In this paper, the free vibration response of a laminated composite rectangularplate supporting a rotating circular patch mass is studied. The two variable refined platetheory that employs only two unknown functions as against three in the case of simpleshear deformation theory is applied to define the third order displacement field of acomposite rectangular plate. The plate is considered to have simply supported boundaries.The equations of motion for the rectangular plate are obtained by calculus of variation. Dueto significance of the fundamental frequency of the plate, its variation with respect to thenon-dimensional geometrical parameters such as aspect ratio of the plate, size and locationof the rotating patch mass, is investigated. It will be shown herein that the proposed theoryis simple in solving the free vibration problems of plates with patch masses. پرونده مقاله

Buckling analysis of thin cylindrical shells is very important due to their production process. Usually longitudinal and transversal stiffeners are used to increase the buckling stiffness. In this paper, considering a thin cylindrical shell with longitudinal and transversal ribs subjected to axial force and lateral pressure, the influence of different aspect of axial force to lateral pressure on buckling load is investigated for different ratios such as thickness to radius and length to radius. The analytical results based on Donnell’s classical linear stability equations for anisotropic cylindrical shells are compared with FEM results of ANSYS software. The results show that the analytical method of Donnell can be used for special aspect ratios. Furthermore, by increasing the axial to lateral load ratio, the axial buckling load is increased for most of the aspect ratios, while the lateral buckling load decreases. پرونده مقاله

Due to their light weights and high load carrying capacities, composite structures are widely used in various industrial applications especially in aerospace industry. Stiffening ribs are the main features of lattice type composite structures. Strength to weight ratio is known to be as one of the most critical design parameter in these structures. In this study, the effect of some parameters such as the physical characteristics of the material, shell thickness, angle, thickness and number of ribs on distribution of stresses and buckling loads of shell are investigated. For this purpose, 3D finite element analysis using ANSYS software explicitly was done and then compared with experimental test results. Increasing the thickness of the outer shell causes the structural strength will rise to 50 percent. The next effective parameter is reduction of rib angle which provides an increase of 30 percent in specific load. Although Stiffenerrs (ribs) have a major role in load carrying, but increasing the rib number causes the structural weight rises, thus compared with the two previous parameters do not have a significant effect on the strength of structures پرونده مقاله