Large amplitude free vibrations of FGM shallow curved tubes in thermal environment

Hadi Babaei,Yaser Kiani,M. Reza Eslami 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.6

In the current investigation, large amplitude free vibration behavior of shallow curved pipes (tubes) made of functionally graded materials is investigated. Properties of the tube are distributed across the radius of the tube and are obtained by means of a power law function. It is also assumed that all thermo-mechanical properties are temperature dependent. The governing equations of the tube are obtained using a higher order shear deformation tube theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the tube. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large displacements and small strains. Uniform temperature elevation of the tube is also included into the formulation. For the case of tubes which are simply supported in flexure and axially immovable, the governing equations are solved using the two-step perturbation technique. Closed form expressions are provided to obtain the small and large amplitude fundamental natural frequencies of the FGM shallow curved tubes in thermal environment. Numerical results are given to explore the effects of thermal environment, radius ratio, and length to thickness ratio of the tube on the fundamental linear and non-linear frequencies.

Prediction of fatigue life in cold expanded Al-alloy 2024-T3 plates used in double shear lap joints

Hadi Taghizadeh,Tajbakhsh Navid Chakherlou,Afshin Babaei Aghdam 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5

To predict fatigue crack initiation and fatigue crack growth lives in cold expanded double shear lap joints a numerical method has been employed. The total estimated fatigue lives were compared with available experimental fatigue test results for plain hole and cold expanded hole specimens of Al 2024-T3 in double shear lap joints. Three-dimensional finite element simulations have been performed in order to obtain the created residual stresses field due to cold expansion and subsequent far field longitudinal loading in the double shear lap joint. The obtained stress and strain distributions from the finite element analyses were employed to predict stress concentration factors to calculate fatigue crack initiation and fatigue crack growth lives using AFGROW computer code. The predicted fatigue lives demonstrate that there is a good agreement between the proposed method and experimental fatigue test results.

CO2 separation over light gases for nano-composite membrane comprising modified polyurethane with SiO2 nanoparticles

Mohammdad Hadi Nematollahi,Shahryar Babaei,Reza Abedini 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.5

Owing to the potential of polymeric and nanocomposite membranes for industrial application in CO2 capturing and gas separation processes, permeation properties of CO2, N2 and O2 through the polymer matrix have been an object of extensive research. We measured the permeation rates of gases (pure and mixed gas) within a novel nanocomposite membrane composed of poly tetramethyleneglycol (PTMG), hexamethylene diisocyanate (HDI), and diamine chain extender, 4,4- methylenebis(2-chloroaniline) (MOCA) at various silica loadings and operating conditions. The novel polyurethane was prepared by a two-step bulk polymerization technique based on the molar ratios of the used constituents 1 : 3 : 2 for PTMG: HDI :MOCA, respectively. The FTIR spectra indicated that the extent of phase separation decreased by increase in the SiO2 content. From the DSC and XRD analyses, the existence of small crystalline areas within the soft and hard segments of matrix was proved. High thermal stability of new nanocomposites was authenticated by a 90 oC increase in the decomposition temperature upon including the SiO2 particles into the polymer matrix. By providing a longer diffusion path, a reduction in the permeation of penetrants occurred after the incorporation of SiO2 content. By raising the temperature from 25 to 45 oC, the gas permeation value of CO2, O2 and N2 rose steeply: 35, 54 and 81% in neat PU and 49, 64 and 137% in PU containing 15 wt%, respectively. Conversely, the obtained results for increasing the feed gas pressure from 6 to 10 bar revealed that the penetration of non-condensable gases, O2 and N2, decreased while the permeation rate of CO2 polar gas surged dramatically. Nevertheless, a simultaneous increment in the selectivity amounts of both gas pairs was revealed. For the gaseous mixtures, the trend of changes in permeability and selectivity values were almost identical with those of pure gas: decrease in permeation, and vice versa increase in gas pair selectivity. Eventually, the separation results of the prepared membranes indicated a strong tendency to move towards Robeson’s line by incorporation of SiO2 nanoparticles into the matrix of membranes.

