Design of the levers at the development of new self-equalizing thrust bearings

Plain bearings are undoubtedly one of the main parts of the power machines (such as a turbine or compressor). However, there are many cases when in large power equipment is occurring asymmetrically loading on bearings due to thermal deformations, production inaccuracies, or simple deflection of the shaft. Presented research deals with the numerical analysis of levers being as the first step at the design of a new self-equalizing thrust bearing with the goal to find out its behaviour and base on that to make the improvements. The numerical analysis was done for the bearing with 12 segments using the software ANSYS. The boundary conditions were applied so to prevent the movement (collapse) of the system and at the same time use them to influence the stress distribution in the levers as little as possible. The steel 34CrNiMo6 has been used for the levers in a refined state. The achieved results confirmed the design of the levers, its sufficient stiffness, good functionality, and reliability. (C) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ICSID 2020 Organizers.Ministry of Education, Science, Research and Sport of Slovak Republic [APVV-19-0550, KEGA 005TUKE-4/2021]Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky: APVV-19-0550; Kultúrna a Edukacná Grantová Agentúra MŠVVaŠ SR, KEGA: 005TUKE-4/202

Numerical simulation of the detection of crack in reinforced concrete structures of NPP due to expansion of reinforcing corrosive products using impact-echo method

Nuclear energy boom is starting nowadays. But also current nuclear power plants (NPP) are duty to certify their security for regular renewal of their operating licenses. NPP security can be significantly affected by defects of large amount of ageing reinforced concrete structures. Advanced Impact-Echo method seams to be very hopeful to cooperate at performing in-service inspections such structures. Just these in-service inspections are included in the first priority group of specific technical issues according to the recommendations of OECD-Nuclear Energy Agency, Commission on Safety of Nuclear Installation in the field of ageing management. This paper continues of extensive project dealing with Impact-Echo method application. It will present a method description and main results of numerical modeling of detection and localization of crack caused by corrosive product expansion. Steel reinforcing rods are subjected to corrosion due to diffusion of corrosive agents from structure surface. Corrosive products have up to 7-times larger volume than pure steel. Raised strain can cad lead up to concrete failure and crack development. We investigate whether it is possible to detect these growing cracks by Impact-Echo method in time. Experimental verification of our numerical predictions is prepared on Civil Faculty in Brno

The proper filling confirmation of the cavities in massive concrete structures of nuclear power plants by impact-echo method

Nuclear power plants (NPP) are duty to certify their security for renewal of operating license. Security can be significantly affected by defects of ageing concrete reinforced structures. The methods, how to do in-service inspections of these aging structures of NPP more quickly, cheaply and reliably, are still being looking for. Advanced Impact-Echo method seams to be very hopeful. This paper is a part of extensive project and continues a number of papers published in Czech as well as in foreign. It brings a method description and a main results survey of the numerical modeling of the detection of grouted (repaired) voids in massive concrete structures. Cavities are filled by grouting polyurethan compound CarboPur WF. We try to find out if it is possible or impossible to confirm simply, by Impact-Echo method, if cavities have been filled properly. Consequently, these numerical predictions will be verified on real (scaled 1:1) specimens in NRI Řež as a part of this project as well

Hydrodynamicky mazaný kontakt mezi axiálními kruhy pastorku a kola rychloběžné převodovky: Příspěvek k numerickému hodnocení

In this study, the hydrodynamically lubricated contact between axial rings of high-speed gearboxes considering their steady state operating mode is studied. Perfect geometry of rings and isothermal oil condition are next simplifying assumptions. The assumption that the contact of rings is hydrodynamically lubricated is suitable as the ratio between the minimal oil film thickness, hmin, and roughness, σ, fulfils the precondition hmin/σ >> 3 for the operating mode. The general Reynolds equation for 2D situation is then convenient to use for the determination of the oil pressure field and of the oil flow rate. Results for an example with a geometry of rings and with an operating mode are presented. Important dependence between the nominal film thickness and the value of transmitted axial force is brought out here for the considered lubricated contact. An attention is also devoted to friction losses.Tato studie se zabývá hydrodynamicky mazaným kontaktem mezi axiálními kruhy rychloběžné převodovky pro její ustálený operační režim. Zjednodušujícími předpoklady jsou dokonalá geometrie kruhů a stejnoměrná teplota oleje. Předpoklad, že kontakt je hydrodynamicky mazaný, je vhodný, protože pro uvedený operační režim je splněna podmínka hmin/σ >> 3 poměru minimální tloušťky olejového filmu (hmin) a drsnosti (σ). Pro stanovení pole tlaku oleje a toku oleje je jako vhodná užita obecná Reynoldsova rovnice pro 2D situaci. Výsledky jsou prezentovány pro vybraný případ kruhů a operačního režimu. Je uvedena důležitá závislost přenášené axiální síly na nominální tloušťce filmu. Pozornost je rovněž věnována třecím ztrátám

