جستجوی مقالات مرتبط با کلیدواژه "نقص هندسی اولیه" در نشریات گروه "مکانیک"

In this paper, effects of initial geometric imperfection on free vibration analysis of multi-directional functionally graded nanoplates are studied using an isogeometric approach together with the quasi-3D shear deformation theory. Geometric imperfections may exist inherently in nanoplates or purposely created by researchers. These imperfections strongly affect the plates’ natural frequency. The initial geometric imperfection is considered as an initial curvature and modeled by an analytical function in the governing equations of the nanoplate. The effective material properties distribution is stated based on the Mori-Tanaka scheme, which in addition to the thickness of the plate, also changes in the in-plane directions. A four-variable quasi-3D theory with new distribution function is proposed. Based on Hamilton’s principle, a weak form of free vibration problem for nonlocal plates is derived. These discrete systems of equations are solved using an isogeometric approach. The accuracy of the present study was verified by comparing the results with those given in published papers. Present results indicate the importance of various parameters, especially imperfection amplitude, and material indexes in all directions, on the free vibration behavior of FG nanoplates.

In this research, the nonlinear buckling analysis of Functionally Graded (FG) nano-composite beam reinforced by various distributions of Boron Nitrid Nanotube (BNNT) is investigated under electro-thermodynamical loading with considering initial geometrical imperfection. The analysis is performed based on nonlocal elasticity theory and using the Finite Element Method (FEM). Various distributions of BNNT along the beam’s thickness are considered as uniform and decreasing-increasing functionally graded; and the extended mixture model is used to estimate the properties of nano-composite beam. The elastic medium around the smart nano-composite beam is modeled as elastic foundation. The governing equations of equilibrium are derived using energy method and nonlocal elasticity theory; and the critical buckling load is obtained for various boundary conditions such as simply-simply supported (S-S) and clamped-clamped (C-C) using the FEM. The results indicate that with an increase in the geometrical imperfection parameter, the stiffness of nano-composite beam increases and consequently the stability of the system increases. The effect of FG-X distribution type is more than uniform distributions. Also, the critical buckling load of nano-composite beam increases with an increase in the electric field and elastic foundation.