Stretch then add material

[Techsan123]

Hello,

I have a hollow cylinder that I would like to first stretch and then add material (like corrosion built up in a stretched pipe). My question is how do i add the material after stretching. This will be done in Abaqus 6.8 CAE

Thanks!

 

[rstupplebeen]

Does the corrosion cause the stretching? If so I would add a corrosion volume and thermally expand it to stretch the pipe. I hope this helps.

Rob Stupplebeen

 

[Techsan123]

No it is actually more like plaque building up in a stretched artery. Thanks

 

[rstupplebeen]

Could you explain your problem further including what the end goals of the model are? Pictures are also helpful.

Rob Stupplebeen

 

[Techsan123]

of course...Here is what I have been doing (see attached file):

Model a hollow hyperelastic cylinder to represent an artery with some type of material on the inside wall. This represents a stenosis (narrowing of the inner diameter, see attached file). Arteries are in a stretched state in the body, typically 1.3-1.6 stretch ratio. Once stretched we are then applying internal pressure and observing the effects. This is a simple setup but I would like to try to add the material after stretching becasue in the body the arteries are normally stretched and then plaque builds up over time. I'm not looking for material to be built up over time I am looking for the effect of pressure with an already fixed amount of material along the inside wall.

 

[rstupplebeen]

I will try to explain what you have in your model and then offer suggestions after your confirmation of my understanding. The artery is nominally a straight tube. You have a bulge on the center of the inside representing plaque. You then apply a pressure load on the entire inside of the part. The tube then expands outwards. Because of the bulge it introduces a non-symmetric loading and deflects the tube.

My assumption is that ideally you want the artery to remain relatively cylindrical and apply the plaque to this shape. Is that correct?

I hope to help in the next step.

Rob Stupplebeen

 

[Techsan123]

Right now the tube is stretched (as a BC) before applying the pressure (plaque and all since they are drawn as one in solidworks). I want to be able to stretch the cylinder, then apply the plaque, and the lastly add the internal pressure.

 

[rstupplebeen]

Do you want the tube plastically stretched to that diameter? If so why not just model a larger pipe in SolidWorks? Why do you have both drawn as 1 part? I assume the material properties should be different in the FEA. I hope this helps.

Rob Stupplebeen

 

[Techsan123]

I want to stretch because the artery is typically at a stretch ratio of 1.5 in the body. Thus by stretching it they are more stable under internal pressure. Yes the plaque is given different material constants than the cylinder. So to summarize the cylinder should be stretched to mimic an artery in the body and then the plaque should be added but maybe this can't be done in Abaqus.

 

[MechIrl]

Thought you were trying to model the plaque growing for a minute, which would be interesting as its something I'm looking into at the moment. Maybe you could run the loading analysis and use the final stress state as a user field in a new analysis with the plaque.

There is also the Model Change option (or something similar, haven't used it before) which allows you to modify the model between steps, this would allow you to add the plaque after the initial loading step.

 

[rstupplebeen]

I do believe that this is possible with many methods in Abaqus. I was trying to understand what you were doing and why.

I would try modeling this as 2 parts. Inflate the Artery. Then, apply pressure to the plaque and have contact without separation enabled to stick the plaque onto the artery.

I hope this helps.

Rob Stupplebeen

 

[Techsan123]

Thank you both...I will try out your suggestions