Rolling element bearings are fundamental component parts to be used in rotational mechanical system. During the operation, vibration signals are generated and these signals are related to the technical condition of rotating machinery. The aim of this paper is simulated the vibration signal that propagated by rolling element bearings in mechanical gearbox. The gearbox dynamic model that combined gearbox components, such as, shafts, involute gears, rolling element bearings is developed. The localized fault is created on the inner race of bearing. The model is simulated using multi-body dynamics solution, after that results are analyzed in waveform and spectral in order to assess the behavior of gearbox.
The problem of dismounted operation support with Unmanned Ground Vehicles (UGV) often called robots is widely discussed and many solutions were tested to verify theory and find technological gaps and limitation for such application. In this paper the initial demand and requirements and their evolution is described on an example of US Army. Described changes concerns demanded level of autonomy, fire support possibility, possibility of performing combat engineer tasks, using UGV for reconnaissance, surveillance, and target acquisition, longitudinal and lateral stability, obstacle negotiation and overall terrain mobility and efficiency of make use of the “mule”.
The article presents the results of the study of the effect of combined preload on the change of mechanical properties of the aluminum alloy 2024-T3 at room temperature. The disclosure changes in the mechanical properties of the alloy were explained during the analysis of the deformation process in the material at the micro level (material grain). Experimental studies of the deformation process and its implementation mechanism at the micro level were carried out using the thin foil method using a Hitachi STEM HD2700 transmission electron microscope. Electron microscopic examination of the foil revealed an inclusion of minor phase particles in the aluminum matrix, which create a noticeable contrast in the image - dark inclusions against the background of the light matrix. The change of the dislocation density after combined loading was also found, because the scalar density of the dislocation in the material is in this case lower than after the tensile test, despite the same residual plastic deformation of the samples.
The article deals with military fortification constructions, their evaluation and field experimentation. Furthermore, it discusses legal standards, international and national regulations that set parameters and effects on military fortification structures. The diagnosis of structures can be characterized as a statement of differences between the assumed (projected) state and the current state of the examined structure. While field experimentation is an effect on structures and monitoring behavior and changes in the state of the structure. Considering the specific accidental actions, it is necessary to use diagnostic procedures other than conventional constructions, especially regarding the impossibility of breaking the structure by removing the specimen. It is necessary to evaluate the structure for a different type of action than usual. Some field tests were conducted at the Department of Engineer Technology according to STANG 2280. Some, however, were carried out according to their own procedure. These activities are referred to in the paper as field experiments and were used mainly to verify mathematical simulations of the behavior of actioned structures, and to make the experiments of field experiments more precise.
The objective of the research is to analyze the external ballistic characteristics of middle-range rocket target with a constant thrust and varying rocket motor operating time. The main requirement is to achieve the rocket target with horizontal distance (range) of 20 km and vertical distance (altitude) of 10 km. The rocket motor to be used should be RM-12K designed and built by the Kaunas University of Technology, Institute of Defence technology. This motor can produce up to 12 kN thrust for 3.2 seconds. To achieve the goal, a computational model is designed and numerical modelling for ballistic analysis is carried out. In this research, two different configurations are used to achieve the requirement. In the first test, all four motors are ignited together for 3.2 seconds which produce 48 kN thrust force. In third configuration two motors are used for 3.2 seconds to produce 24 kN and after the burnout, the second two motor is ignited for 3.2 seconds. Comparative analysis of two different configuration shows that the requirement of 20 km range and 10 km altitude was realised by using two plus two motors for 6.4 seconds of operational time.
The support of mobility is one of the main tasks of engineer units. The mobility consists of different parts – mobility of low-endurable terrain, watercourses, forests etc. In this paper the authors focused only to one area – trafficability of areas covered by snow. The snowy terrain covered most of areas, not only in the Czech Republic, during the winter season. But the mobility must be ensured even in such conditions. In some cases, the vehicles mire in the snow layer and they have to be rescued. In the others, the convoy of vehicles stop before the untrafficable place and they have to overcome it. It is not always possible to bypass the place and the units have to negotiate this area. But the removal of snow is very time and human consuming. So it was decided to undergo testing materials suitable for these purposes. The aim of this work is to evaluate the using of perspective materials for self-rescuing works in snow as well as for the negotiation of untrafficable terrain due to the layer of snow. And all this makes it possible to improve the ability of negotiation obstacles such as snowy terrain and thus better mobility of the troops even in such conditions. [1,2,3]
In the paper there are described main modernization trends of face masks. Main construction signs of the fourth-generation masks are introduced in an introductory part. The attention is devoted mainly to masks that can be ordered into a group of the fifth mask generation in further text. A description of development trends is demonstrated on main parts of the facial mask.
In the horizon of 2030, the Ministry of Defense of the Czech Republic set out significant changes, supported not only by an anticipated budget increase, but also by an efficient process of public procurement, and an increase in the number of members of the armed forces to respond to current and future threats.
In 2019, the Czech Air Force capabilities the development was ensured by the acquisition of twelve helicopters, eight MADR mobile 3D radars, and two new CASA aircraft.
An important year for the Air Force development is the year 2027, when the lease agreement for the supersonic aircraft JAS 39, will be terminated.
The paper contains the results of a non-destructive laser ultrasound internal structure analysis made on specially prepared friction stir welded joints made of aluminum samples. The process was conducted using four different groups of welding parameters. Different tool rotation speeds and tool traverse speeds were used. The main purpose of the research was to analyze the joint quality using a non-destructive laser amplified ultrasound method. A microstructure analysis was also conducted to compare the results of both tests.
Nowadays, filtration barrier materials are more often used for providing with long-term protection of the Czech Armed Forces professionals and Fire Rescue Brigades specialists against the effects of toxic compounds. A comprehensive study provided authors with evaluation of their protective properties’ qualitative changes in connection with knowledge development of possibilities of sensor technologies at this time. A solution usable for an electronic detection of the moment of water permeation or a liquid phase of other test chemicals (penetration) through construction materials of a filtration type or permeable barrier materials which are or perspectively can be used for protection against the effects of toxic compounds has been recently proposed. The aim of the solution is to replace a current used subjective way of the visual observation of water or other test chemicals penetration through textile materials used in anti-gas protection with the objective observation of the moment of test chemicals permeation (time of drench) with the help of a conductivity sensor with a possibility of an automatic record of the rate of penetration with the employment of the KONDUKTOTEST device.