension

    , Article Journal of Biomechanics ; Volume 67 , 2018 , Pages 114-122 ; 00219290 (ISSN) Roustaei, M ; Nikmaneshi, M. R ; Firoozabadi, B ; Sharif University of Technology
    Elsevier Ltd  2018
    Due to increased atherosclerosis-caused mortality, identification of its genesis and development is of great importance. Although, key factors of the origin of the disease is still unknown, it is widely believed that cholesterol particle penetration and accumulation in arterial wall is mainly responsible for further wall thickening and decreased rate of blood flow during a gradual progression. To date, various effective components are recognized whose simultaneous consideration would lead to a more accurate approximation of Low Density Lipoprotein (LDL) distribution within the wall. In this research, a multilayer Fluid-Structure Interaction (FSI) model is studied to simulate the penetration...