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Recently, much attention has been paid to the study of the deformation and failure features of high-strength steels under extreme loads, under which they are mainly operated. One of the topical issues is the correct determination of the parameters of deformation models of materials. The use of tests for barrier penetration at high speeds of 100–1000 m/s is quite complicated and expensive, and also does not allow to obtain enough information. Therefore, alternative experimental methods have been developed recently, which include static and dynamic punching tests of thin sheet specimens at speeds of up to 10 m/s. Such tests are simpler and allow to obtain more information about the behavior of high-strength materials in conditions that simulate operational ones. This paper presents the results of static and dynamic punching tests on thin sheet specimens of 50×50 mm size and 1 mm thickness made of Armox 500T armor steel. The static punching tests were carried out on an Instron 8802 servohydraulic machine, for which special equipment was manufactured. The dynamic punching of thin-sheet specimens was carried out on an instrumented vertical impact tester equipped with a high-speed strain and force recording system. To conduct such tests, the experimental equipment was updated, and a design of special supports for the rigid fixing of thin-sheet specimens was developed. The loading speed was varied from 0.5 to 10 mm/min for static punching and from 3 to 5 m/s for dynamic punching. The tests were conducted using three types of punches: conical, flat and hemispherical. According to the test results, new data on the influence of strain rate on the features of deformation and failure of Armox 500T armor steel were obtained. The influence of the type of punches on the nature and mechanisms of failure of thin-sheet specimens under static and dynamic punching was investigated. It was found that an increase in loading speed leads to an increase in specimen failure force. Thus, the resistance to deformation increases by approximately 20% with an increase in the loading speed from 0.5 mm/min to 5 m/s. [ABSTRACT FROM AUTHOR]

The paper presents the results of an experimental study of the deformation properties of 10GN2MFA and 15Kh2MFA steels at different ratios of principal stresses under cyclic loading conditions. Applying the proposed phenomenological approach of an improved elastic-viscoplastic model allows one to qualitatively describe the effects of the influence of structure degradation under the action of temperature and force factors that accompany the operation of actual structural elements significantly affecting the regularities of deformation and damageability and the strength of structural materials under combined stress conditions. An evaluation of the variation rate in the homogeneity of the studied steels at different ratios of principal cyclic stresses under cyclic creep conditions is presented. Based on the experimental results, correlation dependences between the relative values of the homogeneity coefficient and the function of the deformation properties of the material and the type of stress state were obtained, which significantly simplifies the determination of the parameters characterizing the limiting state of the structural element. [ABSTRACT FROM AUTHOR]

The paper summarizes the findings of theoretical and experimental investigations in the range of low-cycle fatigue under irregular multiaxial deformation. It presents the test results for titanium alloys VT9 and VT1-0 under low-cycle regular and block deformation conditions. A method of fatigue life prediction for metal alloys under multiaxial low-cycle block deformation conditions has been elaborated, which is based on the Pisarenko-Lebedev equivalent deformation and the modified Manson-Halford model. The paper demonstrates the advantages of the proposed method over other approaches to the fatigue life prediction for metal alloys under multiaxial block deformation conditions. [ABSTRACT FROM AUTHOR]

The paper provides results of the study of correctness of the mathematical model that includes the influence of stresses on irradiation-induced swelling of metal in the problems of elastic-plastic deformation mechanics. The present-day approaches to modeling irradiation-induced swelling, which take into account a damaging dose, irradiation temperature, and the effect of the stress state on the swelling deformation, are discussed. The constitutive equations that describe the elasticplastic deformation processes allowing for the influence of a stress mode on the irradiation-induced swelling in metal are put forward. Analysis of these equations has made it possible to find the conditions that ensure correctness of the plasticity equations considered and to make a lower-bound estimate of the maximum permissible value of free swelling and irradiation dose. A priori estimates of the maximum permissible value of free swelling and damaging dose are given for 08Kh18N10T steel under various irradiation temperatures. In the practice of strength design such estimates are needed at the stage of problem formulation in order to analyze adequacy of input data, for they enable one to assess a prior the possibility of solving the problem for a given temperature and irradiation dose. The boundary-value problem that describes non-isothermal processes of elasticplastic deformation including swelling strains has been defined in the form of a nonlinear operator equation. Based on the findings regarding the correctness of the constitutive equations, we have established the existence and uniqueness of the generalized solution and its continuous dependence on applied loads, thermal strains and swelling strains. The convergence of the method of elasticity solutions and the method of variable elasticity parameters has been studied as applied to a thermoplasticity problem including irradiation-induced swelling strains. [ABSTRACT FROM AUTHOR]

