The Life-Controlling Particular Size in Initial Pit-Like Flaws Distributed on Pristine Silica Optical Fibers.

Abstract

Chemically assisted growth of pit-like flaws, as blunt stress concentrators, is expected to be a realistic model for predicting static fatigue of pristine silica optical fibers, the initial inert strength of which is very high. This study simulates the flaw evolutions under constant stresses using the Hillig-Charles model together with physically valid modifications on a lower limit in the flaw tip radius, where the evolutions of the equivalent semi-elliptical flaws are formulated adequately. When the initial inert strength of a pristine fiber and the ideal (ultimate) strength of silica glass are known, one can estimate the initial shape of the maximum stress concentrators, but not the size. We found from the simulations that the concentrator of the particular initial size, not the maximum size, controls the lifetime of the pristine fiber, where the maximum stress concentrators of different sizes may exit. Importance of curvature dependence of the surface chemical reaction is also noted in lifetime predictions of pristine silica fibers, which has been ignored in Bouten-With model.