How to define Initial Stress for a Brick Element in Radioss

Chieu Hua
Chieu Hua Altair Community Member
edited November 2020 in Community Q&A

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:

image

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?

image

image
are they like this??
image
image

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.

image

I have 2 more questions to ask regarding to this, that is:

2.1. What is Bulk in equation (1012)? Is it as below?
image
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!

 

Tagged:

Answers

  • Rogerio Nakano_21179
    Rogerio Nakano_21179 New Altair Community Member
    edited January 2021

    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

     

  • Chieu Hua
    Chieu Hua Altair Community Member
    edited November 2020
    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!

Categories