Bending Moment

[sullivnc]

Hi everyone,

Wasn't really sure where to post this. I have a problem I'm having trouble wrapping my head around. I have a piece of glass that is clamped around the entire outer edge. The frame is then secured down to a surface. The glass is circular with a flat (OD of 7.95", 281 deg 18'30" arc with a flat 5.04" long). It is flat, 0.197" thick. The frame has a circular OD, with a bolt pattern OD of 8.375". There are several variables I am looking at. Two different tightening patterns (going around the pattern vs. across), different torques (the correct torque of 9 in*lbs vs an over-torque of 15 in*lbs), and a raised fastener pressing up on the bottom of the frame. The fastener is 1/16" raised and at -22.5 deg on the bolt pattern. Basically, to start with, I want to look at modeling the bending stress created by these different conditions. Can anyone give me a good starting point? Thanks for any help.

 

[sullivnc]

Glass99, thank you, this is the type of informstion I've been after. Just got home for the weekend, but I'll start with this on Monday!

 

[glass99]

There are a hundred things which will break the glass. Among the most likely in a such a situation are:
- glass to metal contact
- tensioning bolts through laminated glass. The interlayer will squish and give a local stress concentration.
- holes in non-tempered glass
- stress concentrations at re-entrant corners
- movement of the substrate
- edge damage
- thermal stress
- adhesive shrinkage
- impact (obviously!)