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  Title Running-ductile-fracture control – a novel analytical approach involving the J-integral as a toughness measure
  Author(s) Dr Alexander Völling, Christoph Kalwa, and Dr Marion Erdelen-Peppler  
  Abstract In recent years, several full-scale burst (FSB) tests have been performed in order to confirm the ability of a chosen pipeline design to achieve arrest of a running-ductile fracture (RDF). These tests have been particularly aimed at verifying the related main relevant resistance measure, i.e. material toughness. Over a longer period, designers could rely on the well- established analytical approach originating from the early 1970s, the Battelle two-curve (BTC) method. This method is part of several design codes, such as ISO 3183 and DNV OS-F101. The BTC method enables evaluation of a toughness requirement for material resistance to RDF in terms of Charpy V-notch (CVN) impact energy. But over the last two decades experience has shown that, within pipeline designs involving modern materials, the reliability of the BTC method can reach its limits. A demand for increasing operating pressures requiring higher steel grades, as well as more- challenging operating conditions –¬ for example for rich gas or CO2 transportation ¬– have led to uncertainties regarding its applicability.

As the outcome of full-scale burst testing more frequently failed to match with the preceding BTC predictions of arresting a RDF, up to now several attempts have been undertaken to overcome this shortcoming. The majority of these attempts are aiming at introducing a correction factor matching the predicted CVN energy to the corresponding results from full-scale burst testing. Originally, this way forward was driven by the belief of being able to adjust the BTC method, extending its applicability to modern pipeline design. But up to now, a generally valid and reliable solution has not been found, which has put the value of CVN energy as main involved toughness measure into question. As the whole BTC method is based on CVN energy, this is of major concern to designers and operators of gas pipelines worldwide.

 
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