Multi-scale morphologically realistic models for pipeline steels

输送高压天然气或二氧化碳的管道可能破裂，向大气中释放对环境有害的气体。由于破裂传播速度与气体中声速之间的差异，发生了一种称为“快速断裂”的现象，这可能导致破裂传播数公里，直到遇到裂缝拦阻器。为了减轻这种情况，管道由钢制成，使用测试来评估，其中将重物落在钢的缺口样品上。然后对试样进行测量，以评估钢阻止快速断裂的能力。在这个项目中，我们建议开发一个设计框架，允许钢的微观结构工程，使钢的动态强度可以阻止破裂。结合显微镜和先进的有限元计算，我们开发了评估潜在微观结构的方法，以阻止破裂的能力。仪器纳米压痕与优化技术相结合，用于估计构成钢的各个相的力学性能。然后将后者用于大规模计算以预测钢的力学行为。提出的框架旨在减少目前用于钢材设计的试错方法所花费的时间和精力。

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.