Central Cutout Research Articles

Stress and strain analysis of functionally graded plates with circular cutout

Stress concentration is an interesting and essential field of study, as it is the prime cause of failure of structural parts under static load. In the current paper, stress and strain concentration factors in unidirectional functionally graded (UDFGM) plate with central circular cutout are predicted by carrying out a finite element study on ANSYS APDL platform. The present study aims to bridge the lacuna in the understandings of stress analysis in perforated functionally graded plates. It is found that the material variation parameter is an important criterion while designing a perforated UDFGM plate. By selecting a proper material variation parameter and direction of material gradation, the stress and strain concentrations can be significantly reduced.

Fiber Path Optimization of Symmetric Laminates with Cutouts for Thermal Buckling

Automated fiber placement technology has pushed for the need to explore nonconventional fiber paths in laminated composites. This paper investigates optimal spatially varying fiber paths in a symmetric linear orthotropic laminate, which could increase the critical buckling temperature under uniform applied thermal loads. The key idea here is to achieve gains in buckling performance yet focus on manufacturability of the obtained optimal fiber path. The subject of this study is a four-layer symmetric orthotropic laminated plate, with a central circular cutout that is clamped on all the edges. A novel finite element algorithm is proposed, which imposes a condition on the definition of discrete fiber angles within each element. The main objectives of the proposed finite element approach are to maintain continuity of the fiber paths and to use a computationally efficient model by reducing the number of optimization variables.

Free vibration analysis of rectangular plates with central cutout

AbstractA nine-node isoparametric plate element in conjunction with first-order shear deformation theory is used for free vibration analysis of rectangular plates with central cutouts. Both thick and thin plate problems are solved for various aspect ratios and boundary conditions. In this article, primary focus is given to the effect of rotary inertia on natural frequencies of perforated rectangular plates. It is found that rotary inertia has significant effect on thick plates, while for thin plates the rotary inertia term can be ignored. It is seen that the numerical convergence is very rapid and based on comparison with experimental and analytical data from literature, it is proposed that the present formulation is capable of yielding highly accurate results. Finally, some new numerical solutions are provided here, which may serve as benchmark for future research on similar problems.

Analysis of Stress Concentration in Orthotropic Laminates

The current paper presents a comprehensive finite element analysis on stress concentration in orthotropic laminates. This research investigates the Stress Concentration Factor (SCF) in isotropic and orthotropic plates due to presence of a central cutout with respect to ply orientation angle (θ). The numerical simulations are carried out by using an 8 node shell element in ANSYS APDL environment. It is established from the simulations that the SCF is dependent upon the orientation the fibers. For orthotropic laminates, SCF depends on material properties. It increases with increase in Ey/Ex ratio and decreases with increase in μxy.

Stress concentration and deflection in isotropic and orthotropic plates with opening. Finite element study

In this paper, stress concentration factors (SCFs), in-plane displacements and transverse deflection in orthotropic as well as in isotropic plates with central circular cutouts were studied. This study was made by using a quadrilateral finite element with thirty-two degrees of freedom. The element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The main objective of this study is to demonstrate the accuracy of the present element for analyzing the effect of (d/b) ratio (where (d) is hole diameter and (b) is plate width) upon (SCFs), in-plane displacements and transverse deflection in isotropic and orthotropic plates under different in-plane and transverse static loading conditions. Also, in order to understand the effect of the support conditions on the transverse deflection, different plates with various (d/b) ratios are studied. The variations of in-plane displacements, stress concentration factor and transverse deflection with respect to (d/b) ratio are presented in graphical form and discussed. The numerical results obtained by the present element are compared favorably with the analytic solutions, which demonstrate the accuracy of the present element.

Local buckling of aluminium and steel plates with multiple holes

This paper considers local buckling of perforated square aluminium plates. Plates of various slenderness with simply supported edges and subjected to uniaxial compression are studied using the finite element method. Different perforation patterns are investigated, from a single circular hole to 25 circular holes distributed over the plate. A number of aluminium alloys are considered and compared to steel grade A36. Results show that the resistance of the plates containing a single central cut-out is higher than that of plates with more holes and of equal total cut-out size. A further refinement beyond 5 holes does not influence the resistance.

