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Hello sir Good morning, I was running the full vehicle model for crash and i am facing the problem in time step for which run is being terminated. Please Help me, thank you.

                                               

tstep.PNG

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Hi Ramakiran,

Do you have /DT/BRICK/CST keyword in your model?. If so, check the minimum time step, Tmin, defined for the same.

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Hi Ramakiran,

Please remove the /DT card and try running, It seems like some solid elements are getting compressed and the time step of those elements are going below the specified Tmin.

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Hi Ramakiran,

/DT/BRICK/CST is used in order to prevent the solid elements from negative volume, this happens when solid elements are very deformed and their characteristic length goes to 0. At those cases in solid property  Ismstr =2 is used which will use large strain formulation while their time step remains greater than tmin, and will then switch to small strain formulation.

In order to impose a time step in the model use /DT/NODA/CST keyword.

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Hi Ramakiran,

You can try with the same same value for /DT/BRICK/CST, or you can slightly increase the same also.

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hello sir, even when i changed the time steps still its showing negative volume and constant time step for solid elements error..i'm dropping the starter out and result out files in drop box. Thank you.

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On 8/10/2017 at 12:37 PM, George P Johnson said:

Hi Ramakiran,

/DT/BRICK/CST is used in order to prevent the solid elements from negative volume, this happens when solid elements are very deformed and their characteristic length goes to 0. At those cases in solid property  Ismstr =2 is used which will use large strain formulation while their time step remains greater than tmin, and will then switch to small strain formulation.

In order to impose a time step in the model use /DT/NODA/CST keyword.

Hi George

I used /DT/BRICK/CST but my model until does not work, the error is ZERO OR NEGATIVE VOLUME FOR 2D-ELEMENT

How can I fix this problem?

Thank you

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On 5/25/2018 at 2:36 PM, pohan said:

Hi George

I used /DT/BRICK/CST but my model until does not work, the error is ZERO OR NEGATIVE VOLUME FOR 2D-ELEMENT

How can I fix this problem?

Thank you

@pohan what elements type you are using?

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Hi Prakash 

I did with this:

/DT/BRICK/CST
0.900000000000000    0.000000000000000
/DT/NODA/CST/0
0.900000000000000    0.000000000000000 

But it still does not work

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6 hours ago, Nachiket Kadu said:

With ismstr=2? and did you had any warnings regarding incompatible BC? 

Hi

I used ismstr=2 and I had this warning: ** INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL

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1 hour ago, pohan said:

Hi

I used ismstr=2 and I had this warning: ** INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL

Use ismstr=2 and u please check the boundary condition applied are correct? make sure u are not giving load to a contrained dof.

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23 hours ago, Nachiket Kadu said:

Use ismstr=2 and u please check the boundary condition applied are correct? make sure u are not giving load to a contrained dof.

Hi.

I check the boundary condition, in my opinion it is correct. The warning ** INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL caused by the Rigid wall.

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46 minutes ago, pohan said:

Hi.

I check the boundary condition, in my opinion it is correct. The warning ** INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL caused by the Rigid wall.

Delete that wall and try preparing it again.

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On 5/31/2018 at 11:09 AM, Prakash Pagadala said:

@pohan

 

Please share the model file using  the file transfer link in my signature.

Hi

I sent you my files

Thank you

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On 6/4/2018 at 1:56 PM, Prakash Pagadala said:

Hi,

 

I shared a file with you. Please try that. 

Thank you.

It work. Could you please tell me how did you determine the ΔTmin 

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