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Problem with fatigue analysis and MAT ADD EROSION

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javat33489
Posts: 25
Topic starter
(@javat33489)
Paid Intern
Joined: 2 years ago

Hi all.

I made a test model like the LSTC for drilling with a smooth drill. I simulate drilling an SPG ram:

изображение

 

I want to carry out a fatigue analysis of the drill, but the stresses on the drill are constantly increasing even after the drill passes through the die (I think this is a singularity).
Due to the increase in stress, my SN curve has an error when fatigue analyzing:

изображение

The stresses increase even after the drill passes through the die:

изображение
изображение

 I came up with the idea of removing singular elements during the solution using MAT ADD EROSION. I set the stress above which elements will be removed:

изображение

 

But when the task started, the elements began to deform immediately and the drill had not even touched the die:

изображение

 

Why is this happening? Can you help me? Thank you!

9 Replies




javat33489
Posts: 25
Topic starter
(@javat33489)
Paid Intern
Joined: 2 years ago

Help please

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Posts: 1
 CFL
(@cfl)
Barista
Joined: 6 months ago

Is there any initial penetration or like unit missing. Also at the outermost of the drill, is there any boundary conditions. Moreover, could there be a problem in defining the angular velocity or initial condition given to the part?

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javat33489
(@javat33489)
Joined: 2 years ago

Paid Intern
Posts: 25

@cfl

There is no initial penetration. Touching occurs during calculation. At the border of the drill there is only contact with the die. The angular velocity is selected correctly:

 
 
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Negative Volume
Posts: 641
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(@negativevolume)
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Joined: 6 years ago

@javat33489 seems like a problem with the material / section / hourglass of the drill. Or you could have something weird going on with your mesh or a contact involved with the drill? 

Do you have initial stress or anything similar involved here?

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1 Reply
javat33489
(@javat33489)
Joined: 2 years ago

Paid Intern
Posts: 25

@negativevolume Touching occurs during the calculation; initially there is no touching. At first the stress is 0. Perhaps my mesh is too rough for a drill, but that’s why I wanted to use MAT_EROSION to remove bad elements.

Screenshot 3
Screenshot 2

 

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javat33489
Posts: 25
Topic starter
(@javat33489)
Paid Intern
Joined: 2 years ago

Maybe I specified few settings in the MAT_EROSION map? I only used SIGVM. Let me remind you that my goal is to remove elements exceeding a given stress value.

Screenshot 1
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