Mounting Bracket

by HaveVun
Tags: bearing load, bolted joint, bracket, screw size, shear load
HaveVun is offline
Apr29-12, 12:33 AM
P: 2
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.

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.
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