Advanced Fastener Help

[hammerpe]

I am confused about the the fastener pre-load force. In reading through the help documentation it seems like this is the tensile load of the fastener due to torquing or some other form of bolt pre-load. Attached is a simple assembly that represents a more complicated model that I can't show. I wanted to double check that the fastener pre-load was working correctly so I offset the two components and used a constraint, rather than allowing the two parts to be clamped. I then applied a measure to this constraint so that I could double check that the screw pre-load forces were generating the proper reaction. I want the screw preload to be 900lb for each bolt thus generating a 1800lb reaction (there are two screws). However when I put in a 900lb pre-load the reaction is nowhere near the correct value. When I put in 9,000lbf it is close. Can anyone help me understand what is going on here?
2011-03-11_164053_plate.rar

 

[indigo2]

Here's a pretty good PDF that discuses preloading from PTC.
it might be a little dated, at WF2, but the concept should still apply.

-tsl


2011-03-11_165621_preload_in_fasteners.rar

 

[hammerpe]

Thanks, I used the information to get it to work!