Date of Award

2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Sundaresan, Mannur J. Dr.

Abstract

In this research, the acoustic emissions from simulated crack growth and incremental crack growth in a cyclically loaded aluminum panel were detected by acoustic emission sensors. One of these sensors comprised of an array of thin strips of piezoelectric material bonded to the specimen and electrically connected. The geometry of these sensor strip arrays and their orientation to the fracture site enabled the sensors to capture the shear horizontal component of the acoustic emission waveform. Cyclical loading was used to grow the crack, allowing sensor performance to be assessed and compared to bonded piezoelectric sensors and resonant frequency acoustic emission sensors. The detection of the shear waves is of particular interest as significant amplitudes of shear horizontal component is expected only from crack growth events. Other mechanically generated stress wave signals are not expected to have recognizable shear horizontal components. Hence the new sensor can provide a means of discriminating between critical events (crack propagation) and sources of minimal concern (fretting). Shear modes were detected in the acoustic emissions from both the simulated crack growth and the crack growth due to cyclical loading.

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