In this paper, a method is proposed for specifying the parameters of the exponential hereditary function kernels of the endochronic theory of plasticity to describe the ratcheting (cyclic creep) effect of metallic materials under stress-controlled complex non-proportional loading. The method involves the dependence of the difference of plastic moduli on the ratcheting rate on the steady-state portion of the cyclic stress-strain curve. The plastic moduli are determined at the points where the maximum stresses act in different half-cycles of asymmetric loading. It is believed that the greater the difference of plastic moduli towards the mean stress in the cycle, the greater the strain increment in each cycle of loading. The statements of our previously proposed approach were used to determine the rate of plastic strain accumulation at the steady-state stage of deformation under biaxial loading. This approach, based on the data of uniaxial experiments under cyclic asymmetric loading in tension-compression and reversed torsion with the known value of the cycle nonproportionality parameter, is developed to analyze the cyclic loading paths with equal mean and amplitude von Mises stress values. With some simplifications, the expression is proposed to determine the parameters of the exponential kernel of the hereditary function depending on the cyclic path geometry and the known ratcheting rate for the basic loading path. Similar values for the exponential kernel parameters of the hereditary function are obtained in terms of the difference of plastic moduli by using a simpler bilinear model of elastoplastic deformation. The obtained values of the hereditary function parameters were used to simulate the ratcheting effect under uniaxial and biaxial cyclic loading. The loading programs and data of experiments were taken from the literature. The results of simulation have shown that the parameters of the constitutive equations for cyclic plasticity obtained with this method allow one to describe satisfactorily the kinetics of the stress-strain state of metallic materials subjected to biaxial non-proportional loading under cyclic creep. [ABSTRACT FROM AUTHOR]

The paper considers a nonlinear deformation-strength model of a rebar structure. Within framework of the reinforced concrete mechanics, it allows one to take into account the specific features of the joint operation of concrete and reinforcement components at all loading stages, including failure, in the structure cross sections under the general stressed state conditions. The model is found to be instrumental in practical applications due to the possibility of its application to the design or strengthening of beams, cross-bars, columns, elements of girder frames with the rectangle cross section, as well as to verification of bearing capacity of existing reinforced concrete bar structures, which operate under conditions of complex stress-strain state, including low-cycle pulse loading. The assessment algorithm of the bearing capacity of a reinforced concrete bar (rebar) cross sections under multiaxial stress conditions is proposed. The general physical dependencies for such cross section are reduced to the stiffness matrix. The proposed algorithm includes the input data block, main block, supplementary subprograms of load vector increment check and exhaustion of the bearing capacity, as well as the output data printout block. At each computation stage, all iterations are executed until the accuracy of determining all components of strain vector reaches a certain preset value. The variation patterns of normal and tangential stresses, generalized linear and angular strains are considered. The equilibrium equations of a concrete rebar operating under multiaxial stress conditions are derived. [ABSTRACT FROM AUTHOR]

This paper presents the methods used to determine the depth of the plastically deformed top layer in the roller burnishing process. An analytical method was developed for determining the depth of the plastically deformed layer on the basis of the Hertz-Bielayev theory. The depth of deformation was obtained as a function of the process parameters: burnishing force, material strength and roller radius. The analytical solution has been verified using an original method based on the measurement of the face profile of rings. A mathematical model for a theoretical solution and a plan for experimental tests have been developed. The numerical simulation of the depth of the plastically deformed layer was carried out based on the finite element method. The results of deformation depth as a function of roller force, material strength and roller geometry show a good agreement between analytical and experimental methods. [ABSTRACT FROM AUTHOR]

