Evaluating the structural integrity of high strength low alloy steels considered for shipbuilding using acoustic emission

by Shengrun Shi

Institution: University of Birmingham
Department: School of Metallurgy and Materials
Year: 2015
Keywords: TN Mining engineering. Metallurgy
Record ID: 1406557
Full text PDF: http://etheses.bham.ac.uk/5740/


The main objectives of this project have been to assess the applicability of various HSLA steel grades in ships as a possible replacement to conventional maritime steel grades such as the AH36 and DH36 high strength steels. For this reason, the mechanical properties of three different HSLA steel grades (X65, S690 and FCA) of different plate thicknesses were assessed using metallography, fractography, hardness, tensile, fatigue and impact testing. Acoustic emission (AE) testing was carried out in parallel with tensile and fatigue testing in order to ascertain qualitatively and quantitatively the evolution of damage in the samples tested and verify the level of severity. Various methods have been applied for the analysis of the AE data acquired in order to correlate them with the mechanical testing results obtained in parallel. It has been revealed that HSLA steel grades exhibit superior crack initiation and propagation resistance than conventional steel grades. Moreover, they exhibit better or comparable tensile properties and thus they qualify for ship building applications. It has been found that indeed AE can be used to detect crack growth. It can also potentially be used to assess the rate at which a crack grows using AE energy release rate.