calculating force from strain

Discussion in 'General Electronics Chat' started by Vindhyachal Takniki, Nov 5, 2014.

  1. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
    349
    6
    Is it right way to calculate force from known strain & young modulus :

    1. E = stress / strain
    from where stress is calculated

    2. Then stress = Force/area
    From here force can be calculated

    3. How to convert this force (in newton) into Kg.
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    1) Correct, but be clear here whether mean shear stress or direct stress and do not mix them up.
    Strain for electrical engineers is usually measured in millistrain units.

    2) Correct, but again make sure you have the correct area.

    3) You can't convert N into kg, since the first is a measure of force and the other a measure of mass.
    This is a unit of force the kg-force which you obtain by dividing Newtons by g, but you should not be using this as is is non standard.
     
    Last edited: Nov 6, 2014
  3. Vindhyachal Takniki

    Thread Starter Member

    Nov 3, 2014
    349
    6
    1. I have square metal plate of .15m.
    2. I was looking at formula , let say how much Kg-force for 1 microstrain
    3. material is glass fibre. From below link young modulus of glass fibre is 17Gpa
    http://www.engineeringtoolbox.com/young-modulus-d_417.html


    Stress = E x strain = 17 * 10^9 * 1 * 10^-6 = 17000
    Force = Stress * area = 17000 * .15 * .15 = 382.5

    So kg-force = 382.5 / 9.8 = 39.03


    1. One microstrain produces 39.03Kg force. Such small strain with such high Kg-f Is there any mistake in calculation I am doing?
    2. My material is glass fibre. Or I have selected wrong young modulus??
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    You took note of my comment 3, but do not seem to have bothered with 1 and 2.

    I think you have the wrong area and have mixed up shear and direct force.
    What about the plate thickness?

    Can you not draw a diagram?
     
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