Optomechanics – Fabricate Glass to Meet Proof Test Requirements

Colleagues:

Well, AEH has had another full year with no broken glass!

We do this by defining, for the glass fabricator, a proof test that his product must pass to meet the project’s service life requirements.

The strength of glass is knowable to the engineer if the glass suppliers will provide some simple fracture properties for their glasses:  the critical stress intensity factor and two or three points on the stress corrosion curve.  The glass suppliers tend to not publish these data.  So most of AEH’s successes are steering designs into using optical glasses for which the data have been published (or using that client’s proprietary data).  The balance of AEH’s successes have used larger factors of safety with conservative estimates of the glass’s fracture properties.

In either case, AEH feeds the service conditions (the thermal-structural dynamic stress profile and the initial surface crack size) into Jade with the appropriate fracture properties to analyze the service life of the glass product.  The independent variable is the initial surface crack size.  With the acceptable initial crack size determined AEH then designs a static proof test for the glass fabricator to demonstrate that the glass product will meet the required service conditions.  The glass fabricator may then design the fabrication process (grinding and polishing) to meet the proof test requirements.

There are some disappointed glass suppliers but it’s their choice whether (or not) to publish the fracture properties of their glasses.

Spring arrived right on time.

Joy.  And thanks, Jade!

When the safety of glass is at risk AEH has these tools too!

Al H.
3-28-18

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