Keywords

vibration, structural dynamics, turbomachinery, mistuning, reduced-order modeling, sensitivity analysis

Abstract

The vibrational behavior of bladed disks, or blisks, is highly sensitive to variations in its cyclic symmetry due to variations in mass, stiffness, damping, or a combination of these factors. These inconsistencies can arise from manufacturing tolerance inconsistencies, operational wear, impacts during usage, and intentional mistuning. This thesis develops an analysis of the sensitivity of both tuned and intentionally mistuned blisks to random mistuning in their structural properties. Sobol sampling combined with state-space eigen-analysis is utilized to develop a set of randomly mistuned systems. Modal Assurance Criterion is used to track the mode shapes of each randomly mistuned system back to the mode shapes of the baseline system. This allows the mistuned modes to be grouped according to their corresponding nodal diameters. Once the mode shapes are associated with a specific nodal diameter, the logarithmic decrement damping values can be calculated and compared across the different random mistuning types and percentages. Randomness is applied to mass, stiffness, and damping matrices individually. The effects of different intentional mistuning patterns, including AB and ABC blade type mistuning are also studied. Results show that random mistuning alters the logarithmic decrement damping ranges across the three systems examined. Random damping mistuning produces consistent linear trends across all three systems. In contrast, stiffness and mass mistuning produce nonlinear damping responses. These findings show damping mistuning affects system response more predictably, and stiffness and mass mistuning produce more dynamic responses, potentially indicating a breakdown of cyclic symmetry within the systems. The methodology developed provides a foundation for predicting the vibrational response of blisks under random structural mistuning, and gives guidance for design optimization and reliability assessment for blisks in turbomachinery design.

Completion Date

2026

Semester

Spring

Committee Chair

Kauffman, Jeffrey

Degree

Master of Science in Mechanical Engineering (M.S.M.E.)

College

College of Engineering and Computer Science

Document Type

Dissertation/Thesis

Identifier

DP0053268

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