Oleg Morachkovsky

National Technical University "Kharkiv Polytechnic Institute" | KhPI · the theoretical mechanics Department

The primary purpose of this study is tumerical homogenization of the nonlinear creep properties of unidirectionally reinforced fiber composites. The constitutive relations for a homogeneous material, equivalent to composite, are based on the hypothesis of the existence of a potential for the strain rates of steady-state creep. The generalization of...

Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A low-frequency case is considered. The paper provides results of experimental studies of the short-term creep of St3 steel under static and stepwise cyclic loading at room tempe...

Deformation and damage of nuclear power station fuel element shells under irradiation and cyclic loading due vibrations are studied. Constitutive equations include dependencies for a creep-damage equation with a scalar damage parameter, as well as terms for thermal and irradiation creep strains, elastic, thermal, and swelling strains. The accelerat...

Zusammenfassung In der vorliegenden Arbeit wird die Verformung elektrisch leitender metallischer Bauteile unter Einwirkung elektromagnetischer Felder untersucht. Zu diesem Zweck wird eine Variationsformulierung vorgestellt. Die Kopplung der Ausbreitung von elektromagnetischen Feldern mit den Verformungen wird durch die Einführung von elektromagneti...

The deformation and fracture of impact loaded thin steel square plates is studied experimentally and numerically. Impacts with low velocities (10–15 m/s) are calculated and an inductive machine (IM) is used as an impact loading device in a developed experimental unit. Impact tests are made for different velocities which correspond to the cases of e...

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 mat...

Inelastic deformation of conductive bodies under the action of electromagnetic fields is analyzed. Governing equations for non-stationary electromagnetic field propagation and elastic–plastic deformation are presented. The variational principle of minimum of the total energy is applied to formulate the numerical solution procedure by the finite ele...

The paper presents the description of methods, algorithms and software were developed for numerical simulation of two- and three-dimensional creep-damage problems. Special attention is stressed on the problems of solid’s behavior at conditions of cyclic varying of stress and temperature fields which is widely spread in modern aerospace and power in...

Creep of cyclically loaded bodies and their fracture due to creep mechanisms are studied. Creep damage equations are built by use of tensor parameter for titanium alloy. Similar equations were derived for stress cyclic varying using the method of asymptotic expansions and averaging in a period. 2d plane stress problems were solved by FEM and fields...

The new method of solving thermal creep problems, accounting for cyclic variations of external force and thermal fields was put forward. Asymptotic expansions and period averagings were used to derive the systems of basic and auxiliary equations. The equation of state for cyclic thermal creep was proposed and validated. Numerical simulation of the...

We present results of the investigations on flexural-flexural-torsional nonlinear vibrations of twisted rotating beams described by the system of three nonlinear integro-differential equations expressed in partial derivatives. Cross-sectional deplanation of beams is adjusted to the equations and it is assumed that centre of gravity and shear centre...

We present a method for solving problems of high-temperature cyclic creep and damage accumulation in structural elements. The asymptotic expansion and averaging techniques both over the period of forced vibrations of a body and that of slowly varying loads are used for the set of equations describing the creep and damage processes in thin-walled st...

The computational methods and outcomes of the analysis of strength of the moulds elements from carboneum - carbonic composite materials (CCCM), used in NSC "KhFTI" for pressing items by a method of pseudo-isostatic pressing under pressure up to 100 MPa and temperature up to 1800 degrees C are submitted, The wall of the barrel of a mould is modeled...

The paper proposes computer algebra system (CAS) algorithms for computer-assisted derivation of the equations of motion for systems of rigid bodies with holonomic and nonholonomic constraints that are linear with respect to the generalized velocities. The main advantages of using the D’Alembert-Lagrange principle for the CSA-based derivation of the...

The theory behind analytical algorithms for computer-algebra systems is discussed. A computer system is described which is capable of optimizing input data, constructing equations of equilibrium and motion, formulating and solving the basic mechanics problems for a broad class of holonomic systems with elastic and dissipative constraints on the bas...

The models for description of creep-damage behaviour in materials and thin shallow shells and plates deforming in conditions of joint action of static and fast cyclic load are given. The properties of the proposed material model were established by comparison of experimental and numerical data. The method for numerical simulation by in-house code o...

The models for description of creep-damage behaviour in materials and thin shallow shells and plates deforming in conditions of joint action of static and fast cyclic load are given. The properties of the proposed material model were established by comparison of experimental and numerical data. The method for numerical simulation by in-house code o...

A method is presented for solving boundary-value elastic problems on the basis of the variational–structural method of R-functions and Reissner's mixed variational principle. A mathematical formulation is given to problems on the deformation of elastic bodies under mixed boundary conditions and bodies interacting with smooth rigid dies. Solutions s...

The method of solving for boundary value problems of the theory of elasticity is presented. It is based on the variational-structural method of the R-functions and Reissner's mixed variational principle. The mathematical statement of problems of elastic bodies deformations under mixed boundary conditions (including bodies interacting with smooth ri...

