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A surprisingly popular blog-post written here is Exporting Stiffness Matrix from Ansys. A sensible follow up question is what can one do with the exported stiffness matrix? In a recent Xansys Forum post, a question was raised on how we can edit the stiffness matrix of a superelement and use it for our model.

An approach presented below is to first create a superelement that has the same number of DOF and nodal location that will serve as a template. An APDL script can then be written to edit the stiffness matrix entries as desired before exporting to a new superelement *.SUB file for use in future models. The self-contained script below demonstrates this.

**/prep7**

et,1, 185

mp, ex, 1, 200e3

mp, prxy, 1, 0.33

w = 0.1 ! single element (note nodal locations)

n, 1, w, -w, -w

n, 2, w, w, -w

n, 3, -w, w, -w

n, 4, -w, -w, -w

n, 5, w, -w, w

n, 6, w, w, w

n, 7, -w, w, w

n, 8, -w, -w, w

e, 1, 2, 3, 4, 5, 6, 7, 8

**/solu**

antype, substr ! analysis type: substructure

seopt, myse,1 ! saves stiffness matrix

m, all, all

**solve**

! Imports sub info into APDL-math form

*DMAT, myse, d, import, sub, myse.sub, stiff

! Export to apdl array for editing

*EXPORT, myse, apdl, apdlmat

! Make edits as desired

apdlmat(2,2) = 28 ! example edit to be checked later

! Put back to APDL-math form

*DMAT, myse, ,import, apdl, apdlmat

! exports desired sub file

*EXPORT, myse, sub,

**newse.sub**, stiff, , done**!! To verify it works as expected**

finish

/clear ! start from scratch

**/prep7**

et, 1, 50

se,

**newse****/solu**

eqslv, sparse

wrfull, 1

solve

finish

*DMAT, MatK_check, D, import, full, file.full, stiff

*EXPORT, MatK_check, apdl, apdlmat_check

shouldbe28 = apdlmat_check(2,2)

*stat, shouldbe28

**Other Resources**

Matrix Transfer between MATLAB and Ansys link

Export Stiffness Matrix from Ansys link

APDL Math Example link

Ansys's Website APDL Math Example link

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