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Vraar M.S.,Military Technical Institute Belgrade
Journal of the Acoustical Society of America | Year: 2011

This paper presents the results of hydroacoustic noise research in three large European rivers: the Danube, the Sava, and the Tisa. Noise in these rivers was observed during a period of ten years, which includes all annual variation in hydrological and meteorological conditions (flow rate, speed of flow, wind speed, etc.). Noise spectra are characterized by wide maximums at frequencies between 20 and 30 Hz, and relatively constant slope toward higher frequencies. Spectral level of noise changes in time in relatively wide limits. At low frequencies, below 100 Hz, the dynamics of noise level is correlated with the dynamics of water flow and speed. At higher frequencies, noise spectra are mostly influenced by human activities on river and on riverbanks. The influence of wind on noise in rivers is complex due to the annual variation of river surface. The influence of wind is less pronounced than in oceans, seas, and lakes. © 2011 Acoustical Society of America.

Milovic L.,University of Belgrade | Vuherer T.,University of Maribor | Blacic I.,Military Technical Institute Belgrade | Vrhovac M.,Institute Soldadura e Qualidade ISQ | Stankovic M.,University of Belgrade
Materials and Design | Year: 2013

The subject of this paper is the microstructural and mechanical characterisation of regions of the heat-affected zone (HAZ) in steels containing 9-12% Cr that are used for operation at elevated temperatures. Tests were performed on regions in the HAZ, which was created by physical simulation using a thermal welding simulator. Half of the simulated samples (SSs) were tested at room temperature (RT) and at an operating temperature (OT) of 600. °C immediately after simulation/welding, while the rest of the simulated samples were tested at RT and at the OT after heat treatment following the welding, i.e., post-weld heat treatment (PWHT). In addition to the results from mechanical testing, the results from microstructural analysis using light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are also presented. The manner in which PWHT contributes to the creep resistance of the HAZ in P91 steel is demonstrated. © 2012 Elsevier Ltd.

Pasagic S.,Ministry of Defense | Antonovic D.,University of Belgrade | Brzic S.,Military Technical Institute Belgrade
Central European Journal of Energetic Materials | Year: 2015

The specific purpose of a pyrotechnic mixture for a Gas Generator (GG) of Base Bleed (BB) projectile requires a carefully balanced combustion velocity for obtaining the maximum projectile range and avoiding a reactive propelling force. The development of the pyrotechnic element is done under laboratory conditions which often differ from the real usage conditions. To be able to fairly predict the combustion process characteristics in the real GGs of BB projectiles, some influential technological factors and their influence on the combustion velocity have been investigated. Factors which were observed to have the most significant influence on the combustion velocity of pyrotechnic compositions are charge density, oxygen balance, combustion chamber wall thickness and material type. Individual and combined influence of these factors on the combustion velocity will also be presented in this paper.

Minic D.M.,Military Technical Institute Belgrade | Maricic A.,University of Kragujevac
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2010

The influence of heating on the electrical and magnetic properties of Fe75Ni2B13Si8C2 amorphous alloy is studied under non-isothermal as well as under isothermal conditions. According to thermal analysis the amorphous alloy was stable up to a temperature of about 500 °C when the process of multi-step structural transformations begins. According to the X-ray diffraction analysis, the primary crystallization starts by forming iron-silicon (Fe3Si, 70 wt%) as main phase and two minor phases, iron-boron (Fe2B, 10 wt%) and iron-boron-silicon (Fe15B2Si3, 20 wt%). With the increase of the temperature, the change of weight composition, as well as the ratio of present phases occurs, and at 650 °C it was confirmed the presence of only two stable phases, Fe3Si (74 wt%) and Fe2B (26 wt%). It was shown that the observed change of structure had significant influence on both the electric and magnetic properties of alloy. The electric resistivity in crystallized alloy is higher than the amorphous one, but the crystallized alloy possesses better magnetic susceptibility and retains the ferromagnetic properties in the whole investigated temperature range. © 2010 Elsevier B.V.

Zivanovic Z.,Vinča Institute of Nuclear Sciences | Milic M.,Military Technical Institute Belgrade
Strojniski Vestnik/Journal of Mechanical Engineering | Year: 2012

The paper presents the results of thermal load investigations of multidisc friction assemblies used as service brakes of a high speed tracked vehicle. By simulating the corresponding braking regimes and measuring the characteristic quantities on an inertial test stand, the relevant parameters of the braking process have been determined. The obtained results have been analyzed and compared to the permitted values of thermal load of the material of the tested friction discs. After a certain number of braking cycles by visual inspection of the brakes the state of the friction elements have been determined. The speed limits for braking the vehicle at higher transmission gear ratios, which may result in a permanent damage of the brakes, have been determined. © 2011 Journal of Mechanical Engineering. All rights reserved.

