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mechanical-analysis
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Dynamic mechanical analysis of compatibilizer effect on the mechanical properties of wood flour - High-density polyethylene composites
, Article International Journal of Engineering, Transactions B: Applications ; Volume 17, Issue 1 , 2004 , Pages 95-104 ; 1728-144X (ISSN) ; Tajvidi, M ; Ebrahimi, G ; Falk, R. H ; Sharif University of Technology
National Research Center of Medical Sciences
2004
Abstract
In this study, effect of MAPE (maleic anhydride polyethylene) as the compatibilizer on the mechanical properties of wood-flour polyethylene composites has been investigated by using Dynamic Mechanical Analysis (DMA). Composites were made at 25% and 50% by weight fiber contents and 1% and 2% compatibilizer respectively. Controls were also made at the same fiber contents without the compatibilizer. Static mechanical tests including tensile and bending tests were performed. Temperature scans in the range of- 110 to +100°C was also conducted. Results indicated improvements in the mechanical properties due to the compatibilizer addition. Storage modulus values were higher in the case of coupled...
Modeling of hot isostatic pressing of metal powder with temperature–dependent cap plasticity model
, Article International Journal of Material Forming ; Volume 6, Issue 3 , September , 2013 , PP. 363-376 ; Molaeinia, Z ; Keshavarz, Sh ; Sharif University of Technology
Abstract
In this paper, the coupled thermo–mechanical simulation of hot isostatic pressing (HIPing) is presented for metal powders during densification process. The densification of powder is assumed to occur due to plastic hardening of metal particles. The constitutive model developed is used to describe the nonlinear behavior of metal powder. The numerical modeling of hot powder compaction simulation is performed based on the large deformation formulation, powder plasticity behavior, and frictional contact algorithm. A Lagrangian finite element formulation is employed for the large powder deformations. A modified cap plasticity model considering temperature effects is used in numerical simulation...
Kinematical and dynamic analysis of biped robots' locomotion using dynamic object manipulation approach
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Nili Ahmadabadi, M ; Meghdari, A ; Sharif University of Technology
2006
Abstract
In this paper, we try to interpret "Duality of Dynamic Locomotion and Dynamic Object Manipulation". Since our main goal in this paper is to offer the duality concept and to validate it with a case study, we deal with the problem in a simple and abstract system. As a case study, we describe the duality between the problem of 2D dynamic object manipulation of a sphere using two planar manipulators and 2D dynamic locomotion of lower part of a biped robot. Having obtained the equations of dynamic object manipulation, we change the boundary conditions of the problem in such a way that both radius and mass of sphere object tend to infinity. Simultaneously, both of size and mass of manipulators'...
Investigation into occurring dynamic strain aging in hot rolling of AA5083 using finite elements and stream function method
, Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 138-145 ; 09215093 (ISSN) ; Sheikh, H ; Sharif University of Technology
2008
Abstract
Two-dimensional finite element analysis together with stream function and neural network models are employed to determine thermo-mechanical behavior during hot strip rolling of AA5083. An appropriate velocity field and stream function is first determined using the rule of volume constancy and upper bound theorem and then temperature field within the metal is predicted by means of a two-dimensional conduction-convection model. In order to consider the effect of flow stress and its dependence on temperature, strain and strain rate, a neural network model is also employed in the analysis. Based on the performed tensile tests, two different neural network models are constructed one for smooth...
Characterization of reinforcing effect of alumina nanoparticles on the novolac phenolic resin
, Article Polymer Composites ; Vol. 35, Issue 7 , July , 2014 , pp. 1285-1293 ; ISSN: 02728397 ; Shojaei, A ; Sharif University of Technology
Abstract
Very fine alumina nanoparticles were loaded in novolac type phenolic resin (PF) using solution mixing method. The concentration of nanoalumina in PF was varied between 2.5 to 20 wt%. All the compounds were compression molded and then subjected to scanning electron microscopy (SEM), tensile, flexural, and dynamic mechanical analysis (DMA) tests. SEM analysis showed that the nanoalumina were dispersed uniformly at low concentrations, however, at high concentrations, dispersion was suppressed leading to agglomerates in the composites. Mechanical testing revealed that the nanoalumina had a great influence on the strength and stiffness of PF resin particularly at concentrations below 5 wt%....
