Effect of damping in layered beam using structural joints

Mostly in the area of the structural engineering designs such as trusses and frames, aircraft and aerospace structures, bridges, machine members, robots and many other applications, connections are built up with mechanical connectors or joints. Under the dynamic loads, such assembled designs need sufficient damping to avoid catastrophic situations effect due to uncontrolled vibration. For various jointed structures the damping mechanism can explained by considering the energy loss because of the dynamic slip and friction produced at the joints interfaces from two sources. One is structural damping because of joints and other is the material or internal damping. It is seen that structures with bolted or riveted members contribute up to 90% for damping and rest by others. So we need to study the damping characteristics of the mechanical joints. Which are influenced by logarithmic decrement, micro-slip kinematic coefficient of friction and the intensity of pressure distribution at the interfaces. In this paper the mechanism of damping have studied by considering the effects of all above parameters. These basic parameters are mostly influenced by the beam material, beam thickness ratio, etc. and there by effect on structures damping capacity. The theoretical analyses done by considering Euler-Bernoulli beam theory as the test specimens dimensions are satisfy the required criterion of thin beam theory. It is seen that the damping capacity can be increased considerably by using larger beam length and lower thickness ratio of the beams. Series of experiments have been performed on a number of aluminum and mild steel specimens under fixed-fixed end condition for validating the accuracy of the developed theory. It is observed that the damping capacity of bolted joint is averagely 4.05% higher than riveted joint.