Modeling and Analysis of Nonlinear Damping and Mistuning Mechanisms in Rotating Systems

Turbomachinery;Nonlinear dynamics;Reduced order model;Damping and Mistuning;Contact mechanics;Amplitude dependent coatings;Mechanical Engineering;Engineering;Mechanical Engineering

Mitra, MainakZucca, Stefano ;

University of Michigan

关键词: Turbomachinery;    Nonlinear dynamics;    Reduced order model;    Damping and Mistuning;    Contact mechanics;    Amplitude dependent coatings;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/144064/mitram_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Turbine bladed disks (blisks) which constitute critical components of most modern turbomachinery, are known for their complex vibratory behavior. A good blisk design necessitates the knowledge of the dynamic behavior of the component in different regimes of operation. However, small parametric uncertainties and inter-blade structural variations called mistuning are known to affect blisk dynamics drastically under certain conditions. Introduced by manufacturing tolerances, thermal stresses, wear and other causes, these variations make the design process especially challenging. The dynamics of blisks often also involve nonlinearities, such as those arising from friction damping structures such as shrouds or under-platform dampers or from nonlinear damping coatings adhered to the blades. Since it is not possible to eliminate uncertainties due to mistuning, the designer must ensure safe operation within the field of uncertainty of all the design parameters. Presently, the widely accepted method for obtaining a comprehensive understanding of the effects of these uncertainties is to conduct probabilistic analyses with many simulations of different systems generated by applying random mistuning to the nominal tuned system. Finite element modeling techniques when applied in isolation prove too cumbersome and time-intensive to use for this task. To make these simulations computationally feasible, reduced order models which accurately capture the nonlinear mistuned dynamics while being computationally tractable must be developed. This work presents model reduction methods for blisk dynamics involving two specific nonlinear mechanisms. An adaptive microslip projection method is developed to reduce the dynamics of blisks with frictional contacts characterized by complex stick-slip behavior. A reduced order modeling technique developed for blisks with nonlinear coatings using an amplitude dependent mistuning framework to simulate the dynamics is presented also. Both reduced order models are found to provide significant computational time savings, while retaining high accuracy in comparison to their higher order baseline models. Another practical challenge for accurate nonlinear dynamic simulation of blisks, is the identification of physical parameters which represent the physics of the system and are thus employed by both the full and reduced order models. Contact parameters are identified from experimental data using optimization techniques and are used to validate the reduced order model. The specific effects of variations in these contact parameters on the dynamic response of the blisk are also studied by carrying out probabilistic analyses.