A size-dependent nonlinear Timoshenko microbeam model based on the strain gradient theory
, Article Acta Mechanica ; Volume 223, Issue 6 , 2012 , Pages 1233-1249 ; 00015970 (ISSN) ; Kahrobaiyan, M. H ; Nikfar, M ; Ahmadian, M. T ; Sharif University of Technology
2012
Abstract
The geometrically nonlinear governing differential equations of motion and the corresponding boundary conditions are derived for the mechanical analysis of Timoshenko microbeams with large deflections, based on the strain gradient theory. The variational approach is employed to achieve the formulation. Hinged-hinged beams are considered as an important practical case, and their nonlinear static and free-vibration behaviors are investigated based on the derived formulation
Development of thermo-elastic tapered and spherical superelements
, Article Applied Mathematics and Computation ; Volume 265 , 2015 , Pages 380-399 ; 00963003 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
Elsevier Inc
2015
Abstract
Special superelements are often used to improve the computational efficiency and improve accuracy of finite element modeling. Structures with tapered and spherical geometry exist in many engineering problems. In this work, special tapered and spherical superelements are presented that can be used for modeling of tapered and spherical bodies in thermo mechanical analyses with computational efficiency. The performance of these superelements under thermal and structural loads is demonstrated by presenting several examples and comparing the results with those from conventional 3D brick elements, which shows high accuracy at reduced computational cost
Reinforcing mechanisms of carbon nanotubes and high structure carbon black in natural rubber/styrene-butadiene rubber blend prepared by mechanical mixing-effect of bound rubber
, Article Polymer International ; Volume 64, Issue 11 , July , 2015 , Pages 1627-1638 ; 09598103 (ISSN) ; Shojaei, A ; Sharif University of Technology
John Wiley and Sons Ltd
2015
Abstract
The reinforcing effect of high structure carbon black (HSCB) and multi-walled carbon nanotubes (MWCNTs) on natural rubber/styrene-butadiene rubber blend processed using mechanical mixing was comparatively investigated. In-depth analysis by dynamic mechanical analysis, the Eggers-Schummer model and Medalia's relationship showed that HSCB aggregates provided large internal pores leading to significant immobilized macromolecules in filled rubber. Additionally, a tubular immobilized rubber layer with a thickness of 8nm was estimated for the rubber/MWCNT system based on dynamic mechanical analysis data. The mechanical performance of the HSCB filled blend was higher than that of the MWCNT filled...
A complete treatment of thermo-mechanical ale analysis; Part 2: Finite element equations and applications
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 34, Issue 2 , 2010 , Pages 149-165 ; 10286284 (ISSN) ; Movahhedy, M. R ; Farrahi, G. H ; Sharif University of Technology
2010
Abstract
In the first part of this paper series, a complete formulation for fully coupled ALE analysis of large deformation solid mechanic problems was developed. The formulation incorporated inertial, rate and thermal effects, and the treatment of rate and temperature dependent constitutive equations were presented. In this part, the ALE equations are discretized to form finite element equations. An algorithm for the treatment of mesh motion is described and example problems are presented to demonstrate the capability of the proposed formulation
A complete treatment of thermo-mechanical ale analysis; Part I: Formulation
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 34, Issue 2 , 2010 , Pages 135-148 ; 10286284 (ISSN) ; Movahhedy, M. R ; Farrahi, G. H ; Sharif University of Technology
2010
Abstract
Arbitrary Lagrangian Eulerian (ALE) finite element method is extensively used for numerical simulation of solid mechanics problem. The versatility of the mesh in ALE approach makes it particularly effective and efficient in solving large deformation problems. In this work, a complete treatment of fully coupled ALE formulation is presented incorporating inertial, rate and thermal effects. The formulation may be used in conjunction with thermo-elasto-viscoplactic material models. A consistent and efficient tangent operator is developed in closed form to handle stress integration. The applications of this formulation are given in the second part of this paper
Improvement in mechanical performance of anionic hydrogels using full-interpenetrating polymer network reinforced with graphene oxide nanosheets
, Article Advances in Polymer Technology ; Volume 35, Issue 4 , 2016 , Pages 386-395 ; 07306679 (ISSN) ; Bagheri, R ; Kabiri, K ; Ossipov, D. A ; Jokar, E ; Asadian, E ; Sharif University of Technology
John Wiley and Sons Inc
Abstract
Weak mechanical possession is one of the limiting factors in application of hydrogels. To modify this inherent disadvantage, different approaches have been studied including synthesizing interpenetrating polymer network (IPN) and nanocomposite hydrogels. So, this study has focused on preparation of a novel full-IPN structure based on anionic monomers of 2-acrylamido-2-methylpropane sulfonic acid/acrylic acid–sodium acrylate via facile solution polymerization technique in an aqueous media with incorporation of graphene oxide (GO) nanosheets. Mechanical performance of materials in the “as-prepared condition” and “swollen state” was characterized via tensile, compression, and rheology tests,...
