Hello,

I have a question regarding the output Stiffness Matrix (get matrix). I have a sandwich structure, with shells and solids, connected with tie constraints. Now i want to get the Stiffness Matrix, therefore i added the command:

*MATRIX GENERATE, STIFFNESS

*MATRIX OUTPUT, STIFFNESS, FORMAT=MATRIX INPUT

After performing in Matlab:

Stiffness=getMatrix('Random_load_MPC_YES_STIF1.mtx',format,S);

i get the siffness Matrix, which works fine. But for plotting and different calculations, i have to know all nodes with their degree of freedoms considering the rows of the stiffness matrix.
Can someone explain me how to export the Nodes with their degree of freedoms considering the rows of the stiffness matrix?

The numbering of the DOFs is not unique. Depending on what you want to do with the stiffness matrix, you generally define your own numbering of DOFs of the Abaqus model. Could you tell me more details about what you would like to plot or in which way you would like to postprocess the stiffness matrix?

Thank you for your answer. I tried this, but i don't get the relationship between the stiffness matrix (matrix Input, file: Random_load_MPC_YES_Stif1.mtx) and the stiffness matrix (Coordinate, Random_load_MPC_YES_Stif1_Coordinate.mtx).

Becaue getMatrix delivers the Stiffness Matrix as it delivers Random_load_MPC_YES_Stif1_Coordinate.mtx, I don't know which degree if freedom is which row.

The first rows:

Random_load_MPC_YES_Stif1.mtx

4,1, 4,1, 2.753065285000000e+03

4,2, 4,1, -9.375000000000000e-01

18,1, 4,1, 2.749404857500000e+03

18,2, 4,1, 9.375000000000000e-01

41,1, 4,1, 2.749404857500000e+03

41,2, 4,1, -9.375000000000000e-01

81,1, 4,1, 2.748125000000000e+03

81,2, 4,1, 9.375000000000000e-01

110,1, 4,1, -1.374360071250000e+03

110,2, 4,1, -4.687500000000000e-01

110,3, 4,1, -2.062500000000000e+02

110,4, 4,1, -1.171875000000000e-01

110,5, 4,1, 3.435900178125000e+02

111,1, 4,1, -1.375000000000000e+03

111,2, 4,1, -4.687500000000000e-01

111,3, 4,1, -2.062500000000000e+02

111,4, 4,1, -1.171875000000000e-01

111,5, 4,1, 3.437500000000000e+02

116,1, 4,1, -1.375000000000000e+03

116,2, 4,1, 4.687500000000000e-01

116,3, 4,1, 2.062500000000000e+02

116,4, 4,1, 1.171875000000000e-01

116,5, 4,1, 3.437500000000000e+02

117,1, 4,1, -1.375639928750000e+03

117,2, 4,1, 4.687500000000000e-01

117,3, 4,1, 2.062500000000000e+02

117,4, 4,1, 1.171875000000000e-01

117,5, 4,1, 3.439099821875000e+02

The first rows :

Random_load_MPC_YES_Stif1_Coordinate.mtx

1 1 2.753065285000000e+03

1 2 -9.375000000000000e-01

2 1 -9.375000000000000e-01

1 13 2.749404857500000e+03

13 1 2.749404857500000e+03

1 14 9.375000000000000e-01

14 1 9.375000000000000e-01

1 58 2.749404857500000e+03

58 1 2.749404857500000e+03

1 59 -9.375000000000000e-01

59 1 -9.375000000000000e-01

1 70 2.748125000000000e+03

70 1 2.748125000000000e+03

1 71 9.375000000000000e-01

71 1 9.375000000000000e-01

1 109 -1.374360071250000e+03

109 1 -1.374360071250000e+03

1 110 -4.687500000000000e-01

110 1 -4.687500000000000e-01

1 111 -2.062500000000000e+02

111 1 -2.062500000000000e+02

1 112 -1.171875000000000e-01

112 1 -1.171875000000000e-01

1 113 3.435900178125000e+02

113 1 3.435900178125000e+02

1 115 -1.375000000000000e+03

115 1 -1.375000000000000e+03

1 116 -4.687500000000000e-01

You have to load all the contents of the mtx file that is generated after the Abaqus analysis has been completed. If the mtx file is in MATRIX INPUT format, as you have spoecified in your input file, then each row in the mtx file contains the following 5 comma-delimited values:

1) Row node number

2) Degree of freedom number for row node

3) Column node number

4) Degree of freedom number for column node

5) Matrix entry

By loading the contents of the mtx file in Matlab, you can play with the nodes and degrees of freedom of your Abaqus model as you wish.