Measurement of Damping in a Chain of Bolted Joints

A chain of bolted joints forming a series system has been investigated theoretically and experimentally with the objective of understanding how damping is generated by a combination of bolted elements. The overall aim is to be able to predict damping so that computer based simulations can include damping effects. The theoretical simulation shows that adding more bolted joints with damping to a chain of joints will generally decrease the damping. An experimental investigation of a chain of joints showed that there are significant non-linear effects that must be taken into account when attempting to measure the damping of joints. A novel signal processing procedure was developed for this purpose and the damping of a chain of joints measured for one to ten joints. It is observed that the damping is very small (damping ratios of about 0.00004 are typical). Furthermore in the conditions investigated (where there is no slip in the joints) the damping is similar to the damping of the material from which the system is constructed.