1304 Influence of Electron Beam Irradiation on Crack Nucleation for Glassy Ceramics
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Effects of electron beam irradiation on the fracture resistance of glassy ceramics were studied. EB-irradiation could not change the resistance to crack propagation, which was estimated by fracture toughness evaluated by means of standard indentation fracture method. On the other hand, EB irradiation increased the plastic deformation energy to generate the crack. In addition, if EB-irradiation formed dangling bonds in glassy network structure, they probably relax the residual stress and should prevent the crack generation. As the results of electron spin resonance spectra, the EB irradiation generates dangling bonds in these glasses, partial relaxation of residual strain mainly occurs around dangling bonds in the network structure. The increasing the generation energy of crack was therefore mainly due to the relaxation of the strong bonded metal -oxygen atomic pairs in network structure, as well as annihilation of crack origin.
