Development of experimental, analytical, and numerical approximations appropriate for nonlinear damping coatings

Hard coatings, such as magnesium aluminate spinel, offer the potential to satisfy the damping requirements of turbine engine components. Unfortunately, the characterization of these materials is complicated by several nonlinearities thus making it difficult to qualify the materials for use in an engine. An experimental and computational research program was initiated with the hope answering some of the questions surrounding these materials.; The major contributions of this research program are a new experimental apparatus and method that is able to more accurately determine the nonlinear material properties of these materials, an exhaustive set of material properties data at higher strain levels than previously tested, and, for the first time, a quantification of the effect of strain history on material properties. The use of a reduced order computational model provided several important and unique insights. Specifically, this portion of the research proved that the log decrement method is able to more accurately predict the damping of a nonlinear reduced order frictional model. Additionally, the behavior of the reduced order model indicates that internal friction is the dominant, but not sole, mechanism responsible for the nonlinearities in magnesium aluminate spinel. Finally, modifications of the reduced order model were suggested to include a dependence on the initial conditions of the model, a trend seen in the experiment but not present in the original reduced order model.