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Seminar by Ata Donmez (Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH, USA)

Abstract: Mechanical systems are subjected to varying levels and types of nonlinearities, ranging from non-smooth, clearance-type discontinuities in machine elements to friction- and damping-induced nonlinearities, as well as smooth geometric and material nonlinearities. The study of such nonlinearities often requires computationally expensive models and specialized measurement techniques. This poses a significant challenge to the analysis, control, and design of these mechanical systems. This seminar will focus on a specific class of such nonlinear behavior, vibro-impacts in geared systems, which are prevalent in various automotive drivetrains and lead to durability concerns and excessive noise issues. The first objective of this study was to develop a methodology along with novel measurement systems to quantify the vibro-impact dynamics in a laboratory environment in a tightly controlled and repeatable manner. This experimental methodology will be presented first, including its application to address various design aspects. A new vibration-based design metric, vibro-impact severity index, will be defined, and its correlation to the resultant impact noise levels will be demonstrated. The second objective of this study was to develop a family of reduced-order nonlinear dynamic models at varying levels of complexity and validate them through comparisons with the measurements. These validated models implemented by a computationally efficient solution methodology will be used to characterize and map periodic and non-periodic impacting motions, providing insights into the mechanisms governing their complex bifurcations. This study offers a comprehensive experimental and theoretical framework to investigate a complex design problem from a nonlinear dynamics perspective, aimed at enhancing drivetrain design. The seminar will conclude with a discussion of various theoretical and experimental research extensions, potential proposal ideas, funding opportunities, and collaborative prospects.