D.K. Maiti

New Nonpolynomial Shear-Deformation Theories for Structural Behavior of Laminated-Composite and Sandwich Plates

In the present study, new nonpolynomial shear-deformation theories are proposed and implemented for structural responses of laminated-composite and sandwich plates. The theories assume nonlinear distribution of transverse shear stresses, and also satisfy the traction-free boundary conditions at the top and bottom layers of the laminates. The governing differential equations are derived for a generalized shear-deformation theory by implementing the dynamic version of principle of virtual work and calculus of variations. A generalized closed-form solution methodology of the Navier type is implemented to ensure the validity and efficiency of the present theories for bending, buckling, and free-vibration responses of the laminated-composite and sandwich plates. It is observed that the proposed formulation in conjunction with the solution methodology is capable of handling all existing five-degree-of-freedom-based shear-deformation theories. The comparison of results also shows that the adequate choice of shea...

Damage assessment of truss structures from changes in natural frequencies using ant colony optimization

Abstract A method is presented to detect and assess structural damages from changes in natural frequencies using ant colony optimization (ACO) algorithm. It is possible to formulate the inverse problem in terms of optimization and then to utilize a solution technique employing ACO to assess the damages of structures using natural frequencies. The study indicates the potentiality of the developed code to solve a wide range of inverse identification problems in a systematic way. The developed code is used to assess damages of truss like structures using first few natural frequencies. The outcomes of the results show that the developed method can detect and estimate the amount of damages with satisfactory precision.

Bending, free vibration and impact response of thick laminated composite plates

In the present paper, the higher-order shear deformation theories (HST6, HST9, HST11, HST12) and the conventional first-order theory (FST) are employed to develop finite element analysis methods using eight-noded isoparametric elements to study the bending, free vibration and impact behaviour of laminated composite plates. The present results, based on higher-order theories, compare well with those existing in the literature. The effects of various parameters, such as span to thickness ratios, support conditions and stacking sequences on the laminate response are investigated. It is revealed that the first-order theory provides reasonably dependable results for natural frequencies, contact force, impact response and velocity profile of impactor for both thin and thick laminates. However, the higher-order theories are needed to compute stresses accurately in thick laminates.

Structural damage assessment using FRF employing particle swarm optimization

This paper evaluates the use of Frequency Response Function (FRF) with the help of Particle Swarm Optimization (PSO) technique, for structural damage detection and quantification. The robustness and efficiency of the above method has been established after comparing results between the two methods namely Genetic Algorithm (GA), and PSO, considering natural frequencies as response quantities. The performance of these methods has been evaluated for beam and plane frame structures with various damage scenarios. FRF based damage detection technique is employed subsequently along with PSO. It is observed that the use of FRF as response of damaged structure has led to better accuracy, since it contains data related to mode shape in addition to natural frequencies.

A comparative study on crack identification of structures from the changes in natural frequencies using GA and PSO

Purpose – The early detection of cracks, corrosion and structural failure in aging structures is one of the major challenges in the civil, mechanical and aircraft industries. Common inspection techniques are time consuming and hence can have strong economic implications due to downtime. The paper aims to discuss these issues. Design/methodology/approach – As a result, during the past decade a number of methodologies have been proposed for detecting crack in structure based on variations in the structures dynamic characteristics. This work showcases the efficacy of particle swarm optimization (PSO) and genetic algorithm (GA) in damage assessment of structures. Findings – Efficiency of these tools has been tested on structures like beam, plane and space truss. The results show the effectiveness of PSO in crack identification and the possibility of implementing it in a real-time structural health monitoring system for aircraft and civil structures. Originality/value – The methodology presented establishes t...

