Learning Forum

[javat33489]

Hi all.
I have a problem with fatigue calculation when calculating drilling.
On the drill, some elements have much higher stress compared to others, I wrote this in the post:

/forum/forums/topic/error-with-sn-curve/

I came up with this idea. I want to use the MAT ADD EROSION card to remove unnecessary elements in the calculation.
for example, I know that I do not need stress elements higher than 550 MPa.
The MAT ADD EROSION map is very large and I am afraid of making a mistake.
Please tell me how to indicate in the map so that all elements whose stresses exceed 550 MPa are removed? Can I assign a SIGVM card? What else is needed? Thank you.

[javat33489]

HELP please

[Ashish Khemka]

Hi,

Please see if the following link is of use to you: LSDYNA Contact Eroding I — Welcome to LS-DYNA Examples (ansys.com)

Regards,

Ashish Khemka

[javat33489]

 

Thanks for the answer. I saw this example. I looked at all the examples. But my question is this. Can I just use the only material selection and SIGVM map to remove elements I don’t need? 

The remaining cards were left in default condition.

 

[javat33489]

I NEED HELP. PLEASE

[Reno Genest]

Hello Javat,

Yes. The best way to learn about LS-DYNA is to create a simple model (single element model) and do some quick tests. You should be able to erode your elements with SIGVM only defined in *MAT_ADD_EROSION. See the LS-DYNA user manual Vol II for more information about *MAT_ADD_EROSION:

https://lsdyna.ansys.com/manuals/

 

Reno.

[javat33489]

Thanks for the answer. Yes, I studied the materials. But it doesn't say that there. The problem is that I cannot generate the correct binot file to read the fatigue data. Some elements are strongly stressed throughout the entire calculation (singularity). They interfere with the fatigure calculation and I get an error that the voltages are greater than the Wöhler curve. Therefore, I decided to remove singular elements directly during the calculation. The criterion for removal is von Mises stress. The MAT ADD EROSION map is very large, but the parameter I need is only one - SIGVM. I plan to use only it and the material indication. Thank you. I hope I'm thinking correctly.

[javat33489]

Unfortunately, it doesn’t work well with the drill, it starts to warp.

Is there a similar way to remove elements exceeding the specified stress limit?

[javat33489]

Help me please. I need a way to get rid of the singularity. So that I can carry out an analysis on Fatiuga.

[javat33489]

Help me please. I need a way to get rid of the singularity. So that I can carry out an analysis on fatigue.

[Reno Genest]

Hello Javat,

*MAT_ADD_EROSION should work. What is the problem with it? Without a model, it is difficult to troubleshoot. Have you created a small simple model? Are you able to have elements deleted based on a VM stress limit with your small simple model?

Note that Ansys employees are not allowed to upload and download files on the Ansys Forum. But, you can post your model anyway and maybe another user will be able to have a look and help you.

 

Let me know how it goes.

 

Reno.

[javat33489]

Hello SIR!

I didn’t make a small model because my model is already small and the test model is just right for such tests, I drill the SPG die with a simple drill without a blade:

When the drill passes the die, during its free downward movement, a voltage increases (I think a singularity) which prevents me from conducting a fatigue analysis:

 

For this purpose, I decided to use the MAT ADD EROSION card to cut off all stresses above, for example, 510 MPa when the drill has already passed the die. But when I turn on the MAT ADD EROSION card:

it immediately begins to remove elements when the drill has not even touched the die and the calculation goes on to infinity:

[Reno Genest]

Hello,

Have you tried the latest R14.1 version of LS-DYNA?

It is difficult to troubleshoot this problem without the model. If you have a commercial license, please create a support case and we will have a look:

customer.ansys.com

 

Or maybe another user will be able to download your model here on the Forum and help you.

 

Reno.