Prediction and Control of Interface Damping in Built-up Structures

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Interface damping is a primary source of energy losses in built-up structures such as weapon systems, space vehicles, aircrafts, ships, automobiles, buildings, bridges, and turbine engines. Accurate prediction and control of interface damping is critical for safety, reliability and energy efficiency of built-up structures operating in dynamic conditions. Interface damping results mainly from frictional energy losses over contacting surfaces. Variability, nonlinearity and uncertainty in contact interactions limit the ability to accurately predict and model interface damping. This research project aims at identifying the main mechanisms that govern interface damping, its magnitude and its nonlinear characteristics. The project will investigate and outline effective methods to adjust such characteristics to desired values. Results from this award will enable designs of structural interfaces with desired interface damping. The expected outcome is the improvement of safety, reliability and energy efficiency of built-up structures. The results from the research will be shared with the community and K 12, undergraduate and graduate students through design projects involving vibrations and acoustics of simple built-up structures.Time and load dependent stochastic interfacial events introduce nonlinearity to interface damping, and deter predictability of dynamical response. The current state-of-the-art in estimating interface damping is through phenomenological models, which cannot ensure predictive results for untested conditions. Physics-based models cannot account for all possible events and changes occurring at the interfaces. This research offers an effective alternative to complicated modeling whereby the mismatch of elastic properties across interfaces are adjusted, and loading conditions are identified to reduce and if possible eliminate nonlinearities and variability in interface damping. Additional benefit of this alternative approach is the ability to tune interface damping over several orders of magnitude based on operational needs. The research approach is a concerted effort in modeling and experimentation that bridges two distinct disciplines such as tribology and structural dynamics. The PI will systematically study interfacial mechanics, geometry, friction, material properties and loading conditions to identify the major contributors to interfacial energy dissipation. Built-up structures containing interfaces with controlled material properties, preloads and geometries will be designed and constructed. Finally, forced and free vibrations tests will be performed on the built-up structures to explore tunable interface damping in dynamic response. An education and outreach program will also be conducted to disseminate the research results to a broader audience, and introduce important concepts of damping and friction to the students at various stages of their education process.