How to define whole compression/tension plastic strain-stress curve in Law 36?
Hello,
I'm trying to apply an elasto-plastic law in Radioss which contains both compression and tension aspects. It seems that Law 36 and Law 66 are two elasto-plastic laws considering both compression and tension aspects, as is discussed in this post:
https://community.altair.com/community?id=community_question&sys_id=f086c83a1b2bd0908017dc61ec4bcb01.
However, the simulation has errors (ERROR ID: 23) when using Law 66 because the shell property /PROP/SHELL is not compatible with Law 66, as is discussed in this post:
https://community.altair.com/community?id=community_question&sys_id=fb86cc3a1b2bd0908017dc61ec4bcbb2.
Therefore, Law 36 seems to be the suitable one. But I have some queries when inputting the material data. Here are my questions:
How to define the whole compressive and tensile plastic strain-stress curves in Law 36? Because in Law 66, we can respectively input compressive and tensile plastic strain-stress data via functions "fct_IDc" and "fct_IDt". But in Law 36, in my opinion, only tensile plastic strain-stress data at different strain rates can be input via "Nfunct". While for compressive plastic strain-stress relationship, how to define it? It seems "fct_IDp" is used to distinguish the behavior in tension and compression, and the effective yield stress is then obtained by multiplying the nominal yield stress by the yield factor corresponding to the actual pressure i.e. Sig_y=Sig_y * yield factor, as illustrated below:
The problem is that I have the compressive plastic strain-stress curve, how to use it correctly in Law 36? As I really don't understand the usage of "fct_IDp" , it seems to be relevant to pressure and the default value is zero.
Could someone help me solve this problem? Any help would be appreciated.
Best.
Answers
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LAW36 will only allow you to scale yield in compression, apart from that, you can't specify a specific compression behaviour different to tensile.
I think to get the behaviour you are looking for you may have to use LAW76 (SAMP) which does allow separate compression/tension functions
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Hello Paul,
Thank you for your response. Yes, Law 76 can define separate compression/tension plastic strain-stress curves. But there exists a same problem as using Law 66, the simulation has errors (ERROR ID: 23) because the shell property /PROP/SHELL is not compatible with Law 76...
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is there any further information given for this error? /PROP/SHELL is compatible with both LAW66 and LAW76
Can you share your model where you get the error?
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Ok, I think Error 23 is regarding using global integration (N = 0 on property card?) that is only compatible with a few laws. I guess you are using an older version of Radioss though as in newer versions it is automatically changed if set incorrectly so that message wouldn't come up any more.
If you set a number of integration points through thickness on your /PROP/SHELL (N=5 recommended as a usual value) then you shouldn't get that error and be able to use LAW66 or LAW76
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Paul Sharp_21301 said:
Ok, I think Error 23 is regarding using global integration (N = 0 on property card?) that is only compatible with a few laws. I guess you are using an older version of Radioss though as in newer versions it is automatically changed if set incorrectly so that message wouldn't come up any more.
If you set a number of integration points through thickness on your /PROP/SHELL (N=5 recommended as a usual value) then you shouldn't get that error and be able to use LAW66 or LAW76
Hello Paul,
Thank you for your helpful advice. Yes, you are right. I am using an old version (V14) of Radioss.
Best
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