Vliv výrobních odchylek tvarů paty protuberantních zubů na namáhání ozubení rychloběžných převodovek

Příspěvek popisuje řešení aktuálního problému spojeného s technologií výroby ozubených kol rychloběžných převodovek. Cílem je stanovení spolehlivých podkladů a postupu hodnocení vlivu výrobních odchylek tvarů paty protuberantních zubů na namáhání a únosnost ozubení. Možnosti dosud používaného software přinášejí spíše nejistotu. Byla vyřešena řada náročných MKP výpočtů napětí pro různé varianty odchylek tvaru paty zubu, které v praxi nastávají. Diskutován je vliv změny mechanických vlastností materiálu, s hloubkou zabroušení. Výsledky budou využity jak při návrhu ozubení, tak i jako podklady pro rozhodování, jak nakládat s díly s vadami, zda je dále použít nebo vyzmetkovat. To přispěje ke zvýšení efektivity výroby i spolehlivosti převodovek.The paper describes the solution of a current problem related to the technology of production of gear for high-speed gearboxes. The aim is to establish a reliable basis and procedure for evaluating the influence of manufacturing variations in the shape of the heel of the protuberant teeth on the stress and load capacity of the gearing. The capabilities of the software used so far bring rather uncertainty. A number of challenging FEA stress calculations for different variations of tooth heel shape deviations that occur in practice have been solved. The effect of changing the mechanical properties of the material with the depth of grinding is discussed. The results will be used both in the design of gearing and as a basis for deciding how to handle parts with defects, whether to continue using them or to scrap them. This will help to increase the efficiency of production and the reliability of gearboxes

A study of hydrodynamically lubricated contact between axial rings of a high-speed gearbox

The pressure field and losses in hydrodynamically lubricated contact between axial rings of the pinion and the wheel of a high-speed gearbox under steady-state loading are investigated. For that reason a computer program was developed to numerically solve the general Reynolds and energy equations simultaneously, with consideration of a viscosity-temperature relation. The Barus’ empirical equation was used to express a viscosity-pressure relation as well. For chosen design parameters, dissipative heat in the lubricated contact is shown as a function of transmitted axial force. It is presented that the contact axial force and losses are influenced by the state how the gap between rings is filled

Finding the Stiffnesses of Interface Contact Elements for the Computational Model of Steam Turbine Blading

V této práci je navržena metoda stanovení tzv. kontaktních tuhostí (CS) kontaktních prvků nelineárního dynamického výpočetního modelu (NDM) olopatkovaného disku se zabudovanými kontakty mezi lopatkami. Metoda je založena na porovnání rezonančních frekvencí NDM a známých vlastních frekvencí odpovídajícího lineárního systému. Za tímto účelem uvádíme efektivní postup výpočtu rezonanční odezvy NDM, což umožňuje stanovit CS jednotlivě. Metoda je demonstrována na příkladu olopatkovaného disku parní turbíny, který je osazen lopatkami o délce 48 palců.A method is proposed for fitting the so-called contact stiffnesses (CSs) of interface elements for a nonlinear dynamic model (NDM) of a bladed disk with integral contact couplings. The method is based on comparison between frequencies of the resonant response of NDM and known natural frequencies in limiting linear cases. For this purpose, an effective approach for calculation of the resonant response NDM is presented allowing CSs to be picked individually. The method is demonstrated for the case of steam turbine bladed disk equipped with 48 inch blades