The paper considers a problem of stress relaxation calculation of nonlinear viscoelastic materials under unsteady deformation conditions. To describe the deformation process, a nonlinear creep model of the Rabotnov type with time-independent nonlinearity is used. A fractional exponential function is used as a heredity kernel. An experimental evaluation of the calculation results under the conditions of one-step deformation, partial unloading and cyclic deformation of plexiglass has been performed. [ABSTRACT FROM AUTHOR]

We describe the application of the dual boundary element method for the determination of stress intensity factors in plate bending problems. The loadings considered include internal pressure, and also combined bending and tension. Mixed mode stress intensity factors are evaluated by a crack surface displacement extrapolation technique and the J-integral technique. The boundary element results for the case studies considered in the paper have been compared with either analytical or finite element results and in all cases good agreement has been achieved. [ABSTRACT FROM AUTHOR]

Predictions by numerical simulations are strongly influenced by availability and reliability of input data. In the most used computational models, the material behavior during deformation is described only by static tensile test in combination with Lankford coefficients of anisotropy. However, for some specific materials like highly anisotropic aluminum alloys, such description of material behavior is insufficient and, in many cases, the calculated results are not in good agreement with the measured ones. In this paper, the implementation of advanced material model for deep-drawing process to explicit FE code and the procedure of measurement of the most important input material data for calculations on the aluminum alloy AW 5754 are discussed. Results of the numerical simulation are compared with the experimental ones and exhibit a close correlation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to develop a set of creep aging constitutive equations for Al-Cu-Mg alloys containing plate- or rod-like precipitates. Average length, aspect ratio and relative volume fraction are introduced to quantitatively analyze the effect of the precipitates of such alloy on creep aging process. The strong interaction between creep deformation and aging treatment is considered by the intermediate state variables of dislocation density and precipitate characteristic dimension. A unified creep aging constitutive equation is derived, in which the correlations between microscopic characteristics and macroperformances of material are linked by the yield strength of the material. Using AA2124 alloy, a series of uniaxial tensile creep tests are carried out at 185°C for 12 h with different stresses. The material constants within constitutive models are determined from the experimental data. A good agreement between experimental and computed values confirms that the established constitutive equations can well characterize the creep behavior. [ABSTRACT FROM AUTHOR]

Cu-Zn alloy is an advanced material with deformation twinning mechanism, which is complicated by coupled effects of temperature and strain rate. In this paper, a theoretical model of Cu-Zn alloy is proposed, which accounts for the coupled effects of strain rate and temperature. The model can accurately predict the experimentally observed tendency of the spacing evolution of twin boundary (TB), and it confirms that low temperature and high strain rate promote deformation twinning. Moreover, it is shown that deformation twining is more susceptible to low temperature than to high strain rate, while TB spacing and twin layer thickness values decrease at high strain rates and low temperatures. [ABSTRACT FROM AUTHOR]

The paper considers the irreversible deformation of steam turbine rotors due to the circumferential non-uniformity of the material mechanical properties based on the numerical analysis of their three-dimensional stress-strain state. It is shown that this non-uniformity can be one of the causes for the occurrence and development of progressive creep deflection of high-temperature rotors that have been in long-term operation and also their bending in case of excess of the rated rotational speed. [ABSTRACT FROM AUTHOR]

The paper considers the possibility of determining stresses and strains in elastoplastic deformed body from hardness spreading parameters. [ABSTRACT FROM AUTHOR]

The paper presents the results of approximate calculations of vibrodiagnostic parameters indicating the presence of a closing fatigue edge crack in bars with different boundary conditions versus the crack parameters and exciting load under subharmonic resonance in principal bending mode. [ABSTRACT FROM AUTHOR]

Due to the increased use of lightweight sheet materials, there has been a significant increase in the use of self-pierce riveting. This paper deals with the ultimate tensile strength of coach peel self-pierce riveted joints. The online window technique was introduced in the coach peel self-pierce riveting processes for evaluating the quality of joints. Signals obtained from sensors were amplified and transferred to the data acquisition system which measures, processes and saves the signals. Monotonic tensile tests were carried out to measure the ultimate tensile strengths for coach peel self-pierce riveted joints with different material combinations. Deformation and failure of the coach peel self-pierce riveted joints under monotonic tensile loading were studied. The normal hypothesis tests were performed to examine the rationality of the test data. [ABSTRACT FROM AUTHOR]

