Solid State Phenomena Vols. 147-149

Abstract: Selection of a constitutive model from commonly used ones, which in the best way describes dynamic behaviour of material during electromagnetic expanding ring test, is our primary goal in this work. Five more popular constitutive models are examined, i.e., Johnson-Cook, Steinberg-Guinan, Zerilli-Armstrong, MTS, and Preston-Tonks-Wallace model. As a criterion of the selection, qualitative/quantitative agreement of the numerical results with analogous data obtained from experiment presented in the work was taken [1]. It was found that the numerical results obtained by using Steinberg-Guinan or Preston-Tonks-Wallace model gave the best agreement with experimental data.

Abstract: This paper introduces the results of theoretical investigation on the dynamic characteristics of tilting 3-pad journal bearing that operates with turbulent oil film. The Reynolds, energy, viscosity and geometry equations determine the oil film pressure, temperature distributions, and oil film resultant force that are the grounds for the dynamic characteristics of bearing. These equations were solved simultaneously on the assumption of adiabatic laminar or adiabatic turbulent oil flow in the bearing gap. The stability and system damping of Jeffcott rotor operating in tilting 3-pad journal bearing was determined.

Abstract: The paper presents the analytic and simulation model of the rail launcher in a static state. The force acting on the projectile and the magnetic flux density were investigated. The mathematical description of the force acting on the projectile was derived. The simulation model was build with help of the COMSOL Multiphysics software. The computer simulation results were compared with the results obtained in the analytic way.

Abstract: In the daily life and in using technologies people interact with continuous medium like air or water. In present article a motion of the vibrator with constant air or water flow excitation is observed. In the first part of the article a motion of the vibrator with constant air or water flow velocity excitation is investigated. The main idea is to find optimal control law for variation of additional area of vibrating object within certain limits. The criterion of optimization is the time required to move object from initial position to end position. For the solution of high-speed problem the maximum principle is used. It is shown that optimal control action is on boundaries of area limits. Examples of synthesis of real mechatronic systems are given.

Abstract: Considered here are the questions of the simplification of the building process of the computer models. Suggested here is the “screwdriver” technology of the model building. The technology is based on the application of the set of the symbols of the typical elements and their models. The models of the object are built by the assembling of the element models in correspondence with the object structure. The application of the technology is illustrated on the example.

Abstract: In first part of the report motion of magnetic powder materials in a vertical or inclined pipe are investigated. Mathematical models are analyzed, taking into account intensity of a pulse electromagnetic field, parameters of a powder and its interaction with the surface of the pipe and air. Experimental device, including control and measure system with the analysis of parameters by computer, is described. Second part of the report investigates a motion of non-magnetic materials. For this reason an additional magnetic container with open surface is used. After an impulse action the container stops before bound. Non-magnetic materials continue flying motion. In third part of the report the authors investigate motion excitation with impulse generator for plane vibrotransporters. It is shown that this excitation is very stable, because after impulse action the mechanical system continues vibration with a non-periodical motion and stops waiting for next impulse.

Abstract: An electro-mechanic brake system, which has the potentiality to be used in future cars, has been studied and a prototype of the brake system has been produced. The electro-mechanic brake system has different working principles then hydraulic brake system. Hydraulic force or air pressure is used to obtain the braking force on the wheels in the hydraulic braking systems, whereas a solenoid valve push force is used to stop the car in electro-mechanic systems. A censor controlled the RPM of the wheel and the data was passed to a micro controller and micro controller produced PWM signals according to obtained signal. Thus, push force of the solenoid valve was controlled by micro controlled according to the braking ratio. If the wheel slows down the turning speed, then micro controller stops to sending PWM signals and solenoid is relaxed until wheels turns again. This cycle continues until the all wheels are stopped. A prototype of the system has been constructed and tested. The initial results indicated that the system can be potentially used in the automotives.

Abstract: The fault identifiability problem – determining necessary conditions of non-redundant set of symptoms that distinguish system’s faults – is considered. The diagnostic model is a multi-valued one. The information-theoretical approach enables determining redundant symptoms as well as indispensable symptoms - necessary elements of every diagnosis algorithm.

Abstract: A new method for the diagnosing of leaks from liquid transmission pipelines is proposed in this paper. The solution consists in the acquiring of the new diagnostic information (i.e. the new diagnostic signals). These signals result from the operation of special testing objects joined to a tested pipeline. This paper presents the results of the application of the proposed method upon the laboratory pipeline. During experimental tests it has been determined that thanks to the use of these new diagnostic signals improving the efficiency of diagnosing of leaks is possible.

Abstract: While an aircraft engine is being used, its wear takes place. Its gain coefficients decrease and at the same time its time constants increase (engine becomes „weak“ and „slow“). Therefore, the rigorously definite adjustment of engine according to the principles of automatics and manufacturer recommendations is carried out periodically during the ground service of engine. The practice shows that during ground tests an engine works in „easy“ surrounding, however, during flight an engine works in „difficult“ surrounding. After good adjustment of an engine from changing the set value w during the ground service, this engine may not meet requirements of the work quality by variable disturbances z during the flight. Therefore arises a problem of the synthesis of quantification of the control possibility of engine which will result in connecting the operation status of engine (automatics) with the maintenance status of engine (diagnostic). The measure of this relationship can be named „the control potential“ of the engine. The control potential can be determined from the equation of state: , where: y – operational signal of engine, u – diagnostic signal of engine, b – coefficient of intensity of influence of the maintenance status of engine on its control possibilities, a – control potential of engine,  - operation time (Bergson’s time). The parameter „a“ calculated with help of static and dynamic identification methods will permit to estimate the functional value of engine during its ground tests.