Calculating Minimum Diameter for Steel Pin w/ Partial Uniform Load

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Discussion Overview

The discussion revolves around calculating the minimum diameter for a cold rolled steel pin subjected to a partial uniform load of 25,000 lbs, with a factor of safety of 2. The context includes considerations of the pin's placement between two welded plates and the implications of varying thicknesses in the clevis design.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses uncertainty about the equations for partial uniform loading on a pin and seeks to determine the minimum diameter needed.
  • Another participant suggests a paper on double shear analysis as a potential resource for understanding the problem.
  • A participant notes the challenge of assessing stress changes due to different thicknesses in the clevis and considers using the lesser thickness for calculations.
  • There is a suggestion that running a finite element analysis (FEA) model may not be feasible for the specific geometry involved.
  • One participant proposes simplifying assumptions for modeling, suggesting a beam bending model of the pin as a worst-case scenario.
  • Another participant emphasizes the importance of calculating Von Mises stress to account for combined shear and tensile/compressive stresses.
  • A request for a 3D model or a hand-drawn view of the system is made to better understand the design.
  • Concerns are raised about the strength of the design, particularly regarding the bracket holding the pin and the potential limiting factor of the 1/4" plate.
  • One participant recommends checking for tear out shear on the plate section as a critical aspect of the design evaluation.

Areas of Agreement / Disagreement

Participants express various concerns and suggestions regarding the design and analysis of the pin, but no consensus is reached on the best approach or solution. Multiple competing views and uncertainties remain regarding the modeling and evaluation of stresses.

Contextual Notes

Participants acknowledge the complexity of the scenario due to the gap between the clevis components and the asymmetry in thickness, which complicates finding an analytical solution.

roldy
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I'm a bit rusty on partial uniform loading on a pin. I want to find the minimum diameter a cold rolled steel pin has to be using a factor of safety of 2 with a loading of 25000 lbs. The pin in the picture is welded between two plates (the right plate bends in and is welded to the left plate below the pin) . These plates are welded to a box (another pin is located on the opposite side of the box). A hook grabs onto this pin. I've tried finding equations regarding partial uniform loading. The equations I've turned up show the center piece the same width as the gap.
 

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I think this paper may provide some insight for you, it is an analysis of a pin in double shear: http://www.ewp.rpi.edu/hartford/~kw...es/Edward Kwon - Preliminary Final Report.pdf

upload_2016-7-27_10-36-31.png
 
Thanks for the paper. However, this does not show how the stress changes if the clevis has two different thicknesses. I guess I could take the worst case scenario and use the lesser of the two thicknesses for my t1.
 
Based on the posts so far I'm guessing that running an FEA model for your specific geometry is not an option?
 
You are correct. I was hoping that I could come up with an equation for this type of scenario.
 
Your scenario is challenging to find an analytical solution for because there is a gap between the inner and outer clevis which will cause a bending load on the pin, and the outer clevis's plates are asymmetric in thickness.

Have you considered making some assumptions to simplify your modeling task? I think you could consider a beam bending model of just the pin with a simply-supported beam. This would be a "worst-case" analysis because the pin would not be stiffened by the clevis in this case. Otherwise, FEA really may be your best option.
 
Yes I've considered beam analysis and I am currently working on this.
 
Make sure to calculate the Von Mises stress to combine shear and tensile/compressive stresses for your analysis.
 
Do you have a 3D model of the same? Its hard to properly understand the system...
A hand drawn 3D view would also suffice.
 
  • #10
A lifting hook goes around the pin.
 

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  • #11
Looks like a questionable strength design to me. How are you evaluating the strength of the bracket holding the pin?
 
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  • #12
I would agree with Mech_Engineer, I think you'll find that the 1/4" plate will be a limiting factor in this design.

Maybe you haven't got there yet, but I think you should check tear out shear on that plate section.
 

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