Several of the readers here helped me with this story. Thank you! http://www.amerisurv.com/PDF/TheAmericanSurveyor_Penry-Invar_Vol9No10.pdf
Superb article, well written. I did not see any mention of the "lore" or "rumor" that Invar "jumps" unpredictably sometimes and sometimes not. Did you ever run across such rumors? I think I might have read something to that effect with regard to Invar wires used to check structural deformation in Swiss & German Alpine dams.
I was under the impression that such is the reason why USC&GS/NGS wants or used to want Invar rods re-calibrated every so many years or so.
I have heard about the “jump” phenomena before, and it seems like I read somewhere that it “might” be due to molecular instability inherent in the alloy. But then again, I have found that I remember far too much that isn't so these days.
Oh, and...Nice article Jerry!
Loyal
Did you read anywhere about a phenomena where invar tapes suddenly changed length? I have read something like that in either a C&GS or Army manual or readily available sourse. I think it was related to temperature exposure or perhaps being pulled to hard to material changes and the tape is then useless.
The source cautioned frequent checks so it must not have been that rare. The tests you mentioned surprised me that seemed to never have had an anomoly? Perhaps it is folklore. It would probably take me a while to find the reference, but a google search does reveal something called 'invar shock'.
- jlw
"invar shock" is when you see the pricetag....:-P
I really enjoyed it. I knew a little about invar being used in surveying for chains, level rods and subtense bars, but never really thought much about its application in other areas such as machining. I really enjoy these types of articles. Keep up the good work.
Jerry
That was absolutely excellent and I enjoyed reading it thoroughly. Well done sir!