MS, University of Cincinnati, 2021, Engineering and Applied Science: Mechanical Engineering

Vibration-based damage detection methods have been extensively used in structural health monitoring as these are response-based techniques and can be applied to experimental/operational data. The conventional methods of obtaining full-field vibration measurements are limited due to the location and number of sensors. Advancements in imaging technology have enabled the use of the digital image correlation (DIC) technique to measure the full-field deformation of a vibrating structure. In this study, the DIC technique was used to obtain vibration measurements from an impact test of a cantilever beam for damage identification. The application of curvature mode shapes (CMSs) developed from the mode shapes (MSs) of the beam is studied to detect and locate the damage. The CMSs of the undamaged state of the beam are determined only from the damaged state of the beam, without prior information about the associated undamaged beam, provided the beam is geometrically smooth. It is shown that the polynomial fit of the appropriate order of measured MS is equivalent to the associated MS of the undamaged beam. The objective of this study was to investigate the use of DIC technique and CMSs to locate and detect damage in the form of a machined area with reduced thickness in a cantilever beam. The modal parameter estimation (MPE) was done using X-Modal software, based on the unified matrix polynomial approach (UMPA), to obtain mode shapes and natural frequencies from the vibration measurements. It is shown that the proposed method can successfully detect and locate damage in the beam, for the data obtained from a single-input impact test. The work focuses on understanding how the parameters used in the DIC technique and MPE influence the damage detection. The influences of parameters such as subset size and step size used in the DIC technique are studied. The influences of parameters such as type of MPE algorithm, frequency band selection and model order during MPE are studied. (open full item for complete abstract)

Committee: Yongfeng Xu Ph.D. (Committee Chair); Randall Allemang Ph.D. (Committee Member); Allyn Phillips Ph.D. (Committee Member) Subjects: Mechanical Engineering