Nonlinear Finite Element Analysis of Laminated Composite Doubly Curved Shells in Hygrothermal Environment

In the present investigation, the geometrically nonlinear analysis of laminated doubly curved shells in a hygrothermal environment is presented using the finite element method. The laminated composite shells may be exposed to moisture and temperature during their service life. Hygrothermal effects induce residual stresses and the laminated shell may undergo large bending deformation. The shell geometry used in the formulation is derived using the orthogonal curvilinear coordinate system. Based on the principle of virtual work the nonlinear finite element equations are derived. A total Lagrangian approach associated to the arc-length method is implemented to solve the equilibrium equations. The present results are found to compare well with those available in the open literature and parametric studies are performed to analyze the nonlinear deflections of [0°/±45°/90°]s laminated spherical, cylindrical and conoidal shell panels under hygrothermal condition.

Free vibration and buckling characteristics of laminated composite and sandwich plates implementing a secant function based shear deformation theory

A generalized finite element modeling of recently developed secant function based shear deformation theory is formulated and implemented for free vibration and buckling characteristics of laminated-composite and sandwich plates. The shear deformation is expressed in terms of a secant function of thickness coordinate. The theory inherently satisfies the zero transverse shear conditions on top and bottom surfaces of the plate. An eight-noded C0 continuous element is chosen by an adequate choice of nodal field variables. The governing equations are obtained for the free vibration and buckling responses of laminated-composite and sandwich plates. Intensive numerical experiments are conducted to investigate the influence of span-thickness ratio, boundary conditions, etc. on the free vibration and buckling behavior. The comparison of present results with the published results indicates the performance and range of applicability of the present theory in the framework of finite element analysis.

Flutter Control of Smart Composite Structures in Hygrothermal Environment

Flutter control of smart composite plates under subsonic airflow is investigated in hygrothermal environment. The active fiber composite (AFC) which is more effective and adaptive than the conventional monolithic piezoelectric material is used in the present analysis to control the undesirable response due to hygrothermal effect. The velocity and displacement feedback control algorithm are subsequently established to reduce actively the response of the plate. Numerical examples of isotropic and laminated composite plates with or without hygrothermal effect are presented. It is observed that the structures become weak in the presence of hygrothermal load in the form of reduced flutter boundary. The flutter boundary can be enhanced with the help of AFC. The parametric study is performed and it is observed that the flutter boundary can be enhanced with the help of a feedback-control system activating the AFC. Therefore, one can say that the AFC is effective to enhance the flutter boundary of the present aero...

Crack Assessment in Frame Structures Using Modal Data and Unified Particle Swarm Optimization Technique

The present paper deals with the application of unified particle swarm optimization (UPSO) technique for solving crack assessment problems in frame like structures. UPSO is a scheme for improving performance of standard particle swarm optimization (SPSO) by harnessing its exploration and exploitation ability simultaneously. The objective function formulated for crack assessment purpose uses the changes in natural frequencies and mode shapes as the damage indicators. The efficiency of present crack assessment algorithm is demonstrated by conducting several studies. First, a numerical study conducted among several PSO variants, such as global best SPSO, local best SPSO, PSO with constriction factor, PSO with time varying acceleration coefficient and UPSO for accessing their performance in solving inverse problem for crack assessment. Secondly, the performance of UPSO based algorithm is validated with experimental results. Finally, numerical studies are conducted to investigate the performance of UPSO based algorithm in crack assessment using noisy modal data. The results of these studies indicate that the developed method is capable for crack detection and quantification with satisfactory precision.

Vibration-Based Structural Damage Detection Technique using Particle Swarm Optimization with Incremental Swarm Size

A simple and robust methodology is presented to determine the location and amount of crack in beam like structures based on the incremental particle swarm optimization technique. A comparison is made for assessing the performance of standard particle swarm optimization and the incremental particle swarm optimization technique for detecting crack in structural members. The objective function is formulated using the measured natural frequency of the intact structure and the frequency obtained from the finite element simulation. The outcomes of the simulated results demonstrate that the developed method is capable of detecting and estimating the extent of damages with satisfactory precision.