Solid State Phenomena Vols. 147-149

Abstract: The FDM-A diagnostic method [2, 4] based on a frequency modulation measurement of a pulsation component as well as the FAM-C method of an alternating current frequency have been elaborated in Air Force Institute of Technology. These methods to define a level of an assembly abrasive wear as well as its localization during a normal work of a power unit. A diagnostic signal is derived from onboard generators or alternators. Each damaged part of the generator’s or alternator’s power unit is a vibration generator or modulator. The vibration is turned into oscillation in onboard generators or alternators. After many years of the FAM-C and FDM-A methods’ using it is possible to localize and define value of many faults of power units: a coupling eccentricity, a shaft skew, extender longitudinal clearances of turbine engine’s rotor assembly, a frictional resistance of bearings, a smoothness of bearing’s rolling and a bearing cage, a break of rolling bearing’s separator, a misalignment of a rotor assembly’s support, etc. In FAM-C and FDM-A methods two kinds of presentations are used: first a presentation as characteristic patterns (analogous to Fourier spectrum lines but providing to observe periodical and stochastical phenomena) as well as the presentation of the frequency versus time. From the point of view of authors in many cases they are similar to presentations known from a theory of a radio signals transmission. It is possible to find carrier wale and side spectrum lines, beats caused by summation of two signals with approximate frequencies as well as many others. If analogy is so univocal, it is possible to use many systems and dependences used in telecommunication. For example: coherence demodulation (synchronous), which authors intend to use for separation characteristic patterns of two different mechanical assemblies with approximate vibration frequencies. At the end there are presented authors’ considerations, related to superposition of signals and beats as well as reflection of these phenomena in observed power units.

Abstract: The paper presents a definition of a new energy based parameter which allows to better describe fatigue proprieties of materials, especially cyclically unstable materials in comparison with the Lagoda-Macha parameter. The proposed parameter distinguishes positive and negative work of external force and depends on the sign of the stresses in paths of strain in materials. It is used in laboratory tests for control of a fatigue process on hydraulic stand. A close-loop control system has been equipped with computer program based on MATLAB/Simulink module.

Abstract: In the following paper we consider a problem of fault detection for a mobile robot. The robot which our work is related to, is based on a new type of the steering principle [1]. The crucial part of the steering system are axle position sensors. A failure of one of them might result in an interruption of operation and/or serious damages to hardware and environment elements. To avoid the risk of such events, a reliable fault detection system has to be implemented. Fault detection is facilitated by incorporating measurements from various sensors located on board of the robot (incremental encoders, absolute encoders, sonar, cameras, compass, GPS). In our work we consider the Bayesian approach (Kalman filter [2,3] and particle filters [4,5,6]) to create a diagnostic system of the robot. Due to the limited resources of the computing unit it is necessary to strongly optimize the efficiency of applied algorithms. In our work we plan to perform simulations to find the best suited algorithm for our vehicle. Accordingly, we build a numerical tool in MATLAB to simulate mobile robot navigation and fault diagnosis tasks. We also present the construction of our robot and explain how a reliable fault detection system is important for the proper functioning and safety of the mobile robot. We introduce the fault detection algorithms which we plan to apply in the described hardware solution. At the end, we summarize our work and provide an outlook on our future research plans.

Abstract: The paper presents various types of turbine scoops damages that are being found in the operating process of air turbine engines (TSO). When dividing them, having in mind a genesis of their origin, a special attention has been paid to corrosion and high-temperature erosion, often being a reason for destruction of the entire unit. The damages hereto described have been illustrated with examples collected during endoscope surveys of TSO internal spaces or their post-failure disassembly. The summary points out to the ways and directions of works aiming at early detection of TSO turbines units damages, and thus at improvement of their operating safety.

