Correlation Of Fractographic Examinations With Numerical Calculations Regarding Dynamic Fracture

In practice, cleavage fracture assessment for ferritic reactor pressure vessel steels is standardized by the quasi-static Master Curve concept (ASTM E 1921) on a macroscopic level. This standard is technically valid for dynamic loading conditions, yet recent work has shown that experimentally determined fracture toughness values under rapid loading lead to discrepancies regarding the shape of the Master Curve. It is assumed that one reason for these discrepancies is the profound adiabatic heating. The investigation of this, as well as related phenomena, is subject of this work.Regarding this work, these experimental discrepancies are specified by a wide range of experiments. Moreover, fractographic investigations were performed on this experimental database to determine the exact origin of cleavage fracture, and compared to data from quasi-static experiments. In a second step numerical simulations were conducted for various crack-tip loading rates and testing temperatures, whereupon the temperature development in the cleavage fracture relevant region was quantified. This also allowed a determination of the individual initiation temperatures, which were analyzed and discussed whilst also taking into account the increase in local strain rate at the origin of cleavage fracture.Finally, fractographic examinations also revealed the relevance of local crack arrest (crack stop) which was quantified, and also linked to the mentioned experimental discrepancies regarding the Master Curve concept.