Two numerical crack propagation models, namely the cohesive model and the CTOA model, are compared regarding their ability to predict the crack propagation behaviour of fracture specimens made of thin walled Aluminium sheets, which can be simulated using plane stress assumption. The experimental database is presented and it is shown, how the various quantities are measured by different techniques (optically and with various clip gauges). It is explained how the respective parameters for the numerical models are determined by use of a selected set of fracture specimens. Other types of specimens are then used to validate the simulations with these parameters. In order to investigate the behaviour of the models under different constraint conditions and the transferability of their parameters, C(T) specimens are used for parameter evaluation and M(T) specimens for validation. It is shown that for all types of specimens, a single set of parameters can be used for both models.

KurzfassungIn dem von der EU geförderten Projekt BIMET wurde eine geschweißte Rohrverbindung aus ungleichen Grundwerkstoffen und mit einem Oberflächendefekt auf das Verformungs- und Versagensverhalten untersucht. Dazu wurden bruchmechanische Vorhersagemethoden anhand von Bauteiltests validiert. Es werden die bei GKSS durchgeführten Analysen basierend auf analytischen und numerischen Methoden dargestellt.

A "correct" limit or yield load is an essential element of flaw assessment procedures of the R6 or SINTAP type. In the present paper the authors propose a definition of this quantity which is based on the SINTAP Option 3 failure assessment function. This "reference load" can be determined for any component geometry by finite element analyses. The method is applied to two kinds of thin walled structures (notched plates and curved stiffened panels) this way extending the existing thin wall module of SINTAP.

The residual strength of a curved and stiffened panel containing a two-bay crack was assessed using the cohesive model. This panel represents a section of a wide-body aeroplane fuselage. The tests were conducted at IMA GmbH Dresden in cooperation with Airbus Industries Germany. The structural panel was modelled using 3D finite elements and a layer of cohesive elements ahead of each crack tip allowing for 70 mm crack extension. Identification of the cohesive parameters was done on small laboratory test pieces. Special effort was made for the transfer of these parameters to the structure.Reasonably conservative predictions of the residual strength of the panel were achieved.The boundary conditions of the loading devices of the test rig are shown to have substantial influence on the predictions.