Influence of toughness on the crack arrest behavior in modern line pipe steels

  Simulation and fracture surface of a BDWTT sample Copyright: IEHK Pic 2: Simulation and fracture surface of a BDWTT sample [Novokshanov et al. - 2015 - A new model for upper shelf impact toughness assessment with a computationally efficient parameter identific]

The resistance to long-running cracks, ensuring crack arrest is one of the most important safety requirements for gas-conducting pipelines. In order to meet these requirements, line pipe steels with excellent toughness properties have been developed by the European steel industry. However, the potential of these modern and very tough materials cannot be exploited yet. due to phenomena which did not occur in steels of moderate toughness. These are separations and inverse fracture behavior. Especially the latter may be observed during the Battelle drop-weight-tear test (BDWTT) which also is consequently the focus of the investigations. Due to the unusual behavior of the very tough materials and the lack of experience in handling these steel grades, there is a great deal of uncertainty among design engineers. Since this situation is faced by conservative design , it is currently not possible to exploit the lightweight potential of very tough steels. The aim of this research project is to overcome this treatment of modern high-tensile pipeline steels. For this purpose, it is to be shown that both, the inverse breaking behavior and the breaking surface tears, can be represented by damage mechanics modeling approaches. In addition, it is examined how relevant these phenomena are for the application in pressurized pipelines. Furthermore, based on component simulations, it is examined to what extent inverse fracture behavior and separations have an effect on the crack resistance.

This project is being carried out in collaboration with Prof. Nonn from OTH Regensburg.