Properties of Energy Transfer Within A Dry Friction Damped Structural System

Friction in connecting joints plays an important role in the damping capacity of built-up structures. The damping supplied by dry friction depends on a number of factors including joint preload and on the location and orientation of the joints relative to modal vibration patterns. Thus it is difficult to predict the level of damping that one can expect from a particular built-up structure. Friction produces a loss of energy whenever relative motion takes place across the contacting surfaces within a connecting joint, however friction can also provide a means by which low-frequency vibrational energy can be pumped or converted to high-frequency vibrational energy, residing in higher structural modes. Since energy can be dissipated faster at higher frequencies, this transfer of energy to higher resonances may serve as a tool for increased energy dissipation. In this paper, the concepts of energy transfer and dissipation are examined for a nonlinear, flexural system. The role of internal resonances on passive damping is studied, as well as how overall energy dissipation is affected by tuning relations between the natural frequencies of substructures. To quantify the structure’s potential for damping, a metric is developed that rates particular configurations based on their potential to dissipate energy through dry friction. The metric is based on the treatment of the nonlinear friction force as a “control input” in an otherwise linear system. The metric gives a scalar measure of the “controllability” of the system and is shown to have a close qualitative agreement with the results of numerical simulations.