Abstract: The intended aim of the paper was to present a short review of more than 15 years of experience of ITWL in the field of applying the signal of actual rotational speed (aperiodic and oscillation components thereof) to the expert diagnosing of aero-engines, including identification of low- and high-cycle fatigue (LCF, HCF) of critical structural members. What has been presented is some essential metrological bearings of the non-contact technique of measuring the engine’s rpm with some flexible key phasors (i.e. vibrating compressor/turbine blades). Also, methods of numerical analysis of measuring signals, in use nowadays, have been discussed. With the jet engine of the SO-3 type (in use on the TS-11 “Iskra” combat trainer) as an example, are discussed algorithms of both the identification of disadvantageous aeromechanical effects (energy state of the engine - i.e. the source of accelerated HCF wear of structural components) and the early detection of symptoms of fatigue failures to compressor blades and the bearing system. The discussed problems have been illustrated with examples selected as to emphasise practicalities of applying a new source of diagnostic information to ‘actively’ control the process of fatigue wear (HCF + LCF) of engine components and to forecast the engine health/maintenance status.

Abstract: This paper presents the load carrying capacity (load capacity) and friction coefficient calculation of hydrodynamic HDD micro-bearing with parabolic profile of journal. One of the reason of such journal profile is that this journal profile contributes to the variation (an increase or decrease) the memory capacity of HDD drive operating on hydrodynamic micro-bearings. Such properties are very important and required in HDD micro-bearings. Up to now, the dynamic behavior of HDD spindle system with fluid micro-bearings was considered by Jang at al. [3]. They simulated an increase in the memory capacity by increase in the bearing width and by application herringbone or spiral grooves on the sleeve and journal surfaces of HDD micro-bearings.

Abstract: The paper presents selected results of tribological tests on ball bearings. The elements for tests were obtained from their manufacturer. Two groups of ball bearings were evaluated: 134-781TNG-2RS and CBK 441TNG. Tribological tests were conducted with SMT-1 device in two-stage cycle. The first stage involved tests based on the authors’ own method. In the second stage the tests were conducted according to the manufacturer’s recommendations (methodology). The obtained results indicate varied tribological characteristics of the tested ball bearings, both in reference to the parameters of the external function and the applied test method.

Abstract: Results of tribological research of mineral motor oil with and without twisted nematic liquid crystal additive (stearic acid cholesteryl ester) are presented in the article. Experimental research was performed by means of a “fixed segment – rotating roller” tribometer according to the central three-factor second-order rotatable factorial design. The following parameters were accepted as controllable factors: contact pressure (3.32–6.68 MPa), concentration of liquid crystal in lubricant (0.16–1.84 ) and the average height of surface roughness of contacting surfaces of roller and segment (2.5–37.5 μm). The friction coefficient and friction zone temperature were served as output parameters. Regression equations describing the friction process were obtained and tribological efficiency of liquid crystal additive was established.

Abstract: The paper deals with possibility of selective transfer phenomenon generation in couples consisting of materials of railway traction trolley wire and of pantograph slider material. Some examinations are described concerning tribological characteristics evaluation of above couples. The most characteristic condition of selective transfer phenomenon (known also under the name of “Garkunov effect”) is generation of specific protective metallic layer on friction surfaces of both frictionally cooperating elements that minimize wear and friction resistance. Obtained results led to the conclusion that the selective transfer phenomenon was generated in the model friction pairs examined in the frames of presented work. The magnitude of this phenomenon depended on minimal differences in quantities of additives and impurities in copper.

Abstract: In this paper we present a software model of the Winner Takes Most (WTM) Kohonen neural network (KNN) with different types of the neighborhood grid. The proposed network model allows for analysis of the convergence properties such as the quantization error and the convergence time for different grids, which is essential looking from the hardware implementation point of view of such networks. Particular grids differ in complexity, which in hardware implementation has a direct influence on power dissipation as well as on chip area and the final production cost. The presented results show that even the simplest rectangular grid with four neighbors allows for good convergence properties for different training data files.