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## #1 2019-06-03 19:36:45

austin_downey
Member
Registered: 2019-06-02
Posts: 2

### High-level questions, linear transient analysis with moving BC

Greetings,

I have a high-level question about using code_aster and salome_meca for a linear transient analysis of a beam with a moving boundary condition (displacement =0). I have attached a picture of what I am trying to do. My questions are:

1) Is this something code_aster can do?
2) Will this require a lot of scripting (e.g., remeshing at each step and solving 1 time step at a time)
3) Is there a better tool to use for this type of problem
4) Would somebody be kind enough to give a quick (3-5 step) general instruction for trying to solve this problem?

I am new to code_aster but I do have a fair amount of experience in Abaqus and hard coding of simple FEA problems. However, my 1-D 300 element FEA for this beam is unable to capture all the complexities of the system and falls apart if I add more than 300 elements due to numerical issues.

All the best,
Austin.

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## #2 2019-06-04 08:00:22

jeanpierreaubry
Guru
From: nantes (france)
Registered: 2009-03-12
Posts: 3,625

### Re: High-level questions, linear transient analysis with moving BC

hello

with a moving load and fixed boundary condition it is quite easy (there is a similar example in my book)

with a moving fixed displacement it is not so straight forward
but i guess a few chained solver (DYNA_NON_LINE for example) could do the job
without any remeshing

what do you mean by "falls apart"?

jean pierre aubry

consider reading my book
freely available here https://framabook.org/beginning-with-code_aster/

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## #3 2019-06-04 09:18:16

nirmaljoshi
Member
From: Japan
Registered: 2018-10-12
Posts: 161

### Re: High-level questions, linear transient analysis with moving BC

If this is static analysis, you can write python code that loops to change the code_aster commands with change in boundary node in each step.

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## #4 2019-06-07 16:45:34

austin_downey
Member
Registered: 2019-06-02
Posts: 2

### Re: High-level questions, linear transient analysis with moving BC

All,

Thanks for the feedback. I also think this would have to have some sort of chained analysis where the state of the beam (displacement, acceleration) is fed forward to the next time step with a new boundary condition. This is repeated with changing BCs until I get to the end of my simulation. I need to do this in a dynamic solver because the mass in an important consideration for me. I will have to look into how I can do this.

By falls apart, I wrote my own python FEA code and to solve for the displacement in state space my A matrix ends up with numbers that are too big (1e209) that tend to break the code. This is why I am limited in how small the elements can be in my code.

Austin.

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