| dc.contributor | Molina-Vicuña, Cristián | |
| dc.contributor | UNIVERSIDAD DE CONCEPCION | |
| dc.creator | Rayo-Ramírez, Sabina Maria | |
| dc.date | 2020-07-29T16:27:20Z | |
| dc.date | 2022-08-16T20:04:14Z | |
| dc.date | 2020-07-29T16:27:20Z | |
| dc.date | 2022-08-16T20:04:14Z | |
| dc.date | 2020 | |
| dc.date.accessioned | 2023-08-22T03:37:15Z | |
| dc.date.available | 2023-08-22T03:37:15Z | |
| dc.identifier | 22181313 | |
| dc.identifier | https://hdl.handle.net/10533/242115 | |
| dc.identifier.uri | https://repositorioslatinoamericanos.uchile.cl/handle/2250/8315813 | |
| dc.description | The Very Large Telescope (VLT) has a set of rotation mechanisms allowing the positioning of the dome for night observations. The rotation mechanism (RTM) is a critical equipment, because a failure significantly affects the astronomic observation time. During recent years, the fixed bearings of the vertical wheels of the RTMs have been experiencing damage. Slight misalignments of the bogies can induce significant axial forces when the bogie wheel suddenly slips to release the strain energy (stick-slip effect). This energy is built up when the wheel tracks off of the desired circular path. The stick-slip effect depends on the friction force, and thus on the normal force (that means dome weight divided by number of RTM wheels). Therefore, a normal force higher than the nominal, that means an unequal distribution of the dome weight on the bogies, could cause an excessive axial thrust damaging the bearings. Accordingly, the first general objective of this work is the development of a method to determine the static load distribution of the dome weight on the RTM of the VLT. The associated specific objectives are the selection of the measurement method and signal processing tools for determining the actual load distribution, as well as the estimation of the actual load supported by each vertical wheel. The method consists in using Fujifilm´s Prescale measurement films which permit the obtainment of images of the contact pressure and its distribution between the wheel and the rail. The images were processed by a software program written in Python and the results revealed that some RTMs present an important underload up to 32% less than considered by design. Contrary, neighboring RTMs compensate this situation by supporting an overload up to 43% higher compared to the nominal load. The results lead to the conclusion that unequal load distribution of the dome weight on the RTMs exists. Furthermore, the minimum axial force which is released when the wheel of a RTM with normal load suddenly slips already exceed the maximum permissible axial load of the bearings of the RTMs. Therefore, it can be concluded that the stick-slip effect already per se contributes to excessive axial thrust, which can damage the bearings of the RTMs. From the fact that it is difficult to avoid any bogie misalignment the second general objective of this work arises, which consists in the development of a RTM condition monitoring method. The associated specific objectives are the identification of measurement variables potentially suitable for the condition monitoring of the RTMs, field measurements of the selected variables in different RTM units and the analysis of the measured data as well as the evaluation of results. The RTM wheel shaft has a very slow rotational speed which makes it difficult to monitor the bearings because of the generation of low impact energy due to the relative motion of the components when defects are present. Four RTMs were selected for the measurements. One which had been replaced three months before, and three which have never been changed since telescope´s first light. The recently replaced RTM was selected as a reference of defect-free condition. For the analysis of the bearing condition, acoustic emission (AE), acceleration vibration and displacement vibration of the shaft were measured. The signals were processed using time- and frequency-domain based techniques such as enveloping method and spectral kurtosis. An incipient bearing failure of the outer race of the RTM could be identified by the AE measurements, whereas acceleration and displacement vibration did not provide any signs of defect. These results lead to the conclusion that the AE analysis can detect incipient defects even in slow-speed bearings, whereas acceleration and shaft displacement vibration measurements are not as suitable for the detection of early stage bearing failure in the RTMs. | |
| dc.format | application/pdf | |
| dc.relation | instname: Conicyt | |
| dc.relation | reponame: Repositorio Digital RI2.0 | |
| dc.relation | info:eu-repo/grantAgreement//22181313 | |
| dc.relation | info:eu-repo/semantics/dataset/hdl.handle.net/10533/93488 | |
| dc.rights | info:eu-repo/semantics/openAccess | |
| dc.rights | Attribution-NonCommercial-NoDerivs 3.0 Chile | |
| dc.rights | info:eu-repo/semantics/openAccess | |
| dc.rights | http://creativecommons.org/licenses/by-nc-nd/3.0/cl/ | |
| dc.subject | Ingeniería y Tecnología | |
| dc.subject | Ingeniería Mecánica | |
| dc.subject | Ingeniería Mecánica | |
| dc.title | Analysis of the load distribution of the dome weight on the rotation mechanisms of the Very Large Telescope located at the Paranal Observatory, and development of a condition monitoring method. | |
| dc.type | info:eu-repo/semantics/masterThesis | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | Tesis | |
