• International Journal of Ocean System Engineering
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• 제1권2호
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• pp.95-101
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• 2011

Perforated plates with cutouts (or holes) are widely used in structural members. These cutouts provide stress concentration in plates. Extensive studies have been carried out on stress concentration in perforated plates, which consider cutout shapes, boundary conditions, bluntness of cutouts, and more. This study presents stress concentration analyses of perforated plates with not only various cutouts and bluntness but also different cutout orientations. Especially, the effect of cutout orientation on stress concentration is emphasized since structural members have become more complicated recently. To obtain stress concentration patterns, a finite element program, ANSYS, is used. For the designated goal, three parameters are considered as follows: the shapes of polygonal cutouts (circle, triangle, and square), bluntness (a counter measure of radius ratio, r/R), and rotation of cutouts (${\theta}$). From the analyses, it is shown that, in general, as bluntness increases, the stress concentration increases, regardless of the shape and rotation. A more important finding is that the stress concentration increases as the cutouts become more oriented from the baseline, which is the positive horizontal axis (+x). This fact demonstrates that the orientation is also a relatively significant design factor to reduce stress concentration. In detail, in the case of the triangle cutout, orienting one side of the triangle cutout to be perpendicular to the applied tensile forces is preferable. Similarly, in the case of the square cutout, it is more advantageous to orient two sides of square cutout to be perpendicular to the applied tensile force. Therefore, at the design stage, determining the direction of a major tensile force is required. Then, by aligning those polygon cutouts properly, we can reduce stress concentration.

• Steel and Composite Structures
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• 제29권1호
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• pp.39-51
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• 2018

Position of a circular or elliptical cutout within an orthotropic plate has great influence on its buckling behavior. This paper aims at finding the optimal position (both location and orientation) of a single circular/elliptical cutout, within an orthotropic rectangular plate, that maximizes the critical buckling load. We consider linear buckling of simply supported orthotropic plates under uniaxial edge loads. To obtain the optimal positions of the cutouts, we have employed a MATLAB optimization routine coupled with buckling computation in ANSYS. Our results show that the position of the cutout that maximizes the buckling load has great dependence on the material properties, laminate configurations, and the geometrical parameters of the plate. These optimal results, for a number of plate geometries and cutout sizes, are reported in this paper. These results will be useful in the design of perforated orthotropic plates against buckling failure.

• Steel and Composite Structures
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• 제29권5호
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• pp.681-688
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• 2018

In this paper, buckling load of edge stiffened composite plates is assessed. The effect of stiffener edge size, circular hole, and the fiber orientation angle on buckling behavior of composite plates under uni-axial compressive load is investigated. This paper includes two parts as experimental and numerical studies. L-shape composite plates are manufactured in three different layups. Then the buckling loads are experimentally determined. Subsequently, by using the numerical simulation, the size variation effects of stiffener edge and circular cutout on the plate buckling loads are analyzed in five different layups. The results show that cutout size, stiffener edge height and fiber orientation angle have important effects on buckling load. In addition, there is an optimum height for stiffener edge during different conditions.

• Steel and Composite Structures
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• 제17권4호
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• pp.359-370
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• 2014

In this experimental and numerical study, the effect of plate thickness, the diameter of circular cutout, the distance between circular cutouts and rowing orientation angle effect (${\theta}$) on the buckling load of E-glass/vinylester pultruded composite beams with single and double circular cutouts, were investigated. The composite beam having 2, 4, and 6 mm thicknesses was produced as [Mat/${\theta}$ /Mat/${\theta}$ /Mat] by using pultrusion technique. Seven different fiber angles as $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$, and $90^{\circ}$ were chosen for investigation of rowing orientation angle. The distances between each circular cutout were selected as 15, 30, 45, 60, and 75 mm in the case of double circular cutouts. The diameters of circular cutouts were chosen as 2, 4, 6, 8, and 10 mm to investigate the effect of cutout size. The experimental buckling loads were compared with the results calculated from the numerical analysis. ANSYS 11 commercial software was used for numerical study. A good agreement was obtained between numerical and experimental results.

• Steel and Composite Structures
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• 제42권4호
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• pp.427-446
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• 2022

Cutouts in the beams or plates are often unavoidable due to inspection, maintenance, ventilation, structural aesthetics purpose, and sometimes to lighten the structures. Therefore, there will be a substantial reduction in the strength of the structure due to the introduction of the cutouts. However, these cutouts can be reinforced with the different patterns of ribs (stiffener) to enhance the strength of the structure. The present study highlights the influence of the elliptical cutout reinforced with a different pattern of ribs on the stability performance of such stiffened composite panels subjected to non-uniform edge loads by employing the Finite element (FE) technique. In the present formulation, a 9-noded heterosis element is used to model the skin, and a 3-noded isoparametric beam element is used to simulate the rib that is attached around a cutout in different patterns. The displacement compatibility condition is employed between the plate and stiffener, and arbitrary orientations are taken care by introducing respective transformation matrices. The effect of shear deformation and rotary inertia are incorporated in the formulation. A new mesh configuration is developed to house the attached ribs around an elliptical cutout with different patterns. Initially, a study is performed on the panels with different stiffener schemes for various ply orientations and for different stiffener depth to width ratios (d_s/b_s) to determine an optimal stiffener configuration. Further, various parametric studies are conducted on an obtained optimal stiffened panel to understand the effect of cutout size, cutout orientation, panel aspect ratio, and boundary conditions. Finally, from the analysis, it can be observed that the arrangement of the stiffener attached to a panel has a major impact on the buckling capacity of the stiffened panel. The stiffener's depth to width ratio also significantly influences the buckling characteristic.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.272-281
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• 1999

Cylindrical panels are widely used as aircraft fuselages and rocket etc, and the cutouts for weight reduction or wiring at such structures tend to cause the stress concentration and the local radial displacement so that seriously effect the stability of structures. In this paper, for the cylindrical composite panel with coutout at the center, the buckling and postbuckling behaviour regarding the shape and size of cutout is analyzed by finite element method. Also the lamination mechanism , changing bending stiffness and fiber orientation angle variation are researched to be regarded in studying the laminated composite materials.

• Structural Engineering and Mechanics
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• 제61권2호
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• pp.255-266
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• 2017

In this study, self-supporting roofing elements especially convenient for large-span structures such as stadium, airport terminal, mall, coliseum, etc. were examined with respect to critical buckling load. These elements were assumed as laminated composite plates and, variation of free-edge forms, cutout types and lamination configurations were used as design parameters. Based on the architectural feature and structural requirements, the effects of curvilinear free-edge form on critical buckling load were focused on in this research. Within this scope, 14 types of lamination configuration were specified according to various orientation angle, number and thickness of plies with a constant value of total plate thickness. Besides that, 6 different types of cutout and 3 different free-edge forms were determined. By combining all these parameters 294 different critical buckling load analyses were performed by using ANSYS Mechanical software based on finite element method. Effects of those parameters on critical buckling load were evaluated referring to the obtained results. According to the results presented here, it may be concluded that lamination conditions have more significant influence on the critical buckling load values than the other parameters. On the other hand, it is perceived that curvilinear free-edge forms explicitly undergo changings depending on lamination conditions. For future work, existence of delamination might be considered and progression of the defect could be investigated by using non-linear analysis.

• Steel and Composite Structures
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• 제28권1호
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• pp.25-37
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• 2018

For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.