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Homework Help: Mounting Bracket

  1. Apr 28, 2012 #1
    1. The problem statement, all variables and given/known data
    I have to create a design to mount a steel (yield=250MPa) weight 100kg and thickness of 15 mm to aluminum plate (Yield = 100MPa) with a tap hole of 15mm in vertical direction with 6 of M6 screws.

    2. Relevant equations
    σ (bearing load) =F/A
    τ (shear load) = F/A

    3. The attempt at a solution
    Assuming that the force came from the weight of the steel (1000N)
    I treated this problem as a rivet joint
    Bearing on bolt = 1000/(6*15*6) = 1.85 MPa
    Bearing on aluminum plate = 1000/(6*15*6) = 1.85MPa
    Shear on Bolt (on the thread) = 1000/(6*(phi*6^2)/4) = 0.59 MPa

    If you look at the calculation, the stress is 100 times smaller than the material properties of the aluminum and steel. This is a very big safety factor. Does that mean I can hang a weight of 100kg with just 1 screw of M1 and still have a safety factor more than 1?? I do not see this make sense. Please advise on how to approach this.

    Attached Files:

  2. jcsd
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