Mechanical properties of buckled pipe materials

在役管道的机械屈曲是一个重要的技术问题。由于地震事件，由于永久冻土融化或甚至重型设备在埋地管道上的移动，管道在施工后可能会经历复杂的加载路径。因此，有必要建立模型来预测管道在使用中的材料行为，例如屈服应力和初始加工硬化行为。在这里，有几个重要的相关冶金现象。首先，定性地知道，当载荷的方向改变时，这会影响屈服应力（经典地称为鲍辛格效应）。在这种情况下，相关的情况将是在形成管道期间的变形方向可以正交于管道在使用中经历的弯曲应变。其次，还已知在塑性变形和在环境温度下的静止期之后，由于碳原子向晶体位错的偏析，可以产生“屈服点”。然而，人们缺乏对基本机制的了解，预测这种行为的能力仅限于定性值。

The in-service mechanical buckling of pipelines is an important technological problem. The pipeline can experience complex loading paths after construction due to seismic events, soil shifting due to melting of permafrost or even the movement of heavy equipment over the buried pipeline. Thus, it is necessary to have models to predict the material behaviour of the pipe in service, such as the yield stress and the initial working hardening behaviour. Here, there are several important metallurgical phenomena which are relevant. First, it is qualitatively known that when the direction of the loading changes, this can affect the yield stress (classically known as the Bauschinger effect). In this case, the relevant scenario would be that the direction of deformation during forming the pipe can be orthogonal to bending strains that the pipe experiences in-service. Second, it is also known that the after plastic deformation and a static period at ambient temperatures, a "yield point" can be produced due to segregation of carbon atoms to crystal dislocations. However, there is a lack of knowledge on the basic mechanisms and the ability to predict this behaviour is limited to qualitative values.