Non-dimensional Analysis of Orthotropic Plate with Circular Cutout

A B S T R A C T Stress concentration is the localization of stresses due to discontinuation or abruption in the geometry. To find the localized stresses, Stress Concentration Factor (SCF) is used. SCF depends on the material and geometry of the specimen. In the present paper an orthotropic plate with a central circular cutout subjected to normal pressure is studied. Based on material properties variation of the non-dimensional parameters E2/E1, G12/E1 and µ12 have been considered within their feasible range. The effect of these nondimensional parameters at different values of polar angle on SCF is studied here. Formulation of mathematical equation for SCF has been done in MATLAB and subsequently results are presented here. The work successfully highlights that for orthotropic material (unlike isotropic materials) SCF depends on material properties. It increases with increase in E2/E1 ratio and decreases with increase in µ12 and G12/E1 ratio.

Post-buckling progressive damage of CFRP laminates with a large-sized elliptical cutout subjected to shear loading

Cutouts are always located in aerospace composite structures to meet specified requirements on the service and functions. The presence of cutout, especially large-sized cutout, would result in a significant stress concentration, and consequently a complicated failure mechanism. This paper presents an experimental and numerical study on the post-buckling damage process of high-performance carbon fiber reinforced polymer (CFRP), T800/X850, multidirectional composite laminated specimen. The simply supported specimen is with a central large-sized elliptical cutout and subjected to shearing load. In the numerical analysis, a damage model incorporating both advanced strain softening schemes and cross-coupling effect between the failure mechanisms is constructed for the damage simulation. Regularizations are implemented for coupling the damage variables to address the deficiencies of the existing model and access the real physical damage behavior of laminated composites. The strain invariant failure theory is employed for evaluation of delamination. To assess the objectivity of the present numerical model, the numerical predictions are compared with experimental data. The predicted damage and propagation patterns show good agreement with experiment results.

Numerical model of crack growth in hydraulic re-fracturing

Crack propagation simulations with FEM employ remeshing to provide more accurate results. This raises a question about the direction and criterion of mesh modification. In the case of general-purpose CAE-packages, we have to deal with a stationary mesh, and the crack trajectory is usually represented as a chain of elements with degraded properties. The accuracy of the solution is heavily dependent on the choice of mesh topology, the degree of mesh refinement in the unpredictable crack propagation zone, and correct crack surface loading in this case is impossible. The algorithm proposed in this paper is based on the ANSYS Mechanical APDL language for stepwise geometry reconstruction and mesh modification in accordance with the current configuration of a growing crack and assures a more accurate description of its shape. The crack propagation process is divided into stages. Each subsequent stage differs from the previous one by the crack shape modified due to the crack length increment in the calculated direction, and the linear stationary boundary value problem of elasticity is solved under the assumption of small deformations. To check the adequacy of the model, an experiment on crack propagation in glass samples with an initial cutoff under uniaxial compression has been performed. Samples of size 200×100 mm with a 2.5×40 mm central cutout at an angle of 30 ° to the horizontal axis are made from 4 mm thick window glass. Vertical loading is increased until the crack passes through the sample. The relative difference between the calculated and experimental crack paths does not exceed 5%. The numerical model developed is used to solve the problem of secondary crack growth for different values of stress field anisotropy in the oil ground layer. The factors of crack propagation re-fracturing along the normal to the crack primary gap are defined: 1) stress anisotropy ratio> 0.8; 2) growth of discharge pressure; 3) increase of primary crack disclosure.

