Hi
I am trying to look at material instabilities in Lee Fenves non-associated plasticity model (aka Concrete damaged plasticity in abaqus) in form of $\det(E_{t})=0$
looking at element stiffness matrix, I am suspicious that the values provided by abaqus is really a tangential stiffness matrix because:
what I get from abaqus is in contradiction with my expectations. I get a symmetric positive definite matrix with the highest rank possible (18 for case of C3D8 element) which is not the case that i am looking for. That is why i am trying to get DDSDDE matrix from abaqus, which is in constitutive level, but I don't have idea about extracting it as an output. I would appreciate it if anybody can help.
PS: I attached my abaqus input file
Thanks Shah
the problem that i have with *ELEMENT MATRIX OUTPUT is that i don't have control on the output format. It gives me binary format while i need more compatible format.
I change the lines in my code by cannot get mtx file. instead, i get binary *.sim file which is not really readble for me.
*STEP
**MATRIX GENERATE, STIFFNESS,ELSET=element_middle
**MATRIX OUTPUT, STIFFNESS, FORMAT=MATRIX INPUT
******
******
*MATRIX GENERATE,STIFFNESS,ELSET=element_middle
*ELEMENT MATRIX OUTPUT,MASS=no, STIFFNESS=YES, ELSET=element_middle, OUTPUT FILE = RESULTS FILE
*****
*****
*END STEP
Shahriyar
abaqus mtxasm job=matrix_outX3.sim
[oldjob=matrix_outX3.sim]
[text]
is working for versions 6.13 and later but for earlier versions, I found the way. I've attached the input file.
I changed it this way:
*MATRIX GENERATE, STIFFNESS,ELSET=element_middle
*ELEMENT MATRIX OUTPUT,
ELSET=element_middle, STIFFNESS=YES,
OUTPUT FILE=USER DEFINED,FILE NAME=reza12
the option "file name" helps us format the output in .mtx instead of .SIM
Alireza
Sorry for my late response.
My post is good if you need the "Element level" matrix. In the case you need the "Global " matrix, based on the option you want, you can use different options. Basically, you need to remove *ELEMENT MATRIX OUTPUT, from my comment above
https://www.sharcnet.ca/Software/Abaqus/6.11.2/books/key/default.htm?startat=ch13abk12.html
Hi
I'm using the following format according to what ABAQUS documentation says in my .inp file and the .mtx file for the stiffness matrix is generated, but the .mtx file for LOAD does not exist. Why? What is wrong?
*STEP
*MATRIX GENERATE, STIFFNESS, LOAD
*MATRIX OUTPUT, STIFFNESS, LOAD, FORMAT=MATRIX INPUT
*END STEP
here is the result in .dat file that shows tube_LOAD2.mtx is created but it's not
S T E P 2 M A T R I X G E N E R A T E
THE FOLLOWING GLOBAL MATRICES WILL BE GENERATED AND WRITTEN TO tube_X2.sim
STIFFNESS
LOAD
IF MULTY-POINT CONSTRAINTS ARE SPECIFIED IN THE MODEL, THEY WILL BE APPLIED
THE FOLLOWING GLOBAL MATRICES WILL BE WRITTEN TO THE FOLLOWING TEXT FILES
STIFFNESS TO tube_STIF2.mtx
LOAD TO tube_LOAD2.mtx
MATRIX OUTPUT FORMAT - MATRIX INPUT
@Saeed
Please attach your input file. Do you want the whole global load vector or the load vector for each element?
Dear Reza,
thanks for your answer. I want the whole global load vector. the input file is attached. It's a tube with pressure from inside.
I even used this in your attached input file.
*STEP
*MATRIX GENERATE, STIFFNESS, LOAD
*MATRIX OUTPUT, STIFFNESS, LOAD, FORMAT=MATRIX INPUT
*END STEP
same results. no LOAD.mtx is created but .dat file says it is created.
Saeed Torbati ,Have you generated the mtx file? I encountered the same problem and would like to know your solution.
Reza Mousavi , could you tell me how to generate the mtx file of the GLOBAL stiffness matrix with the above tube.inp file? Thanks.
Ling-Ze Bu it is an old thread. I don't have the software anymore. I remember I used some instructions in the manual. Please refer to this link as start point (If you haven't done already):
https://abaqus-docs.mit.edu/2017/English/SIMACAEANLRefMap/simaanl-c-mtxgenerationperturbation.htm
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