Multi-scale morphologically realistic models for pipeline steels

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Pipelines that convey high-pressure natural gas or Carbon Dioxide may rupture and release environmentally harmful gasses into the atmosphere. Owing to the difference between the rupture propagation speed and the speed of sound in the gas, a phenomenon called "fast fracture" occurs and this can lead to the rupture propagating for several kilometers till it encounters a crack arrestor. To mitigate against this, pipelines are made from steels that are evaluated using a test wherein a heavy mass is dropped onto a notched specimen of the steel. Measurements on the specimen are then used to assess the capacity of the steel to arrest fast fractures. In this project, we proposed to develop a design framework that allows the engineering of the steels' microstructure so that the dynamic strength of the steel can arrest the rupture. Using a combination of microscopy and advanced finite element computations, we develop methods to assess potential microstructures for the capability to arrest the rupture. Instrumented nano-indentation in combination with optimization techniques is used to estimate the mechanical properties of the individual phases that constitute the steel. The latter are then used in large-scale computations to predict the mechanical behavior of the steel. The proposed framework is intended to reduce the time and effort currently expended in trial-and-error methods used for the design of steels.