Is it possible to change the stiffness value in nodes of elements in Abaqus ? I just found how to export the global stiffness matrix with the code below but can't change it and give it to Abaqus.
*STEP, name= exportmatrix
*MATRIX GENERATE, STIFFNESS
*MATRIX OUTPUT, STIFFNESS, FORMAT=MATRIX INPUT
*END
Depending on your goals, I see a few ways you can proceed. Judging by your question, I'd suggest looking at #1 or #2 before you seriously consider #3.
1. If you really want to directly manipulate the global stiffness matrix, use the
matrix generate,matrix outputapproach you've shown above. Make the changes you want, then run a new job usingmatrix input. This keyword is discussed in the manual.However, assuming you understand how to generate the stiffness of an individual element, you may want to look into the following two options, instead.
2. Abaqus/Standard (the implicit solver) allows you to define a linear "user element" with nothing more than the terms in it's stiffness matrix. These values are entered directly into the job input file. Look up the keyword:
*user element. It is not complicated once you understand.3. On the other hand, a general element can be programmed using a (Fortran-based) user subroutine called UEL. It must be suitably coded, compiled, and linked to the job when it is run. This approach requires much more work and expertise, and is much more powerful. It's not for everyone. Alternatively, your needs might be better suited by the user subroutine called UMAT, where you only program your material behavior.