Date of Award

2013

Document Type

Thesis

First Advisor

Sundaresan, Mannur

Abstract

In the following research, the aim is to develop relationships between signal content and high-speed digital imaging to assist in determining key components of the AE source. Thick aluminum bar samples are experimentally subject to cyclic loading utilizing three point bending setup to observe the crack growth. The crack growth thus generated is monitored simultaneously with the help of a high-speed camera system to record the expansion of the crack tip, and by piezoelectric (PZT) sensors bonded over the specimen surface to collect the AE signals. Analysis is provided to differentiate between the AE signals occurring due to crack growth and fretting occurring during the closing of the crack. Furthermore, a 3D model was studied to differentiate between surface and interior crack growth signals. The fracture results show clear indication of the interior crack growth propagating at a different rate to the crack growth along the free surface of the specimen. This phenomenon is attributed to the plane stress and plane strain conditions in the specimen. This important result comes from the video recordings showing the future of the crack path as it propagates over the surface.

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