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Pipeline Indentation and Collapse

Pipeline Indentation and Collapse

Pipeline Indentation and Collapse

(OP)
Hi,

I am modelling the indenatation and collapse of a subsea pipeline. The hemispherical indenter is modelled as an analytical rigid surface. The pipeline is modelled resting on a perfectly flat seabed which is also analytical rigid.

The displacement of the indenter is moved downwards until it reaches 1/3 of the pipeline diameter before being incrementally retracted in a seperate step. Both these steps work well with no significant warning messages being shown.

The problems arise when i try to initiate collapse of the pipeline by applying an external pressure to the deformed geometry. I am using STATIC, RIKS for this step. As the pressure is applied the pipeline begins to collapse, forming the figure of 8 shape I would expect to see. However, the pipline never reaches the fully collapsed mode, and the collapse process reverses before the pipeline begins to expand across its cross-section. Not what I am expecting!

Can anyone help me out with this step?

My aim is to understand how the collpase pressure changes with varying dent depth.

Many Thanks



   

RE: Pipeline Indentation and Collapse

Have you tried changing the monitoring degree of freedom in your external pressure step? That is, don't use the same dof as you did in indentation.

RE: Pipeline Indentation and Collapse

(OP)
Thanks for yoyur reply mrgoldthorpe.

I managed to obtain a solution using a *Dynamic, Implicit step. This shows the pipeline in the collapsed mode I was expecting to see. Now I'm trying to understand why this works as opposed to the *Static, Riks method I was trying to use before.

 

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