X80 Grade Steel for RAN Warships

Dr Robert Phillips (Defence, Science & Technology Organisation - Aeronautical & Maritime Research Laboratory)

Dr Daniel Brooker
Dr Michael Morris-Thomas

Bluescope Steel
Defence, Science & Technology Organisation - Aeronautical & Maritime Research Laboratory
 

Novelty

The potential use of grade X80 steel as a method for saving weight in ADF ship structures has been proposed for some time. The future use of this grade of steel is dependent on significant weight savings resulting from its usage. These weight savings require that extensive optimisation of existing ship structures, to best make use of the higher strength available from X80 steel. Previous work under this project has shown that based on the collapse strength of typical panel section, weight savings in the order of 10-20% are possible. This project will focus on weight optimised design, including ultimate strength, fatigue performance of the structure. This project will examine fatigue issues, which have yet to be systematically investigated in this context. This optimisation must also be carried out within the context of existing classification rules. This project will aim to consolidate current knowledge on the design of stiffened plates using high strength steel, which may be outside of the ship building industry. In particular, it is proposed to seek information on fatigue issues.

Summary

The potential weight saving that can be achieved through the use of high strength steel can be limited by several possible criteria: the ultimate strength capacity, fatigue capacity or serviceability criteria. Within a typical ship structure, the governing criterion may differ from site to site; therefore weight savings through the use of X80 will not be uniform throughout a ship or ship section. The proposed scope of work is aimed at assessing the overall weight benefit over a relatively large ship section taking into consideration all design criteria, including global and local loading, strength, serviceability and fatigue.

Benefits

X80 steel has a yield strength much higher than that of typical steels used in the ship building industry. Before extensive use of it can be made, it must be proven that the use of X80 steel can result in significant weight savings. By optimising a number of typical plate sections, these potential weight savings may be identified. Also design issues such as the code formulation need to be examined, to show that this steel can perform as well as currently used steels. By examining the background of current design codes, this project will allow for the use of X80 to be better justified to the various classification societies.