The work is focused on developing testing methods for investigating of the deformation mechanisms of magnesium alloys. The work involves the measurement of in-situ acoustic emission and neutron diffraction and comparison to the theoretical models. Mg + 1wt.% Zr alloy was selected for investigation of the compression - tension asymmetry. Advanced analysis of acoustic emission and neutron diffraction data revealed activation of different slip systems during deformation. Moreover, the different evolution of twinning was explained. The same methods were used to investigate the aluminum influence on deformation mechanisms. The hardening of basal slip and twinning and increasing importance of prismatic slip was observed.

CSÁKI, Štefan: Thermophysical and electrical properties of illite-based ceramics. [Doctoral thesis]. Constantine the Philosopher University in Nitra. Faculty of Natural Sciences. Charles University. Faculty of Mathematics and Physics. Supervisor: prof. RNDr. Libor Vozár, CSc. (Constantine the Philosopher University in Nitra), doc. Ing. Patrik Dobroň, PhD. (Charles University). Nitra & Prague, 2018. 107 p. Illitic clays are of special importance in the ceramic industry. Therefore, a deep knowledge of the thermophysical processes, as well as the electric properties, is of special importance. The illitic clay originated in Northeastern Hungary was used in this thesis. The reactions, occurring during firing, were studied using thermal analyses (Differential thermal analysis, Thermogravimetry, Thermodilatometry) and special attention was paid to the measurement of the electrical conductivity (both DC and AC). Up to 250 řC, where the removal of the physically bond water (PBW) takes place, the dominant charge carriers were the H+ and OH- ions. After the PBW was removed, Na+ and K+ ions became the dominant charge carriers. During dehydroxylation (450 - 750 řC) H+ and OH- ions were freed from the illite structure, which supported the electrical conduction in the samples. At ~ 970 řC glassy phase appeared...

This thesis studies the possibilities of exploiting the acoustic emission method as a tool for more detailed identification of the radial bearings damage formation. The work includes comparison of different evaluation methods in laboratory tests. Applied couplant between the contact sensor areas and sensing surfaces is also taken into account. The practical part includes the presentation of the experimental station and structural adjustments made. The main part of the work comprises the examples in detail of three types of experimental tests that simulate the possible failure of bearings and their manifestation in the sensing signal. Testing methodology developed with recommended values for setting common AE signal measurement, vibration and temperature is a part of the thesis, too.

The thesis proposes a methodology for damage identification of thrust bearings using acoustic emission method. The work is the way of the hydraulic loading of specimens and thrust bearings with programmable settings severity and duration of load cycles during contact fatigue tests at stations Axmat. They are designed structural adjustment elements (waveguides) to capture the acoustic emission signal selected apparatus, including the modification of software to capture the data. At the described experiments is verified functionality of the circular test specimens and axial bearings . Part of this work is to propose a new methodology for identifying early stages of contact fatigue using a combination of diagnostic methods.

The goal of this diploma thesis is to clarify possibilities of usage of acoustic emission as a hydraulic machinery diagnostics tool. Especially for exposing presence of ruptures or cracks in the parts of machine, assuming changes in acoustic exposure of the part during operation. This clarification is based on series of simple measured experiments, which consist of monitoring the bolt placed in fluid stream inside of a pipe. This bolt was preloaded against inner wall of pipe by appropriate tightening torque. This preload is supposed to simulate effects of the size of rupture. High preload simulates small rupture or none in object and respectively small preload is supposed to simulate big rupture. A group of pressure sensors and accelerometers measures experiments and their evaluations are processed by script created in software MATLAB. Outputs of this script are charts with effective values of respective sensors from the entire record split into individual frequency spectrums. These charts compare spectrums of each configuration to judge effects of parameters changes.

