CAREER: Nonlinear Dynamics of Assemblies at High Temperatures

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This CAREER project will support research that will contribute new knowledge related to the failure of structures that operate at high temperatures. This is particularly important for engines, such as the aeroturbines found on jets, or the gas turbines found throughout power plants. One challenge facing design engineers working on these engines is that they must design a structure that has to operate at temperatures often in excess of 1400 degree Celsius. Temperatures this high significantly change the way in which components perform; however, very little knowledge exists for how the specific fatigue (i.e. damage) mechanisms in these components evolve with temperature. This project focuses on fundamental research that can lead to the needed knowledge for improving the design process of these structures. The new knowledge will enable engineers to design more efficient structures that don't need frequent maintenance and will provide computational tools to predict the performance of a structure over its entire life cycle. This project is built on the PI's efforts to create a research experience that engages underrepresented groups, provides mentorship, and builds a peer and external support network.The primary research objective of this CAREER project is to test the hypothesis that interfaces dissipate more energy in assemblies at high temperatures than predicted by fretting experiments or models calibrated to low temperature environments. A second objective is to apply the complex step theorem and the field of generalized complex number theory to create a new method for parameterizing nonlinear structural dynamics models as functions of temperature. To accomplish these objectives, both experimentation and theoretical advancement will be pursued. Experiments will focus on discovering how nonlinearities in structures evolve as a function of temperature, and how multiple nonlinearities interact (e.g. a rocket panel that has geometric nonlinearities due to in-plane stretching and interfacial nonlinearities due to bolted joints). In parallel, a new, parameterized reduced order model will be proposed that expresses the numerical model of a system in terms of temperature and will be validated by the experiments. This modeling framework is based on an extension of the complex step theorem to evaluate sensitivities of a system with respect to a specified variable through the introduction of generalized complex numbers in the system?s definition.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.