drawoh
Mechanical
- Oct 1, 2002
- 8,959
I am being challenged on the strength of an airborne structure I have designed.
I have some plates connected at the edges with tapped holes, helicoil thread inserts and structural screws. I am being told that these are fairly weak against loads normal to the plate. I am now trying to analyse this. The attached sketch shows the loading, only.
I started by assuming that the stresses would be similar to those of a bolt lug as per E.F.Bruhn, section D1.10, as shown on the sketch. Now I am trying to model this with SolidWorks Simulation. I tried Bruhn's mounting lug just for the heck of it, and I got stresses similar to the hand calculations. I can do something similar to this on the blind tapped holes, but I am not confident of this.
My latest model is a straight ID representing the OD of the thread insert. I have a fairly small, tapered contact area on one side of the hole, representing a fairly loose screw, tilted, and loaded in shear. A screw tightened down hard creating a friction contact would make things much easier, but this is not how things are analysed.
Does anybody aware of literature, or practical experience on this? I would like to get some real numbers to back up my FEA.
--
JHG
I have some plates connected at the edges with tapped holes, helicoil thread inserts and structural screws. I am being told that these are fairly weak against loads normal to the plate. I am now trying to analyse this. The attached sketch shows the loading, only.
I started by assuming that the stresses would be similar to those of a bolt lug as per E.F.Bruhn, section D1.10, as shown on the sketch. Now I am trying to model this with SolidWorks Simulation. I tried Bruhn's mounting lug just for the heck of it, and I got stresses similar to the hand calculations. I can do something similar to this on the blind tapped holes, but I am not confident of this.
My latest model is a straight ID representing the OD of the thread insert. I have a fairly small, tapered contact area on one side of the hole, representing a fairly loose screw, tilted, and loaded in shear. A screw tightened down hard creating a friction contact would make things much easier, but this is not how things are analysed.
Does anybody aware of literature, or practical experience on this? I would like to get some real numbers to back up my FEA.
--
JHG