Morphology development and mechanical properties of unsaturated polyester resin containing nanodiamonds
, Article Polymer International ; Volume 66, Issue 6 , 2017 , Pages 950-959 ; 09598103 (ISSN) ; Shojaei, A ; Sharif University of Technology
Abstract
Unsaturated polyester/styrene (UP) resin was filled with nanodiamonds (NDs) containing carboxyl and methacrylate functionalities using mechanical mixing. Field emission SEM exhibited a uniform dispersion of tightly bound aggregates of nanosized spherical NDs with good interfacial interaction. Rheological measurements exhibited a step increment in the shear viscosity of a UP/ND suspension at 0.6 wt% ND resembling a percolation state at this loading. Shear viscosity data supported by dynamic mechanical analysis results suggested the development of effective ND particles in which ND aggregates were covered by only polyester macromolecules. Accordingly, the morphology of UP/ND composites...
Modeling the interphase region in carbon nanotube-reinforced polymer nanocomposites
, Article Polymer Composites ; 2018 ; 02728397 (ISSN) ; Jam, J. E ; Arab, B ; Firouz-Abadi, R. D ; Sharif University of Technology
John Wiley and Sons Inc
2018
Abstract
Carbon nanotubes are regarded as ideal fillers for polymeric materials due to their excellent mechanical properties. Mechanical analysis without consideration of nanotube–matrix interphase, may not give precise predictions. In this work, the impacts of interphase on the behavior of polymer-based nanocomposites are studied. For this purpose, a closed-form micromechanical interphase model considering the diameter of nanotube, the thickness of interphase, and mechanical properties of nanotube and polymer is proposed to estimate the overall mechanical properties of nanotube-reinforced polymer nanocomposites. Furthermore, the effective elastic constants of the nanocomposites for a wide range of...
Experimental and thermomechanical analysis of friction stir welding of poly(methyl methacrylate) sheets
, Article Science and Technology of Welding and Joining ; Volume 23, Issue 3 , 2018 , Pages 209-218 ; 13621718 (ISSN) ; Simchi, A ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
In the present work, the feasibility of friction stir welding (FSW) of poly(methyl methacrylate) sheets was studied experimentally and theoretically by employing thermomechanical simulations. The effect of processing parameters including tool plunge depth, tilt angle, tool rotational speed (w), and transverse velocity (v) was investigated to determine suitable conditions to attain sound and defect-free joints. It is shown that a low tool plunge depth of 0.2 mm and a tilt angle of 2° provide suitable material flow to gain sound joints. By controlling the heat input into stir zone by increasing the tool rotational speed and decreasing linear velocity, the formation of defects can be minimised....
Modeling the interphase region in carbon nanotube-reinforced polymer nanocomposites
, Article Polymer Composites ; Volume 40, Issue S2 , 2019 , Pages E1219-E1234 ; 02728397 (ISSN) ; Jam, J. E ; Arab, B ; Firouz Abadi, R. D ; Sharif University of Technology
John Wiley and Sons Inc
2019
Abstract
Carbon nanotubes are regarded as ideal fillers for polymeric materials due to their excellent mechanical properties. Mechanical analysis without consideration of nanotube–matrix interphase, may not give precise predictions. In this work, the impacts of interphase on the behavior of polymer-based nanocomposites are studied. For this purpose, a closed-form micromechanical interphase model considering the diameter of nanotube, the thickness of interphase, and mechanical properties of nanotube and polymer is proposed to estimate the overall mechanical properties of nanotube-reinforced polymer nanocomposites. Furthermore, the effective elastic constants of the nanocomposites for a wide range of...
