Under the influence of a variety of combinations of microparticles in space, or a complex of these combinations, materials are formed that differ in the type of bonds, the order of adhesion of particles and properties. It is possible to change the steady-state combinations and ratios of particles or their complexes under the influence of temperature deviations, changes in the values ​​of external pressures or other external factors, which affects the stability of the equilibrium of the structure and numerical values ​​of the properties. At each deviation that has arisen in the structure of the material, mechanical properties are the most rapid change. However, it is not easy to establish and, moreover, express in a concrete or abstractly logical form the nature of the established relationship between structure and properties. Different characteristics of the micro- and macrostructures of materials can correspond to the same property index, for example, to the strength limit, and different strength or other properties can correspond to the same structural index (Figure 3.5). It should be noted that the test results for the so-called "peers" the conditions of the experiment differ significantly. To establish the direct or reverse interdependence (correlation) between qualitative and structural indicators, it is necessary to compare them not with equal to & quot ;, but under the appropriate conditions, when the structures are optimal, and the materials (ICS) become similar to each other.

Fig. 3.5. The graph of the relationship between the structural and qualitative characteristics of materials (line A, B characterizes the decrease in the strength of concrete with increasing porosity.) The line CD characterizes the decrease in the strength of the stone with increasing its porosity. equal to porosity The strength of concrete may be higher than the strength of the stone and that for an equal strength R the porosity of the stone is less than that of concrete)

Fig. 3.6. The general character of the forces P and of the interaction energy U a) and the resulting force (o):

1 - the forces of attraction increase with decreasing distance r

2 - the repulsive forces rapidly increase with decreasing r, 3 - the resultant force. For r = r0, the force P - 0, and the interaction energy (A-mmn

In optimal structures, the particles are not only uniformly distributed in the bulk of the material, especially at the microlevel in the crystal lattices, but also at distances at which the attractive and repulsive forces are equal, and the magnitude of their resultant is zero, which is characteristic of the equilibrium state of the atoms in the lattice. Energy takes a minimal value (Figure 3.6), as a result of which the system (material) has a relatively stable equilibrium state, positively affecting the stability of property indicators. The latter assumes extreme values ​​for optimal structures. It should, however, be taken into account that the equilibrium state can be not only stable, like the state of particles in a crystal, but also unstable, as, for example, the state of particles in crystallites and gels. In solids, the stay of particles in an unstable equilibrium can last indefinitely.

The nature of the optimal structure depends on the composition and technology of the conglomerate. In natural conditions, it is associated with genetic processes, the regular course of which is often violated by spontaneous factors. With the change in technological or genetic conditions, the structure is optimized for other ratios of components, the new material composition of the conglomerate.

Building materials with the optimal structure inherent in certain patterns in the formation and preservation of structure-sensitive properties. These laws are referred to as the laws of optimal structures. It is known that by law is meant an essential, stable, necessary (that is, nonrandom) connection and mutual conditioning of phenomena and processes. The laws of optimal structures express the internal connection and interdependence of the properties and structural parameters of the material. They apply to heterogeneous in composition and manufacturing techniques

The materials and, like many other laws, have an objective character. The latter indicates that in a similar expression they also exist in nature. Man seeks to know them in nature and use them in his practical activities.

thematic pictures

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