Fill a gap between two surfaces, using pressure as variable 1

[SM1994]

Hello
According to the attached picture, I have two surfaces (Master surface and slave surface) where there is a gap between them. The slave surface can be inflated with the pressure "P".
I aim to find an appropriate "P" magnitude to fill the gap and only TOUCH the master surface without applying considerable stress.
My question is:
Is there any way Abaqus can use "P" as a variable and iteratively (or any other technique) change it until the Gap becomes zero or very close to zero?
To clarify, I am looking for a way to give the Gap as input, and Abaqus find corresponding "P" to fill the Gap?

Thank you

 

[FEA way]

Abaqus solves nonlinear problems incrementally anyway. You can use this fact to reach your goal. Define pressure that you think will be too high and monitor the progress of the analysis to find the moment when the gap closes. You can use contact output variables such as CPRESS or CSTATUS for that. There’s also a tool called DOF monitor that will let you observe the displacement in a given direction of a selected node. You could choose the node on top of that inflatable membrane and see when it moves by the distance necessary to cross the gap between both parts.

 

[SM1994]

Thank you for your response, I am not sure if I have understood you solution completely.
I use quasi-static in dynamic implicit with 60 sec time. Let say that I use P=500 kPa which I am sure it is way more than enough and ABAQUS solve it in 120 increment (0.5 time step, and no backward increment).
Let`s assume that touch occurred at the increment 40 (equal to time 20), in this case the pressure at the contact is: P= (500*40)/120 = 167 kPa
is it what you mean?
Thank you

 

[FEA way]

That's what I meant but Abaqus offers a variety of history and field outputs that should save you some time and effort. For example, there's an output variable for applied pressure (so that you will know its magnitude for each increment). If you combine these outputs, it will be even easier. What's more, Python scripting would let you automate this. However, if you don't want to do it many times for different models then scripting likely won't be necessary.

 

[SM1994]

Perfect, thank you for your response.

 

[Mustaine3]

Thank you for your response, I am not sure if I have understood you solution completely.
I use quasi-static in dynamic implicit with 60 sec time. Let say that I use P=500 kPa which I am sure it is way more than enough and ABAQUS solve it in 120 increment (0.5 time step, and no backward increment).
Let`s assume that touch occurred at the increment 40 (equal to time 20), in this case the pressure at the contact is: P= (500*40)/120 = 167 kPa
is it what you mean?
Thank you

Weird approach. In a nonlinear analysis you typically cannot predict precisely how many increments are needed.

It's quite simple in my opinion:
Apply the pressure linear over time, request P as field output, run the analysis and then look at the result frame that shows the first contact of the two faces. P shows the pressure at that moment.
Or, if you have small increment sizes but no field output every increment to keep the size of the result file down, you can request additional history output for every increment. Use CFN for example. Plot the curve and as soon as CFN is not zero anymore you have contact. With the time of that moment you know the pressure value.

 

[SM1994]

Thank you Mustaine3 for your response.

 

[IceBreakerSours]

I do not know the physics involved here but I am wondering why simply moving the master surface closer to the slave surface prior to running the analysis won't work.

*********************************************************
Are you new to this forum? If so, please read these FAQs:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083