K.A.V. Pandalai

Bio: K.A.V. Pandalai is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Transverse isotropy & Rotary inertia. The author has an hindex of 2, co-authored 2 publications receiving 15 citations.

On the modal equations of large amplitude flexural vibration of beams, plates, rings and shells

Abstract: In a simple and straight forward manner the modal equations applicable for the large amplitude flexural vibrations of plates and shells are obtained by the Lagrange's method. These equations can easily be specialised to obtain the corresponding equations applicable for beams and rings. The basic nature of the modal equations for beams and plates on the one hand and rings and shells on the other hand are shown to exhibit hard and soft spring characteristics, respectively.

Non-linear vibrations of transversely isotropic rectangular' plates

Abstract: The large amplitude free flexural vibration of transversely isotropic rectangular plate, incorporating the effects of transverse shear and rotatory inertia, is studied using the von Karman field equations. A mode shape, consisting of three generalised-coordinates together with the Galerkin technique, results in a system of three non-linear simultaneous ordinary differential equations which govern the motion of the plate. These equations are integrated using a fourth-order Runge-Kutta method to obtain the period for each amplitude of vibration. The non-linear period vs amplitude behaviour is of the hardening type and it is also found that transverse shear and rotary inertia effects increase the period and that this increase is quite significant even for thin transversely isotropic plates. The results are compared with earlier results which were based on a one-term or one generalised coordinate solution and using the Berger approximation or the von Karman field equations.

Non-linear behaviour of free-edge shallow spherical shells: Effect of the geometry

Abstract: Non-linear vibrations of free-edge shallow spherical shells are investigated, in order to predict the trend of non-linearity (hardening/softening behaviour) for each mode of the shell, as a function of its geometry. The analog for thin shallow shells of von Karman's theory for large deflection of plates is used. The main difficulty in predicting the trend of non-linearity relies in the truncation used for the analysis of the partial differential equations (PDEs) of motion. Here, non-linear normal modes through real normal form theory are used. This formalism allows deriving the analytical expression of the coefficient governing the trend of non-linearity. The variation of this coefficient with respect to the geometry of the shell (radius of curvature R, thickness h and outer diameter 2 a) is then numerically computed, for axisymmetric as well as asymmetric modes. Plates (obtained as R → ∞) are known to display a hardening behaviour, whereas shells generally behave in a softening way. The transition between these two types of non-linearity is clearly studied, and the specific role of 2:1 internal resonances in this process is clarified. © 2006 Elsevier Ltd. All rights reserved.

Normal form theory and nonlinear normal modes: Theoretical settings and applications

Abstract: These lecture notes are related to the CISM course on ”Modal Analysis of nonlinear Mechanical systems”, held at Udine, Italy, from June 25 to 29, 2012. The key concept at the core of all the lessons given during this week is the notion of Nonlinear Normal Mode (NNM), a theoretical tool allowing one to extend, through some well-chosen assumptions and limitations, the linear modes of vibratory systems, to nonlinear regimes. More precisely concerning these notes, they are intended to show the explicit link between Normal Form theory and NNMs, for the specific case of vibratory systems displaying polynomial type nonlinearities. After a brief introduction reviewing the main concepts for deriving the normal form for a given dynamical system, the relationship between normal form theory and nonlinear normal modes (NNMs) will be the core of the developments. Once the main results presented, application of NNMs to vibration problem where geometric nonlinearity is present, will be highlighted. In particular, the developments of reduced-order models based on NNMs expressed asymptotically with the formalism of real normal form, will be deeply presented.

Advances in nonlinear vibration analysis of structures. Part-I. Beams

Abstract: The development of nonlinear vibration formulations for beams in the literature can be seen to have gone through distinct phases — earlier continuum solutions, development of appropriate forms, extra-variational simplifications, debate and discussions, variationally correct formulations and finally applications. A review of work in each of these phases is very necessary in order to have a complete understanding of the process of evolution of this field. This paper attempts to achieve precisely this objective.

A study of large deflection of beams and plates

Abstract: OF THE THESIS A Study of Large Deflection of Beams and Plates by Vinesh V. Nishawala Thesis Director: Dr. Haim Baruh For a thin plate or beam, if the deformation is on the order of the thickness and remain elastic, linear theory may not produce accurate results as it does not predict the in plane movement of the member. Therefore, a geometrically nonlinear, large deformation theory is required to account for the inconsistencies. This thesis discusses nonlinear bending and vibrations of simply-supported beams and plates. Theoretical results are compared with other well-known solutions. The effects of geometric nonlinearities are discussed. The equation of motion for plates with ‘stress-free’ and ‘immovable’ edges are derived using modal analysis in conjunction with the expansion theorem. Theoretical results are compared with a finite element simulation for plates. ‘Immovable’ edges are studied for beams. For large bending of beams with ‘stress-free’ edges, a theory by Conway is presented. A brief introduction to Duffing’s equation and Gaussian curvature is presented and their relevance to nonlinear deformations are discussed.