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Enhancement of local approach models for the assessment of cleavage fracture based on micromechanical investigations

: Hardenacke, V.; Hohe, J.; Friedmann, V.; Siegele, D.

Bundesanstalt für Materialforschung und -prüfung -BAM-, Berlin; American Society for Testing and Materials -ASTM-, Philadelphia/Pa.; Deutscher Verband für Materialforschung und -prüfung e.V. -DVM-, Berlin; European Structural Integrity Society -ESIS-:
ECF 2010, 18th European Conference on Fracture. CD-ROM : Fracture of Materials and Fractures from Micro to Macro Scale, 30.08.-03.09.2010, Dresden
Dresden, 2010
European Conference on Fracture (ECF) <18, 2010, Dresden>
Conference Paper
Fraunhofer IWM ()

The objective of the present study is the development of a micromechanically based prob-Abilistic model for the assessment of the cleavage fracture probability of ferritic steels. The brittle fracture of metals is triggered by the failure of randomly distributed brittle particles. The failure of the particles resulting in the nucleation of micro-cracks is governed by the plastic deformation of the surrounding ferritic matrix, whereas the local stress state controls the pos-sible instability of the defects. As a third parameter, the local stress triaxiality is assumed to govern the blunting and thus the criticality of freshly nucleated micro defects. The probabilis-Tic cleavage models available in literature account for this parameters only in a simplified manner. By a micromechanical modelling of the cleavage initiation process the effects and the interactions of the relevant parameters can be identified more precisely. For this purpose Representative Volume Elements (R VEof the microstructure are generated, accounting for both, the grain structure as well as the brittle particles. This RVE's are loaded based on the local mechanical field quantities at the cleavage origin determined numerically for a variety of specimens. Thereby, the behaviour of the brittle particles against the resulting microme-chanical conditions can be specified. Based on the results, an enhanced probabilistic cleav-Age model is proposed. The model proves to be accurate and provides transferrable results for a wide range of specimen types.