DNV Pad Eye Contact stress Calculation explanation

[Cleaves]

Hello all,

I am looking at the DNV's Design of Padeye (Appendix D) and came across a formula for contact stress (Figure D-1 Padeye) and was wondering if someone could explain the formula to me please.

The formula states that:

Contact Stress = 23.7 x (SQRT(RSL/DH x t))

RSL being Resultant Sling Load
DH being Bolt hole diameter
t being thickness
and 23.7 is a constant

What I am getting confused about is the SQRT. Using this formula in MathCad the end units are not MPa but end up being kg^0.5 / m^0.5 x s

Have I missed something obvious.

Many Thanks

 

[Cleaves]

Attached is my result to the calculation:

 

[jbeckhou]

Hope this helps. it's out dated but should help.

Petrotrim Services, LLC

http://www.petrotrim.com

 

[bananapeople]

I believe this is a very simplified hertzian contact calculation. The 23.7 constant isn't just a constant, it is the product the safety factor of a couple of other things which have units and shouldn't vary as long as you are doing the calculation for steel, and you can give it units of MPa^1/2 to output the correct units in your calculation.

 

[Cleaves]

Many thanks for the replies people

calculator looks awesome!