Michel, Jeffrey Louis (2015-08). Characterization of Acoustic Emissions from Steel Pipeline Dents. Master's Thesis.
Acoustic emissions monitoring is a novel form of nondestructive testing by which the elastic waves that propagate through materials and structures are detected and observed. It allows previously unknown information about the material to be acquired and analyzed. Deformation events often cause a sudden change in a material's stress field which is manifested as an elastic wave. Monitoring the emissions generated by deforming a material can lead to conclusions about the nature of its deformation that might otherwise go unseen. Acoustic activity varies based on the size, shape, and composition of the material, as well as the process by which the material is loaded. This study is an attempt to apply the methods of acoustic emissions monitoring to pipe dent tests, in which a dent is gradually induced into a steel pipeline segment. The purpose of these dent tests is to determine the critical strain at which the existence of a crack within the pipe is probable. Successful acoustic emissions monitoring would ideally be able to predict the generation of a crack and help sharpen the understanding of critical strain. An ultrasonic acoustic emissions monitoring system was acquired and applied to three pipe dent tests carried out over the course of this study. It was also used during a pipe burst test and steel tensile tests. All of these tests are analyzed using established characterization techniques. Some conclusions regarding the nature of the acoustic activity in the pipe dent tests are reached. Additionally, a number of general heuristics for the application of the acoustic emissions monitoring system are provided.