Influence of pitting corrosion on strength of steel ships and offshore structures

• Autorzy: Jakubowski Marek
• Języki publikacji: EN

Abstrakty

EN

The present paper deals with the influence of pitting corrosion on mechanical properties of mild and low alloy steels and strength of steel structures under static and quasi-static loads. Pitting corrosion is a very important phenomenon that influence local strength of ship hull members. The present paper is based mainly on Japanese publications. Analyzing the standard tensile diagrams one can see that that pitting corrosion reduces the load corresponding to yield stress (YS) and, even more markedly, tensile strength UTS, reduces almost to zero plastic flow strains at YS load level and dramatically reduces the total elongation to fracture. Nominal UTS load for uniformly corroded specimens is higher than that for pitted specimens at the same average thickness loss. The strength related to the true fracture surface area (i.e. reduced by pits, taking into account real path of the crack through the pits) is almost independent of the thickness loss and is almost the same as for uniform thickness loss. For wide specimens the tensile strength depends mainly on the local deformation ability, and the maximum loading ability for large members, predicted on the base of the total true fracture surface area, can be overestimated. Concept of equivalent thickness loss for plates under bending and compression and for more complex structural models as well as relation between the average and the equivalent thickness losses has been presented. Approach based on degree of pitting (ratio of pitted area to total plate surface area) has been shown as a real and more convenient than the approach based on the thickness loss.

Słowa kluczowe

EN

pitting corrosion; strength; shipbuilding steels; ship structures

• Wydawca: Gdańsk University of Technology, Faculty of Ocean Engineering & Ship Technology
• Czasopismo: Polish Maritime Research
• Rocznik: 2011
• Tom: nr 4
• Strony: 54--58
• Opis fizyczny: Bibliogr. 12 poz., rys., tab.

Twórcy

autor

Jakubowski Marek

• Faculty of Ocean Engineering and Ship Technology Gdansk University of Technology Narutowicza 11/12 80-233 Gdansk, POLAND,

Bibliografia

• 1. Jakubowski M.: Influence of pitting corrosion on fatigue and corrosion fatigue of ship structures. Part I: Mechanism and modeling of pitting corrosion of ship structures. To be published in Polish Maritime Research.
• 2. Jakubowski M.: Influence of pitting corrosion on fatigue and corrosion fatigue of ship structures. Part II: Loading – pitting – cracking interaction. To be published in Polish Maritime Research.
• 3. Melchers R.E.: Pitting corrosion of mild steel in marine immersion environment – Part 1: Maximum pit depth. Corrosion, 2004, Vol.60, No 9, pp.824-836.
• 4. Wang Y., Wang Y., Huang X. Cui W.: A simplified maximum pit depth model of mild and low alloy steels in marine immersion environment. Journal of Ship Mechanics, 2008, Vol.6, No.1, pp.401-417.
• 5. Nakai T., Matsushita H., Yamamoto N.: Effect of pitting corrosion on the ultimate strength of steel plates subjected to in-plane compression and bending. J. Marine Science and Technology, 2006, pp.52-64.
• 6. Matsushita H., Nakai T., Yamamoto N., Arai H.: Effect of corrosion on static strength of hull structural members (1st report). J. Society of the Naval Architects of Japan, 2002, Vol.192, pp.357-365 (in Japanese).
• 7. Nakai T., Matsushita H., Yamamoto N., Arai H.: Effect of corrosion on static strength of hull structural members (2nd report). J. Society of the Naval Architects of Japan, 2004, Vol.195, pp.221-231(in Japanese).
• 8. Nakai T., Matsushita H., Yamamoto N., Arai H.: Effect of corrosion on static strength of hull structural members (3rd report). J. Society of the Naval Architects of Japan, 2004, Vol.195, pp.233-242 (in Japanese).
• 9. Nakai T., Matsushita H., Yamamoto N., Arai H.: Effect of pitting corrosion on local strength of hull structural members. ClassNK Technical Bulletin, 2005, pp.29-49.
• 10. Nakai T., Matsushita H., Yamamoto N.: Assessment of corroded conditions of webs of hold frames with pitting corrosion. ClassNK Technical Bulletin, 2007, pp.23-32.
• 11. Polish Register of Shipping (PRS) Rules: Publication No. 84/P, Requirements concerning the construction and strength of the hull and hull equipment of sea-going bulk carriers of 90 m length and above, 2009, Chapter 13.2.3.2.3.; as well as International Association of Classification Societies (IACS): Common Structural Rules for Bulk Carriers, Chapter 13.2.3.2.3.
• 12. Polish Register of Shipping (PRS) Rules: Publication No. 85/P, Requirements concerning the construction and strength of the hull and hull equipment of sea-going double hull oil tankers of 150 m in length and above, 2010, Chapter 12.1.3. – 13.1.6.; as well as International Association of Classification Societies (IACS): Common Structural Rules for Double Hull Tankers, Chapter 12.1.3. – 13.1.6.