Ask and thou shalt receive!
I am now in receipt of a genuine photograph of a genuine failure of a glass lens in a metal ring mount. It was in a laser cavity and failed (fractured) during high rep-rate operation. The engineer avers that “there may also [have been] some stress concentration in the mount such as a burr or particle” but he feels they solved the problem by replacing the clamping ring with a fillet of adhesive. Good show!
I pass this along to you because I know there have to be problems out there with ring-mounted glass lens assemblies. I was beginning to think no one was reading my correspondence (and that hurt my feelings!). Now that I feel better, I’ll stay out of your mailboxes for a while.
I also want to honor the engineer who sent this example in. Broken glass is not pretty and sometimes it takes courage to talk or write about it.