m. e. golmakani

In this paper, the nonlinear thermal buckling of moderately thick functionally graded cylindrical panels is analyzed based on the first-order shear deformation theory (FSDT) and large deflection von Kármán equations. The highly coupled nonlinear governing equations are solved using the combination of dynamic relaxation approach with the finite-difference discretization method at various boundary conditions. The material properties of the constituent components of the FG shell are considered to vary continuously along the thickness direction based on simple power-law and Mori-Tanaka distribution methods, separately. The critical thermal buckling load is considered based on the thermal load-displacement curve derived by solving the incremental form of nonlinear equilibrium equations. In order to consider the accuracy of the present results, a comparison study has been carried out. The effects of the boundary conditions, rule of mixture, grading index, radius-to-thickness ratio, length-to-radius ratio and panel angle are studied on the thermal buckling loads. It is observed from the results that in high values of radius-to-thickness ratios, there is no difference between the values of critical buckling temperature differences for linear and nonlinear distributions.

In this article, the thermal buckling behavior of orthotropic circular bilayer graphene sheets embedded in the Winkler–Pasternak elastic medium is scrutinized. Using the nonlocal elasticity theory, the bilayer graphene sheets are modeled as a nonlocal double–layered plate that contains small scale effects and van der Waals (vdW) interaction forces. The vdW interaction forces between the layers are simulated as a set of linear springs using the Lennard–Jones potential model. Using the principle of virtual work, the set of equilibrium equations are obtained based on the first-order shear deformation theory (FSDT) and nonlocal differential constitutive relation of Eringen. Differential quadrature method (DQM) is employed to solve the governing equations for simply-supported and clamped boundary conditions. Finally, the effects of the small scale parameter, vdW forces, aspect ratio, elastic foundation, and boundary conditions are considered in detail.

In this paper, a different method, incremental load technique in conjunction with dynamic relaxation (DR) method, is employed to analyze the buckling behavior of composite plates reinforced with functionally graded (FG) distributions of single-walled carbon nanotubes (SWCNTs) along the thickness direction. The properties of carbon-nanotubes reinforced composite (CNTRC) plate were determined through modified rule of mixture. The nonlinear governing relations are obtained incrementally in the form of partial differential equations (PDEs) based on first-order shear deformation theory (FSDT) and Von Karman nonlinear strain. In the proposed method, for finding the critical buckling load, the mechanical loads are applied to the CNTRC plate incrementally so that in each load step the incremental form of PDEs are solved by the DR method combined with the finite difference (FD) discretization technique. Finally, the critical buckling load is determined from the load-displacement curve. In order to verify the accuracy of the present method, the results are compared with those available in the literatures. Finally, a detailed parametric study is carried out and results demonstrate that the change of carbon nanotube volume fraction, plate width-to-thickness ratio, plate aspect ratio, boundary condition and loading condition have pronounced effects on the buckling strength of CNTRC plates. It is seen that for all types of loading, boundary conditions and both cases of with and without presence of elastic foundation the FG-X and FG-O have the highest and lowest values of buckling loads.

Today the adhesively bonded joint of FRP/steel for repair and strengthening are being widely used. In this case, investigating the effect of various mechanical loading, as well as harsh environmental conditions on this joint, is very important. In this paper, the strength of the damaged-steel plate reinforced with CFRP patches under acidic environment is investigated experimentally. The damage is considered in the shape of a central hole with two narrow central notches on two sides of the hole. In order to simulate more realistic conditions, the bonding of the patch to the steel plate is considered one-sidedly. To evaluate the amount of strengthening, the specimens are subjected to the simple tensile test at room temperature. The results of dry patched-specimens compared to non-patched specimens show significant reinforcement with at least 40% increase in load-carrying capacity and at least 50% increase in displacement. The comparison between the patched-specimens immersed for 8 weeks in concentrated sulfuric acid and the dry patched-specimens show no significant effect on the load-carrying capacity. However, the tests of standard CFRP specimens in a similar immersion environment show a reduction in modulus of elasticity and tensile strength compared to the dry CFRP ones.

This article investigates the buckling behavior of orthotropic annular/circular bilayer graphene sheet embedded in Winkler–Pasternak elastic medium under mechanical loading. Using the nonlocal elasticity theory, the bilayer graphene sheet is modeled as a nonlocal orthotropic plate which contains small scale effect and van der Waals interaction forces. Differential Quadrature Method (DQM) is employed to solve the governing equations for various combinations of simply supported or clamped boundary conditions. The results show that small scale parameter does not have any effect on critical buckling load of cases without elastic medium in simply supported boundary condition. Also, increase of vdW coefficient leads to increase of critical buckling load smoothly then it has no impact on critical buckling load after a certain value.

In this study, using the dynamic relaxation method, nonlinear mechanical and thermal buckling behaviors of functionally graded cylindrical shells were studied based on first-order shear deformation theory (FSDT). It was assumed that material properties of the constituent components of the FG shell vary continuously along the thickness direction based on simple power-law and Mori-Tanaka distribution methods separately. An axial compressive load and thermal gradient were applied to the shell incrementally so that in each load step the incremental form of governing equations were solved by the DR method combined with the finite difference (FD) discretization method to obtain the critical buckling load. After convergence of the code in the first increment, the latter load step was added to the former so that the program could be repeated again. Afterwards, the critical buckling load was achieved from the mechanical/ thermal load-displacement curves. In order to validate the present method, the results were compared with other papers and the Abaqus finite element results. Finally, the effects of different boundary conditions, grading index, rule of mixture, radius-to-thickness ratio and length-to-radius ratio were investigated on the mechanical and thermal buckling loads.