Deformation behavior of two continuously cooled vanadium microalloyed steels at liquid nitrogen temperature

The aim of this work was to establish deformation behaviour of two vanadium microalloyed medium carbon steels with different contents of carbon and titanium by tensile testing at 77 K. Samples were reheated at 1250°C/30 min and continuously cooled at still air. Beside acicular ferrite as dominant morphology in both microstructures, the steel with lower content of carbon and negligible amount of titanium contains considerable fraction of grain boundary ferrite and pearlite. It was found that Ti-free steel exhibits higher strain hardening rate and significantly lower elongation at 77 K than the fully acicular ferrite steel. The difference in tensile behavior at 77 K of the two steels has been associated with the influence of the pearlite, together with higher dislocation density of acicular ferrite. [Projekat Ministarstva nauke Republike Srbije, br. OI174004

Experimental and Numerical Evaluation of a Steamline Behaviour Using Local Approach

Results of the experimental and numerical comparative analysis of steamline pipes have been presented. New pipes and the pipes used for more than 117,000 hours at 540 °C under pressure of 42 bars have been simultaneously tested. This testing has been carried out because frequent failures of the equipment components exposed to elevated temperatures, such as steam pipelines, make it necessary to pay particular attention to the analysis of the materials used. The most frequent failures were those connected with occurrence of cracks, particularly expressed in case of steel 14MoV6 3. Local approach to fracture has been developed for complete understanding of fracture mechanism. This approach combines theoretical, experimental and numerical solution

Influence of friction stir welding parameters on properties of 2024 t3 aluminium alloy joints

The aim of this work is to analyse the process of friction stir welding (FSW) of 3 mm thick aluminium plates made of high strength aluminium alloy - 2024 T3, as well as to assess the mechanical properties of the produced joints. Friction Stir Welding is a modern procedure which enables joining of similar and dissimilar materials in the solid state, by the combined action of heat and mechanical work. This paper presents an analysis of the experimental results obtained by testing the butt welded joints. Tensile strength of the produced joints is assessed, as well as the distribution of hardness, micro-and macrostructure through the joints (in the base material, nugget, heat affected zone and thermo-mechanically affected zone). Different combinations of the tool rotation speed and the welding speed are used, and the dependence of the properties of the joints on these parameters of welding technology is determined

Lasersko čišćenje tekstilnih eksponata sa korodiranim metalnim nitima - optimzacije parametara procesa

This paper presents the results of the laser cleaning effects on textile samples with corroded metallic threads. In many museum collections, there are textile exhibits like uniforms, national costumes, flags and home textile, embroidered with metallic threads. Corrosion of metal threads is one of the most common problems that damage embroidered items. In the practice, the application of conventional cleaning methods rarely gives the expected results, and the implementation of laser technology was the next step for corrosion products cleaning. The Nd:YAG laser was used to clean the corrosion of embroidered items from a museum study collection. The effects on the laser irradiated zones were investigated by optical and SEM microscopy and the EDX analysis. The laser irradiation process parameters of the metal threads corrosionU radu su prikazani rezultati čišćenja korozije na tekstilnim eksponatima sa metalnim nitima pomoću lasera. U mnogim muzejskim zbirkama nalaze se eksponati kao što su uniforme, narodne nošnje, zastave i kućni tekstil, ukrašeni vezom metalnim nitima. Korozija metalnih niti je jedan od najvećih problema, koji oštećuje vezene eksponate. U praksi, veoma često, klasične metode ne daju očekivane rezultate i primena lasera je sledeći korak čišćenja korozionih produkata. Nd- YAG laser je korišćen za čišćenje korozije vezenih eksponata iz muzejske, studijske zbirke. Efekti u zonama ozračenim laserom su ispitivani optičkim mikroskopom, SEMom i EDX analizom. Određeni su izabrani parametri za uspešno i bezbedno čišćenje korozije na metalnim nitima.В этой статье приведены результаты очистки коррозии на экспонатах из текстиля с металлическими нитями с помощью лазера. Во многих музейных коллекциях представлены экспонаты, такие как формы, народные костюмы, флаги и домашний текстиль, вышитые металлической нитью. Коррозия металлических нитей является одной из самых больших проблем, которая повреждает вышитые экспонаты. На практике, очень часто, классические методы не дают ожидаемых результатов и применение лазера является следующим шагом очистки следов коррозии. Nd-YAG лазер используется для очистки коррозии вышитых экспонатов из музейных исследовательских коллекций. Эффекты в областях облученных лазером были исследованы с помощью оптического микроскопа, SEM и EDX анализом. Некоторые параметры определяются и выбираются так, чтобы успешно и безопасно очистить металлические нити от коррозии.Dans ce papier on a présenté les résultats du nettoyage de corrosion chez les objets exposés en textile aux fils métalliques réalisé au moyen du laser. Dans plusieurs collections de musée on trouve les objets tels que uniformes, costumes nationaux, drapeaux et textile de maison qui sont ornés de broderie faite en fils de métal. La corrosion des fils en métal est un des plus grands problèmes car elle endommage les objets exposés brodés. En pratique les méthodes classiques ne donnent pas souvent les résultats espérés et l’utilisation du laser est le pas suivant dans le nettoyage des produits de corrosion. Le laser Nd-YAG a été utilisé pour le nettoyage de corrosion sur les objets brodés appartenant à la collection d’étude de musée. Dans les zones irradiées par laser les effets ont été étudiés au moyen du microscope optique et en utilisant les analyses SEM et EDX. On a déterminé les paramètres choisis pour le nettoyage en sécurité et avec succès de la corrosion chez les fils en métal

