Software in the field of the metal materials testing

Razvoj softvera u oblasti ispitivanja metala tekao je uporedo sa razvojem računarske opreme - hardvera. Osnovni cilj ovog rada je pokušaj pružanja pregleda postojećeg softvera u oblasti ispitivanja metala. Drugi postavljeni cilj je definisanje osnovnih svojstava koje karakterišu kvalitetan softver. Industrija softvera je danas izrazito veliki biznis sa velikim brojem proizvoda slične ili iste namene, zbog čega je otežan izbor optimalnog paketa ili sistema za ispitivanje za odgovarajuću cenu. Treći cilj ovog rada je prikaz savremenog softvera i mogući pravci razvoja softvera. Prikazan je i osnovni spisak adresa koje se odnose na softver vezan za ispitivanje metala.Software development in the field of the metal materials testing is coupled with development of the computers hardware. The aim of the paper is giving the review of software packages in the field of the metal material testing. Base properties which characterize the good quality software are presented. A large number of the software from the field of material testing could be finding in the market, so it is difficult to recognize best software characteristics for optimal price and it is discussed in the paper. A basic list of the modern software and directions of software development in the future are presented

Comprehensive approach to weld repair on elements of power transmission – case study for hydro turbine shaft

Turbine and generator rotors and shafts undergo high stresses during regular working life and, from a safety and operational aspect, are the most significant components of a power generation system. Depending on the appropriate operating conditions, like temperature and/or corrosion the, shafts can be fabricated out of low/high alloy heat resistance material or of low alloyed, highly toughened material for different application. Despite known good practice and developed operation procedures, the failures of shafts sometimes occurs. The right and well defined failure analysis is the basis for feasibility analysis of repair method in the power generating industry. The analysis of direct and indirect costs of repair after the failure analysis as well as the analysis of the repair and post-repair conditions of the repaired element is the vital for decision on the key question. Is it possible to repair this element and what is the optimal repair strategy? This paper compares and analyses two approaches, by weldability analysis and weld cycle simulation, in order to determine welding feasibility analysis of cracked hydro turbine shafts

Finite element model for stress analysis and nonlinear contact analysis of helical gears

Određivanje naponskog i deformacionog stanja na bokovima i u podnožju zubaca jedan je od osnovnih zadataka u toku proračuna opterećenja i provere nosivosti zupčanika. U ovom radu opisan je postupak razvijanja modela konačnih elemenata za istovremeno praćenje naponskog i deformacionog stanja bokova zubaca, podnožja zubaca i segmanata zupčanika sa kosim zupcima u toku sprezanja jednog para zubaca. Takođe, opisano je i simuliranje kontaktnih uslova kod evolventnih zupčanika sa kosim zupcima metodom konačnih elemenata (MKE). Izvršena je odgovarajuća analiza za izbor modela spregnutih zupčanika koji je istovremeno dovoljno ekonomičan i dovoljno geometrijski precizan. Razvijen je poseban algoritam za crtanje evolventnog profila zubaca. Ovaj algoritam ugrađen je u postojeći MKE softver i na taj način je obezbeđeno crtanje realne geometrije bokova zubaca u kontaktu. Takođe, izvršen je i izbor optimalne gustine mreže konačnih elemenata. Opisani modeli konačnih elemenata razvijeni su za jedan konkretan par zupčanika sa kosim zupcima. Dobijeni numerički rezultati pogodni su za praćenje promene deformacionog i naponskog stanja u toku perioda sprezanja para zubaca. .One of the main goals during load calculations and load capacity check for gears is determination of deformation and stress state in teeth contact zones and teeth fillets. This paper describes development of the finite element model for simultaneously monitoring the deformation and stress state of teeth flanks, teeth fillets and parts of helical gears during the tooth pair meshing period. The paper also describes the Finite Element Method simulation of contact conditions for helical gears teeth with an involute profile. A suitable analysis is performed in order to select a meshed gears model which is sufficiently economic and in same tame sufficiently geometrically accurate. The special algorithm for the tooth involute profile drawing is developed and built in a currently available software for Finite Element Analysis to assure drawing of real flanks contact geometry. The optimal mesh size level is chosen, too. The described finite element models are made for the particular helical gear pair. The obtained numerical results are suitable for tracking deformation and stress variables during the tooth pair meshing period.

