# Cedric_w

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1. ## Problem: Plastic strain results do not match with the Von Mises stress results.

Hi Andy, Thank you for you're response and insight. So it could be that the plastic strain of 0,008 is realistic. When I calculate the stress with the JC formula, I get a true stress value of 435 MPa at a plastic strain of 0,008. Which could match the true stress strain plot. Could you tell me how the Plastic strain is calculated for post processing purposes? Thanks, Cedric
2. ## Problem: Plastic strain results do not match with the Von Mises stress results.

Hi all, I'm getting very low plastic strain results in my simulations. the Von mises stress (422 MPa) clearly passes the yield point (355 MPa), however plastic strain only reaches a value of 0,008. This Von mises value approaches the UTS value of 455 MPa, the strain at uts is defined as 0,09. Can someone please explain to me how i can solve this, or explain why this is happening? beste_contactparameters_0000.out beste_contactparameters_0000.rad beste_contactparameters_0001.out
3. ## Computation checks in Radioss

Could someone tell me the physical meaning of the Explicit calculation error check? I know the meaning of each term. Internal Energy and External work. But why is it important in an explicit calculation to make sure it stays below 5%?

I know this exists, however I need to be able to stop and resume. The HWU's need to be used by other people during the day otherwise I could just keep it running all day and night.

Can anyone tell me if it's possible to restart a radopt run? I'm dealing with an optimisation which takes a long time for each outerloop so I want to be able to start the run in the evening, end it in the morning and restart it the next evening. I know you can restart a previous radioss runs if the /RERUN card is used, however this will only restart the radioss run not the radopt run.

repost*

Disregard both responses, I found my own mistake.

Hi @Ivan Thanks for the quick response. I was already using this template, but didn't know they needed to be aligned to the right. I've noticed in the attached file that you use the /BULK/DATA/1 to use BULK Data Inputs from OptiStruct. Do you know if al these Bulk Data Sections are useable? I does not seem to be mentioned in the Radioss Optimization information. They do reference /BULK but don't really give any extra information. (I'm not really familiar with Optistruct but however I do have colleague's that can help).

Hi, Is there a standard amount of space there needs to be between the different parameters in a .radopt file. I'm adapting an existing .radopt file (with notepad++), and have tried finding a pattern in the amount of spaces between the parameters of the different cards. However, there doesn't seem to be one. Any help with this would be appreciated. Kind Regards Cedric
10. ## Problems with type 7 contact, quasi static load

This may be a stupid question, but could you explain to me how this makes the case more non linear? I'm guessing this is due to the friction force changing over time and thus making the behaviour more non-linear? Or am i totally wrong with my assumption?
11. ## Problems with type 7 contact, quasi static load

Hi @Pranav Hari, Thank you for helping me with this. This confirms what I thought might be the cause, I also ran it without friction and got the same resulst. However It seems unrealistic to run the simulation without contact friction.
12. ## Problems with type 7 contact, quasi static load

@Pranav Hari Are you able to give me any advice regarding my contact settings? I just want to know if the reason for not being able to get the contact energy in the 5% range is due to my contact or just due to the model itself.
13. ## Problems with type 7 contact, quasi static load

In case of the impactor, they don't specify anything, only the maximum size. This is why it's very hard to make a decent impactor assumption and why I went for a rigid. Another aspect which I'm not sure about, do I need to add a self-contact when the bumper is only one part?
14. ## Problems with type 7 contact, quasi static load

I need to simulate the crash test of a bumper, the Bumper needs to withstand the applied force for atleast 0.2 seconds and the forces need to be applied as rapidly as possible. The regulation states that a force of max 80kN needs to be applied at a point P1. In real life testing this force application needs to be done as follows :
15. ## Problems with type 7 contact, quasi static load

Could you tell me were you found this information about the load distribution? It would be nice to be able to reference a document in my thesis.
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