Svojstva standardnog polimernog i vodorazredivog premaza za vojnu maskirnu zaštitu sa dodatkom neorganskih fulerenskih nanočestica volfram disulfida (IF-WS2)

The possibility of improving the properties of the standard polymeric and a water-based coating for military camouflage protection by adding nanoparticles of inorganic fulerene-like tungsten disulphide (IF-WS2). Nanoparticles were added and dispersed in paint by ultrasonic irradiation. The paints were applied to standard steel plates, and dried, for examinations of chemical resistance to aggressive media and of the following physical-mechanical properties: hardness, flexibility, elasticity, abrasion resistance, resistance to steel balls impact and adherence. These properties were compared for paint without and with IF-WS2 nanoparticles. The effect of adding IF-WS2 on rheological properties of the paints has been examined using Dynamic Mechanical Analysis (DMA), observing viscosity as a function of the shear rate. Camouflage properties were also examined - IR reflection and colorimetry. Significant improvements of mechanical resistance to abrasion and steel balls impact, as well as hardness, have been achieved.Istraživana je mogućnost poboljšanja svojstava standardnog polimernog i vodorazredivog premaza za vojnu maskirnu zaštitu dodatkom neorganskih fulerenskih nanočestica volfram-disulfida, IF-WS2. Nanočestice su dodate i u boji dispergovane ultrazvučno. Boje su nanešene na standardne čelične pločice, nakon toga osušene, u cilju ispitivanja hemijske otpornosti na agresivne medije i sledećih fizičko-mehaničkih karakteristika: tvrdoća, savitljivost, elastičnost, otpornost na abraziju, otpornost na udar kuglica i prianjanje. Ova svojstva su poređena za boje bez i sa dodatkom IF-WS2 nanočestica. Uticaj dodatka IF-WS2 na reološka svojstva ispitivanih boja praćen je pomoću Dinamičkog Mehaničkog Analizatora (DMA), posmatrajući promenu viskoziteta u funkciji od brzine smicanja. Takođe, ispitivane su i maskirne karakteristike- infracrvena refleksija i kolorimetrija. Postignuta su značajna poboljšanja tvrdoće, mehaničke otpornosti na udar čeličnih kuglica i abraziju

Utjecaj triboloških procesa mehanizma slobodnog hoda na radne karakteristike impulsnih tarnih varijatora

The impulsive friction variators are very specific transmitters. They are characterised by the periodical impulse transmission of power and motion. For research purposes, the device was made to simulate wear of the tribomechanical system: external envelope (coulisse) – roller and roller-shaft in the free motion mechanism with use of the impulsive friction variators. Monitoring of the elements of tribomechanical system was conducted by recording the changes of dimensions depending on the investigation time. Roughness parameters were measured and wear traces of the tribomechanical system were recorded. It was concluded that at the shaft (star), a dominant mechanism of wear is pitting, and that destruction of the oil film precedes the damage at the coulisse (roller). By analysing the change of the gap and influence of the change of wedging angle, it is determined that the period of intensive wear at the beginning and the period of constant wear can be differentiated. It was concluded that the change of the gap clearly represents theImpulsni tarni varijatori su vrlo specifični prijenosnici. Karakterizira ih impulsni periodični prijenos snage i gibanja. U cilju istraživanja izrađen je ispitni uređaj za simuliranje trošenja tribosustava: vanjski prsten (kulisa) - valjčić i vratilo - valjčić u mehanizmu slobodnog hoda pri radu impulsnih tarnih varijatora. Praćenje elemenata tribosustava vršeno je snimanjem promjena dimenzija u ovisnosti o trajanju ispitivanja. Mjereni su parametri hrapavosti i snimani tragovi trošenja elemenata tribosustava. Zaključeno je da je kod vratila (zvijezde) dominantni mehanizam trošenja pitting, a da oštećenju vanjskog prstena (valjčića) prethodi razaranje uljnog filma. Analizom promjene zazora i utjecaja promjene kuta zaklinjavanja utvrđeno je da se mogu razlučiti period početnog intenzivnog trošenja i period ustaljenog trošenja. Zaključeno je da promjena zazora jasno prikazuje krivulje trošenja triboelemenata. Povećanje zazora direktno utječe na promjenu kuta zaklinjavanja, a samim time i na povećanje neravnomjernosti rotacije izlaznog vratila

Uticaj faktora procesa obrade na tehnološke karakteristike prevlaka kod proizvoda namenske industrije

The research topic of this dissertation is on the impact of processing technology on the characteristics of protective galvaniccoatings. Testing was performed with a coating of zinc and chromium, as well as coatings that are most commonly used to protect metal elements. In both examined coatings varied characteristics of the substrate (roughnessand hardness) for its application depending on the manner of production or applied technology, finishing and electrolysis parameters, current density and deposition time. In addition to the traditional methods for the characterization of coatings, the defined standards in the paper studied and methods that are less common in tests of metal coatings such as "scratch" test for the determination of adhesion and testing tribological characteristics of coatings deposited. The external appearance of the coatings was evaluated visually, and morphology by optical microscopy and AFM microscopy application. The thickness of the coatings was determined by magnetic method. The adhesion of coatings to the base material is determined by standardized methods, method of heating and "scratch" test. Microhardness testing was performed by the method Vickers HV0.1. Wear tests were performed under conditions with "block-on-disk" contact geometry and the resulting wear traces were quantified using optical measuring microscope. Comprehensive analysis of results showed the influence of the surface condition of the individual characteristics of electrolytic coating of zinc and chromium. Implemented comprehensive researches have created a basis for the development of expert systems in the field of galvanic coatings. In the paper are given the starting point of knowledge about expert systems and neural networks for creation a database and development of modules for predicting the characteristics of the coatings on the basis of the deposition parameters

Fire protection of sacral structures in Vojvodina, Republic of Serbia

Sacral structures are part of everyday life and essential elements of civilization and culture of the people they belong to. In the Republic of Serbia, after a long period of atheism, traditional churches and religious communities are trying to find their place and role in the society. Each of them has a basic need to have buildings that serve as places of worship and gathering of the congregation. Fires in sacral structures are frequent due to various causes. The way to protect them from this danger is a question for numerous participants in the field of protection in Vojvodina. Results of the investigation realized in 2005 and 2006 have contributed to a better understanding of the need for their protection. The obtained results confirm the fundamental hypothesis that fire protection of such structures is not adequately defined in the society. Furthermore, they are a base for defining measures and activities of all subjects responsible for fire protection of sacral structures. In Serbia, the observed problem cannot be discussed only as a technical question, which can be easily solved by fire protection experts, nor is the protection an exclusive obligation of services dealing with heritage and users of immovable cultural goods. The solution of the problem requires a sensitive approach of the entire social community