GEBT Constitutive Equation Modification: Piezoelectric

  1. Mann Kyo Cho

    Hello All,

    I am attempting to modify GEBT in order to input the non-mechanical stress resultants from VABS from Piezoelectric Actuation. As well as eventually editing the constitutive equations to include the additional terms needed for the sensor case as well.

    I am however having some difficulty in handling how to go about doing this in GEBT. I have some experience with Fortran, but mostly from self-study for a CFD course. Currently I'm also looking at the fact GEBT seems to have an optional subroutine for the stiffness vs the flexibility matrix and trying to follow the code in order to determine how and where exactly the constitutive equations are solved? If anyone knows the exact subroutine I should be looking and and if there are any suggestions on how to do edit the equations without causing many errors.

    Thank You!


  2. Wenbin Yu

    You need to look for the place where these properties are get read then used. You might have to change a few places for your intended purpose.

  3. Mann Kyo Cho

    I've been trying to follow the the stiffness/flexibility matrix from the pre-process subroutines, I believe all the sectioanl properties are stored in the "materials" variable.  However they seem to dead end in the Analysis.f90 file. 

    I'm having trouble mainly following the logic of the code. And uncertain where the constitutive equations are actually addressed?   Or is it solved differently for each of the run options ?



  4. Qi Wang

    Hi Lance,

    GEBT is implemented based on mixed formulation of finite element method. The constitutive equations does not explicitly shown in the nonlinear governing equations. However, they are being used in the calculation of (1D) strain measures and the linearization of these nonlinear equations. You can look into the Element.f90 file and search for "eFlex" and "eMass" for flexible and mass matrices, respectively, to see where and how they are implemented. 


  5. Sulaiman B Kamarulazizi

    Hi ,

    I have understood how Element.f90 file implements the "eFlex" and "eMass" matrices. However could you explain to me how I can insert an extra term to the constitutive equation when it is not explicitly shown in the nonlinear governing equations?

    Thank you,