Learning Forum

[Jagog]

Hello everyone. For my simulation project I modelled a bending beam in Ansys Mechanical 2022 R2 in order to calculate the node displacements in a static structural analysis under a certain load:

I exported stiffness and mass matrix of the bending beam in a txt-file because I want to programme the same scenario with the exported matrices in Matlab for my project. For the export I used these APDL-commands that saves the stiffness matrix in a txt-file:

 

*SMAT,MatKS,D,IMPORT,FULL,file.full,STIFF

*PRINT,MatKS,Ksparse.txt

 

Unfortunately, I was not able to calculate similar results for the maximal displacements in Matlab with the exported matrix (vary about factor 1000 compared with Ansys analysis). After checking my code and workflow several times without finding my error I was wondering if the units of the exported matrices could be responsible for the error. I used a metric unit system for the Ansys simulation (m, kg, N, s, V, A) and due to the basic equation   K u = f   I assumed that the unit of the stiffness matrix K is [N/m].

 

Is my assumption for the exported stiffness matrix correct or are there different units used for the export? If I am wrong, what unit is used for the exported mass matrix in addition?

 

Thank you for reading my post, I am looking forward to receiving your respond.

[Zoi Stavrothanasi]

Hello Jagog,

You are correct, since a metric unit system (m, kg, N, s, V, A) was used for the simulation the unit of stiffness is Newtons per meter (N/m). The units of the exported matrices will be the same as the units used in your project, as determined by the system of units set in your project settings.

Also note that, when exporting the stiffness and mass matrices using the SMAT and PRINT commands after the solution, the numerical values of the matrices will be exported without any information for the units.

Hope that helps!

 

[Jagog]

Hello Zoi Stavrothanasi, that answers my question. Thank you for the reply and clarification!