BOLT or PIN Bending 1

[tmschrader]

Any body have a good REf/Web site on the above. Roarke?


The thickness of the plate can easily make bending predominant over shear and testing proves this.

The evenly distributed load method is OK for conservative design, but failure testing of davit prototypes I've been working with show this method to be overly conservative on some of the 1/2" pins by about a factor of 2?. PL/10=M seems to be close.

Do You have to use the elastic supported beam bending methods?

One of the searches brought up a possible web site on fasteners which I will download tonight.euler9.tripod.com (45min req)

 

[RHK]

I suggest you find a copy of these two papers

F.P. Cozzone, M.A. Melcon, F.M. Hoblit, "Analysis of Lugs and Shear Pins made of Aluminium or Steel Alloys", Product Engineering, May, 1950 pp.113-117

M.A. Melcon, F.M. Hoblit, "Developments in the Analysis of Lugs and Shear Pins", Product Engineering, June, 1953, pp.160-170.

If you cannot get hold of these papers refer to an Aircraft Design Text, such as Bruhn or Niu.

Little has changed in the design and analysis of pins since then. If you distribute the pressure from the load over a width equivalent to the plastic pressure capacity of the lug, the moment arms in the pin are as short as possible and the moments are lower. Usually, this results in the bending and shear capacities being similar.

Russell Keays

 

[PriamEngineering]

Look at 'An introduction to the design and behaviour of bolted joints' By J Bickford.

I use a combination of FEA and VDI 2230 to design joints. I don't know of a better wat to determine joint flexural stiffness but I'm all ears if you have any suggestions. I used to assume a linear load distribution but some testing on a particular joint put me off this.

 

[tmschrader]

Thank You for responging to my posting.

I spent some time trying to search for the ref's suggested, but will need to spend more time to find them. The NASA tech I downloaded did not get into bending of pins.

I guess in alot of bolt applications (but not always) the bolt is a least as thick as the shear plates, so bending may not govern. In single shear bolt bending seems to always govern. I am surprised that more attention is not given to this topic in the STD texts. Is the attitude "so what", the bolt bends untill the load is distributed closer to the shear planes in a more triangular load distribution minimizing the the moment arms and bending stresses?
The Engineering handbook and Structural calculation guide (for the AISC) I have say to use the evenly distibuted load load across the pins, but this is way to conservative and vary rarely addressed when dealing with bolts.

The FEA seems like a interesting but sometimes time consuming way to go. Most of the simple FEA's (LISA and the cheap ALgor) dont match the displacements across the contact surfaces between the pins and plates to give accurate results, but you can do this with a few iterations. I did this using the FEA program in autocad mech 6 and it does match the testing within 10 to 15% and does not take too long to do. You have to calculate the equivelent rectangular c/s to the circular sect as its only a 2D program with thickness input for the Z only.