Subcritical Crack Growth in a Phosphate Laser Glass

• Published in: Journal of the American Ceramic Society 1999-11, Vol.82 (11), p.3097-3104
• Main Authors: Crichton, Stephen N., Tomozawa, Minoru, Hayden, Joseph S., Suratwala, Tayyab I., Campbell, John H.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; Fundamental areas of phenomenology (including applications); Laser materials; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Optical materials; Optics; Physics
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1151-2916.1999.tb02208.x

The rate of subcritical crack growth in a metaphosphate Nd‐doped laser glass was measured using the double‐cleavage‐drilled compression (DCDC) method. The crack velocity is reported as a function of stress intensity at temperatures ranging from 296 to 573 K and in nitrogen with water vapor pressures ranging from 40 Pa (0.3 mmHg) to 4.7 × 104 Pa (355 mmHg). The measured crack velocities follow region I, II, and III behavior similar to that reported for silicate glasses. A chemical and mass‐transport‐limited reaction rate model explains the behavior of the data except at high temperatures and high water vapor pressures where crack tip blunting is observed. Blunting is characterized by an arrest in the crack growth followed by the inability to reinitiate slow crack growth at higher stresses. A dynamic crack tip blunting mechanism is proposed to explain the deviation from the reaction rate model.