english HARIDASA ANAYAK, N KRISHNAMURTHY, SHAILESH RAO A
Rezumat
In recent years, the coating of different materials inside the cylinder liner has emerged as a prime focus of research among the scientists as it improves the efficiency of the engine. In this paper, the coating material, YSZ + Al2O3 with equal proportion were coated on the cast iron substrate using two bonding materials (Iron Nickel Aluminium composite powder (Metco 452) and Nickel Aluminium cermet (Metco 410 NS)) with the three-coating thickness of 100µm, 200µm and 300µm. Initially, the wear characteristics were carried out and properties like the coefficient of friction (CoF), wear rate for different load conditions were determined. The analyses of the worn sample were studied in details with the aid of SEM images. Further, the scratch studies for the worn samples were also carried out.
Cuvinte cheie
suflare plasmă, purtare, microduritate, grosimea stratului, coeficientul de frecare
MD INSIAT ISLAM RABBY , SITI UJILA MASURI, N.M.S. HASSAN, SK MAHAFUJUR RAHMAN, TAZEEN AFRIN MUMU, MAHFUZ ALAM
Rezumat
A triangular corrugated pipe was studied numerically along with Al2O3-water, CuO-water, and SiC-water nanofluids, to identify the thermal capacity for laminar flow. Ansys fluent software and steady-state control volume method were applied for simulation purposes. Hence, different volume fractions (1% - 5%) of CuO, Al2O3, and SiC nanoparticles were considered to mix with water to suspend nanofluids. 400 to 1200 Reynolds number with a constant wall heat flux of 1000 W/m2 were considered to calculate the heat transfer rate. In addition, the required pumping power for such enhancements was determined as well. The simulation results highlighted that corrugated pipe provided highest improvement in heat transfer with increase in Reynolds number compared to straight pipe. Consequently, the mixing of nanoparticles in the working fluid showed more enhancement. For the corrugated pipe, at Re =1200, CuO-water, Al2O3-water, and SiC-water nanofluids showed a maximum 11.94%, 8.96%, and 9.15% enhancement respectively of Nusselt number compared to water. Furthermore, CuO-water, Al2O3-water, and SiC-water nanofluids showed enhancement in pumping power compared to water. Additionally, a correlation to predict the Nusselt number for nanofluid and triangular corrugated pipe was also developed by using Buckingham π Theorem, which showed good agreement with numerical results. However, it can be concluded that corrugated pipe, along with nanofluids, provide enhancement in heat transfer for the laminar developed region of a pipe.
Cuvinte cheie
număr Nusselt, nanofluide, concentrația volumului, Teorema Buckingham π, forța de pompare
CORINA ANCA SIMION , IULIANA MĂDĂLINA STANCIU, TIBERIU BOGDAN SAVA, DORU GHEORGHE PACESILA
Rezumat
Acest articol prezintǎ rezultatele datǎrii cu radiocarbon prin metoda AMS pentru un eşantion de mortar hidraulic prelevat din fundaţiile vǎmii romane Porolissum - Moigrad, România. Datarea cu radiocarbon dă încredere în eșantionul care urmează a fi prelevat, și anume că acesta aparține perioadei istorice în cauză, și nu ca urmare a unor intervenții tardive sau recente. Studiul de caz oferă o descriere detaliată a metodei de pretratare a probei, stadiului de obținere a fracției de calcit provenit din momentul întăririi mortarului în zidărie, stadiului de separare și purificare a dioxidului de carbon rezultat în urma digestiei chimice a analitului final. Unele aspecte originale au fost dezvoltate la Laboratorul RoAMS, Mǎgurele. Reducerea dioxidului de carbon la carbon depus intim pe catalizatorul de fier (grafitizare), precum și etapa de măsurare AMS, calcule și calibrare sunt de asemenea descrise pe scurt. Rezultatul calibrat și interpretarea acestuia în context istoric și arheologic recomandă utilizarea acestui eșantion de mortar în viitoare analize multidisciplinare privind rețeta originală și posibilele surse de materii prime implicate.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
ANA J. MOMČILOVIĆ-PETRONIJEVIĆ , GORDANA A.TOPLIČIĆ-ĆURČIĆ, DUŠAN Z. GRDIĆ, DRAGAN M. ĐORĐEVIĆ, NENAD S. RISTIĆ ,ZORAN J. GRDIĆ
Rezumat
Caričin Grad is an archeological site dating back to VI century, located in the vicinity of present day Leskovac, Serbia. The city is the legacy of the famous early Byzantine Emperor Justinian I. The city, in the town planning terms, is divided into three large units. Acropolis, Middle town and Lower town, connected by the suburban area. The grandeur and importance of the city are witnessed by the remenants of several lines of city walls, planned street network, cisterns, thermae, aqueduct and sewage, numerous sacral buildings, administrative structures and housing architecture. Considering the complexity of the city, in town planning and architectonic terms, and diversity of building types in it, the mortars taken for analyses were collected from various types of buildings: from housing, public buildings, fortifications and from the aqueduct structure. In the paper, basic physical properties, as well as mineralogic, morphologic and chemical features of the sampled mortars were examined. The testing was performed using optical and scanning electron microscopy, XRF semi-quantitative analysis and XRD (x-ray diffraction). Based on the mentioned analyses, it was concluded that the main binder in the mortar was pulverized brick, which activated its pozzolanic activity. In addition, as an auxiliary binder, there was limestone powder, considering that the mortar contained the crushed limestone aggregates as well. The detected aggregate grains are the river aggregate, pieces of bricks and fine crushed limestone aggregate. These results would be further used for making the mix designs of repair mortars.
