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Finite Element Modeling of Penetration

Hi everyone. I am currently tring to develop a finite element model for penetration process using Ls-Dyna. I have tried many ways of doing this.And even try to follow method that journal of impact engineering but i could not get a successful 2D model. All the projectiles are assumed to be rigid.

Here are the models i tried:

1st MODEL: Material model for the plate is PIECEWISE_LINEAR_PLASTICISITY. This material model has included Cowper-Symond Equations. I only have the material constants for Mild Steel. The model requires at least a few point in the plastic stress/strain curve and also C, P as the strain rate parameters. For mild steel i have successfully assigned all the constants as required. I have constrained my model at the edge of my plate. And, I have got my model run. But the velocity of penetrating the mild steel is too low.

Does anyone have the material constants for other stronger steel? And, Does anyone know how do we determined the C, P strain rate parameter?

2nd MODEL: Material model for the plate is JOHNSON_COOK. I have tried to follow the journal to assigned all the material constants to this model. The model has run successfully. But, the result is strange. It did bend the plate and perforate. But the way the plate deform is not proper. The plastc strain is not at the currect place. And, I also found the journal which also used this model. But, I don't know what are the mistakes.

Does anyone know about the Equation of State? Because the journal i got did not mention anything about the EOS but in LS-Dyna it wad required to include that when i used Johnson_Cook Model.

Please help me if you know wany of these... I really need these advise urgently.

Thank You.

Reply to
damien
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Hi everyone. I am currently tring to develop a finite element model for penetration process using Ls-Dyna. I have tried many ways of doing this.And even try to follow method that journal of impact engineering but i could not get a successful 2D model. All the projectiles are assumed to be rigid.

Here are the models i tried:

1st MODEL: Material model for the plate is PIECEWISE_LINEAR_PLASTICISITY. This material model has included Cowper-Symond Equations. I only have the material constants for Mild Steel. The model requires at least a few point in the plastic stress/strain curve and also C, P as the strain rate parameters. For mild steel i have successfully assigned all the constants as required. I have constrained my model at the edge of my plate. And, I have got my model run. But the velocity of penetrating the mild steel is too low.

Does anyone have the material constants for other stronger steel? And, Does anyone know how do we determined the C, P strain rate parameter?

2nd MODEL: Material model for the plate is JOHNSON_COOK. I have tried to follow the journal to assigned all the material constants to this model. The model has run successfully. But, the result is strange. It did bend the plate and perforate. But the way the plate deform is not proper. The plastc strain is not at the currect place. And, I also found the journal which also used this model. But, I don't know what are the mistakes.

Does anyone know about the Equation of State? Because the journal i got did not mention anything about the EOS but in LS-Dyna it wad required to include that when i used Johnson_Cook Model.

Please help me if you know wany of these... I really need these advise urgently.

Thank You.

Reply to
damien

2D model like plane strain? How are you constraining the plate?

It would a good idea to try something simpler to check out your modeling and so forth. Run a case applying a load to the center of the plate. Either use a point load or a pressure over a small area. See if the deformed shape and stresses seem reasonable.

That's all I can tell you. I only know what LS Dyna is. Good luck.

- CJF.

Reply to
Jeff Finlayson

Yes, I am using a 2D plane strain. And i have constrained the plate at both left and rigth side edges.

Reply to
damien

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