Deterministic and probabilistic buckling response of fiber–metal laminate panels under uniaxial compression

Purpose The purpose of this paper is to study the deterministic elastic buckling behavior of cylindrical fiber–metal laminate panels subjected to uniaxial compressive loading and the investigation of GLAss fiber-REinforced aluminum laminate (GLARE) panels using probabilistic finite element method (FEM) analysis. Design/methodology/approach The FEM in combination with the eigenvalue buckling analysis is used for the construction of buckling coefficient–curvature parameter diagrams of seven fiber–metal laminate grades, three glass-fiber composites and monolithic 2024-T3 aluminum. The influences of uncertainties concerning material properties and laminate dimensions on the buckling load are studied with sensitivity analyses. Findings It is found that aluminum has a stronger impact on the buckling behavior of the fiber–metal laminate panels than their constituent uni-directional or woven composites. For the classical simply supported boundary conditions, it is found that there is an approximately linear relation between the buckling coefficient and the curvature parameter when the diagrams are plotted in double logarithmic scale. The probabilistic calculations demonstrate that there is a considerable probability to overestimate the buckling load of GLARE panels with deterministic calculations. Originality/value In this study, the deterministic and probabilistic buckling response of fiber metal laminate panels is investigated. It is shown that realistic structural uncertainties could substantially affect the buckling strength of aerospace components.

Buckling Behavior and Effective Width Design Method for Thin Plates with Holes under Stress Gradient

This paper aims at investigating the elastic buckling behavior and the effective width method (EWM) to predict the ultimate strength of the simply supported rectangular plates under gradient stress (SSRPSG) with circular or rectangular holes. The analytical models of SSRPSG with circular or rectangular holes were established by using the finite-element (FE) software ABAQUS. The FE parametric study covered the aspect ratio, slenderness ratio, and stress gradients of plate and the dimension and spacing of holes. The FE analysis included eigenvalue buckling analysis and ultimate strength analysis. The eigenvalue results show that the buckling coefficient of the perforated plate gradually decreases, and subsequently, it gradually increases with the increase of the dimension of the hole. The buckling mode changes from the buckling including hole to the buckling of plate strip adjacent to hole at the section of the hole. The increasing stress gradient causes an increasing effect on buckling coefficient. The buckling coefficients are less affected by the aspect ratio and the slenderness ratio of the perforated plate and the spacing of hole when the hole spacing meets a certain limitation. The buckling coefficient equations of the SSRPSG with circular or rectangular holes were developed according to results obtained by FE analysis. Finally, the effective width design method was developed based on FE results and developed buckling coefficient equations. The comparisons on ultimate strength between FE results and the predicted results for SSRPSG with circular and rectangular holes and between the predicted results and test results for perforated columns and beams indicate that the proposed effective width design method is accurate, which can be used to predict the ultimate strength of SSRPSG with circular or rectangular holes.

Buckling of simply supported GLARE cylindrical panels subjected to uniform compression

In this article, the elastic buckling behaviour of cylindrical GLARE (GLAss REinforced) panels with classically simply supported boundary conditions under uniaxial compression is investigated using the finite element method (FEM) and eigenvalue buckling analysis. The buckling coefficient-curvature parameter diagrams of five GLARE grades are obtained and studied along with the diagrams of two glass-fiber composites and monolithic 2024-T3 aluminum, using validated FEM models. It is found that aluminium has a stronger impact on the buckling behaviour of the GLARE panels than the composite layers. From the constructed buckling coefficient - curvature parameter diagrams in double logarithmic scale it is found that there is an approximately linear relation between the buckling coefficient and the curvature parameter of the panels. Based on this finding, appropriate regressions are implemented in order to derive approximate analytical formulas of the buckling coefficient as a function of the curvature parameter for the considered materials.

Elastic Web Buckling Stress and Ultimate Strength of H-Section Beams Dominated by Web Buckling

Numerical analyses and theoretic analyses are presented to study the elastic buckling of H-section beam web under combined bending and shear force. Results show that the buckling stress of a single web with clamped edges gives a good agreement with the buckling stress of an H-section beam web when the local buckling of the beam is dominated by the web buckling. Based on theoretic analyses, a parametric study is conducted to simplify the calculation of buckling coefficients. The parameters involved are clarified first, and the improved equations for the buckling coefficient and buckling stress are suggested. By applying the proposed method, the web buckling slenderness ratio is defined. It is verified that the web buckling slenderness ratio has a strong correlation with the normalized ultimate strength of H-section beams when the buckling of the beams is dominated by web buckling. Finally, a design equation is proposed for the ultimate strength of H-section beams.

Multi-objective optimization and linear buckling of serial chain of a medical robot tool for soft tissue surgery

<p>The slender structures of a medical robot may have a tendency to buckling when a force equal to the critical Euler force and an additional disturbance will work on their structures. In this work, eigenvalue problem that describes the linear buckling, is under consideration. The main goal of the article is to check when linear buckling phenomenon appears in construction of a medical robot with serial chain due to the fact that for safety reasons of a robot’s work, it is necessary to answer the question, whether the buckling may occur in the robot’s structure. For this purpose, a numerical calculation model was defined by using the finite element method. The values of load factor coefficients that are eigenvalue are determinated and also the eigenvectors that have shapes of deformation for the next eigenvalues are presented. The multi-criteria optimization model was determined to aim for the minimum mass of the effector and the buckling coefficient, from which the Euler force results, for the maximum. The solution was obtained on the basis of Pareto fronts and the MOGA genetic algorithm.</p>

Development of methods for calculating rod elements of steel structures under multi-parameter loading

In order to reduce the volume of calculation operations, a reverse course of the study of the strength and stability of the rod elements of steel structures in the general case of loading is proposed. For a given limit state in the cross section of the elastic rod element corresponding to the ultimate strain , using the elastic solution method and the «Section» algorithm, the real ultimate state in strength is established. The results obtained in this way are more reliable, since the development of plastic deformations (and for thin-walled elements - section reductions), are determined by the combined action of efforts. The stability of rod elements is known to be characterized by a violation of the equilibrium deformed state. Therefore, following the solutions of the strength problems, at the same loads, a number of stress states are considered in the most loaded section with various values ( ),according to which the «deformation» forces and the corresponding working cross-sectional area and the rod stiffness are determined. Using the latter, the inverse analytical solution of deformation problems determines the largest general loading parameter corresponding to the buckling coefficient.