Damping estimation of joined plate structures using static contact analysis

Mechanical joints such as bolted and spot welded joints are widely used to join plate structures. The existence of contact interface of the joint increases the vibration damping in the structure because the energy dissipation due to friction occurs at the interface. This paper proposes a procedure for calculating the dissipated energy at the interface using finite element static contact analysis. The structure considered consists of three steel plates bolted together where a long plate is sandwiched between two short plates. We use the mode shapes of linear FE model of the joined structure as a distributed displacement loading in the static contact analysis to estimate the damping for each mode. To accurately calculate the dissipated energy, we apply a surface load on the overlap region of the joint along with the distributed displacement and find the necessary value of surface load. To validate the proposed procedure, the modal damping ratios estimated from the dissipated energy with the necessary surface load are compared with the measured damping ratios. The results show when the mode shapes obtained from the linear FE model approximate the actual deformation, the proposed procedure enables to accurately calculate the dissipated energy of the joined plate structure while the surface load on the overlap region is appropriately set. The necessary surface load increases with increasing mode number and varies almost proportionally to the square of the angular frequency.