| || Large-Amplitude Free Flexural Vibrations of Laminated Composite Curved Panels using Shear-Flexible Shell Element
Author : Ganapathi, M.
Source : Defence Science Journal ; Vol:45(1) ; 1995 ; pp 55-60
Subject : 678 Composite Materials
Keywords : Newton-Raphson ;Spherical shells;Geometrical nonlinearity;Transverse shear deformation;Anisotropic laminated curved panels;Vibrations
Abstract : 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.
| || Large Amplitude Free Vibrations of Axisymmetric Orthotropic
Author : Biswas, P.;Kapoor, P.
Source : Defence Science Journal ; Vol:36(3) ; 1986 ; pp 317-325
Subject : 621 Mechanical Engineering
Keywords : Axisymmetric circular plate ;Vibrations
Abstract : Large amplitude free vibrations of an axisymmetric circular plate of orthotropic have been investigated. Generalised field equations in the dynamic case for such a plate have been derived (in the von Karman sense)in terms of displacement components. Time-periods for linear and nonlinear vibrations have been compared and corresponding results for isotropy have been deduced. Some numerical results for the ratio of time-periods vs. non-dimensional amplitudes have been presented in tables.
| || Influence of Ship Vibrations on Heat Exchangers
Author : Sastry, H.S.N.
Source : Defence Science Journal ; Vol:32(1) ; 1982 ; pp 35-40
Subject : 536 Thermodynamics
Keywords : Phenomenon ;Heat exchangers;Vibrations
Abstract : The effect of vibrations on heat transfer has been described. The study made on a double pipe counterflow heat exchanger clearly shows that vibrations of heat exchnagers cause increase in heat transfer coefficients. The maximum increase in overall heat transfer coefficient achieved is 165 per cent. In places where vibrations are inherently present like in ships, the onboard heat exchangers can make use of this phenomenon and increase the effectiveness of heat exchangers.