Offshore steel platforms are designed to rsist loads elastically, whereas abnormal loads should lead to only local demage. The present investigation has concentrated on the feasibility of employing shell and line spring finite elements in the analysis of the ductile fracture initiation capacity of cracked tubular joints. Ease of analysis without any numerical problems was experienced throughout this work, i.e. the approach is user-friendly. Comparisons with model tests and computer simulations based on alternative methods (solid FE and virtual crack extension) were presented. In all comparisons of global load versus displacement behaviour, the agreement was good, with reasonable prediction of behaviour up to estimated crack initiation levels. The estimated critical values of J for the model tests compared reasonably well with the load-displacement behaviour in the tests. The comparison between J values computed from line springs and the virtual crack extension technique did not reveal any major differences, except the lack of variation of J along the crack front for the line spring based approach. Some characteristics of tubular joint behaviour and their implications on J integral computations were adressed. In ultimate load analyses of tubular joints, hot spots often are subjected to finite rotations. This will affect both the accuracy of the element formulation, and J integral calculations. The detrimental effect of mixed-mode loading on ductile crack growth initiation was discussed, as tubular joints invariably will exhibit some mode II and mode III in addition to mode I. The issue of ductile tearing should also be resolved if the full load-displacement is to be predicted realistically.
Inelastic line springs in non-linear analysis of cracked tubular joints
Inelastische Federelemente in der nichtlinearen Analyse rißbehafteter Rohrverbindungen
Fatigue and Fracture of Engineering Materials and Structures ; 18 , 4 ; 463-475
1995
13 Seiten, 10 Bilder, 29 Quellen
Aufsatz (Zeitschrift)
Englisch
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