Abstract

ABSTRACT

Dynamic behavior of microcantilevers subjected to fluid-structure interaction using Mode Summation method

Pranav Ashtaputre

Several Microsystems exhibit interaction of flexible structures such as beams, plates, membranes with fluid. Some of these systems are micropumps, flow sensors and micro valves. It is crucial to consider the effects of fluid parameters such as density, viscosity, velocity and pressure loading while designing these systems. The design of these systems demand a numerical model to understand the dynamic behavior of various elements involved in these systems. Microcantilever is an important structure which exhibits interaction with fluids in various microsystems. The present thesis focuses on the numerical modeling of dynamics of a microcantilever vibrating under the action of fluid loading. Natural frequencies and mode shapes of cantilever are obtained using characteristic orthogonal polynomials in the Rayleigh Ritz method. Numerical model is formed by solving Euler Bernoulli Equation of beam using mode summation method with normal modes of cantilever. The excitation frequency and fluid pressures are obtained from experimental results are explored for modeling and verification purposes. The results are obtained for the tip deflection of the beam. The results are validated with the results obtained in earlier experiments. The deflection amplitudes from the numerical model and those from experiment are found to be in agreement with each other. A parametric study is also presented with different sizes of microcantilever. The effect of different lengths and widths of microcantilever on the deflection amplitudes is presented. However, the effect of structural deformation due to the changes in fluid pressure is not considered. The model can be further extended to explore the dynamics of microplate used in micropumps with the help of precise fluid pressure data for a particular dynamic system and mode shapes obtained in free vibration analysis. The model provides the first step towards finding a solution to the problems involving fluid loading on microsystems.