Analysis on Transverse Bending of Rectangular Plate

Transverse bending analysis of plates is an important investigation in structural engineering. A number of techniques has been used so far for these investigations. However Finite Element Method is by far the most popular one. In this paper a general first order shear deformation theory (FSDT) is used to analyze the bending behavior of isotropic plates having central cut-outs. A nine node isoparametric element is used. Plates having different aspect ratio (b/a), boundary conditions and different loads- uniformly distributed load and hydrostatic load are analyzed. Both thin (h/a=0.01) and thick (h/a=0.1) isotropic plates are studied. The deflection and bending moment in non-dimensional form are presented at different locations of the plate. Some of the present solutions are compared with those obtained using ANSYS. Numerical solutions obtained by the present formulation are within 1% of the exact solutions found in literature which not only validates the formulation but also has a clear advantage over ANSYS results (which are generally with 5%-10% of exact solutions). Some new results are provided for uniformly distributed load and hydrostatic load.

Static Analysis of Transversely Loaded Isotropic and Orthotropic Plates with Central Cutout

Plate structures are an integral part of engineering and construction industry. Taking into consideration various design and functional aspects, openings are provided in these plates for access and maintenance. The presence of cutout creates stress concentration, which eventually reduces the mechanical strength of the structure and in extreme cases may lead to its failure. Therefore it is of immense practical importance to investigate these stress concentrations. In this work the deflection and induced stresses for isotropic plate and orthotropic plate with central circular and square cutout under transverse loading is studied with the help of Finite Element Method (FEM). The variation in deflection and stresses with change in d/W and b/W ratio for steel (isotropic material) as compared to e-glass/epoxy (orthotropic material) is studied. Dependence of the deflection and Stress Concentration Factor (SCF) on cutout geometry and size is also observed. The effect of orienting the square cutout with positive X-baseline is also studied. Four different boundary conditions are considered. The results so obtained are critically examined and presented in graphical form. A popular finite element package, ANSYS has been used for the analysis.

Neural Network Based Buckling Strength Prediction of Laminated Composite Plate with Central Cutout

Laminated composite plates are greatly used in many applications where high specific strength and stiffness are mandatory. These structures may have holes in order to accommodate windows and doors if it is used for air craft structures or to provide cables and inspection system if it is used in the applications like power transmission systems and automobiles. The laminated composite plates with holes shall be analyzed using finite element analysis. It is necessary to optimize the parameters like thickness, fiber orientation, material and the stacking sequence to obtain the desired characteristics for these structures. But using finite element analysis makes the process more tedious job. With this in mind it is proposed here to construct the artificial neural network to predict the buckling behavior of the composite plate.

Influence of Casting Rate on TiNb Microalloyed Steel Slab Surface Area Microstructure

Two slabs of Ti-Nb microalloyed steel were analysed in this work. The first slab was transitional with the initial pulling rate 0.43 m.min-1 and the final pulling rate 0.9 m.min-1. The second slab was cast at the real production pulling rate 1.03 m.min-1. The presence of larger amounts of oscillation marks was observed on the first slab at both pulling rates. The second slab showed no oscillation marks. At the lowest pulling rate, cracks were discovered below the slab surface, often below oscillation marks. Cracks were seldom observed at pulling rate 0.9 m.min-1. In the first slab, especially at the low pulling rate, the presence of cracks and pores was found. Pores were observed often with clusters of aluminum oxides. The microstructure of the slab surface zone was characterised by heterogeneity of ferrite grain sizes at all three pulling rates. This heterogeneity was manifested mainly in the marginal cut-outs at all pulling rates. In the marginal cut-outs the microstructure was granulometrically finer at all three pulling rates than in the central cut-outs. Non-equilibrium microstructure in the marginal cut-outs was also observed.

Thermal-Static Structural Analysis of Isotropic Rectangular Plates

Static and thermal analysis of isotropic rectangular plate made up of various materials with various types of load applications and different boundary conditions is analysed in this research. Both numerical and by finite element formulation are carried out in the analysis and the FEM formulation is done in the analysis section of the ANSYS package. In this study, flat rectangular plates without cut-out which can be assumed as prefect platesand plates with a central rectangular cut-out that is considered as imperfect plates which are made up of steel, aluminium and invar materials are analysed. Finally comparison has been done between the results obtained from numerical analysis and ANSYS results for isotropic rectangular plate without cut-out. A study on the structural properties such as deflections and thermal behaviour of different materials has been conducted during the analysis which will be helpful in various fields of engineering.

