The Structural Identification approach is used to identify and localize the existence of damage for a steel
frame. The black box linear parametric model called Auto-Regressive Moving Average with eXternal input
(ARMAX) was utilized for the construction of the Frequency Response Functions, based on simulation
results. The Singular Value Decomposition method was adopted to identify how many significant eigenvalues
exist and plot the Complex Mode Indicator Function for the complete frame. Three damage indices were
adopted to evaluate the state of damage in the frame. The results indicated that the ARMAX is a robust
scheme for structural damage detection.
Martin MANTIČ, Jozef KUĽKA, Eva FALTINOVÁ, Melichar KOPAS
The article deals with the design of equipment and its application possibilities for on-line monitoring of
operational stress traverse mechanisms. By processing of load spectra it is possible to predict the remaining life in the selected areas of the construction.
Jozef KRAJŇÁK, Jaroslav HOMIŠIN, Robert GREGA, Matej URBANSKÝ
The article describes the mechanical system developed at our department. It examines shaft couplings and their impact of torsional oscillation and vibrations on noisiness of the mechanical system. The noisiness of the mechanical system is compared with the vibrations measured in a given mechanical system. The article also presents the apparatus used for measurements. Every device is described in detail and highlights its use in practice. These devices were used for measurements in the laboratory and the results of the measurements are shown in the graphs. From the results, we can evaluate that vibration and noisiness are closely related. A detailed evaluation of the changes of individual values using a variety of shaft couplings is summarized at the end of the article.
The paper presents a non-destructive diagnostic technique based on guided wave propagation phenomenon used to assess the adhesive bonding between a steel bar and a concrete cover. Double-layered cylindrical specimens with different levels of debonding and its location were investigated. The influence of bonding length on the excitation of multiple modes of longitudinal guided waves was analysed. Numerical simulations of guided wave propagation in healthy and damaged specimens were conducted and differences in the occurring phenomena were specified. The analysis of the obtained results confirms the possibility to apply the guided wave propagation method in the assessment of degradation level in the adhesive bonding of multi-layered cylindrical structures.
Electronic devices, which are used in safety systems during operation, produce an unintended
electromagnetic field. It can be a source of interference to other devices and systems used in the protected premises (the concept of internal and external compatibility). The value of the individual electromagnetic
field components, which are produced by safety system control panels, depend on their operating state.
Within the individual operating states, these devices consume different values of currents from basic or
backup power supplies. The paper presents the research results of the unintended electromagnetic field generated by the safety system control panels. Measurements were carried out for two frequency ranges – a range of extremely low frequencies ELF (0÷2) kHz as well as a range of very low frequencies VLF (2÷100) kHz. The research was conducted according to the Polish standards on the measurement of electromagnetic fields in a range of low frequencies.
Jozef KUĽKA, Eva FALTINOVÁ, Melichar KOPAS, Martin MANTIČ
This paper deals with questions concerning technical diagnostics and optimisation of fatigue durability for the crane track beams installed in a metallurgical plant. The fatigue durability is determined using a strain gauge measurement in order to calculate the relevant residual durability of the crane track beams. Consequently, there are proposed suitable measures that are necessary with regard to the next operation of the given crane track, which is supporting a bridge crane.
Matej URBANSKÝ, Jaroslav HOMIŃIN, Peter KAŃŃAY, Marek MORAVIČ
At our department we deal with continuous tuning of torsional oscillating mechanical systems during their operation using pneumatic tuners, mainly in terms of torsional vibrations magnitude, whereby we use the methods and means of technical diagnostics. One of the manners of continuous tuning realization is the application of extremal control – experimental optimization, which main advantage is that we don’t need to know the mathematical model of mechanical system. We must know only that the objective function of mechanical system has an extreme. For that reason, it is very important to know this form of objective function not only at failure-free operation but at failure occurrence as well. The objective of this paper is therefore the investigation of the influence of piston compressor inner failure, namely cylinder(s) fall-out on mechanical system objective function form.
The paper presents the results of computational studies on damage localization in beam-like structures
based on an approach of application of selected time-frequency distributions to modal shapes of vibration.
The studies were performed on the results of finite element analysis on determination of modal shapes of vibration of a composite beam. The damage detection and localization procedure was shown on several examples of time-frequency distributions with a discussion of their performance for structural damage detection and localization problems. Additional studies were performed for artificially noised modal shapes in order to investigate an applicability of the proposed approach in noisy conditions. It was shown that application of time-frequency distributions is the effective tool in structural damage detection and localization, and can be a good alternative to the well-known signal processing techniques applied in these problems.
Michał JANULIN, Jarosław GONERA, Wojciech WITKOWICZ
This paper describes the influence of shock absorbers\' technical condition on the vehicle braking process on two types of surface with the Anti-Lock Braking System activated and deactivated. During each of the road tests the vehicle stopping distance, the braking deceleration, and the force applied on the brake pedal were determined. The test plan includes various road surfaces and technical conditions of shock absorbers. The established characteristics of the stopping distance and the deceleration allow the determination of the relations between the technical condition of the shock absorbers, the road surface, and the efficiency of the braking system. In addition, this paper presents the principle of operation of the Anti-Lock Braking System, which is one of the basic active safety systems.
