Frictional interfaces in assembled structure represent a major source of nonlinear behaviour.
Even though the size of these interfaces is small compared to the whole
structure they can considerably change the response of the assembly. Hence the importance
of an accurate control of the contact properties at the contact interface when
it is subjected to friction to facilitate the control of a large assembled structure. This
control can be achieve passively or actively; a passive approach sets the geometry of the
interface and then it leaves is as such during operation, oppositely, an active control of
the contact properties allows to change the properties while it is in the presence of a
frictional event.
To walk in the direction of a better active control, a novel concept of a variable frictional
interface is presented and exhaustively studied in this thesis. The concept is studied
in general such that it becomes a tool that can be deployed in various types of joints
and contact interfaces, hence not limiting it to a one specific application. Nevertheless,
to restrict the design space of possibilities, the study consider representative cases of
Bolted Joints and Under Platform Dampers (UPD).
The concept allows to change the conditions at the contact such as the apparent stiffness
and the dissipated energy. The benefit of controlling these properties is that it would
allow the controller to find the best controlling configuration to, for example, de-tune a
system to avoid a resonant frequency or to reduce the amplitude of vibration by adding
more damping.
Given the relative novelty of the concept, the study of it characteristics start from a
fundamental abstraction of its geometry, by means of simple lumped parameter model,
which then is extensively studied in a more complex Finite Element (FE) model. The
FE model is studied in time domain, observing primarily the changes in the Contact
Pressure Distribution (CPD) at the interface as well as the Hysteresis Loops.
After the modeling the concept is tested and validated experimentally, demonstrating
that it can effectively change the contact properties by introducing small changes in
the geometry of the interface.