Articles
Mechanics Based Design of Structures and Machines (15397742)53(6)pp. 4104-4131
In present study, a numerical analysis of a sandwich structure with a lattice core consisting of two outer layers of sheets and an internal lattice core was undertaken. A two-step finite element method was applied to explore their mechanical behavior. The investigation primarily focused on evaluating the natural frequencies, critical buckling load, and maximum deformations of these plates. In first step, the finite element method was used to meticulously calculate the extensional stiffness, bending-extensional coupling stiffness, and bending stiffness matrices for a unit cell of lattice core. A cell was modeled in SAP2000 initially and then the entire structure was expanded. After that, in second step, the response of lattice structures was conveniently calculated by employing the stiffness matrices that were calculated in the first step. The obtained results were thoroughly compared with existing literature, ensuring the precision and reliability of the findings. These findings offer valuable insights for the design and optimization of sandwich structures with lattice core configurations across various engineering applications. © 2024 Taylor & Francis Group, LLC.
In this study, a novel method termed the Optimum Stiffness Finder (OSF) is introduced to determine the equivalent stiffness matrix for sandwich beams with lattice cores. The OSF method utilizes the Particle Swarm Optimization (PSO) algorithm to simplify the calculation of equivalent stiffness, addressing the challenges posed by the geometric complexity of lattice cores. This equivalent stiffness matrix is crucial for dynamic instability analysis, enabling the determination of dynamic instability regions that conventional finite element software does not calculate. For validation of the proposed method, the free vibration results of both three-dimensional finite element models developed in ABAQUS and OSF method are compared with results from the literature, confirming the accuracy of the finite element modeling. First, the free vibration results of three-dimensional finite element models developed in ABAQUS were compared with results from the literature, confirming the accuracy of the finite element modeling. Once validated, the ABAQUS models are used to obtain displacement values under uniform loading, which served as target data for the OSF algorithm. The OSF algorithm then optimized the stiffness matrix for Timoshenko beam theory in one-dimensional finite element analysis. The equivalent beam's vibration results are subsequently compared with those from the literature to ensure consistency and accuracy. The findings demonstrate the potential of the OSF method to streamline the dynamic stability analysis of lattice core sandwich beams, providing an efficient and accurate approach for engineering applications. © 2025 Institution of Structural Engineers
Structural Engineering and Mechanics (12254568)89(2)pp. 181-197
A numerical method is presented in this paper, for buckling analysis of thin arbitrary stiffened composite cylindrical shells under axial compression. The stiffeners can be placed inside and outside of the shell. The shell and stiffeners are operated as discrete elements, and their interactions are taking place through the compatibility conditions along their intersecting lines. The governing equations of motion are obtained based on Koiter's theory and solved by utilizing the principle of the minimum potential energy. Then, the buckling load coefficient and the critical buckling load are computed by solving characteristic equations. In this formulation, the elastic and geometric stiffness matrices of a single curved strip of the shell and stiffeners can be located anywhere within the shell element and in any direction are provided. Moreover, five stiffened composite shell specimens are made and tested under axial compression loading. The reliability of the presented method is validated by comparing its numerical results with those of commercial software, experiments, and other published numerical results. In addition, by using the ANSYS code, a 3-D finite element model that takes the exact geometric arrangement and the properties of the stiffeners and the shell into consideration is built. Finally, the effects of Poisson's ratio, shell length-to-radius ratio, shell thickness, cross-sectional area, angle, eccentricity, torsional stiffness, numbers and geometric configuration of stiffeners on the buckling of stiffened composite shells with various end conditions are computed. The results gained can be used as a meaningful benchmark for researchers to validate their analytical and numerical methods. Copyright © 2024 Techno-Press, Ltd.