The aim of the study was to assess whether four psychoacoustic parameters (sharpness, roughness,
fluctuation strength and tonality) are useful in describing the perceived annoyance of selected noise sources with respect to an objective assessment based on the acoustics standards. Second goal was to verify if the perceived annoyance of such noises correlates with dominant frequency in electroencephalography (EEG) frequency bands. Twenty sound sources, varying in the degree of nuisance, have been assessed by 178 respondents in an Internet-based psychoacoustic test. Obtained annoyance grades were correlated with calculated psychoacoustic and normative parameters and the positive correlation between perceived annoyance and three psychoacoustic parameters (sharpness, roughness and fluctuation strength) was found. In the second part EEG study during listening of recorded sounds was performed on 18 healthy volunteers. Spearman’s rank correlation confirmed that dominant frequencies in alpha (7-14 Hz) and beta2 band (20-30Hz) were rising with the increasing annoyance of the sounds. Results obtained may be useful in specifying and clarifying permissible noise levels for annoying sounds.
Giulia MORETTINI, Nicola BARTOLINI, Davide ASTOLFI, Lorenzo SCAPPATICCI, Matteo BECCHETTI, Francesco CASTELLANI
Hydraulic shock absorbers are mechanical devices responsible of vibration damping. Although a high level of development and tuning has been carried on, in order to ensure high performance standards in almost every situation, some dynamic phenomenon affecting internal fluid may reduce the damping capacity. In hydraulic shock absorbers, the energy is dissipated forcing the internal fluid through calibrated orifices; this energy is converted in heat and dispersed outwards from the external walls. Hydraulic fluid has therefore a fundamental role for the proper functioning of the overall device, and the most important variations of its chemical-physical properties have to be considered. One of the most dangerous phenomena involving the internal fluid is cavitation, which could affect performances and generate structural damages of the internal components of the damper. The aim of this work is to diagnose the phenomenon of cavitation using experimental data from a prototype of monotube shock absorber equipped with transparent walls and developed for research purposes. The identification of force and displacement parameters is carried out through experimental tests on the prototype, which is a totally adjustable device equipped with pressure and temperature transducers for every chamber. The optical access provided from the transparent wall allows to collect images from a high-speed camera, which could be related to the signals coming from the transducers. This approach is valuable for analyzing the occurrence and the time development of dynamic phenomena of cavitation of the flow or the motion of the main valve blades. Finally, the acquisition of the optical images, coupled with evidences from experimental data, allows to characterize the dynamic events of cavitation, from his onset.
The article deals with the research results of temperature distribution on infrared heater surface.
Mathematical model of the process of heat exchange on infrared heater surface was developed. The
experimental measurements have been carried out and the data of the temperature on infrared heater surface have been obtained for verification the reliability of the results of theoretical studies. The results of the
studies showed that the temperature gradient of the area of heater changed no more than 4.5°C.
Andrzej GĘBURA, Bogdan PIETNOCZKO, Tomasz TOKARSKI
The article discusses the design and principles of operation of three diagnostic testers constructed by the authors of this study, intended for three, different aircraft propulsion units. These design have one common way of processing the original diagnostic signal - they use one FAM-C method. This method is based on natural processing of the rotational speed fluctuations of individual kinematic cells of the propulsion unit, by the on-board generator into frequency modulations. The method, thanks to its properties, is extremely beneficial for the automatic digital diagnostic processing. The tester can be connected at any, convenient for
the crew, location of the power grid, away from dangerous zones of the aircraft.
Ľubomír KAŠIAR, Peter ZVOLENSKÝ, Dalibor BARTA, Lukáš BAVLNA, Martin MIKOLAJČÍK, Paweł DROŹDZIEL
The current very rapid technological development of means of transport with the accompanying high
economic demands gives rise to their modernization, which is technically and financially particularly
advantageous. One of the dominant processes in this reality is modernization of diesel locomotives that seeks, in particular, to improve their operating characteristics, energy, environmental and also maintenance parameters. This paper deals with diagnostics and troubleshooting on a modernized diesel-electric locomotive series 757 ZSSK, a.s. We present details on this traction vehicle diagnostics and specific diagnostic files that originated in real operating conditions, with the subsequent solving of diagnostic problems and tasks.
A complex diagnostic object typically generates a large number of diagnostic symptoms. For proper lifetime consumption monitoring it is necessary to select those which best represent technical condition deterioration. Such selection may be based on the Singular Value Decomposition method. The paper presents a novel alternative approach, which employs an information content measure. As the end of object life is approached, symptoms are to an increasing extent dominated by deterministic lifetime consumption processes and therefore become more predictable. Thus symptoms with the highest information content decrease rate should be considered most useful. For a proper assessment, however, symptom sensitivity to condition parameters should also be addressed. A new measure
referred to as representativeness factor is proposed. Suitability of such approach is demonstrated for the fluid-flow system of a large steam turbine.