Статті КМАМВ (ІПБТ)

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Browsing Статті КМАМВ (ІПБТ) by Author "Hanush, Vasyl I."

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    Estimating the Residual Resource of Basic Structures Using a Model of Fatigue Durability under Complex Loading
    (PC TECHNOLOGY CENTER, Kharkiv, 2022) Belodedenko, Sergey V.; Hrechanyi, Oleksii M.; Hanush, Vasyl I.; Vlasov, Andrii
    ENG: This paper reports the construction of a durability model of basic structures, which takes into consideration the complex stressed state under the cyclic action of the complex load. The models that take into consideration this factor are categorized on the basis of equivalent for a certain indicator of the stressed-strained state. The equivalence models based on the tangent stresses and strains have been recognized as the most effective ones. However, they hold when the ratio of the limits of fatigue under tangent and normal stresses exceeds 0.5. In addition, determining the latter requires specific testing equipment. The concept of basic bearing structures for industrial equipment has been formulated. The issue related to the multi-axis fatigue of basic structures was considered from the standpoint of combining the reliability indicators of systems. The durability model has been derived from the rule of combining resource safety indices. The load is represented as a combination of individual subprocesses of simple types of deformation with their amplitudes and asymmetries. A model of durability with multi-axis fatigue has been built, which takes into consideration the parameters of the form of the strain cycle, and the type of process (synphase, disproportionate, unchanging static stress). The possibility of obtaining parameters for the multi-axis fatigue model during tests for three-point bending under conditions of varying the multiplicity of the span has been confirmed. According to this scheme, fatigue tests of prismatic samples of the steels 09G2 and 40H were carried out. For them, the parameters of fatigue resistance were found; additionally, the ratio of the fatigue limit for tangent stresses of displacement and fatigue limits for normal bending stresses, which is equal to 0.385, was established. A test procedure has been devised to determine the initial data for the multi-axle fatigue model, which is suitable for conventional test machines and simple-shape samples. The latter advantage is important precisely for basic structures, from fragments of which it is difficult to fabricate a sample of a complex shape.
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    Experimental Verification of the Survivability Model under Mixed I+II Mode Fracture for Steels of Rolling Rolls
    (Springer Cham, 2022) Belodedenko, Sergii V.; Hanush, Vasyl I.; Hrechanyi, Oleksii. M.
    ENG: The model of fatigue mixed fracture, which follows from the amalgamation rule of resource safety indices, has been experimentally confirmed. It does not require finding an effective SIF, but is based on the construction of survivability curves for pure modes. Survivability in a mixed process is defined as the result of combining individual fracture processes. Peculiarities of steels of rolling rolls fracture under conditions of cyclic deformation according to the scheme of four-point asymmetric bending are revealed. Although such a test scheme is designed to obtain the fracture of the II mode, in existing studies, this has not been achieved. The crack from the notch, practically, immediately went away at an angle ~45° toward the tensile zone, which indicates a mixed I+II fracture. With sufficient accuracy to predict survivability, the exponent of the Paris’s region of the fatigue crack growth diagram (FCG) can be taken as nI = 4 (I mode), nII = 3 (II mode). As a parameter of schematization, it is possible to use the value of SIF at an FCG rate of 10–7 m/cycle. Its value for steels of rolling rolls can be 60–70 MPa√m in mode I. For mode II, this index decreases by 2.5–3 times.
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    Fatigue Lifetime Model under a Complex Loading with Application of the Amalgamating Safety Indices Rule
    (Elsevier B.V., 2022) Belodedenko, Sergii V.; Hanush, Vasyl I.; Hrechanyi, Oleksii M.
    ENG: The problem of multiaxial fatigue is considered from the standpoint of amalgamating indicators of system reliability. The lifetime model is derived from the rule of amalgamating resource indices of safety. The load is represented as a combination of individual subprocesses of simple types of deformation with their amplitudes and stress ratio. A model of lifetime in multiaxial fatigue has been developed, which takes into account the parameters of the deformation cycle shape, the type of process (inphase, disproportionate, constant static stress). The possibility is confirmed for obtaining the parameters of the model of multiaxial fatigue when tested for three-point bending under conditions of variation of the multiplicity of span. According to this scheme, fatigue tests were performed for prismatic steel samples 09G2 and 40Н. The fatigue resistance parameters were found for them, and also there were found the ratio of the fatigue limit for tangential stresses and the fatigue limit for normal bending stresses, which is equal to 0.385.