FEA Versus Real Life

[rhetths]

FEA told me that my design was very weak.  I didn't think it was that weak, so i decided to look at a somewhat known and similar thing, an aluminium alloy square hitch vehicle recovery device.  It is marked with a Working Load Limit of 5000kgs, which should have at least some safety factor, hopefully at least two, and ideally at least three.  I am very new to this so there is a decent chance of errors in my file.  My simulation says that when loaded to the WLL the part "is expected to bend permanently or break under the current analysis criteria". 

[rhetths]

Somehow the wrong material crept in on me, so i have done an updated version with what i think is likely to be the correct material.  Fusion says the FOS is 0.8.

I decided to see what would be required to get Fusion to say it likes the design. and added 5mm to the outer circumference.  Somehow this lowered the FOS to 0.48.  Fusion reckons its weaker.  I am baffled.

Refer attachments.

[rhetths]

I have another update.

I was using the wrong material for the pin, it should always have been alloy steel.  When i made that change, the original design dropped to an FOS of 0.4.  Which is abysmal if valid.

I then worked towards my best improvement of the design so far.  Changing the pin material to alloy steel actually helped this model, thankfully, but i don't really know why.  I reduced the size of the hole that the pin fits into, which made a big difference.  I noticed that extra meat around the outside is a benefit to this scenario.  So i have got the FOS to 1.76.

[rhetths · Accepted solution]

Deleted, i worked out the answer to the question i had posed in this post.