Coupled hydro-mechanical analysis of underground gas storage at Sarajeh field, Qom formation, Iran
, Article Journal of Natural Gas Science and Engineering ; Volume 92 , 2021 ; 18755100 (ISSN) ; Shad, S ; Zivar, D ; Razaghi, N ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Production or injection of fluids from/in an underground storage site causes variations of pore pressure and stress states. These fluctuations significantly affect implications for hydraulic fracturing, wellbore integrity, top surface subsidence and heave, fault-reactivation, and stability of reservoir and caprock. Therefore, in order to keep optimal conditions during the process of gas injection and production, it is of paramount importance to have accurate estimates of the pore pressure. In this investigation, coupled fluid flow and geomechanical simulations, as well as rock mechanical tests, are performed on the Sarajeh field, Iran to investigate the geomechanical behavior of the Sarajeh...
A hybrid scaffold of gelatin glycosaminoglycan matrix and fibrin as a carrier of human corneal fibroblast cells
, Article Materials Science and Engineering C ; Volume 118 , 2021 ; 09284931 (ISSN) ; Mahdavi salimi, S ; Abdekhodaie, M. J ; Baradaran Rafii, A ; Tabatabei, M. R ; Mehrvar, M ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
A hybrid scaffold of gelatin-glycosaminoglycan matrix and fibrin (FGG) has been synthesized to improve the mechanical properties, degradation time and cell response of fibrin-like scaffolds. The FGG scaffold was fabricated by optimizing some properties of fibrin-only gel and gelatin-glycosaminoglycan (GG) scaffolds. Mechanical analysis of optimized fibrin-only gel showed the Young module and tensile strength of up to 72 and 121 KPa, respectively. Significantly, the nine-fold increase in the Young modulus and a seven-fold increase in tensile strength was observed when fibrin reinforced with GG scaffold. Additionally, the results demonstrated that the degradation time of fibrin was enhanced...
Neural-network-based observer for real-time tipover estimation
, Article Mechatronics ; Volume 15, Issue 8 , 2005 , Pages 989-1004 ; 09574158 (ISSN) ; Naderi, D ; Alam, M. R ; Sharif University of Technology
2005
Abstract
Tipover issue is an important problem in autonomous mobile manipulators. This issue is becoming more important in new generation of mobile robots where their size and weight are reduced, and they are designed to work on uneven terrains with higher speeds. Estimating the distance from the tipover stability margin would enhance the capability of the mobile manipulators in correcting their motion. For a valid estimation of the tipover margin one must take into account the full dynamic interaction between the vehicle and its manipulator. In mobile manipulators with several degrees of freedom a huge amount of time is needed to solve equations of motion while real-time tipover control needs a fast...
Multi-scale modeling of surface effects in nano-materials with temperature-related Cauchy-Born hypothesis via the modified boundary cauchy-born model
, Article International Journal for Numerical Methods in Engineering ; Vol. 97, issue. 2 , 2014 , pp. 79-110 ; ISSN: 00295981 ; Ghahremani, P ; Dormohammadi, H ; Sharif University of Technology
Abstract
In nano-structures, the influence of surface effects on the properties of material is highly important because the ratio of surface to volume at the nano-scale level is much higher than that of the macro-scale level. In this paper, a novel temperature-dependent multi-scale model is presented based on the modified boundary Cauchy-Born (MBCB) technique to model the surface, edge, and corner effects in nano-scale materials. The Lagrangian finite element formulation is incorporated into the heat transfer analysis to develop the thermo-mechanical finite element model. The temperature-related Cauchy-Born hypothesis is implemented by using the Helmholtz free energy to evaluate the temperature...
A coupled hydro-mechanical analysis for prediction of hydraulic fracture propagation in saturated porous media using EFG mesh-less method
, Article Computers and Geotechnics ; Vol. 55, issue , January , 2014 , p. 254-266 ; Pak, A ; Soga, K ; Sharif University of Technology
Abstract
The details of the Element Free Galerkin (EFG) method are presented with the method being applied to a study on hydraulic fracturing initiation and propagation process in a saturated porous medium using coupled hydro-mechanical numerical modelling. In this EFG method, interpolation (approximation) is based on nodes without using elements and hence an arbitrary discrete fracture path can be modelled.The numerical approach is based upon solving two governing partial differential equations of equilibrium and continuity of pore water simultaneously. Displacement increment and pore water pressure increment are discretized using the same EFG shape functions. An incremental constrained Galerkin...