The paper addresses damage accumulation processes that occur during static deformation in steels 45 and 09G2S and in brass L63 in the initial state and upon 'grain annealing.' The authors discuss new experimental evidence on the damage accumulation kinetics during deformation of polycrystalline materials that differ in nature and grain size, including materials in the unloaded state and those under stresses, with small and very small strains (0.05-0.15%). The results obtained have been the necessary physically consistent explanations. Analytical approximations of the correlation between the main mechanical properties of materials (hardness, yield stress, and ultimate strength) and their structure parameters (grain size) are given. [ABSTRACT FROM AUTHOR]

The paper addresses the dependence of acoustic emission produced in rolled hafnium GFÉ-1 under tensile deformation on the material's structural state. A correlation has been established between the material structure, the level of mechanical properties and the values of acoustic parameters. Acoustic emission in non-recrystallized hafnium under tensile deformation is recorded only at the stages that precede fracture. Upon recrystallization annealing at temperatures of 1123 and 1373 K acoustic emission occurs at all the stages of tensile deformation. The highest level of acoustic emission activity in hafnium is observed during the transition from elastic to elastic-plastic strain. [ABSTRACT FROM AUTHOR]

We have developed and implemented a method for calculating the fields of parameters of the crack-tip creep stress-strain state by taking direct account of the higher-order terms. The paper presents some calculated data on the fields of crack-tip stresses, creep strain rates, and amplitude ratios in the creep case. The influence of loading biaxiality on redistribution of stresses between the creep stages and on the constraint parameters in failure is assessed. [ABSTRACT FROM AUTHOR]

We present the results of experimental studies of stability of thin-walled orthotropic cylindrical shells in torsion. The classical solution and the refined theoretical solution as derived in Part 1 are compared with experimental data. Some general conclusions have been made, which define more precisely the current notions of shell buckling under torsion. [ABSTRACT FROM AUTHOR]

The paper presents results of the experimental investigation of deformation behavior and damage accumulation kinetics in a heat-resistant reactor pressure vessel steel at high stress levels under stress-controlled (pulsating), low-cycle loading up to 104 cycles. Hardness measurements have been performed upon various operating time periods under elastoplastic deformation. It has been found that hardness and strength of the steel exhibit qualitatively different behaviors throughout the lifetime. The damage accumulation process in steels under static and cyclic loadings has been studied by means of the LM-hardness method. The curves of Weibull homogeneity coefficient vs. cycling stress and accumulated strains are obtained. [ABSTRACT FROM AUTHOR]

The paper presents a procedure whereby the damage accumulation kinetics in structural materials, such as steel 45, stainless steel 12Kh18N10T, aluminum alloy D16T, and titanium alloy VT22, under elastoplastic deformation is studied based on variation parameters of elastic modulus and resistivity. For complex stress conditions, a continuum model for damage accumulation is proposed which relates the damage parameter to the intensity of accumulated plastic strains. The data calculated by the proposed continuum model are compared to the experimental findings of the investigation of the damage accumulation kinetics for some structural metals. [ABSTRACT FROM AUTHOR]

The paper discusses the findings of the experimental study of deformation in steels of various grades in tension with interim unloading stages where the test temperature was varied. It is demonstrated that not for all the materials this deformation process is described by the hypothesis of thermomechanical surface. The authors propose a constitutive equation for the materials under repeated simple loading with variable temperatures. [ABSTRACT FROM AUTHOR]

The paper presents a physico-mechanical model for predicting creep rupture in neutron-irradiated materials. The model is based on the approach whereby damage is described as voids on grain boundaries. The equations for void nucleation and growth which were proposed by the authors earlier are augmented to include neutron irradiation of material. Constitutive equations are derived to describe viscoplastic deformation of material including void propagation. A criterion for plastic stability of a unit cell is employed as a fracture criterion. [ABSTRACT FROM AUTHOR]

The paper considers methods of accelerated determination of endurance limits of metals and alloys based on the analysis of regularities in their inelastic deformation, strain and energy criteria of fatigue fracture, and methods for life prediction with the use of those criteria. [ABSTRACT FROM AUTHOR]

