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

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

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 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

Feruginozna tjelešca u plućima 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 µm in length. Continuous environmental exposure of the city\u27s population to respirable mineral fibres may therefore pose a health risk.Uzorci pluća 36 slučajno izabranih gradskih pasa pretraženi su na prisutnost feruginoznih tjelešaca s namjerom da se procijeni da li izloženost vlaknatim organskim prašinama, uglavnom azbestu, iz gradskog okoliša, nosi opasnost za zdravlje. U skupini od 15 pasa do četir godine starosti, u dva su nađena feruginozna tjelešca. U drugoj skupini koja je sadržavala 21 psa starija od četiri godine, sedamnaest njih je imalo pozitivan nalaz. Prema Fisherovu egzaktnom testu postoji značajna statistička razlika (P<0.001) između dviju skupina životinja. Prisutnost azbestnih tjelešaca u plućima pasa svjedoči da su javne gradske površine yisoko kontaminirane vlaknatim mineralnim prašinama respirabilne veličine, uglavnom azbestom. Češći nalaz azbestnih tjelešaca u plućima 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 stanovništva

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

Specifična absobcijska energija staklo-poliester kompozitne cijevi pod statičkim tlačnim opterećenjem

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 određivanje statičke energije loma staklo-poliester kompozitnih cijevi poznate struktura materijala i postupka izrade. Cilj ispitivanja je bio odrediti mogućnost primjene ugradnje takvih cijevi u elemente za prigušivače udara. Pod djelovanjem spornog statičkog tlačnog opterećenja ispitivana su dva tipa cijevi različitih presjeka. Pri tom su mjerene primenjene sile i duljine uzoraka sve do potpunog loma cijevi. Na osnovu dobivenih dijagrama su izračunate vrijednosti specifičnih 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 °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 prašini soje nakon ekstrakcije ulja. Prevalencija svih kroničnih respiratornih simptoma bila je viša u eksponiranih nego u kontrolnih radnika, premda razlike nisu bile statistički značajne. Tijekom radne smjene ponedjeljkom utvrđene su statistički značajne 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 još uvijek statistički značajne. Analiza rezultata testiranja ventilacijskih kapaciteta ponedjeljkom prije smjene u radnika na preradi soje upućuje na to da eskpozicija prašini soje u nekih radnika može dovesti do pojave kroničnog oštećenja 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