Development of a Method for Measuring Damping in Bolted Joints

Bolted joints are a significant source of vibration damping but are extremely difficult to model within computer simulations. In order to make progress, good quality experiment data is needed to provide a basis for modelling and an understanding of the mechanisms involved. An apparatus for measuring damping in a lap joint has been developed in which bolted joints are exercised by swinging masses in a resonant configuration. The apparatus is set into vibration and then released so that the vibration decays with the bolt damping controlling the decay. After some signal processing the energy lost per cycle is extracted. The repeatability of the bolted joint behaviour is an issue of concern and this is examined by analysing a series of tests. Although largely successful the system probably applies too large a force to the joint which exhibits some slip which then contributes to the lack of repeatability observed.