The paper covers an experimental study of the laws that govern the variation of yield limit and stress-relaxation limit as a function of stress amplitude and plastic strain in Grade 45 steel and D16T alloy under the conditions of preliminary static and cyclic tension including strain aging. The mechanical characteristics of these materials are shown to grow with increasing plastic strain irrespective of the loading type but decrease with increasing stress amplitude. It has been found that as a certain level of plastic strain is achieved the stress-relaxation levels in the materials become the same irrespective of the type of pre-loading. [ABSTRACT FROM AUTHOR]

The paper deals with dislocation structure of 15Kh2MFA steel upon static tension and elastoplastic strain cycling is studied. The dislocation density within small-angle boundaries is shown to grow with increasing plastic tensile strain and, in the case of elastoplastic cycling, with increasing strain amplitude and number of cycles. The growth of the dislocation density within small-angle boundaries upon elastoplastic cycling results in a smaller shear stress. [ABSTRACT FROM AUTHOR]

The paper covers the experimental study of the influence of cycling frequency ranging from 20 Hz to 10 kHz and the cycle asymmetry on the crack growth resistance of VNS-25 stainless steel. It is demonstrated that as the cycling frequency is raised, the crack growth rate decreases monotonically, while threshold values of the stress intensity factor $\backslash DELTA\; K\_th$ grow. The latter is due to the fact that at high cycling frequencies the plastic deformation processes remain incomplete and the contribution of the fracture mechanisms that facilitate greater energy intensity of fatigue crack growth processes becomes more significant. A comparison of $\backslash DELTA\; K\_th$ and fatigue life values as a function of cycling frequency for smooth and notched specimens demonstrates that if represented in relative coordinates these functions are described by a common relationship. This allows a quantitative assessment of the effect of the strain cycling rate on the above-mentioned properties of a material from the results of tests of one type only. It has been found that the values $\backslash DELTA\; K\_th$ in asymmetrical loading cycles are related to those in symmetrical cycles, as well as to a coefficient of material's sensitivity to the static component, and linearly depend on the load ratio. [ABSTRACT FROM AUTHOR]

The paper describes a method and main results of a refined stress-strain state evaluation for a welded joint of the hot collector to steam generator nozzle of a nuclear power plant with a WWÉR-1000 reactor, which takes into account a fuller range of the actual loading conditions in operation. In calculations, we considered the stresses induced by uncompensated thermal expansion of the reactor elements. The results of 3D finite element calculations suggest that the level of local stresses in the area of the joint exceeds the metal yield stress. The calculated stresses for the outer nozzle surface agree satisfactorily with the in-situ strain measurement data. [ABSTRACT FROM AUTHOR]

The paper presents the results of an investigation into the low-temperature jumplike deformation of BrKh08Tsr bronze and the effect of pulsed magnetic cycling on its regularities. The authors established the regularities of build-up of strain with increasing magnetic field strength and applied load. The possibility of experimental modeling of the phenomenon of intermittent yielding by the method of superposition of magnetic field pulses was demonstrated and a corresponding mathematical model of the deformation process was developed. [ABSTRACT FROM AUTHOR]

The creep test of T91/Super304H joint is carried out at 610°C and 180–150 MPa. OM and SEM were used to characterize the microscopic changes before and after the joint creep, and the finite element simulation was carried out according to the actual operating parameters, which are used to analyze failure reason of the T91/S304H joint. Finally, the creep life prediction is carried out. The results show that the creep deformation of T91/S304H welded joints with nickel-based filler metal is controlled by the part of martensite T91. Meanwhile, the T91 heat-affected zone is the weak location of the joint. When the stress decreases, the creep life gradually increases, and the creep rupture changes from ductile fracture to brittle fracture. The distribution of Nb-containing phases improves the creep strength of S304H steel. In the process of high-temperature creep, stress concentration occurs between the coarser M23C6, the precipitated Laves phase and the matrix interface, which leads to the formation of creep holes and then gradually connected into cracks. The fracture mechanism is a typical type IV cracking model. The revised θ model can better predict the service life of T91/S304H welding. [ABSTRACT FROM AUTHOR]

