Within framework of the continual fracture mechanics, we describe the engineering approach to the assessment of scattered microdamage accumulation kinetics in metallic materials under elastoplastic loading conditions in case of plane stressed state. Automatized experimental stand and the respective investigation technique are discussed. The stand has been developed based on modification of the UMÉ-10T electromechanic test machine. State-of-the-art computer technologies and microprocessing hardware are incorporated in the stand automation. We present the technique of experimental assessment of damage accumulation kinetics in metallic structural materials under complex elastoplastic loading conditions with account of two different fracture (cleavage and shear) processes, which technique is based on measuring the specific electric resistance of the specimen.Keywords: accumulation of defects, complex elastoplastic loading, resistivity of the specimen, testing installation.Introduction. Under conditions of intense elastoplastic deformation and in the processes of creep and low-cycle fatigue of structural elements, microdefects (micropores and microcracks) appear and accumulate in the material in the zones of elevated loading [1][2][3][4][5][6]. The improvement of the accuracy of prediction of the service life of structural elements of this sort in the stage of engineering design and the accuracy of evaluation of the residual service life in the stage of operation mainly depend on the reliability of the system of determining equations which must include the parameters of damageability [4,5]. The damageability of the material characterizes the dependence of the density of microdefects in a certain plane section of an element of the material on the action of external thermal and force factors. At present, there is no common point of view on the physical meaning of the parameter of damageability [7][8][9][10][11][12][13][14].Continual fracture mechanics (CFM) successfully develops for the last 40 years as a promising scientific trend in the mechanics of deformable bodies. The formation of this trend was initiated by Kachanov [4] and Rabotnov [5] who used the concept of internal variables [3, 9, 12] with a system of the corresponding kinetic equations and fracture criteria in the stage of initiation of a microcrack.For the purposes of engineering calculations, the kinetics of accumulation of microdefects is especially conveniently analyzed in terms of macrocharacteristics of the mechanical properties of structural materials in the form of force, deformation, and energy approaches [12,[15][16][17]. In this case, the application of CFM is, as a rule, based on the hypothesis on averaging of microdefects over the volume of the material and the phenomenological parameter of damageability is represented either as a scalar quantity [16], or as a vector [17], or in the tensor form [18]. The analysis of the data available from the literature demonstrates [17,19,20] that, under conditions of complex stressed state, both the general...

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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.

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The paper presents the procedure for calculating and predicting the state of critical structural elements in low-cycle fatigue with allowance for features of the operating conditions. The procedure is based on the nonlocalized damage concept and the allowance for the damage parameter in the system of constitutive equations using fast-rotating parts of laboratory centrifuges as an example. A macro-and microstructural analysis of the material is made, and the static and cyclic tests of the specimens of V95 (7075) aluminum alloy are carried out. The results of the experimental investigations are compared with the theoretical calculations performed based on the finite element method (the ANSYS software package).Introduction. Fast-rotating, multipurpose structural elements have to meet a number of requirements, the main of which are: to ensure the required life and reliability of their operation with a guarantee of trouble-free and safe operation. These requirements should be justified by a high degree of reliability. For this reason, for the purpose of safety, a protective housing is additionally used.High-speed centrifuges with speeds of rotation of up to 15,000 rpm serve for separation of mixtures of different density and often are developed as general-purpose devices. They include different fast-rotating elements, such as rotors, having extensive use. For example, large rotors with the mass of up to 20 kg are used in blood separators.To ensure a safe operation of this kind of structures, the centrifuge protective housing with sufficiently high margin of safety and weight indices is mounted. A reduction in the weight of centrifuges of this type is possible at the expense of the increase in the components of strength of their operational reliability.The centrifuge rotor is a spider with cups. The practice of operation shows that failure of cups occurs in the region of their trunnion mounting and by way of tearing off the bottom. This is supported by the specially performed experimental investigations wherein the loading was accomplished by applying a force to the bottom. To find out the causes of fracture, the analysis of the structure was carried out using microsection techniques, whereas the analysis of the stress-strain state (SSS) was performed using the finite-element method. These investigations testify that the highest stresses are observed at the points of attaching the cups, whereas the separation of the bottom is assisted by a specific structure of a manufacturing origin.Modern experimental and theoretical methods for predicting the life of structures are mainly based on two concepts: a safe operation without macrodefects and a restricted failure model [1][2][3].At present, high-performance diagnostics tools make it possible to bring into service critical structural elements without macrodefects, particularly in those branches of the engineering industry where failure results in serious catastrophic consequences. On this basis, the concept of their safe operation has solid justification, and the