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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.
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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.
i have used /eng/dt with tscale 0.9 and tmin 1.1e-8 according to my min element size?what should be the tmin? in /dt/brick/cst?
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.
then only DT/BRIC/CST is enough to define time step for the full model????
/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.
Thank you sir, what are the values in dt brick cst i must use when i use dt noda cst as tscle 0.9 and tmin 1.1e-8 ?
You can try with the same same value for /DT/BRICK/CST, or you can slightly increase the same also.
okay thank you sir, trying it.
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.
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.
/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.
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
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
I used /DT/BRICK/CST but my model until does not work, the error is ZERO OR NEGATIVE VOLUME FOR 2D-ELEMENT
@pohan what elements type you are using?
Hi Kadu.
I use P14 QUAD 4N
Hi Kadu. I use P14 QUAD 4N
With ismstr=2? and did you had any warnings regarding incompatible BC?
Hi @pohan
Can you add DT/NODA/CST and check if that helps?
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
Hi
I used ismstr=2 and I had this warning: ** INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL
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.
Hi.
I check the boundary condition, in my opinion it is correct. The warning ** INCOMPATIBLE KINEMATIC CONDITIONS IN MODEL caused by the Rigid wall.
@pohan
Please share the model file using the file transfer link in my signature.
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.
@pohan Please share the model file using the file transfer link in my signature.
I sent you my files
Hi,
I shared a file with you. Please try that.
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
Run the analysis and see the time step written by the solver. Use a closer value in DT/NODA
