Physics based reduced order models for frictional contacts

Microslip friction plays an important role in determining vibratory response to external excitation of frictional interfaces. Surfaces in contact undergo partial slip prior to gross slip. This mechanism provides significant energy dissipation as a result of interface friction, thereby considerably reducing vibratory response of the system. Developing physics-based phenomenological models for frictional contacts is the underlying aim of our study. Both analytical and numerical approaches have been employed for characterizing the interface friction behavior.; Numerical approaches have traditionally employed bilinear hysteresis elements to simulate frictional contact. Single degree of freedom (SDOF) models that only include a single hysteresis element have been the focus of research in the past. Though these models capture the interface behavior qualitatively, they cannot be truly representative or predictive of the underlying physics of frictional joints. A multiple degree of freedom (MDOF) model built from a finite number of hysteresis elements can discretize the continuous friction interface, and is inclusive of the microslip approach. However; parameter estimation constitutes an important aspect of these models; and currently it is carried out using a calibration approach rather than physical motivation.; We have developed a class of multiple degree of freedom (MDOF) model that account for microslip behavior of friction joints. The models take into account the damper mass, which was studied by very few models in the past. This adds significant dynamics to the phenomological model, thereby providing a more efficient tool to simulate friction joints using numerical models. These models are successful in capturing hysteresis behavior of frictional contacts. They also depict the exponential scaling of frictional energy dissipation with applied forcing level. As such, the richness of the frictional interface can be captured using these models.; A complimentary analytical solution based on the shear lag approach for single fiber pullout models is developed. The analytical solution is motivated by principles of the theory of elasticity, and takes into account the model geometry and material properties. We have developed a low order numerical model based on the analytical behavior which shall not only capture the interface behavior quantitatively but also attach physical significance to the calibration parameters. It is expected that the order of such a physics based model shall be significantly lower than finite element approaches, thereby reducing computational time and effort.; In this work we have considered both parallel and series configuration of the hysteresis elements to develop the MDOF models. Both models show convergent behavior with respect to parameters such as structural mass amplitude, kinematic state of the elements and frictional energy dissipation per cycle. The requisite model order to capture converged results depends on the goal (static, dynamic or kinematic convergence), and is also a function of applied forcing amplitude and frequency. The parallel configuration is shown to act in the role of narrow band vibration absorption in addition to a broad band energy dissipation.; The low order models presented in this dissertation are shown to be favorable substitutes for conventional analytical and finite element approaches, especially for non-standard frictional contact problems.