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Excessive distortion in shell elements leading to error termination in impact simulation

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anuragdogra
Posts: 18
Topic starter
(@anuragdogra)
Active Member
Joined: 2 years ago

Hi,

I have an LS-Dyna impact simulation set-up where I have shell elements (ELFORM 2) impacting against a target plate (shell elements ELFORM 16) at 250 knots. The impacting elements are smaller in size than the target plate and they show excessive distortion during the simulation leading to error termination. I tried increasing the shell thickness, material modulus (MAT024 is used) but they do not work. I have used stiffness hourglass control 4 and tried playing around with different hourglass settings but it did not work. I also tried nfail in shell control that runs the simulation but my total energy of the simulation increases significantly (energy is not conserved). I tried improving the mesh but it keeps on failing at different elements and even elements with 1:1 aspect ratio show excessive distortion. Can anybody suggest me a way around or should I improve the mesh (the mesh is not good)?

Thanks

Anurag

7 Replies



Mahmoud
Posts: 20
(@mahmoud)
Eminent Member
Joined: 1 year ago

Hi,

check the direction of the normal of shell elements

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anuragdogra
Posts: 18
Topic starter
(@anuragdogra)
Active Member
Joined: 2 years ago

Hi @mahmoud,

Some element normals were not aligned to the rest of the part. I made modifications and submitted the job. I will let you know once I have results.

Thanks!

Anurag

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1 Reply
Mahmoud
(@mahmoud)
Joined: 1 year ago

Eminent Member
Posts: 20

@anuragdogra what kind of contact did you define?

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anuragdogra
Posts: 18
Topic starter
(@anuragdogra)
Active Member
Joined: 2 years ago

@mahmoud Thanks! It helped my model a little but the part still fails due to excessive distortions at a different set of elements now and the job error terminates. I will see if reducing the time-step factor helps. I have attached a new image where the part fails now.

I have defined automatic single surface contact for the projectile and eroding surface to surface between the target and projectile. I have soft 2 because of some foam materials and depth 13. If you think something else might be wrong let me know.

Thanks!

 

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anuragdogra
Posts: 18
Topic starter
(@anuragdogra)
Active Member
Joined: 2 years ago

Hi @mahmoud, I used a time step scale factor of 0.75 and my model is running fine now.

-Anurag

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