Impact source identification on pipes using acoustic emission energy

Abstract

Impact is a common source of damage in pipes and pipeline systems and detecting the location and nature of damage is vital for reliability and safety of these systems. The main difficulty in the use of AE technology for such applications is being able to investigate the extent to which the temporal structure of such a non-impulsive event can be reconstructed using sensors located on the external surface of a pipe at some distance from the source. There is currently no reliable way of relating the temporal structure of the generating event to the temporal structure of an AE source. This work uses a set of matching AE experiments and finite element simulations to study the relationship between the generating AE event (dropped ball on a steel surface) and the resulting stress-time history recorded at a given point on the surface of the pipe. Two test objects were used; a solid cylindrical steel block of diameter 307mm and length 166mm and a 2m pipe length of diameter 100mm and wall thickness 10mm. The AE resulting from the surface impacts was recorded over a period of 2 seconds for both experiments and simulations. The work builds on an earlier study with the same test objects using impulsive sources. The results confirmed that a mechanical disturbance which is extended in time can be identified from its energy-time imprint carried on the stress wave.