 The constitutive model with a single damage parameter describing creep-damage behaviour of metals with respect to the different sensitivity of the damage process due to tension and compression is incorporated into the ANSYS finite element code by modifying the user defined creep material subroutine. The procedure is verified by comparison with sol...

Thin-walled structural elements are often subjected to cyclic loadings. This paper presents a material model describing creep behaviour under high-cycle loading conditions (N greater than or equal to 5 x 10(4)-10(5)). Assuming that the load can be split into two joint acting parts (a static and a superposed, rapidly varying small cyclic component),...

Thin-walled structural elements are often subjected to cyclic loadings. This paper presents a material model describing creep behaviour under high-cycle loading conditions (N ≥ 5 × 104-105). Assuming that the load can be split into two joint acting parts (a static and a superposed, rapidly varying small cyclic component), the asymptotic expansion o...

For the determination of effective elastic properties an energy averaging procedure has been used for particle reinforced composite materials. This procedure is based on finite element calculations of the deformation energy of a characteristic volume element. The proposed approach allows the determination of effective properties of particle reinfor...

We propose a method for the investigation of creep and long-term strength of statically and cyclically loaded elements of power-generating units. We present the results of numerical analysis of creep and fracture of herringbone lock joints of the blades of the second stage of gas-turbine engines as well as of their stress-strain state and accumulat...

Problem statements and methods of nonlinear creep investigations for bodies failing as a result of creep under the joint action of static and cyclic loads are described. One and two-dimensional plane models are presented. Creep and failure numerical examples for continuous plates with a small hole under their in-plane cyclic loading are considered.

A method for calculating creep and fatigue limit under static and cyclic loading the power machine components is suggested. The numerical analysis of fracturing the blade root of gas turbine engine second step is given. Stress-strained state and damage accumulation due to creep are analyzed. The essential influence of high-cyclic loading on stress...

A phenomenological constitutive model for characterization of creep and damage processes in metals is applied to the simulation of mechanical behaviour of thin-walled shells and plates. Basic equations of the shell theory are formulated with geometrical nonlinearities at finite time-dependent deflections of shells and plates in moderate bending. Nu...

Zahlreiche neue Konstruktionswerkstoffe (Leichtmetallegierungen, Polymerwerkstoffe, Komposite usw.) zeigen ab einem bestimmten erhöhten Temperaturniveau, aber, noch mäßigen Belastungen, typische Kriecherscheinungen. Das Kriechverhalten kann dabei auch anisotrop sein, selbst wenn der Werkstoff im Ausgangszustand isotrop ist. Daneben tritt teilweise...

The creep of structures is a nonlinear mathematical problem and the adequate simulation of creep processes involves several difficulties. In order to overcome them, computer numerical methods involving three simulation steps which are all equally important have been used: accurate simulation of the kinematic (possibly nonlinear) and the quasi stati...

The aim of the paper is the presentation of a suitable strategy which enables us to analyses complex problems such as creep of structural members and combines both the important aspects, efficiency and accuracy, in numerical computations. This representation enables us two approaches to models for evaluating the stress-strain state under creep cond...

The problem on the creep of a body under the action of the oscillations loading applied to a part of the body surface is solved. The method is based on application of asymptotic expansions (asymptotic solutions for small parameters with different time scales). An algorithm is described which gives an efficient solution of the nonlinear differential...

Experimental and theoretical data are presented on the creep and long-term strength of D16AT alloy with anisotropic properties. Experimental data on the creep of rectangular plates are compared with calculated ones obtained with regard for geometrical nonlinearity of deformation.

A dependence is suggested between the number of cracks and breaking stresses in glass, which differs from the known empirical dependence by the presence of the characteristic size. The available experimental data are used to check the correlation obtained. The constant characterizing the interrelation between glass strength and the number of cracks...

The construction and methodology is presented for solving nonlinear boundary value problems for supply lines made of synthetic glass, whose deformation characteristics depend on the form of strain state. The supply lines are represented by points on cylindrical capsules. The physical equations are obtained on the basis of the first and second invar...

Methods for calculating creep of thin-walled shells and plates are developed further in relation to creep and long-term strength of three-layer shells with load-carrying layers and stiffening ribs between them. Basic relations, an algorithm and examples of calculations are given.

In this paper we shah present a theory of anisotropic creep, constituting a creep generalization of the theory of plasticity, which allows for the effects of initial anisotropy and the anisotropy induced (workhardening). We shah consider two versions of the theory: of the flow (yield) and aging types. These have been studied for two substantially a...

The title problem is analyzed. The linearization of the nonlinear boundary value problem is carried out by the method of time-dependent steps. The solution to each step is sought by the method of consecutive approximations of the integro differential equation. Creep of a thin-walled pipe in the rigid flange zone is examined as an illustrative examp...