engineering fundamentals Discussion Forum
Directory | Career | News | Standards | Industrial | SpecSearch®
Home Membership Magazines Forum Search Member Calculators






List Recent Topics | Start a New Topic

<< Previous Message No. 21264 Next >>
Author: deajohn5556
Time: 11/10/10 10:28 PST
This is a reply to message no. 21263 by battleship81
Reply | Original Message | New Topic | List Topics | List Messages on This Topic
Current Topic:
Window for pressurized chamber made from laminated glass?


it would take moree space than these boards can print to answer your questions, but let me try to summarize:

The window is mounted to the chamber.  To avoid high edge stresses under load and thermal soak, "potting" is genearlly an RTV (room temperature vulcanized) silicone, manufactured by GE (now done by Momentum ).   it is very soft and attenuates loads in thermal expansion and acts a a simple support boundary.

Th window material is purchased from a supplier who can do the finishing - generally drawing notes are used to specify finish of edges ( for example diamond cut, finish with 220 grit or finer, bevel edges, etc.).   Th efinish prevents severe edge defects where most flaws originate.  The  window surfaces also needs to be commercially polished with specified scratch-dig spec, like 80-10.


To size the window, we use structural analysis techniques.  In your case, for 0.75 inch thick, we get 1200 psi.  We comapre this to glass strength.  Glass is very strong with no flaws, like over 40,000 psi in tension, but small defects and moisture (or amines) will drastically reduce this.  Using fracture mechanics techniques, a strength of greater than 1250 psi is achieved in presence of moisture for 100  micron type flaws. (Most designere use 1000 psi allowable).  Proper finish ( and avoidance of scratching during cleaning) will keep flaws below 100 um( one can redaily detect 100 um flaws visually without magnification).

If the glass should fail, without lamination, it will break into only 2 pieces at that stress and not shatter.  If laminated, crack will not propagate through the lamination.    lamination will incraese thickness somewaht, depending on lamination thickness.

I would suggest a mechanical engineer be involved with design, drawing, and analysis.  The whole process is rather expensive, depending on your requirements.   I am not involved with procurement, only analysis.





[ List Replies to This Message Only ]

Home  Membership  About Us  Privacy  Disclaimer  Contact  Advertise

Copyright © 2018 eFunda, Inc.