Modeling and analysis of own oscillations of the TFB with turbine 500 Mw

Проведен анализ собственных колебаний системы турбоагрегат-фундамент-основание с турбиной мощностью 500 МВт в частотном диапазоне приближенном к частоте колебаний электромагнитной природы от генератора. Объектом исследования является система турбоагрегат-фундамент-основание.. Для исследования выбрана система с паровой турбиной, которая содержит несколько типовых корпусов. Для моделирования и проведения численных расчетных исследований использован метод конечных элементов. Построены геометрические и конечно-элементные модели системы турбоагрегат-фундамент-основание с учетом особенностей взаимодействия гибких корпусов турбины с фундаментом. Проведены расчеты собственных колебаний. Получены собственные частоты и формы колебаний. Полученные результаты дают качественную оценку причин повышенной вибрации отдельных элементов рассматриваемой системы.The analysis of the own oscillations of the turbounit-foundation-base system is carried out. The system includes a reinforced concrete foundation, a 500 MW turbine with five bodies, a generator and four condensers. To study the chosensystem with a steam turbine, which contains several typical buildings. The relevance of the study is due to the presence of turbounit-foundation-base systems with a long operating time and a significant development of the base resource of increased levels of vibration. On the other hand, the relevance and novelty of the results is due to the lack of previousresearch on the given object and subject of research. A system with a steam turbine with four typical identical flexible housings and one rigid body of high weight is considered. The system of turbine-base-base in the frequency range close to the frequency of oscillations of electromagnetic naturefrom the generator was considered. The object of the study is a turbo-base-base system. The method of finite elements is used for modeling and conducting numerical calculations. The geometric and finite-element models of the turbo unit-foundation-base system are constructed taking into account the features of the interaction of flexible bodies of the turbine with the foundation. The modeling of the foundation is done using a system of core and mass finite element. The rigid body of the steam turbine and the generator were modeled using a system of massive finite elements. The most flexible bodies of the steam turbine weremodeled using a shell, coreand mass finite element system. The basis was modeled using the system of stiffness and boundary conditions. Capacitors were modeled using a system of stiffness and boundary conditions. The peculiarity of the calculation models is the detailed three-dimensional modeling of flexible bodies of the steam turbine. The applied simulation technique is unique and allows us to carry out a detailed analysis of the system's own oscillations. The calculations of proper oscillations have been carried out. Own frequencies and forms of oscillations are obtained.The obtained results give a qualitative estimation of the internal oscillations of separate elements of the considered system of the turbo-aggregate-foundation-base and the system as a whole. The results ofthe calculations were used inthe study of the causes of increased vibration of the turbo unit-foundation-base system and its individual elements

Extrusion limits of magnesium alloys

Magnesium alloys are generally found to be slower to extrude than aluminum alloys; however, limited quantitative comparisons of the actual operating windows have been published. In this work, the extrusion limits are determined for a series of commercial magnesium alloys (M1, ZM21, AZ31, AZ61, and ZK60). These are compared with the limits established for aluminum alloy AA6063. The maximum extrusion speed of alloy M1 is shown to be similar to AA6063. Alloys ZM21, AZ31, ZK60, and AZ61 exhibit maximum extrusion speeds 44, 18, 4, and 3 pct, respectively, of the maximum measured for AA6063. For AZ31, the maximum extrusion speed is increased by 22 pct after homogenization and by 64 pct for repeat extrusions. The variation in the extrusion limits with changing alloy content is rationalized in terms of differences in the hot working flow stress and solidus temperature.<br /

Improving the information system of university management

© 2015, Canadian Center of Science and Education. All rights reserved. University management is currently supported by information system providing storage and data structuring of information required. Managing the development and improvement of the educational process quality requires creation of a monitoring system covering all of its objects and various measurement tools, which monitors the set of all features. The paper presents the components of pedagogical management, considers indicators of pedagogical processes and methods of evaluation, which define the basis for monitoring the educational processes at the University. Also the structure of a software module is shown, that works on the principle of the expert system and identifies problem characteristics of the educational activity. The results of the experimental work show the effectiveness of the presented software, that supports management decision-making of university departments’ leadership and faculty

Mechanical properties, microstructure and crystallographic texture of magnesium AZ91-D alloy welded by Friction Stir Welding (FSW)

The objective of the study was to characterize the properties of a magnesium alloy welded by friction stir welding (FSW). The results led to a better understanding of the relationship between this process and the microstructure and anisotropic properties of alloy materials. Welding principally leads to a large reduction in grain size in welded zones due to the phenomenon of dynamic recrystallization. The most remarkable observation was that crystallographic textures appeared from a base metal without texture in two zones: the thermo-mechanically affected and stir welded zones. The latter zone has the peculiarity of possessing a marked texture with two components on the basal plane and the pyramidal plane. These characteristics disappeared in the TMAZ, which had only one component following the basal plane. These modifications have been explained by the nature of the plastic deformation in these zones, which occurs at a moderate temperature in the TMAZ and high temperature in the SWZ

Actual Problems of Kazakh History. Review of the Book by K.A. Pishchulina “Essays on the History of the Kazakh Khanate”

A collection of articles written by a well-known orientalist-historian K.A. Pishchulina and published in 2016 includes papers of different years, written on the basis of Persian and Turkic sources reflecting the most pressing issues related to Kazakh khanate. The publishing of this work immediately became a major event in historical scholarship of Kazakhstan. During the Soviet period, the history of this state, as well as of other states created by nomadic peoples, remained poorly understood. Many questions were debatable, since Marxism-Leninism, which was in forefront of science, could not adapt the formational class theory for a nomadic society and nomadic mode of production etc. However, some researchers, including K.A. Pishchulina, were already thinking about these issues. Particularly she studied the role of Turkestan cities as part of Kazakh khanate. According to her main findings, these cities performed a variety of functions being centers of handicraft production, agriculture and trade. As for Turkestan city itself, it was capital and spiritual center of the state, and the management of settled-agricultural population was carried out by various officials. Furthermore, the collection of Pishchulina’s papers discusses management system of nomadic population, tax system of the Khanate. The author comes to a justified conclusion that monetary system needs to be studied further. Next major issue relates to mythologization of Turkic peoples’ history. The books written by amateurs assert that the Golden Horde was a part of Khanate, and Chinggis Khan was a Kazakh. Therefore, several Pishchulina’s articles were published in order to expose these myths. Thus, in this collection the reader would find answers to a variety of questions related to the history of Kazakhstan and adjacent territories and its impact in modern times

Microstructural evolution in ZK60 magnesium alloy during severe plastic deformation

yesGrain formation during intense plastic straining was interpreted in terms of low temperature dynamic recrystallization. The mechanisms of ultrafine grain structure formation in hcp material during severe plastic deformation and the role of non-basal slip in this process are discussedBelgorod State Universit