ways of creation of heterogeneity

Use of non-uniform designs in practice at present develops quickly enough as non-uniform materials can bear in themselves set of useful properties for designs which work in a various application conditions.

In mechanics of non-uniform designs there is a following grading of the basic types neodnorodnostej: continuous, kusochno-homogeneous, stochastic [15, 45, 62, 70, 82]. Each of the resulted types neodnorodnostej grows out of impact of various factors which can be both indirect, and straight lines (hardening). More often to indirect factors in which result structural materials get structural heterogeneity, applied manufacturing techniques of designs which can influence in the various image structure of applied materials creating in them heterogeneity concern, also operational impacts concern such factors such as radiating irradiations, electromagnetic fields, the various combined himiko-thermal impacts, is high gradientnye temperature fields, such sort of heterogeneity name induced [82]. Such processing method which hardening is called concerns straight methods of creation of structural heterogeneity of structural materials. Hardening is an increase of resistance of workpiece, a component part, a design to destruction or deformation. The modern technology possesses a large quantity of methods of hardening of structural materials. At present in industrial practice distinguish two principal views of hardening of structural materials, namely volume hardening which provides creation of non-uniform structure with smoothly changing physicomechanical characteristics on all volume of a material of a design and, accordingly, a surface hardening, at
Which in a surface layer of a material of a design non-uniform layers with smoothly changing structure and characteristics are created.

Creation of volume heterogeneity in structural materials is applied as a rule seldom and carried out basically by methods of thermal processing [93, 94, 31, 88], ways of impact by various physical fields [15, 25, 40, 45, 48, 59, 70, 91] are in rare instances applied. The Most perspective and demanded way of creation of heterogeneity of a structural material is the surface hardening, and it is connected by that the majority of building designs, component parts of cars, cases of devices and other means work in conditions at which operational impacts in the form of an excited environment, chemical reagents, heating, pressure and the other combined impacts, have basically on material surface layers. Also creation of superficial heterogeneity of structural materials allows to improve substantially physicomechanical characteristics of surface layers of a material of a design [18, 32, 58].

According to the grading accepted in the modern domestic literature, exists two basic ways of creation of superficial heterogeneity of a structural material, namely updating of a condition of a surface layer and drawing of coatings. Heterogeneity creation in surface layers of a structural material by their updating represents process of increase in defects of a crystal structure of a material (the vacancy, the introduced atoms, defects of packing and other). The way of updating of surface layers of a material of a design is the most actual as with its help it is possible to raise substantially prochnostnye characteristics of a surface layer of a material of a design, having provided thus smoothness of a stress distribution in a design.

At present in industrial practice there is enough considerable quantity of methods of hardening of surface layers of a material by their updating and all these methods can be divided into four cores

Categories: a strain ageing, chemical (diffuzionnoe) hardening, thermal hardening and hardening by physical fields. Strain ageing methods concern: the superficial plastic

Warping and repeated mehaniko-thermal processing (naklep). Methods of thermal hardening and hardening by physical fields comprise processing of surface layers of a material by fields of the various nature and intensity (it is high gradientnoe a temperature field, a radiating irradiation and other). The Most volume category by quantity of methods of hardening of surface layers of a material is chemical (diffuzionnoe) hardening. The category of chemical hardening is subdivided into three classes: diffuzionnoe saturation by nonmetals, diffuzionnoe saturation by metals, multicomponent saturation by metals and nonmetals. In turn diffuzionnoe saturation by nonmetals is subdivided on single-component diffuzionnoe saturation by nonmetals (cementation, nitriding, borirovanie, silitsirovanie) and multicomponent saturation by nonmetals (carbon nitriding, nitrocementation, tsianirovanie, sulfoazotirovanie, sulfotsianirovanie); diffuzionnoe saturation by metals is subdivided also into single-component saturation by metals (alitirovanie, a chromating, tsinkovanie, titanirovanie, berillizatsija, saturation by other metals) and multicomponent saturation by metals (alitirovanie together with other metals (Cr, Ti, Zn, V), a chromating together with other metals (Al, Ti, Zn, V)).

The abundance of technological methods of hardening of surface layers of structural materials allows to project non-uniform designs practically for any application conditions, however and an estimation of their is intense-deformed condition use of traditional methods of mechanics of a deformable solid body is already not enough for calculation of such designs. The important achievement in that case is refusal of a hypothesis of uniformity and acceptance in attention of that mechanical
Characteristics of a material of a design can essentially change along spatial co-ordinates.


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A source: MISHCHENKO Roman Viktorovich. CALCULATION of NON-UNIFORM PHYSICALLY NONLINEAR THIN-WALL SPATIAL DESIGNS of the VARIABLE THICKNESS. The DISSERTATION on competition of a scientific degree of a Cand.Tech.Sci. Saratov - 2018. 2018

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