Seminar về chủ đề: "Phân tích Cơ-nhiệt phi tuyến của các Cấu trúc FG-GPLRC"

Vào 14h00, ngày 18/07/2025 Viện IAST tổ chức buổi trao đổi học thuật tại Phòng họp C011 với nội dung chi tiết như sau:

1/ PGS. TS. Đặng Thùy Đông trình bày về "A new analytical approach for nonlinear thermo-mechanical postbuckling of FG-GPLRC circular plates and shallow spherical caps stiffened by spiderweb stiffeners"

Abstract:

For the first time, the problem of nonlinear postbuckling of circular plates and shallow spherical caps reinforced by meridian, parallel stiffeners, and spiderweb stiffeners based on the Donnell shell theory (DST) and von Karm an geometric nonlinearities is presented. The caps/plates and stiffeners are made from functionally graded graphene platelet-reinforced composite (FG-GPLRC). These stiffened structures are subjected to uniformly distributed external pressure or/and uniformly distributed thermal loads and are rested on a nonlinear elastic foundation. By expanding Lekhnitskii’s smeared stiffener technique and employing the Ritz method of energy, the formulas to determine the postbuckling curves of the external pressure–deflection and thermal load deflection relations of stiffened plates/spherical caps are derived. Meaningful discussions of the various influences of FG-GPLRC stiffeners, material distributions of plate/cap and stiffeners, and geometrical, material, and foundation parameters are shown in the content of the numerical investigations.

2/ PGS. TS. Nguyễn Thị Phương trình bày về "Nonlinear Thermo-Mechanical Stability Analysis of FG-GPLRC Circular Plates and Shallow Shell Caps"

Abstract:

This report presents analyses of the nonlinear thermo-mechanical buckling and postbuckling behavior of FG-GPLRC (Functionally Graded Graphene Platelet-Reinforced Composite) circular plates and shallow shell caps based on the first-order shear deformation theory. The first problem is approached using a displacement-based formulation and the Galerkin method, considering various complex geometries of the shell caps, including spherical, parabolic, sinusoidal, and elliptical shapes. Notably, a trigonometric solution form is employed for the first time to examine different axisymmetric buckling modes. Numerical investigations highlight the influence of shell types, geometric and material parameters, and axisymmetric buckling modes on the nonlinear thermo-mechanical response of the structures. The second problem adopts a stress function approach using polynomial solution forms in conjunction with the Ritz energy method. A technique for determining the stress function form applicable to FG-GPLRC circular plates and shallow spherical shells is introduced. Detailed numerical studies on the effects of geometric and material parameters are also conducted.

3/ ThS. Vũ Minh Đức trình bày về "Nonlinear Vibration and Dynamic Buckling of Complex Curved Functionally Graded Graphene Panels Reinforced with Inclined Stiffeners"

Abstract:

This paper presents a new semi-analytical approach for the nonlinear vibration and dynamic responses of functionally graded graphene platelet-reinforced composite (FGGPLRC) panels with complex curvature reinforced by orthogonal and/or inclined stiffeners in the thermal environment resting on the nonlinear viscoelastic foundation with the nonlinearities of von Kármán in the framework of the higher-order shear deformation theory (HSDT). The three curvature types of complexly curved panels are considered to be cylindrical, sinusoid, and parabola panels. Orthogonal and/or inclined stiffeners are modeled utilizing an improved smeared stiffener technique. The stress function form is estimated by applying the like-Galerkin method for complexly curved panels. By applying the Lagrange function and Euler–Lagrange equation, the nonlinear equations of motion of the panels are obtained. The viscous damping effects of the viscoelastic foundation are considered by utilizing the Rayleigh dissipation function. Numerical results are examined utilizing the Runge–Kutta method to acquire the time-deflection curves, and by utilizing the Budiansky–Roth criterion, the critical dynamic buckling loads are determined. From the investigated results, it is possible to evaluate the nonlinear vibration and buckling dynamic responses of three forms of panels with stiffeners.