Linking advanced fracture models to structural analysis
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In this study a link between local material models and structural analysis is outlined. An ”ad hoc” element formulation is used in order to connect complex material models to the finite element framework used for structural analysis. An improved elasto-plastic line spring finite element formulation, used in order to take cracks into account, is linked to shell elements which are further linked to beam elements. In this way one obtain a global model of the shell structure that also accounts for local flexibilities and fractures due to defects. An important advantage with such an approach is a direct fracture mechanics assessment e.g. via computed J - integral or CTOD. A recent development in this approach is the notion of two-parameter fracture assessment. This means that the crack tip stress tri-axiality (constraint) is employed in determining the corresponding fracture toughness, giving a much more realistic capacity of cracked structures. The present thesis is organized in six research articles and an introductory chapter that reviews important background literature related to this work.
Består avChiesa, Matteo; Skallerud, Bjørn; Thaulow, Christian. Line spring elements in a yield strength mismatch situation with application to welded wide plates. Engineering Fracture Mechanics. 68(8): 987-1001, 2001.
Chiesa, Matteo; Nyhus, Bård; Skallerud, Bjørn; Thaulow, Christian. Efficient fracture assessment of pipelines. A constraint-corrected SENT specimen approach. Engineering Fracture Mechanics. 68(5): 527-547, 2001.
Chiesa, Matteo; Skallerud, Bjørn; Gross, Dietmar. Closed form line spring yield surfaces for deep and shallow cracks: formulation and numerical performance. Computers & Structures. 80(7-8): 533-545, 2002.
Chiesa, Matteo; Skallerud, Bjørn. Efficient numerical procedures for fracture assessments of surface cracked shells. European Conference on Computational Mechanics, 2001.
Chiesa, Matteo; Østby, Erling; Skallerud, Bjørn; Thaulow, Christian. An engineering methodology taking into account the effect of local damage on the global behavior of surface cracked shell structures. National Conference on Computational Mechanics, 2001.
Skallerud, Bjørn; Chiesa, Matteo. Iintegrated local/global analysis and fracture assessment og pipelines with defects. 2001 ASME Offshore Mechanics and and Arctic Engineering, 2001.