THEORETICAL CALCULATIONS OF DURABILITY AND THE RESTRICTIONS...

THEORETICAL CALCULATIONS OF DURABILITY AND THE RESTRICTIONS ADOPTED IN THEM

According to the law of congruence, between binding agent and conglomerate on its basis, there is an obligatory correspondence of properties with optimal structures. Providing the conditions under which the necessary longevity of the binding agent of the optimal structure is created, largely predetermines the task of ensuring the durability of the conglomerate itself. And although the presence of other structural elements (aggregate, contact zone, pores, etc.) in ICS, makes its own corrections, sometimes significant, in durability, yet these adjustments do not fundamentally change the nature of the basic relationship between the longevity of ICS and its knitting component for optimal structures. For building conglomerates, this relationship can be expressed by the formula:

where тт.о - durability of a conglomerate of the optimal structure, determined at a temperature Т and voltage о; t * That - the durability of the astringent of the optimal structure under the same conditions for its determination as conglomerates; x is the ratio of the phase relations in the astringent ICA substance and in the astringent substance of the optimal structure, i.e. (c/φ)/(c7f); n is a complex exponent that reflects the nonlinearity of the dependence of durability on the phase relationship of the binder in the conglomerate and is caused by the variety and characteristic of the aggregate, and in the absence of it, the size of the phase interface; as a rule, the exponent n is a positive quantity and, consequently, m

The durability of the binding substance m * as a microdispersed matrix part of a conglomerate can be expressed in the section of the curve 3 (Figure 4.1) by the formula adopted in the kinetic theory of strength and developed in the works of SN. Zhurkov:

where that is the kinetic constant characterizing the material; y - structural coefficient (kJ/mol-MPa); c t is the design stress at a temperature of g, MPa; k is the Boltzmann constant, as the ratio of the universal constant to Avogadro's number: k = R/Na] T is the absolute temperature on the K scale; then, wo, y are constant values, depending on the nature and structure of the material.

The numerator of the exponential u - y Ct has the energy dimension and is called the activation energy of the destruction process, denoted by and. Therefore, we can write:

or quite often the formula (4.3) is written in the form:

The durability formulas (4.5) and (4.6) take into account the action of only mechanical stresses - from the moment of loading to the moment of material rupture, but do not take into account the effects of the aggressive environment. They also do not take into account the possible hardening and stabilization of the structure during the operational period, so they remain insufficiently complete.

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