Square Hole Pin Lift Analysis

[d3con]

Hello everyone,

I would like to verify a few calculations I was doing to estimate the safety factor with a lifting plate. The plate is essentially 5.5" wide x 0.5" thick x 30" long with a square hole (located 1.25" from the 5.5" wide face) that measures 3" wide, 2" long with 3/8" fillets. This plate is being used to carry 5000 lbs (carried by a 2.25" x 1" pin in the hole, the other end of this plate is part of a piece of equipment) and I would like to estimate the safety factor (60 ksi yield strength steel).

I did a quick simulation in solidworks and the plate appeared to be fine with a maximum stress of 19 ksi. When performing hand calculations, I could not find a stress concentration factor for a square hole and so I treated bottom most portion (5.5" x 1.25") as a beam fixed at both ends with a 5000 lbs distributed load. I then applied the resultant moments and shear force onto the two short vertical side members, if I add the axial stress with the bending stress that the inside face of the hole would experience, then it looks like the member will yield.

What would be the method of analysis (hand calculation wise) you guys would use to check its load capacity? Realistically I would expect this to be primarily a axial load issue, but I am wondering how to take into account the stress concentrations of the corners of the hole.

Thanks,

 

[Nereth1]

This seems fairly complex to me due to the stress raiser and the very 'solid chunk of steel' nature of the body with high bending stiffness etc as opposed to something like a series of beams (i.e. difficult to predict where strains will go)

Therefore, my initial instinct is FEA, but then I am not half as smart or as experienced as 80% of the people here so I will be watching this thread with bated breath to see if there is a good way to hand calc it (as I prefer hand calcs where they are viable)

 

[Sparweb]

It's been a few days without much of an answer.
I looked at your sketch, but apart from a rectangle inside a rectangle, I can't figure out the direction of loading, the means of loading the pin, whether the pin is round 2.25" by 1" long, or 1" round by 2.25" long, or maybe a rectangular bar 2.25" by 1". The pin must be able to drift around the opening all over the place. The other end of the plate (as "part of a piece of equipment") may not be relevant, but why keep it a secret so I can't figure out what this is for?

Maybe the loading from the pin is downward, and then the bottom edge of the plate is a "beam" with fixed ends as you suppose. If loading it "into" the page, then it gets more complex.

Your concern about stress concentrations comes from a concern (I believe) with cracking of the corners of the big hole. I think you should worry about fatigue only after you have a handle on the gross loading and stress in the part.


STF

 

[chicopee]

Your attachment s/b in pdf, jpeg or other recognized format. Your tinypic.com allow all sort of add-ons some of which appear malicious, so I did not open anything.

 

[tbuelna]

Like SparWeb I could not make sense of the description and sketch provided. From what I could tell it seems there is a 1" dia pin bearing against the .5" wide lower edge of a rectangular hole in the lift plate, which is subjected to 5000lb lift load. Based on the description provided in the OP of the lift plate material having a 60ksi YTS, it seems likely the surface bearing stress at the pin/plate contact would result in some permanent deformation in the plate, and possibly the pin, depending on its hardness.

 

[Nereth1]

I thought he was looking at tensile/shear failure of the rectangular piece of steel, as opposed to brinelling/plastic deformation of the bearing surface.