دانلود رایگان مقاله انگلیسی تحلیل ثبات ترمو مکانیکی پوسته های عملکردی درجه بندی شده هدفمند - الزویر 2019

ABSTRACT

In this paper, the thermo-elastic nonlinear analysis of various Functionally Graded (FG) shells under different loading conditions is studied. A second-order isoparametric triangular shell element is presented for this purpose. The element is six-noded, and each node has all six independent degrees of freedom in space. It should be added, the first-order shear deformation theory is induced. Furthermore, Voigt’s model is adopted to define the FG material properties, which are considered to change gradually from one surface to another. The critical temperature is predicted. Both the pre-buckling and post-buckling equilibrium paths are traced. Since the linear eigenvalue analysis leads to wrong responses in the problems with strong nonlinearity, the suggested procedure is performed based on the FEM and more exact estimations are achieved using equilibrium path.

Conclusions

Studies on nonlinear analysis of various and arbitrary FG shells under thermo-mechanical loading are limited in the available literature. In the cases with strong nonlinearity, the linear eigenvalue buckling analysis estimated much more or less the true buckling temperature values. To reach more exact predictions and fill the gap, the nonlinear FE based analysis of arbitrary FG shells subjected to thermomechanical loading was performed in this article. A second-order and six-noded isoparametric triangular shell element was developed for the general purposes. Each element’s node had all six independent degrees of freedom in space. It should be mentioned that the material properties were expressed by Voigt’s model. After performing extensive numerical studies, some new outcomes were found.

1. Pre-buckling (primary) path was almost linear, while the postbuckling (secondary) path had a nonlinear nature.

2. Additional disturbance load, like a geometric imperfection, led to reduction of the buckling temperature and vice versa.

3. In FG shallow cylindrical panel, reduction of shell thickness results in a more complex equilibrium path, including snap-through and snap-back responses.

4. The thermal buckling load of annular plate increases as the values of β and δgrows. This is owing to the fact that raising the values of δandβresults in stiffer structure.

5. In all numerical studies, it is observed that structure behaves stiffer as the volume fraction index n decreases.