Vojnotehnicki glasnik / Military Technical Courier

7-25

Authors: Mrdak Mihailo R.

The aim of this study was to optimize the parameters of the plasma spray and to deposit WC17Co layers with optimal structural - mechanical characteristics. The powder was deposited by the plasma spraying process at the atmospheric pressure (APS). When choosing the parameters, the flow of the He plasma gas was taken as the basic parameter. In relation to other gases, helium does not react with the powder, it produces a denser plasma with a lower heat content and it incorporates less ambient air into the plasma jet which reduces decarburization of the powder. The study shows three groups of samples obtained with three plasma gas flows of 12, 22 and 32 l/min He. The coating with the best properties was deposited on the shaft sleeve of the main rotor of the Gazelle H42 helicopter, in order to reduce the influence of vibrations and bearings on sleeve wear up to 500°C. The estimates of the WC17Co layers of the coating were made on the basis of their structural - mechanical properties. The surface morphology of the WC17Co powder particles was examined on the SEM. The mechanical properties of the deposited coatings were tested in accordance with the 'TURBOMECA' standard. The estimate of the mechanical properties of layers was done by examining microhardness with the method HV0.3 and bond strength with tensile testing. Metallographic assessment of the pore proportion in the layers of the WC17Co coating (image analysis) was performed with the technique of light microscopy in accordance with the 'Pratt & Whitney' standard. Studies have shown that the rate of the plasma gas flow significantly affects the mechanical properties and the structure of coatings.

51-62

Authors: Efimov Victorovich Maxim, Ryabtsev Danilovich Anatoliy, Selyutin Andreevich Olexandr, Troyanskyy Anatolievich Oleksandr, Yavtushenko Michaylovich Pavel, Pashynskyi Victorovich Volodymyr

The paper gives the results of work on melting, pouring, forging and heat treatment of 415-ton 45H3M1F steel ingots as semiproducts for manufacturing large backup rolls at the request of 'Severstal' Company. For the production of rollers, a new grade of steel based on 0.45%C and 3%Cr, additionally alloyed by Mo and V, was developed in PJSC 'Energomashspetsstal' and applied in industry. Steel of bainite class provides the best combination of strength and plasticity properties. Metal was prepared by melting 7 heats in arc steel-melting furnaces with the capacity of 100 and 50 tons with subsequent out-of-furnace treatment on ladle - furnace and ladle - degassing units. The pouring of steel was carried out from four steel-pouring ladles into a vertical mould under vacuum through a tundish ladle with the protection of stream by argon. The forging of ingots was conducted on the automated 150MN forging system. The obtained billets were exposed to primary heat treatment which consisted of heating for recrystallization, isothermal soaking, in order to provide the removal of residual stresses, additional dehydrogenization to give the material lower hardness and controlled cooling for the prevention of snowflake formation. Heating of ingots for forging and preliminary heat treatment was carried out in heat treatment furnaces with the carrying capacity of up to 500 tons. For the heat treatment of the backup roll, a horizontal sprayer unit was applied. The tooling of the backup roll was executed on a lathe with one pace-plate and the final mechanical treatment was conducted on the machine-tool of Hercules NWD 1500×18000 CNC. Finished products with 225-ton mass of the following dimensions: a barrel with a diameter and a length of 2,360 mm and 4,800 mm, respectively, at a general length of 10,650 mm were obtained.

72-98

Authors: Šunjevarić Milan M., Đukanović Goran Z., Gospić Nataša M.

In this paper, an overview of the algorithms for access control in mobile wireless networks is presented. A review of adaptive control methods of accepting a call in WCDMA networks is discussed, based on the overview of the algorithms used for this purpose, and their comparison. Appropriate comments and conculsions in comparison with the basic characteristics of these algorithms are given. The OVSF codes are explained as well as how the allocation method influences the capacity and probability of blocking.

113-121

Authors: Markagić Milorad S.

In general, digital forensics could be defined as a compilation of methods of collecting, analysing and presenting digital evidence that could be found on computers, servers, in networks, databases, mobile devices and all other electronic devices where data is stored. This paper explains the methods of collection of digital evidence in electronic mail and their analysis as well as taxonomy (classification) of digital forensics.

141-158

Authors: Majkić Zoran Đ.

Hydraulic servo controls are designed to facilitate rotation in place without providing increased power to steering wheels. In the initial design phase, the dimensions required for control systems are usually obtained through the calculation of their load when wheels rotate in place, where the torque is calculated empirically. The starting point in the project calculation is thus to determine the hydraulic power steering torque torsional resistance which is then used to determine the maximum value of force i.e. the torque on the stering wheel. The calculation of the control system servo control consists of determining the basic parameters, the required pump capacity, the main dimensions of the hub and the pipeline and the conditions for the stability of the system control mechanism.

173-196

Authors: Hristov Nebojša P., Jovičić Gordana R.

This article describes the dynamic processes within the gun barrel during the firing process in exploitation. It generally defines the basic principles of constructing tube elements, and shows the distortion of the basic geometry of the tube interior due to wear as well as the impact it causes during exploitation. The article also defines basic empirical models as well as a model based on fracture mechanics for the calculation of a use-life of the barrel, and other elements essential for the safe use of the barrel as the basic weapon element. Erosion causes are analyzed in order to control and reduce wear and prolong the lifetime of the gun barrel. It gives directions for the reparation of barrels with wasted resources. In conclusion, the most influential elements of tube wear are given as well as possible modifications of existing systems, primarily propellant charges, with a purpose of prolonging lifetime of gun barrels. The guidelines for a proper determination of the lifetime based on the barrel condition assessment are given as well.

217-230

Authors: Luković Branka R., Petrović Veljko P., Mrdak Veselin L.

This article presents a ballistics module as a part of the fire control system of weapons for fire support (mortars, artillery weapons and rocket launchers). The software is 'open' with the prominence of autonomy work. It can be modulated and adapted on the user demand. Moreover, it is independent of the hardware base.

248-267

Authors: Drenovac Aleksandar Ž., Drenovac Bratislav Ž., Drenovac Dušan M.

Modern business is characterized by greater and greater market competition through all business areas and all activities. Establishment of market positions is a very important element of business activities in every organization. Quality of products and/or services provides recognizability at market and raising of ratings. Implementation of the ISO 9001 quality management system opens positions for secure national and international markets; it is also an identifier of an efficiently and effectively process-wise organized system in an organization.

280-300

Authors: Pavlović Rade M.

This work decribes the Archive Digitization Application - ADA. The application was made on the request of the Military Archives of the Ministry of Defence of the Republic of Serbia and follows the complete structure of archives organization. The most important parts of the application for digitization of documents have been described as well as tasks of work posts for digitization of documents. The process of digitization can be divided into three phases in order to protect documents and to present them in the most efficient way to users - researchers. Though a term 'scanning' is commonly used, digitization is a complex process and requires realization of all phases in order to get the final product. At the same time, an increased possibility of access to a larger number of documents is given to researchers with no dependancy on available resourses in terms of bringing out and returning archival material from and to archives depots. This work also presents the visual appearance of the application for some parts of the digitization process.