**Hard question** - Generating weights for MPC equations

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hi everybody,

 

I am currently finishing a program, which is creating MPC equations joining selected independent nodes to a dependent (master node).

 

A typical code to create an MPC is the following, as given on Altair knowledge base (values here are for example sake):

    

*createmark nodes 1 101-103

*createarray 3 13 13 13

*createdoublearray 18 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23 1.23

*equationcreate 1 1 3 1 18 100 5 1.23 5.0

 

THE PROBLEM:

 

I will have hundreds of nodes to link together and to assign different weights to each of them. Parameters like distance to master node, location on the model.. will play a role.

But the best way to code this, is to actually understand how built-in MPC equations creation commands in HyperMesh work, in order to understand the parameters used and deduce an empirical formula.

 

As an example, we generated MPCs on a model by using BCTABLE command (we work with the Nastran solver) which works well for MPC creation (by comparing theoretical results) and here is what we obtained.. I isolated a case to give clarity:

 

*** Please see the images link to this post ***

 

In this situation: Master Node = 1463805 and slave nodes are the 4 others. I give the .bdf file giving the results and weights attributed to each nodes (starts at line 8111 and finish 8116 as shown on the image), and would to know if someone knows about the mathematical relations that are used to generate these values?

 

Thanks very much in advance,

 

Nicolas

 

<?xml version="1.0" encoding="UTF-8"?>BDF weights.jpg

<?xml version="1.0" encoding="UTF-8"?>Situation.jpg

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Answers

  • tinh
    tinh Altair Community Member
    edited September 2017

    I saw hm also calculates wf when creating fe connectors. But i don't know how to do.

    You should use connector panel to create rbe3.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited September 2017

    Tinh, would you have any idea to where to find these equations that are used? They must be stored somewhere no?

     

    Connector panel? Could you please elaborate?

     

    Thanks very much

  • tinh
    tinh Altair Community Member
    edited September 2017

    Connector panel creates rbe3, not mpc

    Anyway rbe3 is a combination of MPCs

    You should use rbe3

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