Issue34

C. Fischer et alii, Frattura ed Integrità Strutturale, 34 (2015) 99-108; DOI: 10.3221/IGF-ESIS.34.10 108 - The crack propagation rate at complex structures is slowed down by: the stress gradient over the plate thickness, the apparent plate thickness, the notch effect and the bending constraint of the detail; - The stress gradient along the weld line does not affect the life but the aspect ratio of the semi-elliptical crack shape; - The notch effect depends on the load-carrying grade of weld, the flank angle and of the layout of the transverse attachment and it affects the local stress concentration, leading to longer life. The obtained influences should be investigated for further configurations, varying in particular the thickness of the axially loaded plate as well as of the attachments. This would lead to different local support of the critical weld toe, especially if the thicknesses are different. R EFERENCES [1] BS 7910:2005, Guide to methods for assessing the acceptability of flaws in metallic structures, British Standards Institution, London. [2] Dijkstra, O, Janssen, G., Ludolphy, J., Fatigue tests on large scale knuckle specimens, in: W.-C. Cui, Y.-S. Wu, G.-J. Zhou (Eds.), Proc. 8th Int. Symp. on Practical Design of Ships and Other Floating Structures (PRADS), Elsevier, Amsterdam, (2001) 1145–1151. [3] Dong, P., A structural stress definition and numerical implementation for fatigue analysis of welded joints. Int. J. Fatigue, 23 (2001), 865–876. [4] Fischer, C., Fricke, W., Realistic fatigue life prediction of weld toe and weld root failure in load-carrying cruciform joints by crack propagation analysis., in: C. Guedes Soares, J. Romanoff (Eds.), Analysis and Design of Marine Structures – Proc. 4th Int. Conf. on Marine Structures (MARSTRUCT), Taylor & Francis, London, (2013) 241–248. [5] Fischer, C., Fricke, W., Consideration of stress gradient effects for complex structures in local fatigue approaches, in: C. Guedes Soares, R.A. Shenoi (Eds.), Analysis and Design of Marine Structures - Proc. 5th Int. Conf. on Marine Structures (MARSTRUCT), Taylor & Francis, London, (2015). [6] Fischer, C., Fricke, W., Rizzo, C.M., N-SIF based fatigue approaches of hopper knuckle details, in: E. Rizzuto, C. Guedes Soares (Eds.), Sustainable Maritime Transportation and Exploitation of Sea Resources, Taylor & Francis, London, (2011). [7] Fricke, W., Recommended hot-spot analysis procedure for structural details of FPSO's and ships based on round- robin FE analysis, in: J.S. Chung (Ed.), Proc. 11th Int. Offshore and Polar Engng. Conf. (ISOPE), International Society of Offshore and Polar Engineers, Cupertino, CA, (2001) 89–96. [8] Fricke, W., IIW recommendations for the fatigue assessment of welded structures by notch stress analysis, Woodhead Publishing Limited, Cambridge (2013). [9] Hobbacher, A., Stress intensity factors of welded joints, Engng. Fract. Mech., 46 (1993) 173–182. [10] Hobbacher, A., Recommendations for fatigue design of welded joints and components, Welding Research Council, New York, NY, (2009). [11] Iida, K., Matoba, M., Fatigue strength of hold frame ends in ship hulls. International Institute of Welding, IIW-Doc. XIII-950-80, (1980). [12] Kang, J, Kim, Y., Heo, J., Fatigue strength of bent type hopper corner detail in double hull structure, in: M.M. Salama, P.K. Gorf, C.F. Mastrangelo, S. Balint (Eds.), Proc. OMAE Specialty Symp. on Integrity of Floating Production, Storage & Offloading (FSPO) Systems, ASME, Houston, TX, (2004). [13] Kim, W., Lotsberg, I., Fatigue test data for welded connections in ship-shaped structures, J. Offshore Mech. and Artic Eng., 127 (2005) 359–365. [14] Lotsberg, I., Sigurdsson, G., Hot spot stress S-N curve for fatigue analysis of plated structures, J. Offshore Mech. and Artic Eng. 128 (2006) 330–336. [15] Osawa, N., Fatigue assessment of bilge knuckle joint of VLCC according to JTP / JBP rules, in: Y. Sumi (Ed.), Comparative studies on the evaluations of buckling/ultimate strength and fatigue strength based on IACS JTP and JBP rules, (2005) 3.1–3.5 [16] Paris, P.C., Erdogan, F., A critical analysis of crack propagation laws, J. Fluid Engng. 85, (1963) S. 528–533. [17] Peterson, R.E., Stress concentration factors, J. Wiley & Sons, New York, NY, (1974). [18] Tada, H, Paris, P.C., Irwin, G.R., The stress analysis of cracks handbook, Del Research Corporation, St. Louis, MO, (1985).