: In this study, a spray approach is applied to produce POM/graphene nanocomposite using a hot press mold and an automatic spray. The layer-by-layer spray method is used to fabricate these composites with different Wt. % of graphene particles, spray pressure, nozzle-to-mold distance at different temperatures. Taguchi approach as a popular method for Designing of Experiments (DOE) was used for statistical control of the parameters influenced by the synthesis process. The main idea in the present study was to determine the optimal characteristics by investigation of interaction effects in the manufacturing of POM/graphene nanocomposite. Thus, the optimal values obtained were 180oC for the mold temperature, 0.55m for the nozzle-to-mold distance and 3*105 Pa for the spray pressure. Finally, the experimental procedure done, showed that in samples fabricated by 1.8 Wt. % of graphene, the fracture strain decreased about 30% and the UTS and elastic modulus improved 40% and 60%, respectively. Manuscript profile

In this research, the friction stir process by adding Al2O3 and graphene nanoparticles at two different distances have been investigated. Nanoparticles are inserted in cavities with a diameter of 2 mm and a depth of 3 mm. Nanoparticles of Al2O3, graphene, and equal compositions of Al2O3 and graphene, each with two cavity spacings of 8 and 10 mm, have been performed in six different groups of friction stir process. From each group, Six Charpy specimens were separated. Charpy impact test was performed on six samples, three of which were heat-treated after the friction stir process. Charpy impact test has shown that the specimens have higher fracture energy after heat treatment. Also, in all cases, the fracture energy at the distance between the two cavities are10 mm more than the distance of 8 mm, this is since nanoparticles do not accumulate at a more distance. Also, to observe the resulting microstructures using optical microscopy and scanning electron microscopy on the friction welding process and the fracture surface of Charpy impact specimens were performed. The results show that the nanoparticles are accumulated in some samples and well dispersed in the materials in others. Manuscript profile

The effects of amine functionalization of carbon nanotubes (CNTs) and CNTs weight percent (wt. %), on the first bending natural frequencies and damping properties of CNT/epoxy composites are investigated in this paper. CNTs and amine functionalized CNTs (AFCNTs), with two different weight percentages, are used to manufacture the beam shaped specimens. Epoxy, CNT/epoxy (0.25 and 0.5 wt. % of CNTs) and AFCNT/epoxy (0.25 and 0.5 wt. % of AFCNTs) were fabricated. Experimental vibrational test is utilized in order to study the free vibration behavior of specimens under clamped-free boundary conditions. Natural frequencies and damping ratios are extracted from the experimental time response graphs. Results indicated that adding AFCNTs (0.5 wt. %) into the matrix material has the most effect on the natural frequency of the beam. In this case, the damping ratio has the lowest value. Moreover, scanning electron microscopy (SEM) images of the fracture surface of the specimens are prepared. The images illustrate that amine functionalization of CNTs leads to better dispersion of CNTs into the epoxy matrix. Further, it can be observed that enhancement in the value of damping ratio is more dominant than enhancement in stiffness value by dispersing AFCNTs into the epoxy resin. Manuscript profile

Steel plates are used in various structures, such as the structures of the deck and body of ships, bridges, and aerospace industry. In this study, we investigate the buckling and post-buckling behavior of rectangular steel plates having circular cutouts with two boundary conditions: first, clamped supports at upper and lower ends and free supports at other edges; second, clamped supports at upper and lower ends and simply supports at other edges, using finite element method (by ABAQUS software) and experimental tests(by an INSTRON servo hydraulic machine). In this research, in addition to the aspect ratio, the effect of changing the location of the cutout on the buckling analysis is investigated. The results of both numerical and experimental analyses are compared and showing a very good agreement between them. Manuscript profile

In this paper, a numerical analysis of stresses and displacements in FGM thick-walled cylindrical pressure vessel under internal pressure has been presented. The elastic modulus is assumed to be varying along the longitude of the pressure vessel with an exponential function continuously. The Poisson’s ratio is assumed to be constant. Whereas most of the previous studies about FGM thick-walled pressure vessels are on the basis of changing material properties along the radial direction, in this research, elastic analysis of cylindrical pressure vessel with exponential variations of elastic modulus along the longitudinal direction, under internal pressure, have been investigated. For the analysis of the vessel, the stiffness matrix of the cylindrical pressure vessel has been extracted by the usage of Galerkin Method and the numerical solution for axisymmetric cylindrical pressure vessel under internal pressure have been presented. Following that, displacements and stress distributions depending on inhomogeneity constant of FGM vessel along the longitudinal direction of elastic modulus, are illustrated and compared with those of the homogeneous case. The values which have been used in this study are arbitrary chosen to demonstrate the effect of inhomogeneity on displacements and stress distributions. Finally, the results are compared with the findings of finite element method (FEM). Manuscript profile

