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Yozo SAWAKI Shigeki SAKAGUCHI Yoshishige ABE Tadashi KAWASAKI
Slow crack propagation behavior in silica glass as a raw material for optical fibers is investigated in various environments based on fracture mechanics. Test results revealed that the critical stress intensity factors for stress corrosion cracking and unstable crack propagation in distilled water are estimaed as 0.37 and 0.89 MPam1/2 (1.2 and 2.9 kg/mm3/2), respectively. Based on these parameters, allowable critical load against crack size for spontaneous breakage of the fiber is discussed for 6-and 8-core cable units.