Vencislav Grabulov - Academia.edu (original) (raw)

Papers by Vencislav Grabulov

Zavarivanje i zavarene konstrukcije

In this paper, welding-remelting of AISI 304L (X2CrNi19-11) austenitic stainless steel was perfor... more In this paper, welding-remelting of AISI 304L (X2CrNi19-11) austenitic stainless steel was performed by using TIG process with activating flux, that is, A-TIG process. Fluxes were prepared by mixing 5, 10, 20, 30 and 40 % SiO2 nano particles with acetone solvent, while the application of the flux was done by a brush, prior to electric arc engagement. Characterization was done by visual testing and macro section analysis, with the main stress aimed at penetration depth as the dominant parameter used to assess the effectiveness of the flux. It was found that the highest penetration was obtained with 5 and 40 % of nano particles, with the wider weld obtained with 40 % of nano particles. However, from the point of welding technology, it was assessed that this is of secondary importance and that the optimal flux contains 5 % nano particles, primarily due to a lower cost, simpler mixing, lower viscosity and an easier flux application on the base metal.

Zavarivanje i zavarene …, 2010

Zavarivanje i zavarene konstrukcije, 2021

Zavarivanje i zavarene konstrukcije, 2022

Zavarivanje i zavarene konstrukcije, 2008

Journal of engineering & processing management, Jun 17, 2021

$Research paper thumbnail of Microstructure and fracture mode of unalloyed dual-phase austempered ductile iron$

Chemical Industry and Chemical Engineering Quarterly

Dual-phase ADI material microstructure consists of different amounts and morphologies of ausferri... more Dual-phase ADI material microstructure consists of different amounts and morphologies of ausferrite and free ferrite, obtained by subjecting ductile iron to specific heat treatment. Its strength is lower compared to comparable ADI materials but exhibits a higher ductility, the major disadvantage of ADI. In the current study, an unalloyed ductile iron was intercritical austenitized in two-phase regions (?+?) at four temperatures from 840 to 780 ?C for 2 h and austempered at 400 ?C for 1 h to obtain dual-phase ADI with different percentages of free ferrite and ausferrite. Light and scanning electron microscopy was performed for the metallographic and fracture studies, respectively. Microscopy results were correlated to tensile testing results. The results indicated that, as the amount of ausferrite present in the matrix increases, higher values of strength and lower ductility are obtained. The fracture surfaces of dual-phase ADI microstructures with 22.8% of ausferrite in their matrix...

Friction Stir Welding is relatively young welding process in solid state which is created in The ... more Friction Stir Welding is relatively young welding process in solid state which is created in The Welding Institute - London, during 1991 year. The first application is connected with railway and aluminum and aluminum alloys welding but later the application range is extended, so today this process successfully welded many pure metals, alloys also, non-metals in all industrial branches (railway, aircraft, automotive, shipyard etc). Two decades after formation, FSW process is the mostly used for aluminum and aluminum alloys welding, so it is not surprise that the first step in FSW standardization is connected to aluminum welding. The aim of this paper is to draw attention to basic terms for FSW which are presented in actual standards and suggested appropriated terms on Serbian language.

Chemical Industry and Chemical Engineering Quarterly, 2019

In this work, the presence of TiO2 nanoparticle-based activated flux combined with orbital weldin... more In this work, the presence of TiO2 nanoparticle-based activated flux combined with orbital welding of seamless thick-walled pipes of stainless steel and lowcycle pulse current was done, representing a novel combination of welding processes parameters. Control specimens were welded without flux and consumable material, and without flux with the consumable material. Experimental welding with different welding parameters was done. Special attention was given to characterize the flux by zetasizer method, representing a new approach, versus the conventional approach where the nominal oxide particle size is reported. The obtained welds were visually tested, macroanalyzed, their microstructures examined, and their tensile and bending properties determined. The results show that the flux influences a significant increase in penetration depth, up to full penetration, which has a positive effect on the increase in the tensile and bending properties of the weld metal. Material behavior model w...

Advanced Materials Research, 2016

Metalurgija, 2014

A. S. Tawengi, A. Sedmak, Faculty of Mechanical Engineering, University of Belgrade, Belgrade, Se... more A. S. Tawengi, A. Sedmak, Faculty of Mechanical Engineering, University of Belgrade, Belgrade, Serbia V. Grabulov, Institute for material testing, Beograd, Serbia In view of the importance of high strength low alloy (HSLA) steels, particularly for critical applications such as offshore plat forms, pipeline and pressure vessels, this paper reports on an investigation of how to weld this type of steel without cold cracking. Using manual metal arc welding process and Tekken test (Y Grove test) has been carried out both to observe the cold cracking phenome non, and to investigate the influencing factors, such as preheating temperature and energy input, as well as electrode strength and diameter. How ever the results of the experiments show that there is a risk of cold cracking.

