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Numerical nonlinear bending analysis of FG-GPLRC plates with arbitrary shape including cutout
Reza Ansari,Ramtin Hassani,Yousef Gholami,Hessam Rouhi 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.2
Based on the ideas of variational differential quadrature (VDQ) and finite element method (FEM), a numerical approach named as VDQFEM is applied herein to study the large deformations of plate-type structures under static loading with arbitrary shape hole made of functionally graded graphene platelet-reinforced composite (FG-GPLRC) in the context of higherorder shear deformation theory (HSDT). The material properties of composite are approximated based upon the modified Halpin-Tsai model and rule of mixture. Furthermore, various FG distribution patterns are considered along the thickness direction of plate for GPLs. Using novel vector/matrix relations, the governing equations are derived through a variational approach. The matricized formulation can be efficiently employed in the coding process of numerical methods. In VDQFEM, the space domain of structure is first transformed into a number of finite elements. Then, the VDQ discretization technique is implemented within each element. As the last step, the assemblage procedure is performed to derive the set of governing equations which is solved via the pseudo arc-length continuation algorithm. Also, since HSDT is used herein, the mixed formulation approach is proposed to accommodate the continuity of first-order derivatives on the common boundaries of elements. Rectangular and circular plates under various boundary conditions with circular/rectangular/elliptical cutout are selected to generate the numerical results. In the numerical examples, the effects of geometrical properties and reinforcement with GPL on the nonlinear maximum deflection-transverse load amplitude curve are studied.
Mohammad Reza Ramezani,Zeinab Ansari-Asl,Elham Hoveizi,Ali Reza Kiasat 한국섬유공학회 2020 Fibers and polymers Vol.21 No.5
Fabrication of nanofibrous scaffolds of biodegradable polymers provides a great premise for several biologicalapplications. In this study, nanofibrous polycaprolactone (PCL) mats incorporating Fe-MOF (PCL/x%Fe-MOF, x=5, 10, 20)were fabricated by electrospinning technique. The Fe-MOFs were separately synthesized by the hydrothermal method andthen were added to PCL solution for preparation of nanofibrous composites. The presence of Fe-MOF in the fibers wasdemonstrated by various methods including FT-IR (Fourier-transform infrared), PXRD (powder X-ray diffraction), EDS(energy dispersive X-ray spectroscopy) mapping, SEM (scanning electron microscope), and TEM (transmission electronmicroscope). In the FT-IR spectra of the nanocomposites, the characteristic bands for the pure PCL and Fe-MOF showed nosignificant change in their positions, suggesting a weak chemical interaction with each other, although they physically mixeduniformly. Nanofibrous structure of the as-prepared nanocomposites was confirmed by SEM and TEM images. The diameterof PCL nanofibers was measured to be 369 nm. Biological investigations indicated that the experimented scaffolds includingPCL/5%Fe-MOF and PCL/10%Fe-MOF nanofibrous scaffolds provided appropriate surface and mechanical properties suchas cellular biocompatibility, high porosity, chemical stability, and optimum fiber diameter for cell adhesion, viability, andproliferation compared with PCL and PCL/20%Fe-MOF nanocomposites. Indeed, our results demonstrated that percent ofFe-MOF in the composites played a significant role in cell attachment and viability. Also, according to the implantationstudies, up to at least 4 weeks, none of the animals showed any inflammatory response. Totally, we can be claimed that themodified electrospun scaffolds have been developed for tissue engineering applications.
Ramin Ansari,Mohammad Khalilzadeh,M. Reza Hosseini 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.3
In today's changing conditions, the random disturbances have caused complexity into the construction project management. In this study, a multi-objective approach is proposed to determine the size of the time buffers in engineering and construction projects. The problem is formulated as a two-stage stochastic programming model. In order to examine the efficiency of the model, the proposed method was compared to the classic and extended critical chain management approaches. The validation is performed using simulation experiments carried out in the benchmark data test and a real case of an engineering project. The numerical examples and case studies were presented to validate the proposed methodology. The results demonstrate the efficiency of the proposed multi-objective time buffering method in the actual situation. The outcomes indicate that the proposed robust buffer sizing method results in a more stable plan, as against the traditional methods.
Hadis Saghatchi,Reza Ansari,H. Zavvar Mousavi 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.7
Dicalcium phosphate nanoparticles (DCP-NPs) was synthesized chemically and used for adsorptiveremoval of uranyl ions from aqueous solutions in a batch system. A commercial grade of DCP (monetite)was also employed for comparison. The synthesized and commercial adsorbents (S-DCP and C-DCP) werecharacterized by FT-IR, SEM and XRD techniques. The investigation of adsorption isotherms indicatedthat the maximum adsorption capacities (qm) for C-DCP and S-DCP were 714.3 and 666.7 mg g 1 (at293 K), respectively. The experimental kinetics were well-described by the pseudo-second-order kineticand the equilibrium data were fitted with both Langmuir and Freundlich adsorption models. Thermodynamicstudies indicated that the adsorption of uranyl ions on the monetite surface was a spontaneousexothermic process. The exhausted adsorbents could be regenerated by washing with 0.10 mol L 1 NaOH.
Thermally induced mechanical analysis of temperature-dependent FG-CNTRC conical shells
Torabi, Jalal,Ansari, Reza Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.3
A numerical study is performed to investigate the impacts of thermal loading on the vibration and buckling of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) conical shells. Thermo-mechanical properties of constituents are considered to be temperature-dependent. Considering the shear deformation theory, the energy functional is derived, and applying the variational differential quadrature (VDQ) method, the mass and stiffness matrices are obtained. The shear correction factors are accurately calculated by matching the shear strain energy obtained from an exact three-dimensional distribution of the transverse shear stresses and shear strain energy related to the first-order shear deformation theory. Numerical results reveal that considering temperature-dependent material properties plays an important role in predicting the thermally induced vibration of FG-CNTRC conical shells, and neglecting this effect leads to considerable overestimation of the stiffness of the structure.
HESSAM ROUHI,REZA ANSARI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.3
In this paper, a nonlocal Flugge shell model is utilized to investigate the axial buckling behavior of double-walled carbon nanotubes(DWCNTs) under various boundary conditions. According to the nonlocal elasticity theory, the displacement ¯eld equations coupled by the van der Waals interaction are derived. The set of governing equations of motion is then solved by the Rayleigh?Ritz method. The present analysis can treat boundary conditions in a layer-wise manner. The e®ects of nonlocal parameter, layer-wise boundary conditions and geometrical parameters on the mechanical behavior of DWCNTs are examined. Furthermore, molecular dynamics simulations are performed to assess the validity of the results and also to predict the appropriate values of nonlocal parameter. It is found that the type of boundary conditions a®ects the proper value of nonlocal parameter.
Thermally induced mechanical analysis of temperature-dependent FG-CNTRC conical shells
Jalal Torabi,Reza Ansari 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.3
A numerical study is performed to investigate the impacts of thermal loading on the vibration and buckling of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) conical shells. Thermo-mechanical properties of constituents are considered to be temperature-dependent. Considering the shear deformation theory, the energy functional is derived, and applying the variational differential quadrature (VDQ) method, the mass and stiffness matrices are obtained. The shear correction factors are accurately calculated by matching the shear strain energy obtained from an exact three-dimensional distribution of the transverse shear stresses and shear strain energy related to the first-order shear deformation theory. Numerical results reveal that considering temperature-dependent material properties plays an important role in predicting the thermally induced vibration of FG-CNTRC conical shells, and neglecting this effect leads to considerable overestimation of the stiffness of the structure.