Chronology of lost structural integrity initiated from manufacturing defects in welded structures

U različitim vremenskim periodima dolazilo je do gubitka integriteta zavarenih konstrukcija zbog razvoja proizvodnih grešaka zavarenog spoja. Mehanizmi otkaza su bili različiti i uvek su predstavljali novo iskustvo, koje je zahtevalo nova znanja i drugačiji pristup u rešavanju problema. Opsežne analize svih otkaza razmatranih u radu i izvedeni zaključci ipak nisu dovoljni da se potpuno izbegnu proizvodne nesavršenosti i obezbedi integritet zavarenih konstrukcija u eksploataciji. Direktive, standardi i preporuke za izradu zavarenih konstrukcija značajno doprinose rešavanju problema, ali ga ne mogu potpuno eliminisati zbog složenosti i velikog broja uticajnih faktora.At different time periods, loss in structural integrity occurs from initiation of manufacture defects in the welded joint. Failure mechanisms are different and present a new experience always requiring new knowledge and approach in solving the problem. Extended analyses of all failures considered here and derived conclusions are yet not sufficient in completely avoiding manufacture imperfections and assuring in-service integrity of welded structures. Directives, standards and recommendations for manufacturing welded structures significantly contribute in problem solving which they cannot completely eliminate due to the complexity and numerous influencing factors

A new methodology for prediction of high-cycle contact fatigue for spur gears

High-cycle contact fatigue is a localized phenomenon that occurs in highly stressed grains of the material on or under the contact region. The contact zones of tooth flanks for meshed gears are subjected to contact fatigue damages that causes pitting and leads to gears failure. The objective of this paper is to give a new viewpoint in contact fatigue prediction in the case of high-cycle fatigue. The main aim of the presented research is to make the methodology for direct calculation of fatigue crack initiation in contact zones. This methodology is developed for spur gears and used up-to-date methods and multidisciplinary approach. Two methods are built in the new methodology: the Theory of Critical Distances (TCD) and the Finite Element Method (FEM). In this paper the comparative analysis of standard and new methodology for prediction of fatigue crack initiation on tooth flanks is presented. The advantages of methods and procedures used in the new methodology are presented through a case study of particular gear pair. The Finite Element Analysis on 3D gear contact model is used for stress and strain calculation and prediction of the maximum stress location in contact zones along the gear face width. The stress gradient curves from the contact zone are made for a pinion tooth in different cross sections along gear facewidth. The Theory of Critical Distances used these stress gradients and material characteristics for fatigue crack initiation prediction. The benefits of presented methodology are shown by the detail analysis of the obtained results

Dvosmjerni učinak prelijevanja između ruskog burzovnog indeksa i odabranih roba

This paper investigates shock and volatility spillover eJect between Russian index RTS and six futures commodities (Brent oil, natural gas, gasoline, gold, platinum and palladium), observing joint time-frequency domain via wavelet decomposed series. Due to the fact that our time-span of almost 16 years is permeated with tranquil and crisis periods, we divided full-sample into three subsamples – before, during and after World financial crisis (WFC) via modified ICSS algorithm. We find that spillover eJects happen mostly from the commodity markets toward RTS index in all three subsamples. However, during relatively calm periods (first and third sub-periods), spillover eJects are very moderate and they occur in relatively few wavelet scales, which points that duration of these eJects is limited in peaceful times. On the other hand, duration of spillover eJects and its intensity increased during WFC. Also, wavelet coherence indicates that there are areas of stronger co-movements in period of WFC at higher wavelet scales for pairs such as RTS-Brent, -gasoline and -platinum. Commodities that have the strongest transmission eJect on RTS index are Brent oil, gasoline and palladium, while gold has strong volatility transmission only during WFC.Ovaj rad istražuje učinak prelijevanja šoka i volatilnosti između ruskog indeksa RTS i šest robnih terminskih ugovora (Brent nafta, prirodni plin, benzin, zlato, platina i paladij), promatrajući zajedničku vremensko- frekvencijsku domenu preko wavelet razloženih serija. Zbog činjenice da je promatrano vremensko razdoblje od gotovo 16 godina prožeto mirnim i kriznim razdobljima, podijelili smo puni uzorak u tri pod-uzorka: prije, za vrijeme i nakon Svjetske financijske krize putem modificiranog ICSS algoritma. Smatramo da se učinci prelijevanja odigravaju uglavnom od tržišta roba prema RTS indeksu u sva tri pod-uzorka. Medutim, tijekom relativno mirnih razdoblja (prva i treća podskupina) učinci prelijevanja su vrlo umjereni i javljaju se u relativno malim wavelet razinama, što ukazuje da je trajanje ovih učinaka ograničeno u mirnim periodima. S druge strane, trajanje učinaka prelijevanja i njezin intenzitet porasli su tijekom Svjetske financijske krize. Takoder, wavelet koherentnost ukazuje na to da postoje područja većeg međusobnog kretanja u razdoblju Svjetske financijske krize kod viših wavelet razina za parove kao što su RTS-Brent, RTS-benzin i RTS-paladium. Robe koje imaju najjaši ušinak prijenosa na RTS indeks su Brent nafta, benzin i paladij, dok zlato ima snažnu prijenosnu volatilnost samo tijekom Svjetske financijske krize

