Memorial University DAI: Fatigue life prediction of offshore tubular T-joints using fracture mechanics approach

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Title	Fatigue life prediction of offshore tubular T-joints using fracture mechanics approach
Author	Bhuyan, Gouri Shankar.
Description	Thesis (Ph.D.) -- Memorial University of Newfoundland, 1986. Engineering and Applied Science
Date	1986
Pagination	xxii, 219 leaves : ill.
Subject	Tubular steel structures; Offshore structures--Dynamics; Welded joints--Fatigue;
Degree	Ph.D.
Degree Grantor	Memorial University of Newfoundland. Faculty of Engineering and Applied Science
Discipline	Engineering and Applied Science
Language	Eng
Notes	Bibliography: leaves [209]-219.
Abstract	The thesis presents the results of an analytical and experimental investigation of the fatigue behaviour of tubular T-joints, using a linear fracture mechanics approach. The analytical study includes the development of a finite element computer program to analyse tubular joints with/without weld toe cracks. The experimental investigation consists of quantifying the effects of sea water, temperature, frequency, load ratio and wave form on fatigue crack-growth-rates in CSA G40.21 M 350 WT steel, which has been'proposed for the Canadian Offshore. -- The actual curved surface and the brace/chord intersection are approximated by the assemblage of flat quadrilateral and triangular plate elements for two dimensional analysis. The analysis uses a plane stress element to account for membrane stiffness and a plate bending element to account for flexural stiffness. For three dimensional analyses, chord/brace/weld regions are modelled using incompatible brick and prism elements. In order to reduce the computer storage requirements as well as the solution costs, the region of high stress gradient is analysed using the rezone technique. Hot spot stress and stress concentration factors obtained from these analyses are compared with the experimental values available in the literature. -- To study the effect of a shallow weld toe crack on through-thickness and surface.stress redistribution, the region at the vicinity of the crack is modelled using special elements which produce singular stress fields at the crack front. The crack-tip stress intensity factors are determined by comparing the crack-tip stresses, obtained from the analyses, with the available theoretical solutions. -- Fatigue crack-growth-rate data and material coefficients, C and m, for various temperature, load ratio and frequency ranges are obtained from compact tension specimen tests in air as well as in sea water. Knowing the crack-growth behaviour in the base metal, the through-thickness-cracking lives of tubular T-joints are predicted analytically using the modified Paris* equation and the estimated lives are compared with reported experimental results. The accuracy of the computer program and the validity of the proposed method for predicting fatigue life of tubular joints are checked by testing a prototype tubular T-joint.
Type	Text
Resource Type	Electronic thesis or dissertation
Format	Image/jpeg; Application/pdf
Source	Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries
Local Identifier	75380713
Rights	The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.
Collection	Electronic Theses and Dissertations
Scanning Status	Completed
PDF File	(23.77 MB) -- http://collections.mun.ca/PDFs/theses/Bhuyan_GouriShankar.pdf
CONTENTdm file name	26497.cpd