Nonlinear vibration of FG-CNTRC curved pipes with temperature-dependent properties

Mingjie Liu,Shaoping Bi,Sicheng Shao,Hadi Babaei 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.4

In the current research, the nonlinear free vibrations of curved pipes made of functionally graded (FG) carbon nanotube reinforced composite (CNTRC) materials are investigated. It is assumed that the FG-CNTRC curved pipe is supported on a three-parameter nonlinear elastic foundation and is subjected to a uniform temperature rise. Properties of the curved nanocomposite pipe are distributed across the radius of the pipe and are given by means of a refined rule of mixtures approach. It is also assumed that all thermomechanical properties of the nanocomposite pipe are temperature-dependent. The governing equations of the curved pipe are obtained using a higher order shear deformation theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the pipe. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large deflection in the curved nanocomposite pipe. For the case of nanocomposite curved pipes which are simply supported in flexure and axially immovable, the motion equations are solved using the two-step perturbation technique. The closed-form expressions are provided to obtain the small- and large-amplitude frequencies of FGCNTRC curved pipes rested on a nonlinear elastic foundation in thermal environment. Numerical results are given to explore the effects of CNT distribution pattern, the CNT volume fraction, thermal environment, nonlinear foundation stiffness, and geometrical parameters on the fundamental linear and nonlinear frequencies of the curved nanocomposite pipe.

On the snap-buckling phenomenon in nanocomposite curved tubes

Dan Chen,Jun Shao,Zhengrong Xu,Hadi Babaei 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.1

The nonlinear snap-through buckling of functionally graded (FG) carbon nanotube reinforced composite (CNTRC) curved tubes is analytically investigated in this research. It is assumed that the FG-CNTRC curved tube is supported on a threeparameter nonlinear elastic foundation and is subjected to the uniformly distributed pressure and thermal loads. Properties of the curved nanocomposite tube are distributed across the radius of the pipe and are given by means of a refined rule of mixtures approach. It is also assumed that all thermomechanical properties of the nanocomposite tube are temperature-dependent. The governing equations of the curved tube are obtained using a higher-order shear deformation theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the tube. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large deflection in the curved tube. Equations of motion are solved using the twostep perturbation technique for nanocomposite curved tubes which are simply-supported and clamped. Closed-form expressions are provided to estimate the snap-buckling resistance of FG-CNTRC curved pipes rested on nonlinear elastic foundation in thermal environment. Numerical results are given to explore the effects of the distribution pattern and volume fraction of CNTs, thermal field, foundation stiffnesses, and geometrical parameters on the instability of the curved nanocomposite tube.

Micromorphology analysis of specific 3-D surface texture of silver chiral nanoflower sculptured structures

Stefan Talu,Miroslaw Bramowicz,Slawomir Kulesza,Atefeh Ghaderi,Hadi Savaloni,Reza Babaei,Shahram Solaymani 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.43 No.-

This study presents research into the three-dimensional (3-D) surface texture of silver chiralnanoflowers with three-, four- and five-folds spatial symmetry, which were produced using obliqueangle deposition method with rotating sample holder. X-ray diffraction (XRD), atomic force microscopy(AFM), and field-emission scanning electron microscopy (FESEM) measurements were carried out inorder to study 3-D morphology and structure of the samples at the nanoscale. Obtained results werefound to provide an insight into important relationships between the structure of prepared nanoflowersand their properties. Results presented in the paper proved the usefulness of the method for preparationof high-quality, sculptured 3-D nanostructures with pre-designed shapes (with narrower and longerpetals) and desired porosity. Specific structure, shape, and length scale of the 3-D deposits can be thenverified in simulations for quick characterization of the samples. This analysis helps to understand theirfunctional role in the test surface, in order to evaluate the relation among the 3-D microtextured surface.