SCALE factor in FATLOAD keycard

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

What does the 'SCALE' value mean in 'FATLOAD' keyword?
After referring to some online manual, it was mentioned to maintain a scale factor of 5. It is mentioned in the same manual that certain fatigue load should be applied and that same load has been applied in LOADCOL and the additional scale factor of 5 in FATLOAD. We aren't sure if they are applying 5 times the load mentioned.
Also, what exactly is LDM in the FATLOAD keycard?

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Answers

  • Rahul_P1
    Rahul_P1
    Altair Employee
    edited December 2014

    LDM is used as a scale factor to normalize the finite element stresses/strains to obtain the stress/strain distribution due to a unit loading.

     

    see image - Below formula shows how LDM, Scale, Offset work together in scaling FEA stress tensor at time point t:

     

    <?xml version="1.0" encoding="UTF-8"?>post-4438-0-87726400-1418365480_thumb.jp

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited January 2015

    but scale apply to which load, time or total interval

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

    but scale apply to which load, time or total interval

     

    Hi, thank you for pasting the equation. But I still feel confused. What this scale factor used for? To scale up/down the statics stress value?  What's the benefit of doing it? I don't get it. 

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited July 2017

    Hi @Vin566

     

    It is used to scale the load on your Time Vs load history curve and scale factor is ignored during transient based fatigue analysis. 

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

    Hi @Vin566

     

    It is used to scale the load on your Time Vs load history curve and scale factor is ignored during transient based fatigue analysis. 

     

    I still cannot understand it quite well. For example, if I put scale factor equal to 10, I know the load has been scaled up 10 times, and the fatigue life will decrease a lot. But what benefit I can obtain from the new results? In my understanding, scaling means the difference between the simulation and real product become large? So I don't know what's the advantage of using it?

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

     

    I still cannot understand it quite well. For example, if I put scale factor equal to 10, I know the load has been scaled up 10 times, and the fatigue life will decrease a lot. But what benefit I can obtain from the new results? In my understanding, scaling means the difference between the simulation and real product become large? So I don't know what's the advantage of using it?

    Maybe can be used as a FoS...?!! Instead of editing entire load data just giving a scale factor will work, 

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