"Вестник МГСУ"

Criteria of plasticity and durability derivative of standard indicators of plasticity (δ, ψ) and durability (σ
_0,2, σ
_B) are offered. Criteria К
_δψ and К
_s follow from the equation of relative indicators of durability and plasticity. The purpose of the researches is the establishment of interrelation of derivative criteria with the Page indicator. The values of derivative criteria were defined for steels 50X and 50XH after processing by cold, and also for steels 50G2 and 38HGN after sorbitizing. It was established that the sum of the offered derivative criteria of plasticity and durability С
_к considered for the steels is almost equal to unit and corresponds to a square root of relative durability and plasticity criterion C
^0,5. Both criteria testify to two-unity opposite processes of deformation and resistance to deformation. By means of the equations for S
_к and С it is possible to calculate an indicator of uniform plastic deformation of σ
_р and through it to estimate synergetic criteria - true tension and specific energy of deformation and destruction of metal materials. On the basis of the received results the expressions for assessing the uniform and concentrated components of plastic deformation are established. The preference of the dependence of uniform relative lengthening from a cubic root of criterion К
_δψ, and also to work of the criteria of relative lengthening and relative durability is given. The advantage of the formulas consists in simplicity and efficiency of calculation, in ensuring necessary accuracy of calculation of the size δ
_р for the subsequent calculation of structural and power (synergetic) criteria of reliability of metals.

The operational capacity of metal materials as part of structural elements of industrial and civil buildings depends on plastic deformability of metals. This property of construction steels is assessed through the employment of the overall elongation coefficient consisting of uniform and concentrated components.For metal structural elements, assessment of steel plasticity using the uniform elongation method (rather than overall elongation) is preferable. This component characterizes the tendency of steels to brittle destruction, fatigue resistance and cold brittleness.Therefore, the study of interrelation between plasticity and elasticity of steels is very important. Dependences of impact elasticity and failure elasticity on their uniform elongation are studied. The values of impact elasticity and failure elasticity are obtained experimentally in the process of testing of the 40ХЛ grade steel hardened at the temperature of 860 °C and tempered at the temperature of 200 °C.The elongation factor is calculated using the formula of uniform elongation. For steels under consideration, formulas of impact elasticity and failure elasticity are obtained, where uniform elongation is expressed as a fraction.

The subject of this paper is the stability and strength of cold-formed and perforated steel sigma-section columns with steel sheathing of different thickness. Ceilings with and without steel sheathing of different thickness are tested to failure in compression on a laboratory machine, which was based on a manual hydraulic jack. Series of 4 experiments with full-scale walls (2.5 m height) were carried out. Also, for examination of the role of boundary conditions, the sheet in a ceiling is either left free or connected to base with screws.In civil engineering there are many experiments and methodologies for calculating the strength and buckling of ceiling with the sheathing of various materials, such as oriented strand board and gypsum board. However, for producing superstructures of ships the materials with high plastic properties and strength characteristics are required. For example steel possesses such properties. It was the main reason for conducting a series of experiments and studying the behavior of cold-formed steel columns with steel sheathing. During the experiments the deformation of the cross-section of three equally spaced cross sections was determined, as well as the axial deformation of the central column in the ceiling with steel sheathing.The test results showed the influence of the thickness of sheathing and boundary condition of a sheet on the strength and buckling of ceiling. According to the results of the tests it is necessary to evaluate the impact of the sheathing made of different materials and if necessary to carry out further tests.

The article represents a brief overview of the properties of steel type 14X2GMR (Russian standards), a high-performance synergetic structural steel exposed to different modes of heat treatment.
The author demonstrates that the best set of the steel properties was obtained upon its normalization (Option 5). An alternative option is Option 1 (water quenching). This steel demonstrates its ≈ 1,0, which indicates the proximity between the uniform δр value and the concentrated δc value as the constituents of δ, the elongation value.
The best set of δр ,Ψр ,p, c, Кзт and p/c values is demonstrated by the steel at the normal temperature of 20 °C. An alternative set of criteria properties is identified at -60 °С.
The final choice of the optimal heat treatment mode and the operating temperature is recommended to be based on the maximal values of = p/c and the static viscosity
c = 0,5(k - σT)1n[1/(1 - Ψ)].
Given the resistance of steel to cracking during welding (Δ= 1,5; PSK= -0,25<0), it can be recommended for heavy-duty welded parts and assemblies.

The primary objective of the research is the synergetic reliability of perlite-reduced structural steel 09G2FB exposed to various thermal and mechanical treatments. In the aftermath of the above exposure, the steel in question has proved to assume a set of strength-related and plastic mechanical properties (σσδ and ψ).
On the basis of the above, an equation is formed\[{{{\sigma }_{\Tau }}}/{{{\sigma }_{\Beta }}+{\delta }/{\Psi }\;=}\;={{\left[ {\left( 1+{{\delta }_{}} \right)}/{\left( 1+{{\delta }_{\Rho }} \right)}\; \right]}^{{1}/{\Psi }\;}},\] and its solution in respect of the uniform component ${{\delta }_{\text{P}}}$ is used to generate the expression \[{{\delta }_{\Rho }}={{\left[ {\left( 1+\delta \right)}/{{{}^{\Psi }}}\; \right]}^{0,5}}-1\]and, hence \[{{\Psi }_{\Rho }}={{{\delta }_{\Rho }}}/{\left( 1+{{\delta }_{\Rho }} \right)}\;.\] To use the synergy criteria, the following expression is applied: \[{{S}_{\Beta }}={{{\sigma }_{\Beta }}}/{\left( 1-{{\Psi }_{\Rho }} \right)}\;,{{S}_{\operatorname{K}}}={{\sigma }_{\Beta }}\left[ {1+\Psi }/{\left( 1-{{\Psi }_{\Rho }} \right)}\; \right],\] as well as the following expression of specific uniform and a specific limit energy :
\[{{W}_{\Rho }}=0,5\left( {{\sigma }_{\Tau }}+{{S}_{B}} \right)\ln \left[ {1}/{\left( 1-{{\Psi }_{\Rho }} \right)}\; \right],{{W}_{C}}=0,5\left( {{\sigma }_{\Tau }}+{{S}_{K}} \right)\ln \left[ {1}/{\left( 1-\Psi \right)}\; \right].\]
\[{{K}_{}}={{{W}_{C}}}/{{{S}_{T}}}\;,G={{{W}_{}}}/{{{W}_{C}},}\;{{K}_{a}}={{{W}_{C}}}/{{{A}_{C}}}\;,\]where static viscosity is calculated according to:\[{{}_{}}=0,5\left( {{S}_{\operatorname{K}}}-{{\sigma }_{\Tau }} \right)\ln \left[ {1}/{\left( 1-\Psi \right)}\; \right].\]
The secondary objective of the project is the identification of the steel brittleness threshold to assure controlled rolling and application of the above steel in construction.