MST Dymalab

Dynamic fracture behaviour of pipeline steel

The occurrence of a longitudinal crack propagating along a high pressure gas pipeline is a catastrophic event, which involves both economic losses and environmental damage. Hence, the fracture propagation control is essential to ensure pipeline integrity. Modern fracture control strategies for high pressure pipelines rely on numerical simulations of ductile crack propagations and arrest. The numerical material models are informed by toughness tests such as Charpy V-notch (CVN) experiments and Battelle Drop Weight Tear Tests (BDWTT).

The constitutive behaviour of the sound pipeline steel is often modelled as merely an elastoplastic law, measured under quasi-static conditions. However, both Charpy experiments and Battelle tests are dynamic events, which require knowledge of the strain rate sensitivity of the pipeline material. In addition, very high strain rates can occur in the vicinity of a running crack in a high pressure gas pipeline. Hence, the constitutive material model for the pipeline steel has to account for strain rate sensitivity.

In recent years, DyMaLab has supported steel suppliers and pipe mills in the safe and reliable design of pipelines by

  • Performing Hopkinson tests on high strength X70 pipeline steels subjected to high strain rates (up to 1000 s-1) and low temperatures (down to -70oC)
  • Evaluating the influence of stress triaxiality on the dynamic fracture behaviour of pipeline steels using notched Hopkinson samples
  • Implementing enhanced material models to capture the dynamic response of modern pipeline steels during Charpy and Battelle tests
  • Assessing the effect of strain rate sensitivity on the behaviour of subsea pipelines subjected to underwater explosions

Key publications