Vujic D.,Military Technical Institute Belgrade
Journal of Applied Engineering Science | Year: 2015

Aircraft industry has to meet a challenge of reducing operational and maintenance costs. One of the possible ways for reducing these costs is the introduction of wireless sensor networks (WSNs). WSNs are already finding a variety of applications for both safety-critical and non-safety critical distributed systems. This paper deals with the application of WSNs for aircraft structural health monitoring. Special attention has been given to the WSNs design issues using available components on the market. A general scheme for aircraft structural health monitoring using MicroStrain components has been proposed.

Samardzic M.,Military Technical Institute Belgrade | Isakovic J.,Military Technical Institute Belgrade | Anastasijevic Z.,Military Technical Institute Belgrade | Marinkovski D.,Military Technical Institute Belgrade
Measurement: Journal of the International Measurement Confederation | Year: 2013

The pitch/yaw apparatus designed for the measurement of the moment derivative due to an aircraft or missile model angular oscillatory motion in a wind tunnel test section is presented. A model is forced to oscillate with the primary angular oscillation around its transversal axis (pitch or yaw). Damping derivatives are obtained as a difference between total damping measured in the presence of aerodynamic load and mechanical damping measured in the absence of aerodynamic load. The main requirements for a new apparatus were: high load capacity, high structural rigidity, high range of the experimental frequencies and high sensors sensitivity. The choice of the hydraulic drive is made considering these requirements. Amplitude of the excitation moment is measured either by internal wind tunnel balance or by a specially designed excitation moment sensor. The T-38 wind tunnel data for the Modified Basic Finner Model and Basic Finner Model obtained using the pitch/yaw apparatus are shown. © 2013 Elsevier Ltd. All rights reserved.

Song T.L.,Hanyang University | Musicki D.,Hanyang University | Kim D.S.,LIG Nexl Co. | Radosavljevic Z.,Military Technical Institute Belgrade
IET Radar, Sonar and Navigation | Year: 2012

Multi-target tracking in clutter, assuming linear target trajectory propagation and linear target measurement equation, naturally leads to a Gaussian mixture (GM) target tracking solution. This study examines and compares two prominent methods that use the GMs: the probability hypothesis density and the integrated track splitting. Both are recursive Bayes methods and both incorporate the false track discrimination capabilities. They are represented in the form of GM target density filters. The modelling assumptions are translated in the algorithmic requirements. The authors compare the algorithms on the basis of these requirements with the future work indicated to reconcile algorithms and requirements. © 2012 The Institution of Engineering and Technology.

Radisavljevic I.,Military Technical Institute Belgrade | Balos S.,University of Novi Sad | Nikacevic M.,Military Technical Institute Belgrade | Sidjanin L.,University of Novi Sad
Materials and Design | Year: 2013

In this paper, an attempt was made to design effective non-homogenous armor in form of perforated plate mounted at close distance from basic armor plate. Perforated plate with three perforation diameters: 9, 10 and 11. mm, two ligaments length: 3.5 and 4.5. mm ligaments, set at 0° and 28° angles, were combined to 13. mm basic plate and tested against 12.7. mm API ammunition. It has been shown that larger perforations gave a more efficient core fragmentation, while angled specimens were the only ones that offer full protection against five API shots when the perforated plate was placed at 100. mm from the basic plate. Perforations that are similar in size to the penetrating core diameter offer a more efficient core fracture, leading to a faster fragment separation. This may enable a smaller distance between the add-on perforated and basic plate to be used. Scanning electron microscopy analysis has shown a ductile fracture mode at impact point, with hardness values on plate basic level. On the other hand, a brittle fracture mode with a rise in local hardness measured near impact point is a result of intensive high speed plastic deformation produced by bending stresses. A drop in local hardness measured near impact point, may be the result of intensive cracking that occur due to repeated projectile impact. © 2012 Elsevier Ltd.

Zivkovic S.,Military Technical Institute Belgrade
FME Transactions | Year: 2016

Replacing or upgrading software packages requires a detailed analysis and testing.This is especially important for software modules that are part of the production process. Machining of free-form surfaces always requires using of a five-axis milling machine. Tool path post-processing for these machines allways attracts special attention. The most important part of the postprocessor is implemented IKS (Inverse Kinematic Solver). Implemented IKS in the postprocessor must accurately describe the kinematics of milling machine in the production plant. Military Technical Institute performed parallel testing of two postprocessing modules of CAD/CAM system Siemens PLM NX: and old GPM (Graphics Postprocessor Module and a new module MOM (Manufacturing Output Manager). Complete analysis was sent to the NX support center and application engineers confirmed that the old and new postprocessors do not behave identically. The paper describes in detail the analysis and explains the solution of the presented problem. © Faculty of Mechanical Engineering, Belgrade.

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