Vibration features of titanium alloy blades with erosive damages
Keywords:
erosive damage, vibration, blade, resource, titanium alloyAbstract
This paper deals with erosive damage influence on the vibration features of the working blades of the fifth-stage of the low pressure cylinder (LPC) of a K-1000-60/3000 steam turbine for a nuclear power plant (NPP). The blades are made of the TS5 titanium alloy and have a length of 1,200 mm. Notable erosive damages were observed in the fifth-stage LPC blades after more than 180,000 hours of operation at the Khmelnytska NPP, the greatest danger arising due to the formation of craters and slit-type damages. Such damage causes stress concentration, which leads to a decrease in fatigue and residual life. The radius of the erosive damage front mouth is noticeably larger than that of a fatigue crack. With such damages to the edge-to-edge contact, no damages can be observed. In the course of research, there was developed a finite-element model of a blade having a more condensed grid in the damage area, but a less condensed one in the main volume of the blade. There have been performed multivariate numerical oscillation studies of blades with different numbers of damages, which are located in different places along the blade length in the stress localization zone arising due to the features of vibration forms. There have been revealed the features of stress distribution in damage zones. It has been shown that an increase in the number of damages leads to an increase in the area of increased stresses but does not increase their concentration. There have been considered vibrations of the blades under the load of a conditional value, which made it possible to determine the real vibration stress concentration factors in the damage zones. This allows one to use the experience of analyzing the vibrations of damaged titanium alloy compressor blades. The degree of reduction of the endurance limit of damaged titanium alloy blades has been revealed. Recommendations on preventing damaged K-1000-60/3000 turbine blades from being used have been developed.References
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Copyright (c) 2019 Yu. S. Vorobiov, N. Yu. Ovcharova, A. S. Olkhovskyi, O. V. Makhnenko, V. M. Torop, O. Ye. Hopkalo
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