A parametric study on the buckling of functionally graded material plates with internal discontinuities using the partition of unity method

In this paper, the effect of local defects, viz., cracks and cutouts on the buckling behaviour of functionally graded material plates subjected to mechanical and thermal load is numerically studied. The internal discontinuities, viz., cracks and cutouts are represented independent of the mesh within the framework of the extended finite element method and an enriched shear flexible 4-noded quadrilateral element is used for the spatial discretization. The properties are assumed to vary only in the thickness direction and the effective properties are estimated using the Mori-Tanaka homogenization scheme. The plate kinematics is based on the first order shear deformation theory. The influence of various parameters, viz., the crack length and its location, the cutout radius and its position, the plate aspect ratio and the plate thickness on the critical buckling load is studied. The effect of various boundary conditions is also studied. The numerical results obtained reveal that the critical buckling load decreases with increase in the crack length, the cutout radius and the material gradient index. This is attributed to the degradation in the stiffness either due to the presence of local defects or due to the change in the material composition.Comment: arXiv admin note: text overlap with arXiv:1301.2003, arXiv:1107.390

Large-Amplitude Free Flexural Vibrations of Laminated Composite Curved Panels using Shear-Flexible Shell Element

Using degree centigrade continuous, QUAD-8 shear-flexible shell element, based on field consistency principle, the nonlinear free flexural vibrations of anisotropic laminated curved panels are studied. The formulation includes transverse shear deformation, in-plane and rotary inertia effects and geometrical nonlinearity. The element is employed to study the large amplitude dynamic behaviour of cylindrical and spherical shells. The frequency versus amplitude curves are obtained from the dynamic response history. The nonlinear governing equations are solved using Wilson-Theta numerical integration scheme with Theta = 1.4. For each time step, modified Newton-Raphson iterations are employed to achieve equilibrium at the end of that time step. Detailed numerical results are presented, showing the effects of thickness, lamination scheme, material properties and boundary conditions, on nonlinear behaviour

Free Vibrations Analysis of Laminated Composite Rotating Beam using C' Shear Flexible Element

The free flexural vibrations of rotating beam made of anisotropic laminated composite beam are investigated using a new three noded finite element. The governing equations for the free vibration of rotating beam are derived using Lagrange's equation of motion. The element employed is based on shear flexible theory. It also includes inplane and rotary inertia terms. The formulation takes care of continuity conditions for stresses and displacements at the interfaces between the layers of a laminated beam. Numerical results for uniform rotating cantilever beam are presented by considering various parameters like slenderness ratio, modular ratio and rotational speed, etc

Supersonic Flutter of Laminated Curved Panels

Supersonic flutter analysis of laminated composite curved panels is investigated using doubly-curved, quadrilateral, shear flexible, shell element based on field-consistency approach. The formulation includes transverse shear deformation, in-plane and rotary inertias. The aerodynamic force is evaluated using two-dimensional static aerodynamic approximation for high supersonic flow. Initially, the model developed here is verified for the flutter analysis of flat plates. Numerical results are presented for isotropic, orthotropic and laminated anisotropic curved panels. A detailed parametric study is carried out to observe the effects of aspect and thickness ratios, number of layers, lamination scheme, and boundary conditions on flutter boundary

A New C Eight-Noded Plate Element for Static & Dynamic , Analyses of Composite Laminates

This paper deals witU a new 48-degrees-of-freedom rectangular finite element for analysing moderately thick multilayered composite plates. The formulation is based on a kinematics which allows one to exactly ensure the continuity conditions for the displacements, and the transverse strsses at the interfaces between the layers of a laminated structure and zeros1lress conditiQns at the top and bottom surfaces of the plate. The shear correction factorsare not required in the formulation, as the transverse shear deformations are defined usingtrigonometric 'runctions that are of higher order. The effectiveness of the element is testedagainst standard problems concerning statics, vibration and buckling, for which exact three dimensional/numerical solutions areiavailable

Theoretical & Experimental Studies on Vibration & Damping of Fibre-Reinforced Cantilever Laminates.

In this paper, vibration and damping analyses  of glass fibre-reinforced laminated composite cantilever beams and plates are studied using C1 finite element using shear deformation theory and alsothrough experiments. The formulation in the theoretical model includes in-plane and rotary inertiaterms. The governing equations for the complex eigenvalue problem based on complex elastic moduliare formulated. The solutions are obtained using QR algorithm. Parametric study is carried out tohighlight; the effects of lay-up and ply-angle of the laminates. A limited number of experimentalinvestigafions on cantilever laminates are conducted for obtaining the natural frequenciqs, dampingfactor and frequency responses. The comparison between the theoretical and the experimfntal resultsshows good agreement

An AI framework for Change Analysis and Forecast Modelling of Temporal Series of Satellite Images

The study focuses on change analysis and predicting future LULC map of capital city of Karnataka state, India. The chosen study area is more prone to urbanisation and greatly affected by population in recent years. Spatial-temporal data from 1989-2019 are considered. LULC classes comprise of Water bodies, Urban, Forest, Vegetation and Openland. An optimal LULC maps from 1989 to 2019 obtained by deep neural network technique are used to perform change analysis which would mainly give the change LULC map with number and percentage of change pixels. According to the analysis performed major change as environmental affecting factor was noticed between 2009 and 2019 where in urban with the area of 189.3861 sq. km remain unchanged and noticeable transitions from other LULC classes to urban. Later, time series classification was performed using Cellular Automata, Cellular Automata-Neural Networks, techniques to predict the LULC map of 2024. Among these CA-NN outperformed with an average kappa coefficient of 0.83. Also, this was validated with projected LULC map of 2024 provided by USGS

Postbuckling Behaviour of Anisotropic Laminated Composite Plates due to Shear Loading

This study investigates postbuckling behaviour of laminated composite plates using a nine-noded shear flexible quadrilateral plate element. The formulation includes nonlinear strain-displacement relation based on von Karman's assumption. The nonlinear governing equations are solved through iteration. A detailed parametric study is carried out to bring out the influence of ply-angle, aspect ratio and material properties on the postbuckling strength of laminates due to in-plane shear loads