SPCF-Problem

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

Hey,

 

I try to simulate a large displacement movement and have a problem. I got two simulations and want to evaluate the SPC-Forces, which are completely different, although the model is the same. The constraint is placed in the middle of the green component and connected to it, with rigids (see Figure). In the first simulation, the total displacement of the green component is 350mm (due to constraint) in x-direction. In the second simulation the total displacement is 50mm. When I evaluate the force-displacement plots and compare them, the results are completely different, which makes no sense. For example, in the first model the force at 50mm displacement is 6,7e+05 N. But for the second model, the force at 50mm is only 8,19e+04 N. But they should be totally the same to my opinion.

 

Somebody any hints?

 

 

<?xml version="1.0" encoding="UTF-8"?>disp_350mm.thumb.JPG.76e2c9b3937833843a3dd188e76d20e1.JPG

 

<?xml version="1.0" encoding="UTF-8"?>disp_50mm.JPG

 

Greets

Elvis

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2017

    I did a simulation with a displacement of 100m also and compared the graphs in one plot. As you can see, the graph history is almost the same, but with different values. Why is the SPC-Force dependent to the total displacement? Does that make sense? 

     

     

     

    compare.jpg.e6605a62312489eeeff4f44efe093b01.jpg

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2017

    Hi Elvis,

     

    I think the way SPCF is calculated is dependent on stiffness and enforced value and SPCF is directly proportional to both. This is why you are seeing such a change in results,

     

    Anyways, I am going to dig a bit deeper into theory to confirm this and I will also check with expert before I come back to you with a proper explanation. 

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2017
    Altair Forum User said:

    Hi Elvis,

     

    I think the way SPCF is calculated is dependent on stiffness and enforced value and SPCF is directly proportional to both. This is why you are seeing such a change in results,

     

    Anyways, I am going to dig a bit deeper into theory to confirm this and I will also check with expect before I come back to you with a proper explanation. 

     

    Hi Prakash,

     

    ok thanks. I am looking forward to your information.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited October 2017

    Hi Elvis,

    guess the problem is solved with the modifications we proposed, isn't it?

    Main issue was the incomplete contact surf,  but also the load application which is much smoother now (NINC in NLPARM, DTMAX in NLADAPT).

    Best regards, Christian

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