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MASS and STIFFNESS matrices in ABAQUS

MASS and STIFFNESS matrices in ABAQUS

MASS and STIFFNESS matrices in ABAQUS

(OP)
Hi, everybody

is there anybody who knows how to get the MASS and STIFFNESS matrices from the ABAQUS and, maybe let them write down to a file?

Thanks in advance,

ridbay

RE: MASS and STIFFNESS matrices in ABAQUS

Look in the keyword manual under *ELEMENT MATRIX OUTPUT

Cheers,

-- drej --

RE: MASS and STIFFNESS matrices in ABAQUS

(OP)
Thanks Drej,

but i have already rewieved the *ELEMENT MATRIX OUTPUT and implemented the keywords therein... unfortunately i could not get the matrices up to now...

Should i write the keywords on "EDIT KEYWORDS" (which can be reached by clicking: Model -> Edit Keywords -> Model_Name)under the History output line?

and under which Procedure can i use it? General procedures such as Static, linear perturbation such as Frequency ?

or can you provide anymore explanation?

thanks

RE: MASS and STIFFNESS matrices in ABAQUS

All structural analyses apart from static will involve calculation and manipulation of the mass matrix.

In the static case:

kx = f (f = nodal forces, k = stiffness matrix, x = nodal displacements hence no mass matrix needed).

Eigenvalue (modal or free vibration):

kx + ma = 0 (m = mass matrix, a = nodal acceleration)

Dynamic (transient):

kx + ma + cv = f(t) (c = damping constant (Ns/m), v = nodal velocity, m = mass matrix)

I don't know the preprocessor you're using, but why not write out the deck manually and add the *ELEMENT MATRIX OUTPUT manually into the applicable part of the deck. Check in the manual for the correct position of this keyword in the deck, but I believe it should be located within the *STEP module. The matrices will then appear in your chosen file (or .dat if none) file.


E.g.


*STEP
etc
etc.
*ELEMENT MATRIX OUTPUT, OUTPUT FILE=FILENAME.EXT, MASS=YES, STIFFNESS=YES, ELSET=ELSET_NAME
*END STEP



Cheers,

-- drej --

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