Force Output from enforced Displacement

Timo Ksr
Timo Ksr Altair Community Member
edited October 2020 in Community Q&A

Hi, 

 

I ran a model with enforced displacement with SPCD, as explained here: 

https://altairuniversity.com/learning-library/how-to-apply-enforced-displacements-correctly/

 

Then I requested the force as ouput via Global Output Request --> SPCF

The model was just a regular beam and from beam theory the cumulative sum of the force should be around 824.99 N.

 

In my .out file the force is extremely low and I cannot find the mistake?

 

The model is in tons, mm, second, so the output should be Newtons. 

 

Thanks for your help everyone. 

 

 

<?xml version="1.0" encoding="UTF-8"?>image.png

<?xml version="1.0" encoding="UTF-8"?>image.png

Unable to find an attachment - read this blog

Tagged:

Answers

  • KemalDemir
    KemalDemir Altair Community Member
    edited September 2020

    Can you share please hand. calc. method ? Because you're using enforced disp. I mean your define directly deflect quantity. You have to go backwards and find the strength. Am I wrong ?

  • Adriano_Koga
    Adriano_Koga
    Altair Employee
    edited September 2020

    in the .out file you will find only the summation of the SPCF and as you don't have a 'load' it will be zero.

     

    Request SPCF in H3D and OPTI formats, and you will be able to check the values in each node.

    It would be easier to check if you use a RBE2 for apllying the enforced displacement, and then get a single SPCD reaction value to compare with your expected value.

  • Timo Ksr
    Timo Ksr Altair Community Member
    edited September 2020

    Hi, 

    I get better results in a .spcf file now. Thank you. 

     

    However, the sum must be close to zero, when only applying an displacement? 

     

    For another model, this are the results. I guess the first line is my Loadmatrix at the node? The sum does noe come to zero, is that an indicator for any mistake?

    image.png.10a13b78c7ab73e799d0dc907c1153a3.png

     

     

    @KemalDemir I used Bernoulli Beam theory for one fixed end and one free end:   6*E*I*w(x) = F*x^2*(3L-x)

  • tinh
    tinh Altair Community Member
    edited September 2020

    SPCF are reaction forces, why do you think sum of them is zero?

  • tinh
    tinh Altair Community Member
    edited September 2020

    Enforced dislpacement equivalences to a set of apply forces NOT only at enforced nodes.

    Check .out file for force equilibrium.

  • Timo Ksr
    Timo Ksr Altair Community Member
    edited September 2020

    Now I got it! Thanks