hexagon logo
Register Sign in
  • State Not Answered
  • Replies 5 replies
  • Subscribers 4 subscribers
  • Views 70 views
  • Users 0 members are here
Options
Related

How can extract the mass, stiffness and structural damping matrices from a .bdf file?

kenny.fernando.conto
Hi,
 
I need to extract the mass, stiffness and damping structural matrices from a .bdf files. Normally I just needed to add the following lines after BEGIN BULK in the .bdf file to get that:
 
"PARAM,EXTOUT,DMIGPCH"
"PARAM,COUPMASS,1"
 
Unfortunately when I'm trying to get that, Nastran is not able to create the .pch file where all information related to the matrices are stored.
 
So, How can I solve this problem? Is needed to add some addicional information inside to the .bdf file?
 
Thank you for your support
Parents
  • 0
    Hi Graff,
     
    I think that is not the problem because I've modified my model in order to use just one material and, even like this, the Nastran cant be able to extract the matrices. I really would like to open a custumer suppor case in order to send you the Apex models and their bdf files.
     
    By the other hand, there is one way to extract the matrices from Nastran but this is not a practical way which is described below:
     
    1.- The only way in which the bdf file can be read by the NASTRAN is: Firstly: I have to copy the first forty lines from an old bdf file (this BDF file corresponts to old model made in APEX, i.e. Template.bdf) and copy all of then into the new BDF file (i.e. MyNewModel.bdf). Second, the following lines must be written after the "BEGIN BULK" and run it in NASTRAN:
    "PARAM,EXTOUT,DMIGPCH"
    "PARAM,COUPMASS,1"
     
    2.- If the matrices are getting using step 1, a PCH file is created. Unfortunately, in the matrices that I obtained, it must be content the information about all nodes, instead of that, the nodes which form part of two different FE-elements are deleted from the matrices in th PCH file.  I don't know if I need to do something else or write another line in the bdf file in order to get the matrices where all nodes are included.
     
    I really hope that issue can be solved shortly.
     
    I'm attaching both the Template.bdf and the new bdf files
     
    Thank you for your help.
     
    Fernando Conto
     
     
     
     
     
    Attached Files (1)
Reply
  • 0
    Hi Graff,
     
    I think that is not the problem because I've modified my model in order to use just one material and, even like this, the Nastran cant be able to extract the matrices. I really would like to open a custumer suppor case in order to send you the Apex models and their bdf files.
     
    By the other hand, there is one way to extract the matrices from Nastran but this is not a practical way which is described below:
     
    1.- The only way in which the bdf file can be read by the NASTRAN is: Firstly: I have to copy the first forty lines from an old bdf file (this BDF file corresponts to old model made in APEX, i.e. Template.bdf) and copy all of then into the new BDF file (i.e. MyNewModel.bdf). Second, the following lines must be written after the "BEGIN BULK" and run it in NASTRAN:
    "PARAM,EXTOUT,DMIGPCH"
    "PARAM,COUPMASS,1"
     
    2.- If the matrices are getting using step 1, a PCH file is created. Unfortunately, in the matrices that I obtained, it must be content the information about all nodes, instead of that, the nodes which form part of two different FE-elements are deleted from the matrices in th PCH file.  I don't know if I need to do something else or write another line in the bdf file in order to get the matrices where all nodes are included.
     
    I really hope that issue can be solved shortly.
     
    I'm attaching both the Template.bdf and the new bdf files
     
    Thank you for your help.
     
    Fernando Conto
     
     
     
     
     
    Attached Files (1)
Children
No Data
© 2025 Hexagon AB and/or its subsidiaries. Privacy Policy | Cloud Services Agreement