Abaqus Explicit

[Alexy@]

Hello everyone ,

I have a question for abaqus users,

Can you please explain me how to parameter a semi-automatic mass scaling in an explicit simulation?

I tried to simulate a simple tensile test on a beam (70*10*1 mm).

In Boundary Condition, I encastre one face and in the other face i applied a velocity (0.007)

For the mesh, I have an uniform mesh with seed = 0.3 mm

I defined the step like this and as I show you in the picture.

Step--> Incrementation --> type: Fixed --> User-defined time increment : 0.0001

I calculated the stable time increment and i found dt= 5.7 *10^-8 s (dt=l/c , l=0.3mm and c=5188.745 m/s)

My question is: I don't know why I have a convergence of my solution even if I putted the time increment and the target time increment higher than the stable time increment.

In the theory, it's specified that the time increment should be less or equal to the stable time increment.

Maybe I don't understand very well. Please can you explain me?


Thanks in advance

 

[Mustaine3]

Your image shows, that you've used mass scaling with a target time increment.
The stable time increment is based on the material wave speed, which depends on the density (mass). Abaqus scales the mass matrix to reach the target time increment you've defined. That's why it is called 'mass scaling'. So your part becomes heavier. Look at the .sta file. There you will find the mass of your model, the original time increment, the change in mass through mass scaling and the new time increment.

All this is explained in the Getting Started.

 

[Alexy@]

Thanks for your answer

I also defined this part.

I fixed the stable time increment to 10^-4 as it's shown in the picture.
I looked in my statut file and there is notified that my stable time estimates don't account for mass scaling.

Sorry I'm a new user of Abaqus

 

[Alexy@]

status file

 

[Mustaine3]

Scroll down the status file to see the defined time increment.

And why are you using a fixed time increment larger than the natural one? I your special case it might be no problem, because you scale the mass also. But in general it is dangerous and the manual says is pretty clear.

 

[Alexy@]

Thank you for your help

I used a fixed increment larger than the natural one just for a test. I didn't undersand the role of each parameter. He's because of that, I have asked you.