Power plant component design using creep and fatigue damage analysis

Structural analysis and design of power plant components requires us to take into account inelastic deformation and material damage processes under constant and variable loading and temperature conditions. The aim of this presentation is to introduce the constitutive models of creep and damage for advanced heat resistant steels. An emphasis is placed on the description of ductilebrittle transition of the damage mode depending on the applied stress level and the duration of the creep process. The model is applied to the lifetime prediction of a real power plant component. For this purpose a user-defined material subroutine is developed inside a general finite element code. The results of computations illustrate basic features of the stress redistribution and the damage evolution during isothermal loading cycle. Based on the obtained stress, strain and damage fields, we discuss the extensions of the proposed method to non-isothermal variable loading

Extreme acoustic anisotropy in crystals visualized by diffraction tensor

Acoustic wave propagation in single crystals, metamaterials and composite structures is a basic mechanism in acoustic, acousto-electronic and acousto-optic devices. Acoustic anisotropy of crystals provides a variety of device performances and application fields, but its role in pre-estimation of achievable device characteristics and location of crystal orientations with desired properties is often underestimated. A geometrical image of acoustic anisotropy can be an important tool in design of devices based on wave propagation in single crystals or combinations of anisotropic materials. We propose a fast and robust method for survey and visualization of acoustic anisotropy based on calculation of the eigenvalues of bulk acoustic wave (BAW) diffraction tensor (curvature of the slowness surface). The stereographic projection of these eigenvalues clearly reveals singular directions of BAW propagation (acoustic axes) in anisotropic media and areas of fast or slow variation of wave velocities. The method is illustrated by application to three crystals of different symmetry used in different types of acoustic devices: paratellurite, lithium niobate, and potassium gadolinium tungstate. The specific features of acoustic anisotropy are discussed for each crystal in terms of their potential application in devices. In addition, we demonstrate that visualization of acoustic anisotropy of lithium niobate helps to find orientations supporting propagation of high-velocity surface acoustic waves.Comment: 12 pages, preprint submitted to EPJ Plu

Inelastic Deformation of Conductive Bodies in Electromagnetic Fields

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 element method. With the proposed method, distributions of vector characteristics of the electromagnetic field and tensor characteristics of the deformation process are illustrated for the inductor-workpiece system within a realistic electro-magnetic forming process

A generalized framework towards structural mechanics of three-layered composite structures

Three-layered composite structures find a broad application. Increasingly, composites are being used whose layer thicknesses and material properties diverge strongly. In the perspective of structural mechanics, classical approaches to analys is fail at such extraordinary composites. Therefore, emphasis of the present approach is on arbitrary transverse shear rigidities and structural thicknesses of the individual layers. Therewith we employ a layer-wise approach for multiple (quasi-)homogeneous layers. Every layer is considered separately whereby this disquisition is based on the direct approach for deformable directed surfaces. We limit our considerations to geometrical and physical linearity. In this simple and familiar setting we furnish a layer-wise theory by introducing constraints at interfaces to couple the layers. Hereby we restrict our concern to surfaces where all material points per surface are coplanar and all surfaces are plane parallel. Closed-form solutions of the governing equations enforce an arrow frame since they are strongly restrictive in the context of available boundary conditions. Thusacomputational solution approach is introduced using the finite element method. In order to determine the required spatially approximated equation of motion, the principle of virtual work is exploited. The discretization is realized via quadrilateral elements with quadratic shape functions. Here by we introduce an approach where nine degrees of freedom per node are used. In combination with the numerical solution approach, this layer-wise theory has emerged as a powerful tool to analyze omposite tructures. In present reatise, e ould ike o arify he road cope f his pproach

Modelling of Creep and Oscillations in Material Described by Armstrong-Frederick Equations