The dissertation thesis deals with the study of non-destructive acoustic methods as instruments for monitoring and analysing corrosion of reinforcing steel in reinforced concrete elements. Four acoustic methods were selected for this task - the impact-echo method, the nonlinear acoustic spectroscopy method, the acoustic emission method, and the ultrasonic pulse velocity method. To verify the functionality of these methods, testing was carried out on three sets of reinforced concrete samples that had been exposed to the effects of sodium chloride, which corroded the embedded steel reinforcement in these samples. Suitable parameters were proposed for individual acoustic methods to monitor corrosion of the reinforcements. In addition, experiments were designed to demonstrate the ability of the selected acoustic methods to reveal the corrosion of steel reinforcement and its influence on the concrete matrix and to assess the condition of the degraded elements and structures. The analysis of the measurement results based on their comparison shows the advantages and disadvantages of the individual methods and of their practical applications. To verify the results, correlation with common methods that are currently used for the study of corrosion was carried out and included for example the electrical resistivity measurement of the reinforcement and simultaneous monitoring of the sample surface using a confocal microscope to record the development of microcracks during the degradation.

This thesis deals with the vibration and noise of the gearbox for an electric vehicle. The gearbox itself acts as an emitter of unwanted noise caused by vibration excitation of the internal components of the gearbox. It is therefore necessary to deal with a complex unit such as the gearbox at system level as soon as it is being designed. This can be achieved using analytical tools and software. In this thesis, in order to evaluate the validity of the designed gearbox, a procedure is developed using both technical experiment and numerical simulations. The effect of the bolt preload is not overlooked for the following computational modelling dealing with the radiated noise of the gearbox. The results obtained from the performed technical experiments were then evaluated and compared with the results of the computational models. In this way, it is possible to compare the different approaches, their limitations and weaknesses. Furthermore, the thesis deals with design modifications that are analyzed using computational modeling. The thesis is concluded with a brief description of the application of each approach and an evaluation of the gearbox design modifications.

The diploma thesis deals with calibration of AE sensors used in diagnostics of bearings. Two different conceptual solutions similar to those used in the diagnostics of bearings were designed in the design. Subsequently, the experimental device was designed for relative calibration using the rotation of bearings as a continuous AE source. The experimental part is oriented to the observation of the RMS parameter, which serves as a sensor sensitivity evaluation parameter. As sources of AE, bearings with a certain type of damage were used, which allowed for the formation of sensitivity characteristics according to the type of damage. Sensitivity characteristics of selected AE sensors have been developed to determine the effectiveness in relative calibration. The exponential sensitivity sensitivity of the MDK-13 sensors was observed on the software amplification of the AE analyzer. A proposal for the calibration method for MDK-13 type sensors was developed on the principle of comparison with the reference sensor.

The diploma thesis deals with the application of acoustic methods for evaluating the technical condition of the shock absorbers. Analysis of acoustic radiation during damping operation leads to the definition of a new non-contact diagnostic methodology that can determine the condition of the shock absorbers. The first part of the thesis focuses on the noise radiation of the shock absorbers, which is caused by discontinuous dumping. Further, the methods for the noise source localization available at The Institute of Machine and Industrial Design are described – with their functionalities, advantages and limitations. Based on all the information, an appropriate method is selected and used in the experimental part of this work. Then, aeration and removing the full volume of oil with damage of the shock absorber tube are caused (induced) on several types of the shocks. Noise radiation is measured by a microphone array and by a sound meter; the acoustic maps, frequency spectra and the synchronous filtration graphs are calculated from the measured data. From the differences in the acoustic radiations of each shock condition, a suitable diagnostic criterion for a specific shock absorber is defined. The final part discusses obtained results. Based on these results, a general diagnostic methodology, applicable to any type of shock absorber, is formulated.

This thesis deals with the study of sudden step changes observed in model testing of standard bearing steel 100Cr6. Methodology of experiments with step change of load is proposed and applied in measurements. Three complete series of experiments were conducted, and rating life was determined for each loading trend. Based on the experiments carried out, it was found that the selected steel is able to withstand the sudden step of load changes, despite the fact that it is not material of choise for this type of load. Part of this work was to verify functionality of the innovated test stations AXMAT with modern diagnostics and a new control system, and also of the hydraulic variant of AXMAT, which allows to remotely derive dynamic loading of the test sample.