TORQUE LOSS AND CRACK MONITORING NEAR FASTENERS FOR ISOTROPIC AND COMPOSITE HELICOPTER TAIL BOOM STRUCTURAL MODELS

摘要

Structural Health Monitoring (SHM) techniques based on high frequency wave propagation (Acousto-Ultrasonics) are of interest due to their sensitivity to incipient damage in structures. Techniques that use small, low profile transducers allow for in-situ sensing and actuation and are particularly useful for integration on aerospace structures. Additionally, signal processing and interpretation of the data becomes important in the diagnosis process. Commonly, the development of an integrated hardware and software system based on Acousto-Ultrasonics is performed on simple structures such as flat metallic panels. In this study, the curved metallic and composite panels are examined as they provide complexity in both geometry and material used to represent helicopter tail boom structures. Damage at the edges of the curved panel is investigated as these locations typically experience damage related to fatigue. Piezoelectric transducers are mounted to the structures and used to excitation and sensing of the wave modes. The data was acquired and damage indices are used to quantify the effect of two types of damage: bolt torque loss, crack propagation between two bolts.