Vojnotehnicki glasnik / Military Technical Courier

5-25

Authors: Holclajtner Marko S., Jeremić Olivera M., Milinović Momčilo P.

This paper presents a procedure for an efficient simulation of MLRS barrage fire as well as of the effects of rocket parameters. The rocket behavior will be analyzed with reference to an ideal trajectory generated by an ideal rocket. The quality of MLRS fire is expressed through dispersion of impact points in the target area thus representing precision and accuracy. This work assumes absolutely correct accuracy and concentrates primarily on the effects of precision i. e. on the dispersion of rockets. Other types of effects on rocket dispersion, such as those of atmosphere, launching, etc. are neglected. The ammunition effects on the trajectory dispersion will be thus identified. The dispersion in the target area will be correlated with the dispersion of trajectory points at the end of the active (rocket motor burn out) phase.

43-52

Authors: Mrdak Mihailo R.

In this paper, the microstructural, mechanical and tribological properties of WCCoNiCrBSi thermal spray coatings, applied to repair the cylinders of helicopter nasal feet, were analyzed. The process used for coating deposition on steel substrate was the Atmospheric Plasma Spraying (APS).The plasma spray process is a procedure widely used for applying coatings with increased resistance to wear. The combination of WCCo and NiCrBSi powders produced coatings for the protection of metal parts exposed to wear abrasion, erosion and cavitation to 540°C. The WCCoNiCrBSi 50/50% powder is specially developed for the production of coatings of high cohesion and adhesive strength. The coatings are very dense, hard and smooth. Microstructures present in the layers are tungsten carbides and chromium layers that increase resistance to wear and abrasion. Powder is deposited on the substrate rugged with Al2O3. The substrates were heated at temperatures up to 200°C. Powder deposition was performed with the optimal deposition parameters The microstructure and micro hardness of the coating layer was investigated on the cross section of samples using the Pratt & Whitney standard. Micro hardness was tested using the Vickers scale with a load of 300g. The microstructure of the layers was investigated on an optical microscope (OM) with a magnification of 400X. Testing of bond strength between coatings and substrates was performed at room temperature with the speed of twitch of 1mm/60sec. The structure is multi-layered and layers are dense and homogeneous. In the WCCo layers there are dark WC phase particles. The NiCrBSi alloy layers contain fine precipitates of white nickel borida. The WCCo layers have micro hardness values ranging from 1097 - 1390 HV0,3. The tribological evaluation of the coating was performed using a pin - on ring tribometer. Lubricate sliding wear tests were carried out at room temperature according to the ASTM G77 standard. The coated blocks were tested on a hardened and tempered steel ring. A constant load of 400 N and a constant speed of 0,5 m/s were applied for a total distance of 3000 m. The values of micro hardness were also measured in the NiCrBSi layers in a narrow range of 823-930 HV0,3 The values indicate that the layers are homogeneous and thick. The coating bond strength is 59N/mm. The value is high because of the warming substrate. The dynamic coefficient of friction has a value of μ = 0,1 to 0,11. The mass loss was small and on average it amounted to Δmb = 0,11 mg. The results of tribology tests showed good reproducibility of the dynamic coefficient of friction. The coating can be reliably applied to surfaces exposed to wear during operation. The advantage of this coating application is in a significant prolongation of service life of parts, together with reduced operating and maintenance costs.

71-89

Authors: Ivković Dejan S.

In all analyses the MUSIC method has given better results than the FFT method. The MUSIC method proved to be better at estimation precision as well as at resolving two adjacent Doppler frequencies. On the basis of the obtained results, the designed estimator of radial velocity can be said to estimate Doppler frequency in the reflected signal from a moving target precisely, and, consequently, the target velocity. It is thus possible to improve the performances of the current radar as far as a precise estimation of velocity of detected moving targets is concerned.

108-126

Authors: Bondžulić Boban P., Petrović Vladimir S.

This paper presents a robust multisensor background extraction and update scheme intended for use in target detection applications. The method uses a number of well known concepts in detection to provide a basic classification of the scene into moving and stationary objects and an iterative procedure to update the background model and deal with transient (slow) changes in illumination conditions. A new fusion- based confidence framework uses the information from multiple registered views of the scene obtained by different sensors in order to update the background model only in areas where there are no moving objects. It was shown on a number of representative multisensor sequences that the proposed method obtains a more complete and robust representation of the background than any estimate based on the individual sensors. Finally, a relatively simple computational architecture of the proposed system makes it ideal for demanding real time multisensor detection applications.

150-164

Authors: Pešić Predrag J.

The purpose of explaining the model of resource management with the signal reserve, the process diagram and the SIPOC model of the supply chain explained was to present the opportunity for applying modern approach of Technical logistic in the management of the supply chains in military organizations. The described model allows efficient management of resources and material stocks by monitoring the changes in resource levels for individual stocks, groups of materials and the overall reserves. By applying ABC and XYZ analysis with the logistic Controlling the AX class materials (large annual demands and with well planned expenditures) could be well managed at short notice, in extreme cases even without any stocks by applying the 'just-in-sequence' strategy.

179-187

Authors: Radojčić Steva M.

The main conclusion is that only when the measures of accuracy and those of reliability are taken together, they form a sufficient basis for the assessment and comparison of the quality of geodetic networks.