The Al-Mg alloy sheets containing 6.8 wt.% Mg were tested under different stretching conditions (... more The Al-Mg alloy sheets containing 6.8 wt.% Mg were tested under different stretching conditions (uniaxial, plain-strain and balanced biaxial) in order to make some surface roughness created by type "A" or type "B" surface markings appearance. The presented results indicate that the stretcher-strain surface appearance was influenced in a great deal by changing the stress state, i.e. the stretching strain path. The harmful stretcher-strain lines appearance is mostly related to dynamic strain aging (DSA) and it can be suppressed in equibiaxial stretching conditions.

In the presented paper a micromechanical model based on a particular flow criterion of a porous s... more In the presented paper a micromechanical model based on a particular flow criterion of a porous solid has been applied. In this study crack initiation in the smooth specimen made of steel 22 NiMoCr 3 7 has been analyzed; the micromechanical model was incorporated into the finite element (FE) program. Initial data related to non-metallic inclusions were determined by the quantitative optical microscopy. The study was performed within the scope of ESIS TC8 Numerical Round Robin on Micromechanical Models, Phase II, Task A.... .U radu je primenjen mikromehanički model zasnovan na posebnom kriterijumu plastičnog tečenja materijala. Nastanak prsline izazvan pojavom, rastom i spajanjem šupljina, analiziran je na osnovu ponašanja pri zatezanju glatke cilindrične epruvete izrađene od čelika 22 NiMoCr 3 7. Ulazni podaci za proračun koji se odnose na zastupljenost i veličinu nemetalnih uključaka su određeni optičkom mikroskopijom. Dobijeni rezultati ukazuju da primenjeni mikromehanički model m...

A metallurgical base of alloying in cryogenic steels is presented in this paper. The common use o... more A metallurgical base of alloying in cryogenic steels is presented in this paper. The common use of these steels is for tanks for liquid gases. Main alloying element is Ni, added in amounts between 2.25 and 9 % due to different service temperatures. Selection of welding technology and filler material, together with welding suggestions, are discussed.U radu su date fizičko-metalurške osnove legiranja čelika za upotrebu na niskim temperaturama. Ovi čelici se najčešće koriste za izradu rezervoara za skladištenje tečnih gasova. Glavni legirajući element Ni se dodaje u količinama 2.25 do 9%, u zavisnosti od radne temperature. Razmotrena su ograničenja u izboru dodatnih materijala i preporuke za zavarivanje

Investigation and analysis of the phenomena during rotational friction welding process of the hig... more Investigation and analysis of the phenomena during rotational friction welding process of the high speed steel M2 (AISI SAE) with quench and tempered carbon steel 1060 (AISI SAE) are presented. Welding parameters as time and friction pressure are varied in experiments. Also different post weld heat treatment (PWHT) regimes, as annealing and quenching are applied. Distribution of the carbon and carbide phases in period of friction during the process of rotation friction welding process and after PWHT and effects on weld quality are analysed. Investigations are performed by the classical and quantitative optical microscopy. Displacement and distribution of carbides in the high speed steel during friction period in viscous layer, than in friction plane and surrounding zones are studied. Results of the quantitative optical microscopy are showed distinct difference of the carbide phase ratio in investigated zones. Obtained results are verified by the EDS analysis of characteristic zones ...

Metals, 2021

Isothermal transformation characteristics of a medium carbon Ti-V microalloyed steel were investi... more Isothermal transformation characteristics of a medium carbon Ti-V microalloyed steel were investigated using light microscopy, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and by uniaxial compressive testing. Samples austenitized on 1100 °C were isothermally treated in the range from 350 to 600 °C and subsequently water quenched. The final microstructure of the samples held at 350 °C consisted of bainitic sheaves and had compressive yield strength, approximately from 1000 MPa, which is attributed to high dislocation density of low bainite. At 400 and 450 °C, acicular ferrite became prevalent in the microstructure. It was also formed by a displacive mechanism, but the dislocation density was lower, leading to a decrease of compressive yield strength to approximately 700 MPa. The microstructure after the heat treatment at 500 °C consisted of coarse non-polygonal ferrite grains separated by pearlite colonies, principally dislocation free grains...

Advanced Materials Research, 2018

Technical diagnostics of hydromechanical equipment, is based on testing procedures including the ... more Technical diagnostics of hydromechanical equipment, is based on testing procedures including the history of the exploitation with expert knowledge of structures and operating conditions, as well as, on the analysis of results performed by experts with appropriate experience and knowledge in design, exploitation, maintenance, reliability, fracture mechanics etc. Degradation of properties of the material and/or welded joints of hydro-mechanical equipment is being caused by the simultaneous influence of a large number of factors. First of all, it is thought of technological, metallurgical, structural and conditions of exploitation. In this paper, the selection of methodology for the rehabilitation of hydro-mechanical equipment is presented based on the previously conducted assessment of state of equipment using the nondestructive testing methods. Repair welding, repair of damaged surfaces by cold metallization, corrections of existing structural solutions of metallic components in orde...