Subcritical Crack Growth in Silica Optical Fibers in Wide Range of Crack Velocities

Abstract

Crack growth in silica optical fibers was measured directly in a wide range of crack velocities d a/ d t (10 −13 < d a /d t < 10 −5 m/s) by improving our previous method. The slope in log‐log plots of the crack velocity versus the stress intensity factor data was revealed to increase with the crack velocity, e.g., slope, 23.3 for d a /d t < 10 −10 m/s, and 39.7 for d a /d t > 1(10 −8 m/s. The data were also found to be fitted well by the exponential law in the whole range of d a /d t , rather than the power law. Additionally, the fiber data were shown to be close to those reported for bulk silica specimens having large cracks for high crack velocities where the bulk specimens were tested.