Cuvinte cheie
Caričin Grad, microscopie electronică B, mortare antice, microscopie optică B, mortare de reparație, metode de raze X
SATISHKUMAR SENGOTTAIYAN, SURESH PARAMASIVAM
Rezumat
The health risks connected with the use of asbestos-based brake linings have sparked research into the use of environmentally benign agro-based biomaterials as reinforcing agents in composite materials used in the manufacturing of brake pad linings. The purpose of this research is to determine the feasibility of employing coconut shell (CS) powder in the manufacturing of asbestos-free brake lining materials. The powders, in conjunction with the appropriate fillers, were utilised in the manufacture of the brake lining. The compositions of the reinforcing powders were varied between 20% and 35%, those of the resin binder were varied between 58 and 43%, and those of the filler metal and curing agents were maintained constant. Weighed, prepared, mixed, cured, and moulded these materials. Water and oil absorption, compressive strength, hardness, and wear tests were performed on the created composite materials. The research indicated that increasing the amount of reinforcing elements leads in an increase in the samples water and oil absorption. Compressive strength of the composite rose proportionately with the addition of up to 35% composition. The coefficient of friction tested was determined to be within an acceptable range. Additionally, when combined with other fillers and confined, CS powder shown great potential for brake lining manufacturing.
Cuvinte cheie
coji de nucă de cocos, garnituri de frână, rezistență la compresiune, duritate, uzură
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Anul
2022
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Numărul
52 (4)
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Paginile
368-373
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Domenii de interes
BIOMATERIALE ȘI BIONANOMATERIALE; SUBSTANȚE, PROCEDURI ȘI DISPOZITIVE PENTRU MEDICINĂ
SASIKUMAR P, MANJU R
Rezumat
This research investigated the axial compression behaviour of high strength concrete Encased Steel Composite (ESC) columns. Six high strength concrete ESC columns were made with M70 grade concrete, including with and without Alkaline Resistant Glass Fibre (AR-GF), all the specimens were tested after curing periods. A study of structural performance was conducted, which included axial load-deformation, ultimate load-carrying capacity, failure mode, ductility, and stiffness. As a result of the experiments, the failure mode of ESC columns without AR-GF are sudden failures once the peak load is reached, and with AR-GF at 1.20% volume prevented concrete covers from spalling and increased the load-carrying capacity. In the whole experimental study, the reinforcement ratio was maintained at a constant. In conclusion, the results of the experimental study were compared with the Finite Element (FE) model results, the FE model is help to prediction of axial compression behaviour of ESC columns.
Cuvinte cheie
coloană din oțel compozit, deformare axială, încărcare axială, ductilitate, beton de inaltă performanță, rigiditate
KARTHICK PALANISAMY , REVATHI VAIYAPURI
Rezumat
Professor Davidovits fathered the idea that geopolymer binder is a viable alternative to Portland cement. Geopolymer can be synthesized by alkali activation of alumina silica rich inorganic materials of industrial by products and natural materials. An exhaustive study carried out on geopolymer concrete by the researchers establishes a strong pathway in the construction field. Furthermore, Self-Compacting Geopolymer Concrete (SCGPC) has been promoted using fly ash, GGBS, rice husk ash, silica fume, etc. In this respect, the present study proposes to carry out experimental studies on self-compacting geopolymer concrete, incorporating bottom ash and GGBS, under ambient curing condition. Bottom ash and GGBS were added in the proportion of 100:0, 75:25, 50:50, 25:75, 0:100. The fresh and hardened properties of the SCGPC were analysed for all the mixes. The test result of fresh concrete properties indicates that it satisfies the limits specified by EFNARC standards. The maximum compressive strength of self-compacting geopolymer concrete was ascribed as 38.5MPa and 54.8 MPa at 3 and 28 days by the mix containing only GGBS. An excellent strength achieved at early age is observed in the GGBS mix. Also, the strength results reveal that increase in the content of GGBS achieved greater strength.
