Acoustic emission examination of high strength steel M250 pressure vessels for aerospace applications

Abstract

Abstract This paper deals at experiences with the Acoustic Emission (AE) monitoring of critical pressure vessels during qualification proof pressure test. Conventional Non Destructive Evaluation (NDE) methods have limitations in evaluating the vessel. There is a high probability that they may not provide information required to evaluate the quality of vessel. In contrary, Acoustic emission technique has a high probability of detecting the likely defects in pressure vessels prior to the failure. This technique has to be applied under pressure load. These pressure loads create stresses in the vessel. During increasing pressure loads AE signals are obtained from discontinuities and other locations of stress concentrations. AE is very useful in estimating the soundness of critical pressure vessels used by aerospace industry that is made up of high strength Maraging steels. AE Testing and result analysis was carried out according to standard procedures. During the tests, AE signals were recorded and post analysis was done to understand the response from the material. The experimentation revealed that the amplitude of AE signals were less than the corresponding AE signals for critical crack opening, during pressurization cycle. Also, at proof pressure, a 2 minutes hold time was observed with no increase in amplitude of signals. AE activity can detect any defect growth during proof pressure test. Inspection was carried-out in accordance with a set of acceptance criteria based on available literature and specimen level tests.