An approach to the determination of steady ratcheting strain rate under biaxial loading depending on the loading cycle geometry is proposed. Based on the data analysis, the microstructural investigation results, as well as the similarity detected between the microstructural formations after deformation at the stress- and strain-controlled modes of loading, it is proposed to use the cycle nonproportionality parameter to predict the ratcheting rate. It is shown that the geometric cycle parameters and basic experiments allow one to adequately predict the ratcheting rate for complex cyclic paths. [ABSTRACT FROM AUTHOR]

The processes of creep of woven materials are investigated. An industrial fabric, which is made on the basis of polymer threads, is chosen as an object of investigation. By analogy with the investigations of threads performed earlier the regions of linearity of viscoelastic properties of woven material are determined, fulfillment of the condition of similarity between the isochronous curves is proven, and the instantaneous stress-strain diagram is plotted. The similarity of viscoelastic nature between the woven material and threads, which form it, is shown. The possibilities of use of linear and nonlinear models of viscoelastic deformation for the description of creep of polymer fabrics are analyzed. [ABSTRACT FROM AUTHOR]

Deformation of rectilinear elements of Du 200 pipeline made of 20 steel under cyclic loading with internal pressure has been studied experimentally. Tests were carried out on a pneumohydraulic bench under conditions close to plane stress state, room temperature, and cycle asymmetry under soft loading mode (stress control). Circumferential and axial strains were recorded at three points of a diametrical section located in the middle of the element under study. Two tubular elements were tested at different values of maximum and amplitude stresses based on 100 cycles of loading. Deformation curves (cyclic creep) of tubes in a circular direction have been obtained, the character of which is significantly non-uniform in comparison with deformation of laboratory specimens. It is shown that even a slight increase in maximum (by 4%) and amplitude (by 8%) stresses significantly (up to 50%) increases the cyclic creep strains in the circular direction. Such growth of deformations can be explained by a peculiarity of 20 steel, the deformation diagram of which in the elastoplastic transition area contains a yield point, which determines intensive deformation of the material. Fixed plastic deformations in the axial direction are more than an order smaller than circular ones, and with increasing loading cycles, they change insignificantly and coincide for the two studied tubular elements. [ABSTRACT FROM AUTHOR]

We study the biaxial stress state conditions in landing gear fuse pins in the fuse groove. This biaxial state comprises a combination of shear stresses which are usually the largest stresses in the fuse pin by design, and compressive stresses which keep the half-section of the fuse pin in equilibrium. Conventional fatigue analysis techniques use an equivalent uniaxial stress, based on the Mises stress of a pure-shear condition. The respective predicted fatigue damages are much higher than those obtained from fuse pin cyclic tests. A new equivalent uniaxial fatigue stress model is proposed that includes the additional compressive stress as a relief on the fatigue damage in the fuse groove, thereby explaining the observations from fuse pin tests. The model is used in conventional uniaxial strain-life fatigue software (Goodrich Aerospace’s Fatigue Life V2) to predict the fatigue damage on a landing gear fuse pin with a sample load spectrum. The results are then compared to the pure shear model, and to a biaxial finite element fatigue analysis. As compared to the equivalent Mises model, the proposed model provides less conservative estimation of the fuse pin fatigue life, the latter value being higher than that provided by the two-dimensional finite element calculation. [ABSTRACT FROM AUTHOR]

The paper considers the neutron irradiation effect on the deformation of viscoelastoplastic layered structural elements under the action of thermal-force loads. A general formulation of the boundaryvalue problem is proposed. A numerical solution for a three-layered metal-polymeric rod is given. [ABSTRACT FROM AUTHOR]

Mathematical simulation of elastoplastic deformation of additionally isotropically hardened materials under proportional and nonproportional cyclic loadings is examined. A rather simple version of the plasticity theory, being a special case of the theory of inelasticity, is discussed. This version belongs to the class of single-surface combined-hardening flow theories. The results of computational and experimental investigations of elastoplastic deformation and fatigue fracture of materials at various nonproportional cyclic loads are cited. An adequate description of nonproportional loading processes, additional isotropic hardening effects, as well as fracture processes within one, rather simple version of the plasticity theory is by for the advantage of examined mathematical simulation. [ABSTRACT FROM AUTHOR]

