Sensitivity Of Buckling Load Research Articles

Design considerations for composite cylindrical shells on elastic foundations subject to compression buckling

Elastic boundary conditions play an important role in the buckling analysis of cylinders under compressive loading. These structures are used widely in aerospace applications and are highly sensitive to geometrical, material, loading, and boundary imperfections. In fact, the presence of these imperfections can lead to catastrophic failure. In 1968, NASA reported relations for obtaining the Knockdown Factor (KDF) based on an empirical method that is valid for isotropic and orthotropic materials; however, these relations do not consider the effect of elastic boundaries that can lead to highly conservative values of KDF. In design practice, a universal KDF of 0.65 has been used for recent designs by NASA, which may not be applicable to new types of structural configuration with different loading and boundary conditions. Therefore, there is a need for robust design factors for future designs which reduce the dependency on testing during preliminary design phases and speeds up the product development process. The availability of up-to-date and different KDF expressions for different structural configurations would help engineers to design lighter structures with improved load carrying capacity and reliability. The main objective of this work is to identify the buckling load sensitivity of cylindrical shells due to their boundary conditions and develop KDF relations considering elastic boundaries. To achieve this goal, the effect of axial, radial and tangential support stiffness on a quasi-isotropic cylinder under axial compression is investigated. A data-driven design approach is used to develop new KDF empirical relations for a quasi-isotropic cylinder on different elastic foundations. The accuracy of these relations is within 5% for any elastic foundation considered.

Partially embedded piles subjected to critical buckling load—Sensitivity analysis

The first variation of the critical buckling load of a pile partially embedded in a soil due to a change of a design variable is derived. The one-dimensional idealization of the pile in conjunction with the soil represented by the Winkler-type elastic foundation is considered. The effect of the skin friction is neglected. The pile material and the soil properties, as well as the pile ends locations are assumed to be the design variables. The accuracy of the approximation of the change of the critical buckling load due to some design variable variations is also investigated.

Sensitivity Analysis of Buckling Load of the Simply Supported Symmetric Laminated Plate.

In this paper, we describe the sensitivity analysis of buckling load of the simply supported symmetric laminated plate with respect to the material constants and the orientation angle of each ply. The objective is to clarify the dominant factor for the buckling load. Since the buckling load is obtained as the minimum eigenvalue by Galerkin's method, the sensitivity of the buckling load is formulated by making use of the sensitivity analysis of the eigenvalue problem. When the buckling load corresponds to a multimodal eigenvalue, the sensitivity should be obtained by another method which utilizes the directional derivatives. However, in the typical case of a double eigenvalue for the laminated plate, it is shown that such a method is not required. Finally, the dominant effect on the buckling load sensitivity is evaluated through numerical simulations. Then, it is demonstrated that the coupling term plays an important role in buckling sensitivity.

Sensitivity of buckling loads of anisotropic shells of revolution to geometric imperfections and design changes

Buckling load sensitivity calculations in the shell-of-revolution program FASOR are discussed. This development is based on Koiter's initial postbuckling theory, which has been generalized to include the effect of stiffness changes, as well as geometric imperfections. The implementation in FASOR is valid for anisotropic, as well as orthotropic, shells. Examples are presented for cylindrical panels under axial compression, complete cylindrical shells in torsion, and antisymmetric angle-ply cylindrical panels under edge shear.