Finite Element Modeling of Hydride Composite Material Subjected to Ballistic Impact

Hybrid composite materials are prepared to combine different properties of materials in order to stop the ballistic impact make consequences milder. First layer is ceramics in order to influence the projectile shape, induce plastic deformation to the top of the projectile, reduce speed, power and strength of the attack. Accomplishing its job ceramics is breaking and overhang projectile to composite layer that prevents further advancement of the projectile due to improved elastic properties. Samples are subjected to impact tests, to determine maximum speed, deep of penetration and fracture. FEM (finite element modeling) provides faster and realistic simulations of ballistic impact. Used software is Abaqus 6.10 CAE

Ocena uspešnosti uvođenja novog proizvoda u različite tehnološke procese

Developments in technology and daily needs have inevitably led to the appearance of new market-based products or in the implementation of new raw materials for the manufacture of such products. The levels of daily needs and consumer demands and total investments in production have justified the scientific and professional efforts. The example of using hemp in the production of special paper is beneficial to this industry in many aspects. Advantage is obvious in stimulating activities at an agricultural complex that is able to provide raw material for the textile industry, and also a portion of raw material for the cellulose industry. As a result, this might relieve the country's economy of unnecessary special-paper imports, since these products could be manufactured in domestic plants, and provide hemp fibers for the textile industry.Razvoj tehnologije i potrebe življenja, neminovno uslovljavaju pojavu novih proizvoda na tržištu, ili primenu novih sirovina za proizvodnju takvih proizvoda. Opravdanost takvih naučnih i stručnih napora, određuje nivo potreba i traženje tržišta, kao i ukupni troškovi uloženi u takvu produkciju. U slučaju primene konoplje za proizvodnju specijalnih papira višestruko je opravdan, u ovoj tehnološkoj oblasti. Opravdanost se ogleda u podsticaju aktivnosti poljoprivrednog kompleksa, koji će obezbediti jednu od sirovina za tekstilnu industriju, kao i delom sirovina za celulozno papirnu industriju, čime bi se zemlja delom oslobodila nepotrebnog uvoza specijalnih papira, koji bi se mogli proizvoditi, u našim fabrikama, kao i vlakna konoplje za potrebe tekstilne industrije

Izražavanje pouzdanosti opreme u procesnim tehnologijama

Every process defined within a specific technology necessitates the exploitation of equipment with a large variety in structures. Procedures in the technology define the purpose of the component, and in-service operations must be followed according to instructions given and distributed by the manufacturer, altogether with the equipment. The instructions for component operation define the conditions for their reliable component operation and functionality. In addition to the conditions, generally, the components should be used in the optimal scope of allocated working capacities, and should be operating within the limited values of physical quantities defined by the technology process, such as: pressure temperature, flux, velocity, and other physical quantities. Equipment reliability assures the continuity of the technology process, uniformity of the final product quality, higher work productivity and ratability of the installed equipment, increased economic efficiency, etc.Svaki tehnološki proces uslovljava korišćenje određene opreme koja je po svojoj strukturi raznovrsna. Namena opreme definisana je tehnološkim postupkom, a koristi se prema uputstvu koje propisuje proizvođač opreme i isporučuje zajedno sa opremom. Uputstvo za korišćenje opreme propisuje uslove u kojima oprema može pouzdano ostvariti svoju namenu. Pored uslova u širem smislu, oprema mora biti korišćena u optimalnim opsezima radnih kapaciteta i u graničnim vrednostima fizičkih veličina, koje određuju tehnološki procès, kao što su: pritisci, temperature, protoci, brzine i druge fizičke veličine. Pouzdanost opreme obezbeđuje neprekidnost tehnološkog procesa, ujednačenost kvaliteta krajnjeg proizvoda, veću produktivnost rada, veću rentabilnost instalirane opreme, veću ekonomsku efikasnost i dr

Effect of solution pH on crack initiation and propagation in glass-polyester pipes subjected to impact

The objective of this study was the determination of the influence of alkaline and acidic solutions on the impact properties of glass-polyester composite pipes. First, the impact test was performed on virgin samples (without the influence of any liquid) to obtain knowledge about the original material properties. Subsequently, the specimens were soaked in water and in alkaline and acidic solutions: sodium hydroxide, ammonium hydroxide, phosphoric acid, and nitric acid. The specimens were left in each liquid for 3, 10, 30, and 60 days at room temperature. The impact toughness and the crack initiation and propagation energies were recorded for all samples. A comparison of the results was made based on the pH values of the aggressive media, as well as based on the original impact properties and number of days of treatment. This way, the service life of pipes for transport of theexamined solutions could be predicted. POLYM. COMPOS., 2012

Micromechanical estimates of the critical values of j-integral for the steel of steam pipelines

We analyze the level of damage to 14MoV63 steel for steam pipelines under the conditions of crack-growth initiation according to the mechanism of ductile fracture. The state of the material after service for about 100,000 h at the power plant is estimated by using a combined experimental and numerical procedure based on the local approach to fracture. The level of damage is determined by analyzing the material taken from the pipeline (aged) and new (virgin) material of the same grade (for the sake of comparison). The critical values of the J-integral are determined on single-edge notched bend (SENB) specimens both experimentally and by using a simplified procedure of local approach without knowing the microstructural parameters. Two micromechanical models are applied: the Rice - Tracey models modified by Beremin (uncoupled) and the complete Gurson model (coupled)