The elastoplastic damage model for concrete is elaborated that can be applied to various stress states. In the previous study (2016) the 3D elastoplastic damage model, based on the Lubliner yield criterion and Drucker-Prager flow rule, was constructed. The simplified forms of the two functions set certain limitations on the calculations in true triaxial compression and high confining pressure. Improved accuracy of yield surface and potential plastic surface is required. The Menétrey-Willam yield criterion is adopted and analyzed in the effective stress space. The methods that define the hardening and softening functions through the volume plastic strain are no longer used in some successful 3D models since they employ double hardening and two-scalar damage to describe an increase in effective yield stress and degradation of stiffness. The suppression of damage evolution in triaxial compression is taken into account through the confining net decomposition of stress. The validation of specific parameters in the potential plastic function of the novel model is verified. The iteration return mapping algorithm is worked out and implemented. The reliability of the proposed model is corroborated by numerical simulation results compared with existing experimental data. [ABSTRACT FROM AUTHOR]

The dynamic response of pavement plates to a localized Friedlander load based on the three-parameter foundation model with the account of soil inertia is analyzed. The pavement plate is represented by a thin orthotropic plate of finite dimensions, which can rotate and transfer deformation along the contour. The subgrade is simulated with the Pasternak foundation model, including the inertia soil factor, the localized dynamic load is simulated with the Friedlander decay function allowing for the positive and negative phases; with the time distribution described by the Dirac function. The governing equation of the problem is solved with the modified Bolotin method for determining the natural frequencies and mode numbers of the system. The Mathematica program is used to define the natural frequencies of the system from the transcendental equations. Analysis results for several parameters related to the dynamic response of plates to a localized dynamic load, which includes both positive and negative phases, are presented. The impact of the Friedlander load with the negative phase added on the response of the pavement plate is numerically simulated. [ABSTRACT FROM AUTHOR]

The surface effect on the mechanical behavior of a nanowire forest indentation is theoretically studied. The use of a large-radius spherical indenter revealed a complex deformation pattern of the nanowire forest. The nanowire forest compression, buckling and postbuckling were analyzed. The effect of surface and packing density on the nanowire forest behavior with the indentation depth is discussed. The results show that the surface effect is of importance for in-depth hardness. The analysis is instrumental in measuring the mechanical properties of the nanowire forest and in designing nanowire-forest devices for various applications. [ABSTRACT FROM AUTHOR]

The experimental data on inelastic cyclic deformation of various metallic materials are analyzed with the aim to determine the mechanisms governing their variation during cyclic loading. Groups of materials with similar kinetics of inelastic deformation are selected, and the analytical relations for their description are proposed. The variation of inelastic strains under conditions of the material fatigue is closely associated with their hardening-softening, which description requires the calculated model of cyclic yield strength variation. The proposed model for the selected groups of materials makes it possible to describe their inelastic deformation and damage behavior under fatigue conditions. [ABSTRACT FROM AUTHOR]

A formulation is presented for the problem of elastoplastic deformation of the system of electrically conductive bodies under the action of pulsed electromagnetic field. The numerical technique for solving the problem is based on the finite element method. Deformation of bodies interacting through contact during the pulsed magnetic treatment of materials is analyzed. The influence of the manufacturing and design parameters of the inductor-workpiece system on its stress-strain state is investigated. [ABSTRACT FROM AUTHOR]

Simulation models of 2A12 aluminum targets with thickness 1 mm stricken by the high strength 38CrSi blunt-nosed projectiles at different yaw angle have been established with the help of ABAQUS, then the failure mode and crack propagation of target was analyzed after the effectiveness of simulation models had been verified by experiment, also the motion and angle variation of projectile was studied. Simulation result indicated that target would experience staged deformation and destruction during impacting, three typical figures of plugs were obtained, and there was a special initial velocity of projectile which could change the extension of target's crack. For projectile, the trajectory deviation was observed, at the same time the trajectory angle and obliquity angle were increased, this phenomenon could be explained by the radial force between projectile and target, more details illustrated that initial yaw angle and velocity of projectile were two main factors to affect the motion of projectile. [ABSTRACT FROM AUTHOR]

