III Международная студенческая научная конференция Студенческий научный форум - 2011

Because of the private nature of the experimental data on the effect of environment on the Construction of the general behavior of plastic materials for all the phenomenological description of fracture based on mechanical performances due to the difficulties and serious shortcomings. It is therefore necessary and molecular interpretation of macroscopic changes in the material. Thus, the phenomenological theory of temporal dependence as would provide a common framework, which must fit the theory of material behavior, and that put a detailed mechanical theory of change of macroscopic and microscopic properties of the polymer. This need arises in the interpretation of the parameters of the phenomenological equation, allowing you to identify not only the common features, as well as the difference between the materials:   1. Because of significant time effects for polymers the process of their destruction more difficult than traditional materials, the phenomenon of viscous and brittle fracture occur simultaneously. Fracture criterion in this case must take into account the achievement of the instantaneous and destructive values  at the time, and their dependence on the development of degradation of material properties.
2. From the analysis of a number of stress-strain curves, it follows that when the ambiguity of physical and mechanical characteristics in the process of corrosive media on polymers some of their characteristics do not change or vary monotonically. For example, for polyolefins yield stress elongation at yield point up to the brittle fracture remains practically unchanged, and the breaking stress and tensile elongation at break decrease, respectively, to yield strength and elongation at up to yield point. After this happens, the catastrophic decline in the strength of . Based on the above dm highly elastic materials can be selected as the characteristic parameter responsible for the performance of the polymer and sufficiently sensitive to the degradation of its properties, elongation at break, and as a stability criterion - Elongation at yield point. This choice can be linked with molecular changes, since the limiting mutual distance of the molecules, which corresponds to the mechanical characteristic  ℮р , attraction between them is weakened, there is a gap.
3. The degradation of physical and mechanical properties of the material over time the main influence of microstresses.
4. Degradation of material properties under the influence of stress and aggressive environment leads to a drop in voltage. Extrapolation of this dependence on the OS-stress gives conditional equilibrium voltage, which can be considered an equilibrium, relegated to the invariable initial state of the material, apply to it the thermodynamic relations.

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