Cuvinte cheie
silice de alumină, cenușă, GGBS, beton geopolimer auto compactant, EFNARC
BENGİ AYKAÇ , ALTAN YAVUZCAN
Rezumat
The presented study investigates the efficiency of repairing damaged reinforced concrete beams by a novel technique, which is the injection of epoxy resin to the cracks. The two main test parameters were the amount of flexural reinforcement (low, medium, and high) and the level of seismic damage before repair (light, moderate, and heavy). Nine cantilever beams were tested under reversed cyclic transverse loading in the undamaged (original) and repaired (after damaging) states. The test results were examined and discussed in terms of the initial flexural rigidity and ultimate load capacity. The technique was shown to be the most effective in damaged beams with mid-sized cracks. The minor cracks particularly in lightly-reinforced beams were not suitable for proper injection of resin, while the major cracks resulted in the epoxy to govern the flexural behavior of the beam after repair. The experimental load capacities were shown to be in close agreement with the analytical flexural capacities of the respective beams. The sizes of the cracks before repair and the longitudinal reinforcement did not affect the repaired beam to reach the load capacity of the original counterpart but affected the extent of deformations before reaching this load level.
Cuvinte cheie
reparație, lățime fisurare, armare la încovoiere, modernizare seismică, structuri beton
GANESH NAIDU GOPU, A. SOFI
Rezumat
The chloride attack on the reinforced concrete structure resulted in a substantial loss of bond strength due to reinforcing bar corrosion. E-glass, Steel and E-waste copper fibers were used in concrete to investigate corrosion-induced bonding behaviour. It was determined to perform pull-out tests in order to evaluate the bond behavior in relation to test variables such as the ratio of concrete cube clear cover (C) to rebar diameter (Ø) and the type of fiber. The bond stress-slip curves produced in this work adequately represented the bond behavior of corroded and uncorroded concrete specimens (with and without fibers). According to the findings, adding fibers to concrete appears to strengthen the connection and reduce corrosion. The bond strength of steel fiber reinforced concrete was found to be higher than that of concrete mixes including E-glass and E-copper wire fibers.
Cuvinte cheie
atac clorurat, forța de legătură, coroziune indusă, testul de extragere, viteza de coroziune
SASIKUMAR P, MANJU R
Rezumat
The present study carried out the axial compressive behaviour of High Strength Concrete (HSC) columns reinforced with GFRP bars under axial compression. Only a limited number of research works only done with GFRP Reinforced (RC) Concrete Columns. Twelve columns of 150x150mm cross-section and 1000mm height made with M70 grade of HSC, including 1.20% of Alkaline Resistant Glass Fibre (AR-GF), were tested under axial loading. The main parameters were studied in this research, including the Axial Load (AL) carrying capacity, axial deformation, failure pattern, ductility, and stiffness. GRFP RC columns are 90% axial load only carried compared to steel RC columns. The analytical study helped to predict the ultimate AL carrying capacity of HSC columns.
Cuvinte cheie
beton de înaltă performanță, încărcare axială, deformare axială, rigiditate, ductilitate bare GFRP
KHAWAJA ADEEL TARIQ, HADHI HASSAN KHAN, FARHAN ASIF, NOMAN JABBAR
Rezumat
The efficient pavement performance depends on the stability of the supporting layers. Road failures mostly occur due to poor selection of material and insufficient drainage arrangements. Subbase layer is an essential component of the pavement along with base, subgrade and surface wearing course. This research work is related to investigating the effect of Lime, Fly ash and Mat fiber on the strength and permeability characteristics of Subbase material. Results show that the maximum dry density and soaked California bearing ratios (CBR) values are increasing with the increase of lime and fly ash ratio in subbase. Whereas, maximum dry density and soaked California bearing ratios (CBR) values are decreasing with the increase of Mat fiber in the subbase. The increase in content of Mat fibers also resulted in increase in permeability of subbase material. It is also observed that higher content of fly ash results in swelling of the subbase material as compared with lime content.
Cuvinte cheie
sub-bază, var, cenușă zburătoare, valori CBR, covor din fibră