From tweagar@MIT.EDU Thu Jan 31 09:55:30 2013 Date: Thu, 31 Jan 2013 09:55:18 -0500 From: Thomas Eagar To: Rai Weiss Cc: Bellmare@MIT.EDU, leak_consultants , lloleak , giaime_j@ligo-la.caltech.edu, harryo@ligo-la.caltech.edu, Mike Zucker , worden_j@ligo-wa.caltech.edu, Rai Weiss , lazz@ligo.caltech.edu, reitze Subject: Preliminary on structural stability of Beamtube Rai, Attached is my promised report on the fracture mechanics of structural collapse. It turns out that my own back of the envelope calc using linear elastic fracture mechanics is valid when the crack gets to be one foot long, so the more elaborate R Curve analysis for non-linear ductile material is not required (but we did the estimate anyway and learned the crack was long enough that the simpler analysis is OK. That means you don't need to read the Structural Life Assessment Chapter on R Curves that I sent you, a few days ago. The bottom line is that structural collapse of the BEamtube will not occur untilwell after you have leaks that are unacceptable. We need to focus more on the remediation of existing cracks and how to prevent future cracks rather than a concern about structural collapse. Tom _=====_ ========== | | | | | | | | | | | | ========== MIT DMSE/ESD Thomas W. Eagar Professor of Materials Engineering and Engineering Systems Massachusetts Institute of Technology Building 4 Room 136 77 Massachusetts Avenue Cambridge, MA 02139 (Voice) 617-253-3229 (Fax) 617-252-1773 (E-mail)tweagar@mit.edu