A.A. Dyachenko - Ph.D. (Eng.), Senior Research Scientist, V.A. Kotelnikov-s Institute of Radio Engineering and Electronics of RAS. E-mail: arhip36@bk.ru O.E. Shushpanov - Dr.Sc. (Phys.-Math.), Professor, Chief Research Scientist, V.A. Kotelnikov-s Institute of Radio Engineering and Electronics of RAS. E-mail: oeshome@mail.ru

The new model of silica fibres failure is developed. The model is based on the exponential dependence of microcracks speed growth on tension loads. It is shown that speed growth of micro cracks in liquid water consists of three components: elementary speed caused by chemical interaction of bonds Si-O with water molecules, with OH- ions and ions. Thermodynamical magnitudes defining speed growth of the micro cracks are found. Speed growth of micro cracks in wet environment consists of one component determined by interaction of SiO bonds with water molecules. The equations for lifetime and dynamic strength of optical fibres giving the possibility for research of failure process under different temperatures, humidity and acidity of external medium are given. The processes influencing on the strength of fibres are exposed and analyzed. Phenomena of the surface microcracks healing by coating materials is investigated. It is shown that cracks can spread both in glass and in healing materials. Influence of process of glass dissolving in water as well as the degradation process of elasticity modulus of the healing materials on the optical fibres lifetime and their dynamic strength are taken into consideration. The calculated data of lifetime and dynamic strength of optical fibres are well agreed with the experimental data, received in a wide interval of tension load value and external space conditions.

 

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