Buckling behavior of aluminum plate with circular and elliptical shapes of central cutout

Buckling behavior of aluminum plate with circular and elliptical shapes of central cutout

大腿骨転子部骨折に対するJapanese PFNA術後にcentral migrationおよびcutoutした症例の検討

大腿骨転子部骨折に対するJapanese PFNA術後にcentral migrationおよびcutoutした症例の検討

적층된 복합소재 경사판의 기하학적 비선형 동적 거동에 미치는 매개변수 영향

This study investigates a geometrical nonlinear dynamic behaviors of laminated skew plates made of advanced composite materials (ACM). Based on the first-order shear deformation plate theory (FSDT), the Newmark method and Newton-Raphson iteration are used for the nonlinear dynamic solution. The effects of cutout sizes, skew angles and lay up sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite plates with or without central cutouts, and the new results reported in this paper show the significant interactions between the cutout, skew angles and layup sequence in the laminate. Key observation points are discussed and a brief design guideline of skew laminates is given.

Maximization of fundamental frequency of axially compressed laminated curved panels with cutouts

Free vibration analyses of laminated curved panels with central circular cutouts and subjected to axial compressive forces are carried out by employing the Abaqus finite element program. The fundamental frequencies of these composite laminated curved panels with a given material system are then maximized with respect to fiber orientations by using the golden section method. Through parametric studies, the significant influences of the panel aspect ratio, the panel curvature, the cutout size and the compressive force on the maximum fundamental frequencies, the optimal fiber orientations and the associated fundamental vibration modes of these panels are demonstrated and discussed.

Effects of flexural boundary conditions on failure and stability of composite laminate with cutouts under combined in-plane loads

In the present study, an investigation on the effects of flexural boundary conditions on prebuckling and postbuckling responses, failure loads and characteristics of a quasi-isotropic [i.e., (+45/−45/0/90)2s] square laminate with and without a central cutout of various shapes is carried out under combined in-plane loads [i.e., uni-axial compression combined with in-plane shear (positive and negative)] using finite element method. The finite element formulation is based on the first order shear deformation theory in conjunction with the von Karman’s assumptions to incorporate geometric nonlinearity. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. It is observed that under combined loading conditions, buckling and postbuckling strengths and failure loads of the laminate are reduced by the introduction of a cutout at the center of the laminate, irrespective of boundary conditions. It is also noted that the laminate with and without cutout has maximum buckling, first-ply failure and postbuckling strengths (at a particular value of transverse deflection) for BC3 (i.e., clamped on all edges) boundary conditions whereas these values are minimum for BC1 (i.e., simply-supported on all edges) boundary conditions, for both directions of shear load.

Buckling analysis of thin rectangular plates with cutouts subjected to partial edge compression using FEM

PurposeThe purpose of this paper is to present elastic buckling behaviour of simply supported and clamped thin rectangular isotropic plates having central circular cutouts subjected to uniaxial partial edge compression. Analysis is carried out for four different kinds of partial edge compression and it is extended to study the effect of aspect ratio of plate on buckling load.Design/methodology/approachA finite element method technique is used in the current work to solve the buckling problem of plate using eight node quadrilateral element and plate kinematics based on first order shear deformation theory. Results obtained from finite element analysis are first validated for isotropic square plates, without cutouts, subjected to uniaxial partial edge compression with some earlier published literature.FindingsFrom the current work it is concluded that the buckling strength of square plates is highly influenced by partial edge compression, as compared to plate subjected to uniform edge compression; but with increase in aspect ratio, influence of partial edge compression on plate buckling load decreases.Originality/valueThis paper usefully shows how partial edge compression of plates affects the buckling strength of plate having circular cutouts. Generally, simply supported plates subjected uniaxial partial edge compression of Type I and Type III are found to be stronger than plates subjected to partial edge compression Type II and Type IV, respectively.