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VOCALIST Résumé de rapport

Project ID: FIKS-CT-2000-00090
Financé au titre de: FP5-EAECTP C
Pays: Germany

Calibration procedure for engineering Weibull models of cleavage fracture

The applied micro-mechanistic models of cleavage and ductile fracture require a calibration of the micro-structural parameters using the results of the small-scale specimens.

The Beremin model represents the basis for the local approach models in the brittle to ductile regime together with a modified Weibull stress model, whereas in the ductile regime the Rousselier model is applied to describe the ductile crack initiation and growth.

In the Weibull stress model the parameters are determined by a calibration procedure using the fracture toughness values of high and low constraint specimens, in the case of VOCALIST the results of SE(B) pre-cracked Charpy V size specimens. By an iterative process where all results are mapped back to the SSY space the necessary parameters are obtained. In the ductile regime the Rousselier model is calibrated by using notched round bars and CT specimens.

Several methods have been applied to achieve the necessary parameters. Although the parameters of each obtained set varied significantly, the final results in the predictive analyses were comparable. It turned out that the stability of the numerical analysis is a good indicator for the appropriate calibration parameters. Convergence problems occurred during the crack growth analysis, depending on the parameter set.

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Elisabeth KEIM, (Research Manager)
Tél.: +49-91311897146
Fax: +49-91311897398