37 research outputs found
Suitability of heat treatment for crack resistance of material in the connection part of heavy transporter for liquid slag
The post weld heat treatment (PWHT) was used to reduce the level of the residual stresses and increase of the crack resistance of the material in the connection part. The article presents the results of the residual stress measurements immediately after welding and after the stress relaxation by the PWHT
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 1250Ā°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
Feruginozna tjeleÅ”ca u pluÄima gradskih pasa
The aim of the study was to assess health hazards induced by environmental exposure to asbestos using urban dogs as biological indicators. Samples of the lung tissue taken from 36 randomly chosen urban dogs were examined. In the group of dogs aged up to four years (n=15) ferruginous bodies were identified in only two. In the dogs older than four years (n=21) 17 were ferruginous body positive. According to Fisher\u27s exact test the difference between the two groups was significant (P<0,001). The presence of asbestos bodies in the lungs of dogs is considered to be evidence of serious contamination of urban areas with respirable mineral fibres. The more frequent presence of asbestos bodies in the lungs of the older dogs indicates long-term accumulation of mineral fibres exceeding 10 Āµm in length. Continuous environmental exposure of the city\u27s population to respirable mineral fibres may therefore pose a health risk.Uzorci pluÄa 36 sluÄajno izabranih gradskih pasa pretraženi su na prisutnost feruginoznih tjeleÅ”aca s namjerom da se procijeni da li izloženost vlaknatim organskim praÅ”inama, uglavnom azbestu, iz gradskog okoliÅ”a, nosi opasnost za zdravlje. U skupini od 15 pasa do Äetir godine starosti, u dva su naÄena feruginozna tjeleÅ”ca. U drugoj skupini koja je sadržavala 21 psa starija od Äetiri godine, sedamnaest njih je imalo pozitivan nalaz. Prema Fisherovu egzaktnom testu postoji znaÄajna statistiÄka razlika (P<0.001) izmeÄu dviju skupina životinja. Prisutnost azbestnih tjeleÅ”aca u pluÄima pasa svjedoÄi da su javne gradske povrÅ”ine yisoko kontaminirane vlaknatim mineralnim praÅ”inama respirabilne veliÄine, uglavnom azbestom. ÄeÅ”Äi nalaz azbestnih tjeleÅ”aca u pluÄima starijih pasa upozorava na akumulaciju vlakana duljih od 10 cm tijekom duljeg vremena, a predvidive su i posljedice takve kontinuirane izloženosti vlaknatim mineralnim kontaminantima za zdravlje gradskog stanovniÅ”tva
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
Microstructural investigation of the heat-affected zone of simulated welded joint of P91 steel
In the process of testing real components exposed to elevated temperature, it is not possible to neglect cracks. The most significant cracks can be induced by welding, which is applied for joining of structural components. Pressure equipment in service is also exposed to high pressure and high stresses. Materials for their manufacturing are designed to resist high stress at elevated temperature, and to meet requirements regarding creep resistance. The objective of this study is to investigate microstructure of different regions of the heat affected zone in T/P91 steels by using thermal simulation instead of welding
SpecifiÄna absobcijska energija staklo-poliester kompozitne cijevi pod statiÄkim tlaÄnim optereÄenjem
The experimental determination of energy of glass-polyester composite tubes static fracture is done. The tubes are of defined structure and known processes of fabrication. The aim was to determine the possibility of their usage as damping elements during impact. Two types of tubular samples with different diameters were tested until fracture under static (low speed) compressive loading. The applied forces and sample lengths were measured until complete destruction of samples. From the diagrams received directly from testing devices, certain energy values explained in the paper were determined.U radu je prikazano eksperimentalno odreÄivanje statiÄke energije loma staklo-poliester kompozitnih cijevi poznate struktura materijala i postupka izrade. Cilj ispitivanja je bio odrediti moguÄnost primjene ugradnje takvih cijevi u elemente za priguÅ”ivaÄe udara. Pod djelovanjem spornog statiÄkog tlaÄnog optereÄenja ispitivana su dva tipa cijevi razliÄitih presjeka. Pri tom su mjerene primenjene sile i duljine uzoraka sve do potpunog loma cijevi. Na osnovu dobivenih dijagrama su izraÄunate vrijednosti specifiÄnih energija apsorpcije
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 Ā°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
Ventilatory capacity in soy bean workers
Ventilacijska funkcija ispitivana je u 27 radnika izloženih praÅ”ini soje nakon ekstrakcije ulja. Prevalencija svih kroniÄnih respiratornih simptoma bila je viÅ”a u eksponiranih nego u kontrolnih radnika, premda razlike nisu bile statistiÄki znaÄajne. Tijekom radne smjene ponedjeljkom utvrÄene su statistiÄki znaÄajne akutne redukcije za maksimalni ekspiratorni protok pri 50% i 25% vitalnog kapaciteta (FEF50: -6,4%; FEF25: - 12,4%). Promjene u vitalnom kapacitetu (FVK: -3,6%) i forsiranom ekspiratornom volumenu u prvoj sekundi (FEV1: -2, 7%) bile su manje, ali joÅ” uvijek statistiÄki znaÄajne. Analiza rezultata testiranja ventilacijskih kapaciteta ponedjeljkom prije smjene u radnika na preradi soje upuÄuje na to da eskpozicija praÅ”ini soje u nekih radnika može dovesti do pojave kroniÄnog oÅ”teÄenja respiratornog sustava.Ventilatory capacity was examined in a group of 29 workers exposed to soy bean dust. The prevalence of all chronic respiratory symptoms was higher in the exposed than in control workers, although the differences were not statistically significant. During the Monday work shift there was a significant mean acute across-shift decrease in maximum expiratory flow rates at 50% and 25% vital capacity (FEF50: -6.4%; FEF25: -12.4%). Changes in forced vital capacity (FVC: -3.6%) and in one-second forced expiratory volume (FEV1: -2. 7%) were smaller, but statistically significant. Analysis of Monday preshift values of ventilatory capacity in soy bean workers suggests that exposure to soy bean dust may lead to chronic respiratory impairment in some workers