How to define Initial Stress for a Brick Element in Radioss
Dear All,
Currently I'm trying to define the initial stress for a brick element in case of pure tensile/compression in Radioss for a simple case as below:
I got 2 unclear points regarding to Initial Stress Define for a brick Command in Radioss (/INIBRI/STRS_FGLO), which are described as below:
1. In Initial Stress Define for a brick Command, there is Eint (Internal Energy of solid element) and RHO (Volumetric mass) which I don't know what is formula of them. Could you please tell me how to calculate them to define Initial Stress correctly?
are they like this??
2. As I read in Reference Guide of Radioss about /INIBRI/STRS_FGLO. There is mentioned that "Before the first cycle, Radioss will check the consistency of input stress tensor with material data (stiffness and density) as image below.
It seems mean that If I define Eint and RHO incorrectly, Radioss will correct the stress value, which may cause Sii(new) not same Sii (initial) as I defined (Sii_new = Sii_inital  D). This is the thing I'm not expected.
I have 2 more questions to ask regarding to this, that is:
2.1. What is Bulk in equation (1012)? Is it as below?
2.2. As image above, "RHO is the density in the state file". is it same as Volumetric Mass in the first image? or they are different? How can I calculate it?
I appreciated for any help.
Thank you very much for your support in advance!
Answers

Hi
If you compute the deformation tensor and having the material data,
You will be able to calculate the internal energy (energy per element volume) and currently density, that will be different than the reference due to the deformation and poison effect.
An alternative way to obtain the the values for the /INIBRI/STRS_FGLO is to run the baseline model and request the /STATE results.
Please refer to documentation of /STATE/DT and /STATE/BRICK/STRES/GLOBFULL.
Regards
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Rogerio Nakano_21179 said:
Hi
If you compute the deformation tensor and having the material data,
You will be able to calculate the internal energy (energy per element volume) and currently density, that will be different than the reference due to the deformation and poison effect.
An alternative way to obtain the the values for the /INIBRI/STRS_FGLO is to run the baseline model and request the /STATE results.
Please refer to documentation of /STATE/DT and /STATE/BRICK/STRES/GLOBFULL.
Regards
Hi Rogerio,
Thank you very much for your response and information.
Could you please tell me what is the formula to calculate Internal Energy of Solid Element and Density in the state of initial stress?Thanks!
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