51314-4023-Influence of Localised Pit Distribution and Bench-Shape Pits on the Ultimate Compressive Strength of Steel Plating for Shipping

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Product Number: 51314-4023-SG

ISBN: 4023 2014 CP

Author: Yikun Wang

Publication Date: 2014

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INFLUENCE OF LOCALISED PIT DISTRIBUTION AND BENCH-SHAPE PITS ON THE ULTIMATE COMPRESSIVE STRENGTH OF STEEL PLATING FOR SHIPPINGY. Wang12* J.A. Wharton1 R.A. Shenoi21National Centre of Advanced Tribology at Southampton Engineering Sciences University of Southampton UK2Fluid Structure Interactions Research Group University of Southampton UK*Email: yw5g10@soton.ac.ukABSTRACTThe worldwide fleet of ships is ageing with many vessels being over 15 years old. For such vessels corrosion is an on-going concern and indeed recently a severe corrosion situation termed ‘super-rust’ [1] with corrosion rates of up to 5 mm/y has been observed within the ullage space of oil cargo holds. Thus to guarantee structural integrity facilitate maintenance decisions economically and even extend the structural life it is becoming essential to investigate the ultimate strength of such aged and corroded ship structures based on a comprehensive understanding of the corrosion mechanisms. This work has developed numerical models simulating steel plate corrosion degradation and presents a series of novel finite element (FE) modelling approaches to assess the influence of localised pit distribution [2] and bench-shape pits (degree of pitting in the range of 2% - 25%) which are often observed in long-term exposures [3]. Four location patterns of one-side corroded shipping steel plates have been considered which include both geometric and material nonlinearities. Validation of the FE method is achieved by a thermoelastic stress analysis which is a full-field measurement technique providing the principle stress distribution over the plate surface thus allowing direct comparison with the FE data. The modelling results demonstrate that localised pit distribution can be more detrimental than randomly distributed pits (up to 10.3%). In addition the typical bench-shape pits may further decrease the ultimate strength by up to 14% compared to the unbenched condition with the same degree of pitting. REFERENCES[1] Canfield C. (2007). ‘Super-rust’ in Castor leads to calls for more stringent inspections [online]. Available at: http://www.professionalmariner.com/March-2007/Super-rust-in-Castor-leads-to-calls-for-more-stringent-inspections/ [Accessed: 28 April 2013].[2] ABS (2007). American Bureau of Shipping: Guidance notes on the inspection maintenance and application of marine coating systems [online]. Available at:http://www.eagle.org/eagleExternalPortalWEB/appmanager/absEagle/absEagleDesktop?_nfpb=true&_pageLabel=abs_eagle_portal_rules_guides_download_page&pub_id=49 [Accessed: 11 March 2013].[3] Jeffrey R. and Melchers R. (2008). "The changing topography of corroding mild steel surfaces in seawater." Corrosion Science 49: 2270-2288.