Numerical Analysis of Stress Concentration in Non-uniformly Corroded Small-Scale Specimens

Abstract

A numerical evaluation of stress concentrations of corroded plate surfaces of small-scale corroded steel specimens is compared with the experimentally estimated ones. Eleven specimens were cut from a steel box girder, which was initially corroded in real seawater conditions. The surface of all corroded specimens was analysed applying photogrammetry techniques, and a statistical description of an idealised corroded surface of each specimen was established. Fatigue lives of specimens are determined from the fatigue tests. Based on experimentally obtained fatigue lives, the stress concentration factors are calculated concerning the ideally smooth specimens. The correlation between the statistical parameters of the corroded specimen surfaces and the estimated stress concentration factors is analysed. Idealised corroded surfaces, converted in graphical format, are then used for the finite element modelling in ABAQUS software, and stress concentration factors are estimated from the finite element results. A convergence study is performed to determine the appropriate finite element mesh density. Comparison between experimentally obtained and numerically estimated stress concentration factors is performed as well as correlation analysis between actual and finite element predicted crack locations.

Keywords

Fatigue life / Fatigue tests / Corrosion / Stress concentration factors / Finite element method

References

[1] BV (1996) Fatigue strength of welded ship structures, Bureau Veritas

[2] DnV (2010) Fatigue assessment of ship structures, Classification Notes No 30.7

[3] Domzalicki P, Skalski I, Guedes Soares C, Garbatov Y. Guedes Soares C, Das PK. Large scale corrosion tests. Analysis and Design of Marine Structures, 2009, Taylor & Francis Group: London, 193-198

[4] Fricke W, Petershagen H (1992, 1992) Detail design of welded ship structures based on hot-spot stresses. In: Caldwell JB, Ward G (eds) Proceedings of the Practical Design of Ships and Mobile Units. Elsevier Science Limited, pp 1087–1100

[5] Garbatov Y. Fatigue strength assessment of ship structures accounting for a coating life and corrosion degradation. Int J Struct Integr, 2016, 7: 305-322

[6] Garbatov Y, Rudan S, Guedes Soares C. Fatigue damage of structural joints accounting for nonlinear corrosion. J Ship Res, 2002, 46: 289-298

[7] Garbatov Y, Guedes Soares C, Parunov J. Fatigue strength experiments of corroded small scale steel specimens. Int J Fatigue, 2014, 59: 137-144

[8] Garbatov Y, Guedes Soares C, Parunov J, Kodvanj J. Tensile strength assessment of corroded small scale specimens. Corros Sci, 2014, 85: 296-303

[9] Guedes Soares C, Garbatov Y. Reliability of maintained ship hull girders subjected to corrosion and fatigue. Struct Saf, 1998, 20: 201-219

[10] Guedes Soares C, Garbatov Y. Reliability of corrosion protected and maintained ship hulls subjected to corrosion and fatigue. J Ship Res, 1999, 43: 65-78

[11] Guedes Soares C, Moan T. Model uncertainty in the long-term distribution of wave-induced bending moment for fatigue design of ship structure. Mar Struct, 1991, 4: 295-315

[12] Guedes Soares C, Garbatov Y, von Selle H. Fatigue damage assessment of ship structural components based on the long-term distribution of local stresses. Int Shipbuild Prog, 2003, 50: 35-56

[13] Haagensen PJ, Maddox SJ. IIW Recommendations on methods for improving the fatigue strength of welded joints: doc. IIW-2142-110, 2013, Paris: International Institute of Welding, Woodhead Publishing

[14] Hobbacher A. Recommendations for fatigue design of welded joints and components, IIW doc.1823-07, Welding Research Council Bulletin 520, 2009, New York: International Institute of Welding

[15] Jiang X, Guedes Soares C. A closed form formula to predict the ultimate capacity of pitted mild steel plate under biaxial compression. Thin-Walled Struct, 2012, 59: 27-34

[16] Moan T, Ayala-Uraga E. Reliability-based assessment of deteriorating ship structures operating in multiple sea loading climates. Reliab Eng Syst Saf, 2008, 93: 433-446

[17] 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 Mar Sci Technol, 2006, 11: 52-64

[18] Niemi E (1992) Determination of stresses for fatigue analysis of welded components. Proceedings of the IIW, Conference on Design in Welded Construction. 57–74

[19] Niemi E (1995) Recommendation concerning stress determination for fatigue analysis of weld components. Abington Publishing

[20] Niemi E, Fricke W, Maddox S (2004) Structural stress approach to fatigue analysis of welded components - designer’s guide. IIW Doc. XIII-1819-00/XV-1090-01

[21] Paik JK, Lee JM, Ko MJ. Ultimate compressive strength of plate element with pit corrosion wastage. J Eng Maritime Environ, 2003, 217: 185-200

[22] Paris P, Erdogan F. A critical analysis of crack propagation laws. J Basic Eng, 1963, 85: 528-534

[23] Parunov J, Ćorak M, Gilja I. Calculated and prescribed stress concentration factors of ship side longitudinal connections. Eng Struct, 2013, 52: 629-641

[24] Petershagen H, Fricke W, Massel T (1991) Application of the local approach to the fatigue strength assessment of welded structures in ships. Int Inst Weld

[25] Radaj D. Design and analysis of fatigue-resistant welded structures, 1990, Cambridge: Abington Publishing

[26] Radaj D, Sonsino CM, Fricke W. Recent developments in local concepts of fatigue assessment of welded joints. Int J Fatigue, 2009, 31: 2-11

[27] Saad-Eldeen S, Garbatov Y, Guedes Soares C. Corrosion-dependent ultimate strength assessment of aged box girders based on experimental results. J Ship Res, 2011, 55: 289-300

[28] Saad-Eldeen S, Garbatov Y, Guedes Soares C. Effect of corrosion severity on the ultimate strength of a steel box girder. Eng Struct, 2013, 49: 560-571

[29] Saad-Eldeen S, Garbatov Y, Guedes Soares C. Effect of corrosion degradation on ultimate strength of steel box girders. Corros Eng Sci Technol, 2013, 47: 272-283

[30] Silva JE, Garbatov Y, Guedes Soares C. Ultimate strength assessment of rectangular steel plates subjected to a random localised corrosion degradation. Eng Struct, 2013, 52: 295-305

[31] Tran Nguyen K, Garbatov Y, Guedes Soares C. Fatigue damage assessment of corroded oil tanker details based on global and local stress approaches. Int J Fatigue, 2012, 43: 197-206

[32] Tran Nguyen K, Garbatov Y, Guedes Soares C. Spectral fatigue damage assessment of tanker deck structural detail subjected to time-dependent corrosion. Int J Fatigue, 2013, 48: 147-155

[33] TSCF Condition evaluation and maintenance of tanker structures, tanker structure co-operative forum, 1992, London: Witherby & Co

[34] TSCF (1997) Guidance Manual for Tanker Structures, Tanker Structure Cooperative Forum

[35] Wang G, Spencer J, Elsayed T (2003) Estimation of corrosion rates of structural members in oil tankers. Proceeding of 22nd International Conference on Offshore Mechanics and Arctic Engineering, Paper OMAE2003–37361. ASME

[36] Yamamoto N, Ikagaki K. A study on the degradation of coating and corrosion on ship’s hull based on the probabilistic approach. J Offshore Mech Arctic Eng, 1998, 120: 121-128