Bovsunovsky A.P.,National University of Food Technologies
Journal of Physics: Conference Series | Year: 2015
The investigations of cracks growth in the fractured turbine rotors point out at theirs fatigue nature. The main reason of turbine shafts fatigue damage is theirs periodical startups which are typical for steam turbines. Each startup of a turbine is accompanied by the connection of turbine generator to electrical network. During the connection because of the phase shift between the vector of electromotive force of turbine generator and the vector of supply-line voltage the short-term but powerful reactive shaft torque arises. This torque causes torsional vibrations and fatigue damage of turbine shafts of different intensity. Based on the 3D finite element model of turbine shaft of the steam turbine K-200-130 and the mechanical properties of rotor steel there was estimated the fatigue damage of the shaft at its torsional vibrations arising as a result of connection of turbine generator to electric network.
Bovsunovsky A.,National University of Food Technologies |
Surace C.,Polytechnic University of Turin
Mechanical Systems and Signal Processing | Year: 2015
The main purpose of the present review paper is to illustrate the principal achievements of numerous researchers who have studied the non-linear effects caused by a closing crack in the most common types of structural elements such as beams, shafts and plates, the aim being to assess the potential and future prospects of using non-linear behaviour to detect damage. Indeed, for a wide range of practical applications, in order to avoid catastrophic failure, the development of diagnostics techniques which are sufficiently sensitive to incipient cracks in structures and machines is a crucial issue. The main potential advantage of using vibration diagnostics based on the use of non-linear effects is the relatively high sensitivity to the damage of the closing crack type, especially for application to beam-like structures and rotating shafts; instead the potential for application to plate-like structures has been found to be limited. After analysing the state-of-art on this subject in detail, a discussion of the respective merits, drawbacks and prospects of a range of non-linear vibration methods for structural damage detection is presented. The general conclusion which can be drawn from the highly encouraging results of recent research is that further development of these techniques for non-destructive testing of structures with closing cracks would be highly worthwhile. © 2015 Elsevier Ltd. All rights reserved.
Bovsunovsky A.,National University of Food Technologies
Engineering Fracture Mechanics | Year: 2012
In a result of experimental investigations of steel R2M cylindrical specimens with a surface transverse and slant crack at torsional vibrations it was revealed that the damping characteristic of the specimens is strongly dependent on the crack sizes and stress amplitude. The energy dissipation in the non-propagating transverse crack is caused mainly by the plastic area along the crack front and practically is not related to the friction between the crack faces. The level of energy dissipation in this crack is determined uniquely by the equivalent stress intensity factor. © 2012 Elsevier Ltd.
Zmievskii Yu.G.,National University of Food Technologies
Petroleum Chemistry | Year: 2015
A laboratory setup has been designed to create the same excess hydraulic pressure at both membrane sides. This setup has been used for the whey ultrafiltration permeate/distilled water system to determine the critical pressure at which pores of an MFFK-3 hydrophobic membrane (Vladipor, Russia) are filled with the liquid phase. This value has been found to be 0.6 MPa. On the basis of several assumptions, it has been supposed that, the membrane pores are partially filled with the liquid phase on the both sides before attaining the critical pressure. This filling leads to a reduction in the distance between the meniscuses of the "hot" and "cold" solutions inside the pore, thereby being theoretically capable of enhancing the membrane flux. The liquid entry pressure (LEP) of this membrane has been also determined, being 130 and 50 kPa for distilled water and whey ultrafiltration permeate, respectivey. © 2015 Pleiades Publishing, Ltd.
Legeza V.P.,National University of Food Technologies
Mechanics of Solids | Year: 2010
The motion of a heavy homogeneous cylinder is considered as a no-slip rolling along the desired curve. We obtain a functional in the form of the total time of the cylinder rolling and solve the corresponding variational problem of minimizing this functional. We obtain an algebraic equation for the directional line of steepest descent, brachistochrone, in parametric form. We use the equation of motion of the cylinder with constraint reaction to determine the conditions of implementation of its pure rolling without separation and slip with respect to the brachistochrone. © Allerton Press, Inc., 2010.