The experimental investigations of the fatigue resistance of various metallic materials were conducted loading in the range of frequencies from a few Hz to 10 kHz with account of the material structure, test temperature, load ratio and availability of stress concentrators. It is shown that the influence of the most process, structural and operational factors on the values of endurance limits manifests itself identically at both low and high loading frequencies. This implies that the main mechanisms of fatigue damage accumulation intrinsic to the particular material remain independent of loading frequency, while deformation rate affects the value of inelastic strains and, consequently, the degree of plastic strain accumulated during a cycle and endurance limit values. The equation is proposed, which describes the material state at the instant of time preceding the fatigue crack growth initiation with account of the cyclic loading frequency as a factor controlling the damage accumulation rate. An experimental verification of the obtained equation showed that difference between the calculated and experimental data on the fatigue resistance is, as a rule, within the experimental data scattering, which confirms the sustainability of the model. The proposed model provides the base for the prediction of the fatigue resistance characteristics, including at large number of cycles, at various frequencies based on high-frequency test results. [ABSTRACT FROM AUTHOR]

Results of experimental room-temperature studies on the deformation and strength of UOL-300-1A and UT-900-3A carbon cloth-reinforced plastics and laminar composites on their basis are presented. All elastic and strength characteristics of the materials are evaluated at the plane stress state. Evaluation lines for elastic and strength characteristics of laminar carbon cloth-reinforced composites are investigated. The prediction efficiency for elastic characteristics of laminar woven composites is analyzed on the basis of corresponding parameters of a single layer. [ABSTRACT FROM AUTHOR]

In this theoretical study, we have chosen to use a body of an ellipsoidal geometric form as an indenter, where we determined the mathematical expression of the static hardness as function of the depth and the radii of the area of projected imprint. We used the general formula of the static hardness expressed by the ratio of a force applied perpendicular on the indenter to the resulting area of the imprint; also, we have established the real imprint (cap) of an indenter of revolution ellipsoid form. Finally, geometrical and mathematical approaches have been used to derive the formula of the static hardness expression. [ABSTRACT FROM AUTHOR]

The conditions of combined deformation for fatigue damage indicator and well-drilling tool joint are studied. The contact stresses on the surfaces of the coupling parts and the relationship between operational load and dimensions of sliding zone at frictional contact have been determined depending on the size of the technological gap. [ABSTRACT FROM AUTHOR]

To reveal the compression deformation behavior of pure copper, the deformation characteristics of pure copper have been investigated by means of compression tests in the temperature range of 400-900°C and strain rate range of 0.001-1 s. The results show that the flow stress of pure copper increases with strain rate and decreasing deformation temperature, which is characterized by work-hardening, dynamic recovery, dynamic recrystallization, secondary work-hardening, etc. The activation energy of hot deformation is associated with deformation temperature and strain rate, and the average activation energy is calculated to be 303.8 kJ/mol. The flow stress prediction model based on GA+BP network provides a very good agreement with the true stress curve, which is instrumental for the guidance of hot working of pure copper. The flow instability occurs in the intermediate strain rate range (0.01-0.1 s). Based on the processing map anakysis, the high power dissipation corresponds to the dynamic recrystallization. Appropriate reduction of the deformation temperature or increased strain rate are beneficial for the grain refinement in the steady-state range of the processing map. [ABSTRACT FROM AUTHOR]

The article presents the investigation of plasticity and microstructure of hot work tool steel during martensitic transformation. Specimens were austenized, then air quenched. During cooling process the specimens were bent under 100 MPa stresses. There were three types of loading during cooling: continuous bending straight after withdrawing of sample from furnace (deformation of initial austenite, and then martensite formation under stresses); bending when martensitic transformation started (deformation of martensite); unloading when martensitic transformation started (main deformation of austenite - measurement of self-deformation). Plastic deflection of bending samples was measured during cooling until room temperature. The incoming martensitic transformation of the material showed significant increasing of plasticity. As bending caused two types of stresses - tensile and compression, its different influence on martensitic transformation was detected by specimen self-deformation. The microstructure of the stretched and compressed surfaces of the samples was determined by XRD, SEM, and EDS methods. [ABSTRACT FROM AUTHOR]

The influence of preliminary deformation of steel 10GN2MFA with consideration of metal damageability under conditions of nonuniform biaxial tension on its plastic properties with the subsequent cyclic tension under plane stress conditions has been analyzed. [ABSTRACT FROM AUTHOR]