There are some structures, particularly in outer space applications but also on earth, which are inherently lightly damped and hence vibrate a long time after excitation. In many cases, much of the damping that does exist comes from dry friction in bolted joints. It has been shown that controlling the clamping force at a joint, thus creating a semi-active damping element, can increase this type of damping.   In this study, simple examples of bending mode subsystems coupled by a controlled joint are analyzed. Using bond graphs, which are particularly useful in the description of vibratory systems, it is shown that certain structural features of the system may limit the added damping achievable by the semi-active joint to very low values for certain system modes.
['Dean Karnopp']
Understanding structural problems in structural damping with bond graphs