Dynamics and Damping of Thin Riveted Beam Composite Structures of Various Configurations

Abstract

Composite structures built up of two or more layers of thin beams connected by an array of rivets or weldments have extensive industrial and structural applications because of their low vibration, high damping, reduced fatigue and low weight properties. In the present investigation dynamic and damping analysis of such structures of various configurations, have been made by classical energy and finite element methods.
In the first case, a continuous model is represented by a partial differential equation with respect to spatial and time coordinates. An analytical exact solution for the motion of composite beam with fixed fixed, fixed simply supported and simply supported simply supported boundary conditions has been obtained. Natural frequencies and normal modes of such structures have been determined by solving the frequency equations. Damping characteristics are evaluated by considering energy dissipation due to friction at the interfaces.
In the later case, the structure is represented by one dimensional beam elements with each element having two nodes, each with two degrees of freedom, i.e. transverse displacement and rotation. The equation of motion involving reduced mass and stiffness matrices has been derived and solved to determine natural frequencies and mode shapes. Energy of dissipation and stored energy has been determined in terms of nodal displacements and used to determine damping factor of beams.
An experimental set up has been developed to measure the dynamic and damping characteristics of prepared beam specimens with various configurations. There has been close agreement between theoretical and experimental results. Effect of geometrical and material parameters of beam, on its dynamic and damping properties have been reported.