Key Engineering Materials Vol. 588

Abstract: The paper concerns problem of diagnostics and transversal vibrations control of rotating beamlike system. The considered system is consisted of a simple prismatic beam. The beam is homogeneous and is being rotated round its end. The beam is fixed on the rotational disk. The most common method of analyzing rotational systems is the Campbell diagram. It gives the short and precise information about resonance points and critical angular velocities. In literature it is a very popular method, but used for shaft systems or rotors rather than for beams rotating round the axis of revolution perpendicular to its own axis of symmetry. In this work the exemplary Campbell diagrams for considered systems derived from the dynamic flexibility of beams are presented. In the used mathematical model the Coriolis forces and centrifugal forces were taken into consideration. Also the different types of boundary conditions were applied in this work. The results after proper adaptation can be used in practical applications such as pumps, turbines or wind power plants.

Abstract: Nowadays rotating systems are equipped with diagnostic systems that are based on collecting and recording measurement data and that process a huge amount of data during the machine operation. An analysis of these data and their interpretation, as well as finding a correlation between process parameters and dynamics of the machine is a very important problem. In the paper, a concept and selected procedures of the specialized software using advanced information technology for the diagnostic system dedicated for systems of rotating machines with active magnetic bearings will be presented. It is used in the actual operation of the machine, enabling an increase of its reliability. The paper presents some selected results of control of the proper operation of the mechatronic rotating system, carried out in the automatic mode.

Abstract: In rotating machinery, the detection of local damage is one of the most important issues. This kind of change of technical condition produce local disturbance according to temporal (local) change of stiffness of kinematic pair (tooth-tooth contact, rolling element-outer/inner race etc). In many practical, i.e. industrial cases, vibration signature of such change is weak in sense of produced energy, so consequently, completely masked by other vibration sources in machine. The general concept of signal processing for local damage detection is to use so called signal enhancement, i.e. a kind of tool that may improve signal to noise ratio. One may find many approaches used in the literature. Most of them use signal filtering (classical, adaptive and optimal filters), decomposition (wavelets) or extraction (blind source separation). Empirical Mode Decomposition (EMD) is one of such techniques that can be used with signal decomposition problem. In this paper, EMD will be used for vibration signal decomposition in order to extract information about local perturbation of arm (carrier) in planetary gearbox used in heavy mining machine, i.e. bucket wheel excavator. As a result of application of EMD, one may obtain several time series with different properties of sub-signal. Due to predefined task, namely local disturbance detection, several criteria have been investigated in order to select the most informative empirical mode. First criterion was kurtosis calculated for every mode with very simple decision rule (max kurtosis is the best). It was found that such approach is not optimal due to some random impulses that are not related to damage. To improve results, it is proposed to combine envelope spectrum and kurtosis. If envelope spectrum contains family of components related to arm (carrier) shaft frequency and signal is spiky (kurtosis is high) result of EMD for given mode is optimal in sense of carried information. However, in this approach decision was made based on visual inspection of the envelope spectra of each mode, which is non-effective way. Finally two parameters have been proposed: 1) Pearson correlation coefficient of an empirical mode and the empirically determined local mean of original signal; 2) a relative power of an empirical mode.

Abstract: The article presents the results of energy diagnosis of the structure of an innovative, mechanized, hand-held demolition tool with application of the Constant Interaction Force Vibroisolation (abbreviated as WoSSO) of a biomechanical system. Sample results refer to the demolition hammer of the weight of 15,6 kg and the frequency of working shocks of 20 Hz. The diagnostic research was to recognise and evaluate the energy and spatial impact of the innovative structure of the hammer provided with anti-vibration system upon human. 3D energy physical and mathematical models of the entire system human demolition hammer with vibroisolation of 18 degrees of freedom were designed and the problem was solved with the digital simulation method. The forces enforcing three directions of vibrations were identified via experiments at the research stand on the model base compliant with the ISO standard and then entered in the simulation program. The obtained results of the energy diagnosis of the structure explained the phenomenon of the energy flow in the examined biomechanical system and confirmed the efficiency of the flow reduction of the energy of vibrations into the human body at all the reduction points in the three directions of vibrations.

