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Thread: Calculating Total Deflection for Constant Load

  1. #1
    Associate Engineer
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    Oct 2015
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    Calculating Total Deflection for Constant Load

    Hi All,

    Newbie here ... I am trying to find an equation to calculate what the total compressed distance would be for a sheet of silicone rubber under a constant load with a known surface area.

    I am not a ME, but am involved in a project where I need this type of info. Any help would be greatly appreciated!

    Thanks,

    Ed

  2. #2
    Associate Engineer
    Join Date
    Oct 2015
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    If you look for the easiest model I think Hooke's law can apply: ΔL = (L0 * F) / (S*E)
    ΔL--> deformation, strain
    L0--> sheet thickness
    F--> load
    S--> surface aera
    E--> Young's Modulus of your material
    This model is extremly simplified thought, more detailed researches are needed if you look for something serious.

    This is in the case where your material has the space freely deform itself (it's not "compression" but "deformation").

    If you material is completely blocked from all sides, then the force you apply will act as an Isostatic Compression, and in this situation there is actually compression of your material, and the law is different.
    The formula: ΔV = (ΔP*V0) / -K
    V --> Volume, P--> Pressure
    K --> Bulk modulus of your material

    Basically your silicon sheet will deform itself until it fills all the space avalaible and then it will compress itself.
    Last edited by Foudzing; 10-14-2015 at 04:25 AM.

  3. #3
    Associate Engineer
    Join Date
    Oct 2015
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    2
    Quote Originally Posted by Foudzing View Post
    If you look for the easiest model I think Hooke's law can apply: ΔL = (L0 * F) / (S*E)
    ΔL--> deformation, strain
    L0--> sheet thickness
    F--> load
    S--> surface aera
    E--> Young's Modulus of your material
    This model is extremly simplified thought, more detailed researches are needed if you look for something serious.

    This is in the case where your material has the space freely deform itself (it's not "compression" but "deformation").

    If you material is completely blocked from all sides, then the force you apply will act as an Isostatic Compression, and in this situation there is actually compression of your material, and the law is different.
    The formula: ΔV = (ΔP*V0) / -K
    V --> Volume, P--> Pressure
    K --> Bulk modulus of your material

    Basically your silicon sheet will deform itself until it fills all the space avalaible and then it will compress itself.
    Thanks Foudzing! This should help.

    Ed

  4. #4
    Associate Engineer
    Join Date
    Oct 2015
    Posts
    4
    You're welcome, oh and I forgot to tell you: if you exceed the maximum elasticity pressure, you'll go in plasticity deformation and your material will never go back to it's original state, so that can be a problem depending on what do you use this silicon sheet for.

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