MOHAMMAD, H. Experimental Investigation of the Rolling Contact Fatigue Behaviour of Toroidal Bearings Using Acoustic Emission [online]. Brno: Vysoké učení technické v Brně. Fakulta strojního inženýrství. 2024.
Assessment of the supervision process In accordance with the study plan the student passed all required exams in specialized subjects and English by the end of February 2021. This period of the study ended with the state doctoral exam, which Eng. Housam Mohammad successfully passed on 6 December 2021. Specialized doctoral studies were concerned to the development of diagnostics of toroidal bearings using modern methods of non-destructive testing (especially by the acoustic emission method). During the studies, the topic of work and research was focused in more detail on the evaluation of toroidal bearings in the gearbox of a real wind power plant. Assessment of the candidate's ability to work independently In the first part of the study, Ing. Housam Mohammad participated in the solution of a number of projects of the Technology Agency of the Czech Republic in the field of bearing diagnostics, which we solved at our workplace. In this part, he was a valid member of our research team. At this time, he also handled several smaller “university” projects, which he handled entirely independently. In the second part of the study, the methodology of bearing testing was verified by the doctoral student at the test stations at the ZKL Research Institute in Brno under the guidance of a specialist supervisor. At the stage of scanning and processing data from the bearings in the real gearboxes of wind power plants, he already worked completely independently. Also, all conclusions in the dissertation are the student's own work. Assessment of the contribution that the research makes to knowledge in the field The use of the acoustic emission method for the diagnosis of rolling bearings is gradually becoming a common method among large manufacturers and users, but information on monitoring the condition of toroidal bearings is still very limited. In the case of this dissertation, diagnostics are not limited to laboratory tests, but have been extended to long measurements of bearings in real facilities where they have been installed. A wireless remote condition monitoring system was developed for this purpose. For a better visual representation of the dominant frequency (DF) representation, the concept of DF maps was introduced and a series of Matlab codes were developed to automate and facilitate its creation. Collecting DF maps into a single chart for specific time intervals and being able to statically analyze them provided an opportunity to quantify defects, which will be a solid foundation for future work. One of the conclusions of this work that contradicts with previous findings in literature, was that AE time-domain parameters, such as RMS, did not completely correspond to the events that were represented by the occurrence of AE hits. In other words, AE time-domain parameters cannot be depended upon solely for condition monitoring (CM) of the bearing. Another output of this work is the successful application of a remote CM system using a VNC server, a 3G internet connection and a PC in the nacelle. This system was motivated by the need for monitoring the long measurements that take days or months in places that are not always accessible. The new monitoring system that is suggested, applied and verified here is an easy-to-apply and easy-to-use method for continuous online monitoring of not just bearings, but any critical asset that requires long time of monitoring.
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