Solution for the actual problems of mechanics, materials science and related sciences of formation of the metal body in high-technological processes was proposed. The paper is related to using pulsed electro-mechanical treatment (EMT) as an example of analysis of production and related problems of structure formation and mechanical properties of the treated body. The algorithm for solving the thermo-elasto-plasticity problem taking into account changes in the thermo-structural state of metal, dynamic, mechanical effects and surface deformation changes in the space of intensity of stresses, strains and temperature was developed. The necessity of formulating and solving specific problems of material science of structure, based on existing empirical correlations was shown. The procedure of time grid confirming the correct numerical solution of various-related thermal, structural and mechanical processes was offered. The convergence, stability and adequacy of the proposed numerical method for solving the technological problems for EMT of steels were developed. Particular attention is paid to the problem of physical processes connectivity and inertial effects in a dynamically changing thermal, structural and stress-strain fields during EMT. Calculation examples of the structural areas and elasto-plastic stress distribution during EMT of steel bodies simulated by semi-infinite regions with a homogeneous structure and a non-uniform two-layer composition of the sample with hardened surface layer were shown. Comparison of the results has allowed identifying and describing the effects in the stress-strain distribution in inhomogeneous bodies with the transforming structure during EMT.

Basic terms and equations of the theory of thermoviscoplasticity (inelasticity) belonging to the class of theories of flow in combined hardening are discussed. The tensor of strain rates is presented as a sum of tensors of the velocities of elastic and inelastic deformations. It should be noted that in this theory there is no conventional separation of the inelastic strain for deformation plasticity and creep. Elastic strain follows the generalized Hooke's law common to non-isothermal loading. The authors introduce a yield surface which isotropically expands or contracts and shifts to the process of loading. The current yield surface is defined by the process loading. The impact of the time factor is the process of loading too. For the radius of the yield surface it became possible to formulate the evolution equation that takes into account additional isotropic hardening under non-proportional (complex) load; and it is also generalized to non-isothermal loading processes and return to mechanical properties after annealing. We accepted parameter Kadashevich-Mosolov (corresponding to the angle between the velocity vectors of strain and stress) as a parameter describing a measure of the complexity of the process of loading,. The displacement yield surface is described on the basis of Novozhilov-Suboshi implying that the total displacement is the sum of displacements; each of them is its evolution equation. The analysis of hysteresis loops of plastic has allowed to allocate three types of microstresses (displacements) and formulate three types of evolution equations generalized to non-isothermal loading processes and relieving of microstresses during annealing. To determine the rate tensor of inelastic deformation we use the associated (gradiently) law of flow. For hard and soft loading regimes, the expressions for determining the rate of the accumulated inelastic deformation were found. The terms of elastic and inelastic states are formulated. To describe the nonlinear process of damage accumulation we introduced the kinetic equation of damage accumulation, where the energy that is required to create damage in the material is taken as the energy equal to the work of microstresses of the second type on the field of inelastic deformations. Here these kinetic equations are generalized to non-isothermal loading and the processes of embrittlement and heal the damage. Material functions closing the theory variant are specified, the basic experiment and method of identification of material functions are formulated. The description of the verification version of the theory of thermoviscoplasticity on a wide range of structural steels and alloys and programmes of experimental research are presented.

This work is devoted to investigation of the heat source evolution during quasistatic tensile testing of titanium alloy specimens using a contact heat flux sensor and infrared thermography. The purpose of the study is to evaluate the possibility of using two different measurement (contact and non-contact) methods to monitor the state of material by changing the heat source value registered on the specimen surface during deformation. The obvious advantages of infrared thermography are non-contact temperature measurements of the material surface under various conditions and heat source field calculations. However this method has a number of limitations associated with the reflectivity of the tested material, noisy signal caused by external factors, heat transfer conditions between the specimen and environment, and accuracy of heat source calculations. These problems do not allow using infrared thermography under operating conditions in order to evaluate the energy state of materials and structures. The paper attempts to verify the heat source value arising during the elastic-plastic deformation of the material using infrared thermography data. For this purpose, a Seebeck effect heat flux sensor has been developed by the authors. Contact sensor and infrared thermography data give time dependence of the heat flux value. The satisfactory agreement of the results shows that contact and non-contact measurements can be used either in combination (to verify the heat source value, its distribution over the material surface and heat exchange conditions for specimen and environment) or separately (as an express method to evaluate material conditions at different stages of loading).

The authors carried out a complex (computational and experimental) research of residual stresses in prismatic samples made of EP742 alloy after ultrasonic hardening and he temperature of 650 °С for 100 hours unloaded. The laws of residual stresses distribution over the thickness of the surface-hardened layer were discovered. The experiments proved that the ultrasonic hardening of the sample caused compression residual stresses in the surface layer. The maximum stresses were observed in the subsurface layer and they decreased on reaching the surface. When the temperature was exposed, the induced compression residual stresses became relaxed, the level of residual stresses decreased by 1.4-1.6 times and its maximum was displaced deep into the sample, but the thickness of the compressed layer was kept to about 200 micron. We developed the mathematical model of residual stresses forming in prismatic samples after surface plastic deformation and relaxation under high-temperature creep conditions. We used the hardened half-space as a model object for the prismatic sample, because the hardened layer was rather thin. We introduced Cartesian coordinate system, where x 0 y plane coincided with the half-space hardened surface, and 0 z axis was directed into the depth of the hardened layer.

The authors set out the methodology of determining the fractal dimension of deformation curves based on the minimum coverage method, allowing to obtain an integral quantitative estimation of destruction process of building composites under compression; and determine the position of the parametric point of destruction curve. The proposed method was compared with the algorithms of the Hurst exponent determination and fractal dimension by the coverage squares method. It became possible to show the advantage of the method based on the determination of the fractal dimension by the minimum coverage method. For the realization of mechanical tests of compositions of fine-grained fiber-reinforced concretes we used hardware-software complex WilleGeotechnik®, which was additionally equipped by a climatic chamber with the possibility of adjusting the temperature (from - 40 to + 100 °C) and humidity (10 to 96 %) in the process of loading. The change of stresses and deformations of samples in the process of load was fixed with a step of 0.01 sec. The following components were used as basic ones in fiber-reinforced fine-grained concretes: cement of CEM I 42,5R class, river sand, densified condensed microsilica DCM-85, polycarboxylate superplasticizer Melflux 1641 F. The dispersed reinforcement of concretes was provided by a separate injection of three types of fibers: polypropylene multifilament fiber, polyacrylonitrile synthetic fiber FibARM Fiber WВ and basalt microfiber “Astroflex-MBM” modified by astralene. As a result, we defined values of fractality index and fractal dimension of the growth stress and strain curves of deformation of fine-grained concrete by the minimal cover method. Based on fractal analysis of time series, the position and neighborhood of the point of transition of the concrete sample from the resting state to the state of the pronounced trend were determined. The position change of parametric point was detected using the dependence of types in the applied fibers. It was established that the introduction of 1 % polypropylene multifilament fiber or 5 % modified astralene basalt microfiber “Astroflex-MBM” leads to a significant increase of the first “critical” level, respectively, to 54 and 47 % as in the analysis of growth stresses and deformations compared with 19 and 28 % for the formulations containing 1,5 % polyacrylonitrile synthetic fiber. The suggested method of fractal analysis of deformation curves based on the method of minimal coverage allows obtaining valuable information about the process related to destruction of composite materials of different natures.