Different structural elements at high temperatures and cyclic loading demonstrate essential creep behavior. Due to variety of materials which are used in modern industrial applications the different forms of creep response have to be analyzed. The one of them presents in materials are characterized by creep processes with essential recovery, which is expressed by strain decreasing after the unloading. Such material behavior is described by well-known Armstrong-Frederick model. The case of cyclic loading leading to forced oscillations at high temperature is studied. The Armstrong- Frederick creep model contains two equations: first for creep strain rate function as well as the second for socalled backstress evolution. The problem is solved by two time scales methods with subsequent averaging in a period of oscillations. The solution was performed for the hyperbolic creep strain rate function which satisfactory describes the high-temperature behavior of advanced steel with primary creep conditions. The stress function is presented by expansion in Fourier series. Asymptotic solution of creep equations was obtained and by use of the procedure of averaging in the period the new model describing ‘slow’ creep motion has been derived. The analytical forms of influence functions for both equations of the model expressing the role of cyclical loading were obtained. Numerical examples which demonstrate the cyclic creep behavior in advanced steel X20CrMoV12-l are presented and discussed

Kontaktwechselwirkung einer Rohrleitung mit der Reparaturbandage aus einem Kompositwerkstoff

In der vorliegenden Arbeit wird die Kontaktaufgabe über die Wechselwirkung einer langen Zylinderschale mit einer koaxialen zylindrischen Bandage aus einem Verbundwerkstoff untersucht. Der Verbundwerkstoff wird als ein homogenes orthotropes Material mit bekannten effektiven elastischen Eigenschaften modelliert. Basierend auf der klassischen Schalentheorie werden die Grundgleichungen für die Kontaktaufgabe sowie allgemeine Lösungen für die Durchbiegungen und Schnittgrößen formuliert. Die unbekannten Integrationskonstanten sowie die Kontaktfläche werden numerisch mit Hilfe des Programmpakets Maple ermittelt. Drei charakteristische Längen der Bandage, bei denen der Übergang von einemKontaktschema der Wechselwirkung zu einem anderen erfolgt, wurden ermittelt. Es wurde festgestellt, dass die Änderung des Innendrucks nicht zum Übergang von einem Kontaktschema zu einem anderen führt. Der Charakter der Kontaktwechselwirkung wird durch geometrische Parameter derVerbindung und elastische Materialeigenschaften der Schale und der Bandage bestimmt.In the present work the contact interaction of a long cylindrical shell with a coaxial cylindrical wrap made of a composite material is investigated. The composite material is modeled as a homogeneous orthotropic medium with known effective elastic properties. Based on the classical shell theory governing equations for the contact problems and general solutions to the deflections and internal forces are formulated. The unknown integration constants and the contact surface area are determined numerically using the software package Maple. Three characteristic lengths of the wrap, for which the transition from one contact mode to another takes place, have been determined. It was found that the change in the internal pressure does not affect the transition between the contact modes. The nature of the contact interaction is determined by the geometric parameters of the contact pair and elastic material properties of the shell and the repair wra

Monochromaticity of coherent Smith-Purcell radiation from finite size grating

Investigation of coherent Smith-Purcell Radiation (SPR) spectral characteristics was performed both experimentally and by numerical simulation. The measurement of SPR spectral line shapes of different diffraction orders was carried out at KEK LUCX facility. A pair of room-temperature Schottky barrier diode (SBD) detectors with sensitivity bands of $60-90$~GHz and $320-460$~GHz was used in the measurements. Reasonable agreement of experimental results and simulations performed with CST Studio Suite justifies the use of different narrow-band SBD detectors to investigate different SPR diffraction orders. It was shown that monochromaticity of the SPR spectral lines increases with diffraction order. The comparison of coherent transition radiation and coherent SPR intensities in sub-THz frequency range showed that the brightnesses of both radiation mechanisms were comparable. A fine tuning feasibility of the SPR spectral lines is discussed.Comment: 7 pages, 7 figures, 3 table

Сучасні тренди підготовки фахівців з управління проектами та програмами

У збірнику матеріалів конференції висвітлено роботи фіналістів Усеукраїнського конкурсу студентських наукових робіт 2018–2019 навчального року з «Управління проектами та програмами» й сучасні тренди підготовки фахівців з управління проектами та програмами, які були обговорені на науково-практичній конференції в м. Луцьку 5 квітня 2019 р. Збірник розрахований на широке коло фахівців з управління проектами та програмами, спеціалістів, що працюють у структурних підрозділах органів державної влади й управління, економістів, викладачів, аспірантів, здобувачів і студентів, а також усіх, хто цікавиться сучасними трендами підготовки фахівців з управління проектами та програмами