In this paper, low cycle fatigue life of CK45 steel and SS316 stainless steel under strain-controlled loading are experimentally investigated. In addition, the impact of mean strain and strain amplitude on the fatigue life and cyclic behavior of the materials are studied. Furthermore, it is attempted to predict fatigue life using energy and SWT damage parameters. The experimental results demonstrate that increase in strain amplitude decreases fatigue life for both materials, strain amplitude has a remarkable effect on fatigue life, and the impact of mean strain is approximately negligible. Furthermore, the energy damage parameter provides more accurate prediction of fatigue life for both materials. Manuscript profile

The novelty of this study is presentation of an exact solution for prediction of postbuckling behavior of shear deformable micro- and nano-scale beams based on modified couple stress theory and using principle of minimum potential energy. Timoshenko and Reddy-Levinson beam theories are applied to consider the shear deformation effect and Von Karman nonlinear kinematics is used to describe the nonlinear behavior of the postbuckling, and the Poisson's effect is also considered in stress-strain relation. Also, the size effect is exposed by introducing a material length scale parameter. Finally, the influences of shear deformation, Poisson's ratio and variations of length and thickness are investigated. The results indicate that the classical theory exaggerates the postbuckling amplitude of the nanobeam and overstates the effect of shear deformation on the postbuckling response of the nanobeam. Manuscript profile

Graphene is a new class of two-dimensional carbon nanostructure, which holds great promise for the vast applications in many technological fields. It would be one of the prominent new materials for the next generation nano-electronic devices. In this paper the influence of various vacancy defects on the critical buckling load of a single-layered graphene nanosheet is investigated. The nanosheet is modeled on the base of structural mechanics approach which covalent bonds between atoms are modeled as equivalent beam elements in a finite element model. The mechanical properties of the nanosheet extracted from the model are in good agreement with those of other research works. Effect of the number of vacancies and their positions on the critical buckling load is investigated in the present work. Our results show that the location of the vacancy has a significant role in the amount of critical buckling load. Furthermore, as the density of the vacancies increases, the value of critical buckling load decreases and the relationship is approximately linear. Manuscript profile

Besides experimental methods, numerical simulations bring benefits and great opportunities to characterize and predict mechanical behaviors of materials especially at nanoscale. In this study, a nano-single crystal aluminum (Al) as a typical face centered cubic (FCC) metal was modeled based on molecular dynamics (MD) method and by applying tensile and compressive strain loadings its mechanical behaviors were investigated. Embedded atom method (EAM) was employed to represent the interatomic potential of the system described by a canonical ensemble. Stress-strain curves and mechanical properties including modulus of elasticity, Poisson’s ratio, and yield strength were determined. Furthermore, the effects of strain rate and system temperature on mechanical behavior were obtained. It was found that the mechanical properties exhibited a considerable dependency to temperature, but they hardly changed with increase of strain rate. Moreover, nucleation and propagation of dislocations along the plane of maximum shearing stress were the mechanisms of the nanocrystalline Al plastic deformation. Manuscript profile

In this paper, accumulation of plastic deformation of AISI 1045 steel plates with circular cutouts under cyclic axial loading is studied. Loading was applied under force-control conditions. Experimental tests were performed using a Zwick/Roell servo hydraulic machine. Under force-control loading with nonzero mean force, plastic strain was accumulated in continuous cycles called ratcheting. Numerical analysis was carried out by ABAQUS software using nonlinear isotropic/kinematic hardening model. The results of the numerical simulations were compared to experimental data. The results demonstrated that the ratcheting response of plates with circular cutouts could be numerically simulated with a reasonable accuracy. It was observed that the local and global plastic deformation increase with increasing the notch diameter. Also, maximum principal stress was the main parameter for initiation of crack around the notch. Based on numerical results, at notch root, both ratcheting strain and local mean stress relaxation was occur simultaneously and due to relaxation of local mean stress, plastic shakedown was occurred. Manuscript profile

In this paper bending and buckling characteristics of third-order shear, and deformation nanoplates were investigated using the modified couple stress theory and Navier type solution. It can be useful for designing and manufacturing micro-electromechanical and nano-electromechanical systems. The modified couple stress theory was applied to provide the possibility of considering the effects of small scales that have only one material length scale parameter. In this theory, the strain energy density is a function of the strain tensor components, curvature tensor, stress tensor, and the symmetric part of the couple stress tensor. After obtaining the strain energy, external work, and buckling equations, the Hamilton principle is employed to derive the governing equations. Furthermore, by applying boundary and loading conditions in the governing equations, the bending and buckling of a third-order shear deformation nanoplate with simply-supported bearings are obtained and the Navier’s solution is used to solve the equations. The results indicate that the third-order nanoplate subjected to sinusoidal loading yields smaller values of dimensionless bending than it does while subjected to uniform surface traction. It was also found that by increasing the length to thickness ratio, the value of the dimensionless bending of nanoplate decreases but by increasing the aspect ratio of the plate, this value increases. Furthermore, it was shown that the critical buckling load of the third-order nanoplate under uniaxial loading increases by increasing the ratio of the length scale parameter to the thickness of the nanoplate but it decreases by increasing the length to thickness ratio of the nanoplate. Manuscript profile