Abstract: The paper deals with diagnostic inference based on uncertain and simultaneously partly inconsistent data obtained, e.g. from different sensors. Such cases are very common in diagnostic practice and therefore there is a necessity to deal with them. Interesting approach to solving that kind of tasks consists in an application of the approximate statement network which represents the mutual relations between statements treated as necessary and sufficient conditions. The paper shows an example of applying a diagnostic model represented as the approximate statement network, to inference about technical state of a chosen object. The model was constructed in the REx system which also makes possible creating Bayesian and multimodal networks. Advantages and disadvantages concerning both constructing and using approximate statement networks were briefly described on the basis of obtained results. It seems that presented example shows the possibility of improving supervision systems, especially in regard to the complicated technical objects, by giving a mechanism of avoiding a confusion while making of diagnosis.

Abstract: The fuel injector acts a double role: it is the valve of the pump supplying fuel to the combustion chamber and the device spraying a supplied dose. As the valve it may operate as a self-opening or self-closing valve, depending on the pressure produced by the fuel pump, or the valve controlled by external signals. Techniques and diagnosis methods for fuel injectors depend on a fuel injectors control system and construction details. For practical reasons the fuel injector is a sectional valve with a separated component called atomizer. Atomizers must be cooled. It is possible to cool with fuel or with external water-or oil-cooling system. In case of liquid-cooled fuel injectors, apart from malfunctions causes known from literature, decrease of the cooling efficiency may appear, as the effect of the penetration of fuel from injector to the cooling system of injector. There are no reports concerning detectability of fuel leakage into cooling liquid with known techniques and diagnosis methods of injection systems and fuel injectors. In the article there will be presented as follows: a connection of the atomizer and injector body as the place of fuel leakage into the cooling system, reasons for loss of leak tightness in connection of atomizer with the body of atomizer and methods applicable for the leak tightness analysis, mechanisms of injectors malfunction caused by the loss of leak tightness. The analysis of applied and possible methods of injectors diagnosis in the aspect of identification of said leakiness will be carried out.

Abstract: Lamb waves are the most widely used guided ultrasonic waves for structural damage detection. One of the major problems associate with Lamb wave propagation is the effect of temperature on wave propagation parameters. It is important that these parameters are more sensitive to damage than to varying temperature. The paper demonstrates how amplitude and arrival time of Lamb waves are affected by temperature. The analysis is performed for the experimental data gathered from Lamb wave propagation in a damaged aluminium plate. A simple clustering algorithm is used to distinguish between "undamaged" and "damaged" conditions in the presence of changing temperature.

Abstract: Analysis of the indicator diagram is the basis of technical state evaluation of marine diesel engines. The indicator diagram contains a large amount of diagnostic information. A major problem for the diagnostic use of the indicator diagram is the pressure sensor location. Indicator channel and valve may introduce significant distortions in the resulting pressure. The paper presents results of research conducted on the medium speed laboratory engine Al 25/30. Pressure measurement (indication) was made by the sensor placed directly in the cylinder (instead of starting air valve), before the indicator valve (with special Kistler adapter) and on the indicator valve. Distortion of heat release characteristics for the sensor placed on the indicator valve is important, but it is estimated that diagnostic information is not erased. For medium speed engines is to be expected the use of a portable pressure sensors placed on the indicator valve. For this reason, further research is needed to assess the impact of channels and valves on different cylinders. During the research the course of heat release rate q and the heat released Q were determined. The curve of heat release rate q is a full equivalent to fuel injection pressure curve in the fuel pipes. It allows identification of the failure of the injection system. The curve of Q allows such determination and assessment of internal efficiency of the cylinder.

Abstract: Ultrasonic transducers are extensively used in medical applications. Any deterioration in their performance can lead to poor quality images. The Local Interaction Simulation Approach (LISA) and Finite Elements are used to model medical ultrasonic transducers. The entire analysis attempts to find out whether the LISA-based methodology could be used for transducer modelling in fault detection applications based on in-air reverberation patterns.

Abstract: Structural health monitoring (SHM) systems will be one of the leading factors in the successful establishment of wind turbines in the energy arena. Detection of damage at an early stage is a vital issue as blade failure would be a catastrophic result for the entire wind turbine. In this study the SHM analysis will be based on experimental measurements of vibration analysis, extracted of a 9m CX-100 blade under fatigue loading. For analysis, machine learning techniques utilised for failure detection of wind turbine blades will be applied, like non-linear Neural Networks, including Auto-Associative Neural Network (AANN) and Radial Basis Function (RBF) networks models.