A. P. Zinkovskii

Influence of the Exciting Force Application Point on the Amplitude Spectrum of Flexural Vibrations in a Beam with a “Breathing” Crack

This paper presents the results of calculations to determine the influence of the exciting force application point on the value of the vibration diagnostic parameter to identify the presence of a breathing crack at sub- and superharmonic resonances of the first flexural vibration mode in a cantilever beam of constant rectangular cross section using a three-dimensional finite element model. The investigation results are compared with the known data obtained by the analytical and numerical methods.

Influence of the Orientation of Shroud Contact Surfaces on the Static Stress State of Turbine Rotor Blades

The paper presents the results of the computational experiments to determine the regularities in the variation of the static stress state characteristics of blades as a function of the inclination angle value of the shroud contact surfaces relative to the plane of rotor wheel rotation with a consideration of the action of centrifugal gravity forces and high temperatures of the gas flow.

Effect of identity violations of contact interaction between shrouds on the static and dynamic stress state characteristics of blade rings

The results of computational investigations to determine the effect of possible identity violations of contact interaction between shrouds on the static stress state characteristics of bladings and the formation of the eigenfrequency and vibration model spectrum of turbine rotor blade rings are presented.

Influence of a Fatigue Crack on the Vibrations of the Simplest Regular Elastic System

Results are presented for computational experiments on the determination of the mechanisms for the generation of vibrations in a discrete model of the tuning fork specimen in the presence of a closing fatigue crack in one of the rods. The plots are constructed that show the influence of the crack parameters on the vibration of the object under investigation.

Elastoplastic Deformation of the Surface Layer of Machinery Constructions on Shot Blasting

Shot blasting results obtained on metal surfaces to be further treated by applying protective nonmetallic coatings were experimentally investigated under different process conditions. The procedure of evaluating the elastoplastic deformation behavior of the surface layer using the experimental-analytical coefficient, which considers the elastoplastic properties of the material, is described. Results of comparing experimental and theoretical data are summarized. The grounds for a possible fracture mechanism on shot blasting of the surface layer of metal products are presented.

On the Rational Choice of the Azimuthal Crystallographic Orientation of Single-Crystal Cooled Rotor Blades in Aircraft Gas Turbine Engines

The influence of the azimuthal crystallographic orientation on the strength of single-crystal cooled turbine rotor blades is studied. The effect of the cooling system features on the rational choice of the azimuthal crystallographic orientation of modern single-crystal cooled turbine rotor blades is shown. The improvement in the structure and cooling systems of single-crystal cooled turbine rotor blades makes it possible to reduce the influence of the azimuthal crystallographic orientation on their stress state.

Determination of the Subsonic Flutter Stability Boundary of Blade Rows at Large Angles of Attack

This paper presents an experimental-and-numerical method for determination of the subsonic flutter stability boundary of blade rows at large angles of incident flow. The aerodynamic test rig for determining the unsteady aerodynamic loads is described. The test results are presented for a straight cascade of airfoils in a wide range of variation in the angle of attack and reduced vibration frequency, based on which the regularities in the effect of the angle of attack on the subsonic flutter stability boundary of blading are established.

Determination of the Vibration Diagnostic Parameters Indicating the Presence of a Mode I Crack in a Blade Airfoil at the Main, Super- and Subharmonic Resonances

The paper presents the results of numerical calculations to determine the regularities underlying the influence of the characteristics of a mode I breathing fatigue crack on the leading edge of the aircraft gas turbine engine blade airfoil – that is responsible for the nonlinearity of the vibratory system – on its flexural forced vibration behavior. Their comparison with similar data for the rod of a rectangular cross section has shown satisfactory agreement. The calculation of the vibration diagnostic parameters indicating the presence of damage is performed using the developed finite element models of the investigation objects whose forced vibrations were excited by the kinematic displacement of fixed edge elements. The breathing crack is modeled as a mathematical cross section, the non-penetration of its faces is ensured by solving the contact problem of their interaction. The problem of the system forced vibrations is solved using the Newmark method and fast Fourier transformation. The obtained amplitude-frequency characteristics of the undamaged and damaged blade airfoil are indicative of the increase in the energy dissipation in the system in the presence of a breathing crack. The change in the resonant vibration frequency of the cracked object of investigation and the amplitude ratio of the dominant harmonics of displacements and accelerations (the ratio of the former to the latter at the superharmonic resonance and the latter to the former at the main and subharmonic resonances) were chosen as the vibration diagnostic indicators of damage. The amplitude ratio of the dominant harmonics of accelerations at the superharmonic resonance and that of displacements at the subharmonic resonance is found to be the most sensitive indicator of the presence of cracks.

On a Procedure for the Determination of the Mechanical Characteristics of Materials in the Case of Tensile Test of Specimens at Elevated Temperatures

The paper presents a procedure for the determination of the mechanical characteristics of materials for modern aircraft gas-turbine engines on the basis of results of uniaxial tension tests under elevated temperature conditions. The procedure permits one to allow for measurement errors, which arise from the misalignment of the load chain and temperature effect when using strain gauges of modern testing systems. The evaluation of the procedure is illustrated for the uniaxial tension of specimens of ÉI962 alloy (11Kh11N2V2MF).

A Study of Correlation Between the Paris Equation Coefficients Based on the Test Results for Titanium Alloy Specimens

The paper gives the results of experimental–computational investigations for the determination of fatigue crack growth rate in titanium alloys. The applicability of correlations between the experimental values of the fatigue crack growth rate at various temperatures has been addressed.