STANFORD UNIVERSITY OFFICE MEMORANDUM STANFORD UNIVERSITY OFFICE MEMORANDUM
DATE. September 25, 1972
To : Dr. Andreja Puharich
From : W. A. Tiller
SUBJECT : Metallographic Analysis of Gold Wedding Ring Cracked by U.G.
This work was carried out by Dr. Anton West, a young colleague who is an expert in the area of fracture of materials. This memo outlines his preliminary results. The enclosed photographs include (a) SEM (scanning electron microscope) pictures of the fracture surface showing the failure mode and (b) micrographs of a polished cross section taken within 1/8″ of the fracture. The sections of the ring and the plastic mount are also included. Attempts made to replicate this type of fracture in conventional ways were unsuccessful.
The SEM pictures show two distinct regions exhibiting different modes of failure. The O.D. is relatively flat and devoid of the expected dimple rupture whereas the interior (labeled MID and ID regions) shows the classic ductile mode of dimpled rupture. The primary mode of failure is one of overload as indicated by the dimple rupture and this is due to ductile void growth and coalescence (under the action of tensile stresses).
Fracture near the O.D. is atypical of what one would expect in a gold alloy. One would expect to see shear dimples instead of the flaky sort of fracture observed. This is the type of thing one sometimes sees in stress corrosion cracking with certain types of ions present; however, the normal ring environment could not be described as being of that sort.
The adjacent microstructure is non-uniform and revealed some signs of cracking but, on the whole, sheds little light on why the ring failed. These microcracks (if they truly are such) don’t appear to be associated with the fracture.
William A. Tiller
WAT/mp
Encls.


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