Comparison of damping on various joint structures

Abstract

Light weight structures commonly have low connate structural damping. The damping mechanism of various jointed structures can be explained by considering the energy loss due to friction and the dynamic slip produced at the interfaces. The frictional damping is evaluated from the relative slip between the jointed interfaces and is considered to be the most useful method for inspect the structural damping. The damping characteristics in jointed structures are influenced by the intensity of pressure distribution, micro-slip kinematic coefficient of friction and logarithmic decrement at the interfaces. The effects of all these parameters on the mechanism of damping have been extensively studied. All the above basic parameters are largely influenced by the thickness ratio of the beam and thereby affect the damping capacity of the structures.In addition to this, beam length of the structures and diameter of connecting rivet and bolt also play key roles on the damping capacity of the jointed structures is assessable. For rivet bolt & welded joints the theoretical analysis proposes two different methods to calculate damping: classical method and finite element method. The analyses are based on the assumptions of Euler-Bernoulli beam theory as the dimensions of test specimens satisfy the criterion of thin beam theory. The effects of all these parameters are studied distinctly in the present investigation. It is established that the damping capacity can be increased appreciably using larger beam length and their diameters as well as lower thickness ratio of the beams. This design concept of using these structures can be effectively utilized in trusses and frames, aircraft and aerospace structures, bridges, machine members, robots and many other applications where higher damping is required. Comprehensive experiments have been conducted on a number of mild steel specimens under different initial conditions of excitation for establishing the accuracy of the theory developed. Finally damping on various joint structures has been compared.