Journal of Dynamics and Vibroacoustics

The presented article demonstrates the work on setting up full-scale and numerical experiments on the milling process of D16 and L63 alloys. The results of field experiments were dependences linking the roughness parameters with the parameters of the milling mode applied to alloys D16 and L63. These dependencies can be used to optimize technological processes when it is necessary to assign such processing modes that will ensure the surface roughness specified by the designer. In addition, these dependencies were used by the authors to modernize the formulas for determining the effective stress concentration coefficient, which has practical benefits at the stages of design and technological preparation of production. The result of the numerical experiment were dependences that allow us to determine the maximum equivalent stresses that occur along the cutting section of the cutters during processing of the alloys studied in this work. The integrated application of the results of this study can have a positive impact on production both in achieving maximum product quality and in ensuring the economic development of the enterprise by choosing processing modes that spare the processing tool.

The developed speckle interferometer setup is intended for automatic study of vibration modes and frequencies of gas turbine engine structures by scanning in a given frequency range. The correlation of each snapshot with a specific vibration frequency of the object is provided through harmonic signal scanning and video stream control using a single computer program. The program result is an interferometric film with information on the object vibration state at all frequencies in a given range. Resonance frequencies are determined by the statistical criterion of speckle interferograms. The developed setup was used to investigate compressor blade vibration modes and frequencies. The transition of compressor guide vane vibration from one mode to another with an increase in the exciting signal frequency was studied.

A brief review of existing and newly developed methods for calculating the friction moment of radial bearings of rocking units is given using the most common domestic articulated steering units of liquid-propellant rocket engines as an example. An analysis of the kinematic diagram of the steering drive is carried out, the leading element of which is the shaft of the launch vehicle steering machine. Analytical dependencies of the time-varying force coming to the actuator of the steering unit are obtained, which were subsequently compared with a similar experimental characteristic recorded during a full-scale fire test. An analytical and graphical dependence of the load on the actuator as a time function at specified angular velocities of the steering unit shift is given, the procedure for converting this force into a radial load on the bearing is shown. The field of application of the obtained refined data in studying the torque characteristics of low-speed radial bearings of steering units is determined.

The article investigates the acoustic power radiation of an isotropic turbulent flow of superheated steam in the flow path of an angle shut-off valve through numerical simulation. The study aims to determine the geometric dimensions of the valve's flow path that minimize the acoustic radiation power into the connected pipeline mains for a given medium velocity in the inlet pipe. Certain parameters of the valve's flow path are subject to design constraints, dictated by the existing component base (bellows with limitations on maximum allowable pressure and compression) and requirements for minimal valve dimensions (particularly the actuator, whose size is determined by the seat diameter). As part of the study, the effectiveness of various measures to modify the base valve design was evaluated through detailed numerical hydrodynamic and acoustic modeling. These measures, aimed at reducing the acoustic power of the flow in the valve, were analyzed both individually and in combination. The authors found that the most effective measures were: changing the lift height of the valve plug and modifying the radial dimensions of the annular cavity between the plug and the bushing. The calculated effectiveness of these measures reaches up to 11 dB. The obtained results are recommended for use in the refinement of shut-off valves in pneumatic and hydraulic systems to reduce the noise they generate.

To analyze the results of measuring the parameters of the inhomogeneous flow at the compressor inlet, a method has been developed for determining the confidence limits of the errors of these parameters. The proposed method makes it possible to determine the marginal errors of the total absolute pressure at various measuring points, as well as parameters characterizing pulsations and uneven flow at the compressor inlet. A distinctive feature of the developed method is the ability to account for both non-excluded systematic and random errors. Testing the method allowed us to recommend the number of atmospheric pressure measurements during the engine test in one mode. It was also possible to establish the possibility of reducing the error in determining the complex criterion for evaluating the heterogeneity of the flow, while increasing the accuracy class of the full pressure measuring instrument at various points in the cross-section at the compressor inlet.