A new methodology for prediction of high-cycle contact fatigue for spur gears

High-cycle contact fatigue is a localized phenomenon that occurs in highly stressed grains of the material on or under the contact region. The contact zones of tooth flanks for meshed gears are subjected to contact fatigue damages that causes pitting and leads to gears failure. The objective of this paper is to give a new viewpoint in contact fatigue prediction in the case of high-cycle fatigue. The main aim of the presented research is to make the methodology for direct calculation of fatigue crack initiation in contact zones. This methodology is developed for spur gears and used up-to-date methods and multidisciplinary approach. Two methods are built in the new methodology: the Theory of Critical Distances (TCD) and the Finite Element Method (FEM). In this paper the comparative analysis of standard and new methodology for prediction of fatigue crack initiation on tooth flanks is presented. The advantages of methods and procedures used in the new methodology are presented through a case study of particular gear pair. The Finite Element Analysis on 3D gear contact model is used for stress and strain calculation and prediction of the maximum stress location in contact zones along the gear face width. The stress gradient curves from the contact zone are made for a pinion tooth in different cross sections along gear facewidth. The Theory of Critical Distances used these stress gradients and material characteristics for fatigue crack initiation prediction. The benefits of presented methodology are shown by the detail analysis of the obtained results

Determination of critical size of corrosion pit on mechanical elements in hydro power plants

Researchers in the field of fracture mechanics, predominantly developing appropriate solution algorithms for problems of solid bodies with cracks. Problems in mechanics generally, related with fracture and fatigue for solid bodies with various geometries of sharp notches, are studied to a much lesser extent. This situation can be explained by analytical difficulties arising in solving problems of elasticity theory for bodies with rounded notches. To solve problems of such class, starting from data on stress concentration in the rounded notch tip with a significant radius of curvature, simplified solutions with are therefore of great importance. Recent years, due to constant rise of computing power and development of numerical methods, re-evaluation of stress concentration factors from a viewpoint of theory of elasticity is present. This is mainly as a feedback from industry, which have requirements toward mega and nanostructures. Corrosion represents an important limitation to the safe and reliable use of many alloys in various industries. Pitting corrosion is a form of serious damage on metals surface such as high-strength aluminum alloys and stainless steel, which are susceptible to pitting when exposed to a corrosive attack in aggressive environments. This is particularly valid for dynamic loaded structures. The basic idea behind this paper is finding links between different scientific and engineering disciplines, which will enable useful level of applicability of existing knowledge. The subject of this paper is application of new method of determine length scale parameter for estimating the mechanistic aspect of corrosion pit under uniaxial/multiaxial high-cycle fatigue loading…

A new methodology for prediction of high-cycle contact fatigue for spur gears

High-cycle contact fatigue is a localized phenomenon that occurs in highly stressed grains of the material on or under the contact region. The contact zones of tooth flanks for meshed gears are subjected to contact fatigue damages that causes pitting and leads to gears failure. The objective of this paper is to give a new viewpoint in contact fatigue prediction in the case of high-cycle fatigue. The main aim of the presented research is to make the methodology for direct calculation of fatigue crack initiation in contact zones. This methodology is developed for spur gears and used up-to-date methods and multidisciplinary approach. Two methods are built in the new methodology: the Theory of Critical Distances (TCD) and the Finite Element Method (FEM). In this paper the comparative analysis of standard and new methodology for prediction of fatigue crack initiation on tooth flanks is presented. The advantages of methods and procedures used in the new methodology are presented through a case study of particular gear pair. The Finite Element Analysis on 3D gear contact model is used for stress and strain calculation and prediction of the maximum stress location in contact zones along the gear face width. The stress gradient curves from the contact zone are made for a pinion tooth in different cross sections along gear facewidth. The Theory of Critical Distances used these stress gradients and material characteristics for fatigue crack initiation prediction. The benefits of presented methodology are shown by the detail analysis of the obtained results

Geometric optimization of shaft transition zone based on stress-strain analysis of nature inspired design

The presented research primarily considers with the geometric solutions that Nature has optimized. In the study presented in this paper, the nature inspired transition shapes are used in the research of innovative design and geometric optimization of transition zones of the high-loaded shafts