P. Novotný, V. Píštěk, L. Drápal and R. Ambróz
The paper deals with the cranktrain development of a new diesel engine for possible military use. The engine utilized potentials are discussed at the beginning of the paper. The cranktrain vibration and fatigue are solved by computational approaches. The computational model incorporating flexible bodies is assembled and solved in Multi-Body System. Slide bearings are solved by a hydrodynamic approach. The results include vibrations of the cranktrain and also fatigue analyses of cranktrain key parts, such as crankshafts or a propeller shaft. There are also presented design modifications enabling reduction of vibrations and fatigue increase of main parts.
Keywords: Diesel engine, cranktrain, dynamics, vibration, fatigue, aircraft, military generator set
Quartz Crystal Microbalance Detection Usage for Study of Permeation of Hydrocarbons in a Homological Line
P. Otrisal and S. Florus
The deflection from classical Chemical Warfare Agents in military use has been currently noticed. That is why questions’ solution concerning contamination after their use importantly decreases. On the other hand, a possibility of contamination development after both military and terroristic Toxic Industrial Chemicals usage is very high. Despite these very important facts, necessity of solutions of questions concerning study of suits’ protective properties used for specialists’ isolative protection increases. In this way, the gained results principally affect the evaluation of effectivity of accepted protective measurements in all kinds of military operations conducted by both Czech Armed Forces Chemical Corps specialists and specialists from Fire Rescue Brigades. The main aim of the article is to point to some properties of butyl-rubber polymer mixture coated on polyamide fabric considering selected liquid aliphatic saturated hydrocarbons in a homological line with the use of the PIEZOTEST method which uses a QCM detector.
Keywords: PIEZOTEST, QCM detector, Toxic Industrial Chemicals, Chemical Warfare Agents, butyl-rubber, aliphatic liquid saturated hydrocarbons
M. Siska and V. Plátěnka
The article deals with the problems of the measurement of VHF transceivers with frequency hopping. A variant of the measuring workplace which was proposed on the basis of LabVIEW program is described. The emphasis is laid on a connecting through the virtual measuring blocks with the real instruments and also on the presentation of the measured results.
Keywords: Measurement of Transceivers, LabVIEW, Frequency Hopping, Spread Spectrum
The Impact of Critical Flow on the Primary Electron Beam Passage through Differentially Pumped Chamber
J. Maxa and V. Neděla
Environmental scanning electron microscope creates new possibilities in the field of examination of various types of specimens and their phases. The article analyses and compares the results of air pumping measurement for selected shapes of the differentially pumped chamber to create vacuum, using the Cosmos FloWorks system.
Keywords: EREM, CAE, SolidWorks, Cosmos, FEI, Differentially Pumped Chamber
J. Štrba and J. Kusák
Calculating of the interior ballistics characteristics using seven-perforated nitrocellulose powder in cartridge assemblies can be used in special techniques and in special projectile sets. Accuracy of interior ballistics characteristics calculations influences construction solutions of special techniques and ammunition; main utilization is in armed forces special techniques and ammunition for country defence. Originally derived relations make geometric coefficients solution of non-treated seven-perforated powder more accurate and easier to use.
Keywords: Interior ballistics, interior ballistics characteristics, ammunition, gun, nitrocellulose powder
Evaluating the Effect of SIGINT Sources Movement to Process Them in the Stationary Reconnaissance Equipment
Z. Matoušek and P. Bučka
Signal Intelligence (further SIGINT) is one of the basic types of reconnaissance, results of which provide commanders and headquarters with important information for their right decision-making process. The article focuses on the analysis of SIGINT sources movement effects on processing the signals in stationary devices. Following the derived relations there are the results of corresponding simulations, which describe the relation of electric field intensity, power density and received electromagnetic energy output in SIGINT device location depending on the location and parameters of movable SIGINT sources.
Keywords: Electrical intensity, electromagnetic energy, power density, power of signal, receiver sensitivity, SIGINT equipment, signal source
Z. Pokorný, J. Kadlec, V. Hrubý, Z. Joska, D. Q. Tran and D. Beran
The nitriding behaviour of heat-treated alloyed steel was carried out on two samples with various diameters. The influence of nitriding conditions on the thickness and hardness of nitrided layer were investigated. Bored cylindrical barrels were quenched and subsequently tempered. Plasma nitriding was performed at 500°C for 6 hours with mixture of H2 and N2 in plasma nitriding appliance. The pressure was changed to 4 and 6 mbar. Microstructure and mechanical properties of nitrided layers were characterized using optical spectrometry, laser microscopy, hardness testing. The nitrided depth was also estimated using cross-sectional microhardness profiles. The results of experiments showed that plasma nitriding process is applicable to cavities. Surface hardness of material was significantly increased. The measurements have shown that the pressure of plasma nitriding process has a remarkable influence on the depth of nitriding in cavities, flat surfaces and on the length of nitriding inside cavities, i.e. the distance from muzzle.
Keywords: Plasma nitriding, nitrided layer, universal hardness, length of nitriding
K. Dejmal and V. Répal
Techniques for forecasting extreme temperature are mostly empirically based, using collections of statistics over a long period of time for a range of weather situations. In the article we have used the McKenzie’s method for forecasting the minimum temperature and Callen and Prescott’s method for forecasting the maximum temperature. Both of methods belong among the successfully and routinely used techniques. Main aim is to adjust these methods for routine application on aerodromes currently used by Czech Air Force.
Keywords: Minimum and maximum temperature, forecasting techniques, meteorological data, correction factor, verification
Security Challenges of Sophisticated Simulation towards Construction Materials Fatigue Phenomena Elimination
M. Kuffová and P. Nečas
Modern societies have become highly dependent on modern technology. Without its tools, their economies can no longer be run and their infrastructure would collapse. Thus technology has offered a high and sophisticated standard of living to societies, but at the same time it has introduced an inherent vulnerability. The efficient Automatic Dynamic Incremental Nonlinear Analysis (ADINA) is a Finite Element Method (FEM) based system, very suitable for solving large variety of personnel security problems; observing construction material processing and growth of fatigue damage, crack propagation and the distribution of stress fields. Leveraged by simulated fracture and damage of material models, it is the catalyst of the problem-solution roadmap towards substantial material cracks elimination.
Keywords: Modelling and simulation, construction material fatigue, experiments, cracks and degradation process, reliability and personnel security, sophisticated numerical tools, propagation direction
J. Pečinka and M. Poledno
It is a common practise not only in turbomachinery to use lookup tables in engine models to describe some characteristics. These characteristics are often available in graphical form of a diagram with multiple plots which were formerly used in calculations for manual reading. Using an example of centrifugal compressor map calculation, this paper shows how a diagram with multiple plots can be transformed into a lookup table that is used in automatic calculation.
Keywords: Centrifugal compressor characteristic, gas turbine engine, off-design performance, lookup table, structured variable
J. Salga and D. Maturkanič
In connection with aircraft accident statistics of small aircraft, the paper deals with modelling applications for flight trajectories of these aeroplanes. The results of the modelling could be used for aircraft accident investigations or for increasing flight safety. The aircraft is considered as a mass point and its real weight, aerodynamic and power plant characteristics are respected for defining acting forces.
Keywords: Aircraft, general aviation, aircraft accident, flight trajectory, modelling, mass point, aircraft characteristics