Dyna MAT 26 vs Radioss equivalent?

Altair Forum User

Hi, i've a big problem. My original model in Dyna format has a structural foam modeled with MATL26 and I cannot find an equivalent card material in Radioss that has the same parameters of the original. I've tried with Radioss Law 28 but the behaviour of the model isn't similar to the original. Can you help me? (I've attached the material card of dyna) 

Thanks

Lo Presti

 

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Altair Forum User

Hi Lo Presti,

The equivalent material laws that are generally used to model honeycomb material structures as crushable foams in RADIOSS are Mat Law 28 and 50. I think, in this material card strain rate effects are included. In that case, check for Material Law 50 where honeycomb material with strain rate dependency is included.

Please go through the Help Menu/Theory Manual of RADIOSS on the same material laws where the formulations are described.

Meanwhile, we have a tutorial on honeycomb (Mat Law 28) modelling. You can access the tutorial and related model files at: http://www.altairuniversity.com/learning-library/modeling-and-analysis-of-honeycomb-impact-attenuator/

 

Altair Forum User

Thanks for your reply. I've just tried mat 28 and mat 50 but the results are bad. 

Altair Forum User

Hi Lo Presti,

Which is the property card you are using?. Please try with  /MAT/LAW50 and property  /PROP/SOL_ORTH (TYPE6).

 

Altair Forum User

Thank you, but i've just tried with this formulation coupled with law 50 and law 28, but the results are the same.

Altair Forum User

Hi Lo Presti,

 As a workaround, you can convert the Dyna model into RADIOSS using HyperCrash.

 Make sure you are using the latest HyperCrash 14.0 for the best translation.  Start HyperCrash and pick the RADIOSS V14 user profile.  After HyperCrash starts, go to

 File>>Import>>LS-Dyna, and select your LS-Dyna model.  During import HyperCrash will convert the model to RADIOSS.  A conversion html report will be created in the directory where your LS-Dyna model was located.

If you still face issues, please share the Dyna model and also the RADIOSS model (where /MAT/LAW50 was used) in the secure dropbox.

Altair Forum User

Hi George, i'm still waiting for my boss authorizes transferring models. I converted from Dyna to Radioss with Hypercrash and it seems to be good, but i've an error on interfaces that has intersections. I resolved intersections and penetration on interfaces (there are many component in contact each other and dyna model had an unique contact interface that had been converted in a type 7 interface). The Radioss model runs but when reaches the interface, the error go to 99,9%. If my boss authorizes, I will send you the models.

Best Regards

Altair Forum User

Hi Lo Presti,
Thanks for the update. 

Please check the model for any Incompatible kinematic conditions which can lead to high energy error. Also, check the model for high interface penetrations/distortions which can also lead to energy error.
 

Altair Forum User

Hi,

I've resolved the intersections (5 couples of part), but i've thounsands penetration of nodes....The model in question is a car b-pillar, and there are many shells that are in contact. Loadcase is a roof crush with a rigid plane on the upper side of b-pillar with imposed velocity. Hypercrash translation gives me 2 type of contact: a type7 with plane and all structure and a type 2 with weldings.

 

Altair Forum User

Hi Lo Presti,

Type 2 interface is a tied interface that kinematically connects a set of slave nodes to a master surface.and thus it will not allow relative motion between the parts. If there is  a relative or sliding motion between parts Type 7 interface should be used, which is a multi-usage impact interface, modeling contact between a master surface and a group of slave nodes.

In HyperCrash,using Quality>>Check all solver interface menu user can check the interfaces for potential penetrations. And using depenetration option, the penetrations can be removed. 

A case study on Roof Crush Analysis can also be accessed at http://www.hanyang.ac.kr/top_news/2013/102/bronze.pdf

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Altair Forum User

Thanks. The model are running in this moment, I'm praying.

Altair Forum User

Bad news: energy error limit reached. In your opinion, could I change the type of interface in type 2 instead type 7? The model is similar to the model in the pdf you have sent, there are shell elements connected each other with a foam in the interior part. 

Best regards

Altair Forum User

Hi Lo Presti,

Please share the out files of the run (_0000.out and _0001.out files)

Altair Forum User

Hi George, excuse me for the delay.

I have checked the model, I'm trying to solve the issues. If I have problems, I'll share out files. Thanks!