Sarmila Sahoo

Free vibration behavior of laminated composite stiffened elliptic parabolic shell panel with cutout

Abstract In this paper free vibration behavior of laminated composite stiffened elliptic parabolic shell has been analyzed in terms of natural frequency and mode shape. Finite element method has been applied using an eight-noded curved quadratic isoparametric element for shell with a three noded curved beam element for stiffener. Cross and angle ply shells with different edge conditions have been studied varying the size and position of the cutouts to arrive at a set of inferences of practical engineering significances.

Geometric nonlinear free vibration of axially functionally graded non-uniform beams supported on elastic foundation

Abstract In the present study non-linear free vibration analysis is performed on a tapered Axially Functionally Graded (AFG) beam resting on an elastic foundation with different boundary conditions. Firstly the static problem is carried out through an iterative scheme using a relaxation parameter and later on the subsequent dynamic problem is solved as a standard eigen value problem. Minimum potential energy principle is used for the formulation of the static problem whereas for the dynamic problem Hamilton’s principle is utilized. The free vibrational frequencies are tabulated for different taper profile, taper parameter and foundation stiffness. The dynamic behaviour of the system is presented in the form of backbone curves in dimensionless frequency-amplitude plane.

Laminated Composite Stiffened Cylindrical Shell Panels with Cutouts under Free Vibration

The free vibration of laminated composite stiffened cylindrical shell panels in the presence of cutout is investigated. A finite element code is developed using eight-noded curved quadratic isoparametric element for shell with a three noded beam element for stiffener and the formulation is validated through solution of benchmark problems which were earlier solved by other researchers. Parametric study is carried out varying the size of the cutouts and their positions with respect to the shell centre for different edge constraints. The results are presented in the form of figures and tables. The results are further analyzed to suggest guidelines to select optimum size and position of the cutout with respect to shell centre considering the different practical constraints.

Relative performance of antisymmetric angle-ply laminated stiffened hypar shell roofs with cutout in terms of static behavior

Abstract A review of literature reveals that bending analysis of laminated composite stiffened hypar shells with cutout have not received due attention. Being a doubly ruled surface, a skewed hypar shell fulfils aesthetic as well as ease of casting requirements. Further, this shell allows entry of north light making it suitable as civil engineering roofing units. Hypar shell with cutout subjected to uniformly distributed load exhibits improved performances with stiffeners. Hence relative performances of antisymmetric angle-ply laminated composite stiffened hypar shells in terms of displacements and stress resultants are studied in this paper under static loading. A curved quadratic isoparametric eight noded element and three noded beam elements are used to model the shell surface and the stiffeners respectively. Results obtained from the present study are compared with established ones to check the correctness of the present approach. A number of additional problems of antisymmetric angle-ply laminated composite stiffened hypar shells are solved for various fibre orientations, number of layers and boundary conditions. Results are interpreted from practical application standpoints and findings important for a designer to decide on the shell combination among a number of possible options are highlighted.

Mode switching phenomenon in geometrically nonlinear free vibration analysis of in-plane inhomogeneous plates on elastic foundation

Abstract Effect of geometric nonlinearity onfree vibration behaviour of a non-uniform in-plane inhomogeneousplate on elastic foundation is carried out with an emphasis on mode switching phenomenon. The formulation is semianalytic displacement based and it is carried out in two distinct steps. First, the static problem is solved to find out the unknown displacement field by using minimum total potential energy principle. Secondly, subsequent dynamic problem is set up as an eigenvalue problem on the basis of the known displacement field. The governing set of equations in dynamic problem is obtained by using Hamilton’s principle. In static analysis, unknown co-efficient of the governing equations are solved using an iterative method, which is direct substitution with relaxation method. The dynamic problem is solved with the help of intrinsic Matlab solver. The results of the present method are validated with existing data. Backbone curve corresponding to different combinations of systemparameters are presented in non-dimensional plane.Mode switching is observed to occur in certain specific situation. The linear and nonlinear mode shapes are also furnished to support the presence of switching phenomenon.

Stiffened Hyperbolic Paraboloid Shell with Cutout

This chapter considers dynamic characteristics of stiffened composite hyperbolic paraboloid shell panel with cutout under free vibration in terms of natural frequency and mode shapes. Finite element method is used for the analysis by combining an eight-noded curved shell element with a three-noded curved beam element. The variations in cutout size as well as positions of the cutouts with respect to the shell centre are considered for different boundary conditions of cross-ply and angle-ply laminated shells. The effects of these parametric variations on the fundamental frequencies and mode shapes are studied in details to arrive at a set of conclusions of practical engineering relevance.

Stiffened Spherical Shell with Cutout

In this chapter, free vibration characteristics of laminated composite stiffened spherical shells with cutouts are studied using finite element method employing eight-noded curved quadratic isoparametric element for shell with three-noded curved beam element for stiffener formulation. Dynamic characters of stiffened spherical shells with different sizes and positions of the cutouts with respect to the shell centre for different edge constraints are analysed in the form of figures and tables. The results are analysed to arrive at guidelines for the selection of optimum size and position of the cutout with respect to shell centre considering different practical constraints.

Stiffened Saddle Shell with Cutout

In this chapter, free vibration characteristics of laminated composite stiffened saddle shells with cutouts are studied using finite element method employing eight-noded curved quadratic isoparametric element for shell with a three-noded curved beam element for stiffener. Free vibration behaviour of stiffened saddle shells with varying size and position of the cutouts with respect to the shell centre for different edge constraints is studied to arrive at useful conclusions for the shell designers. The results are analysed to provide guidelines for the selection of optimum size and position of the cutout with respect to shell centre considering various practical boundary conditions.

Stiffened Elliptic Paraboloid Shell with Cutout

In this chapter free vibration study of laminated composite stiffened elliptic paraboloid shell having cutout has been presented in terms of natural frequency and mode shape. Cross- and angle-ply shells with different edge conditions have been studied varying the size and position of the cutouts. The present free vibration study includes the effects of these parametric variations on natural frequencies and mode shapes and set of inferences of practical engineering significances.

Stiffened Hypar Shell with Cutout

Free vibration characteristics of stiffened composite hypar shell (hyperbolic paraboloidal shells bounded by straight edges) in the presence of cutout are considered following a generalized finite element formulation using eight-noded curved quadratic isoparametric element for shell with a three-noded beam element for stiffener. The size of the cutouts and their positions with respect to the shell centre for different edge constraints are varied to obtain the results in the form of figures and tables. The results are analysed to achieve guidelines for the selection of optimum size and position of the cutout with respect to shell centre considering different practical constraints.