Vol 14, No 3-1 (2015): Special Issue

  • Year: 2015
  • Articles: 25
  • URL: https://journals.ssau.ru/vestnik/issue/view/131
  • Description: посвящённый 85-летию Центрального института авиационного моторостроения имени П.И. Баранова

Full Issue

CIAM’s scientific school of strength and its ties with Samara aerospace cluster (for the 85 th anniversary of CIAM’s foundation)
Nozhnitskiy Y.A., Belousov A.I., Kotcherov E.P.
Abstract

The role of Central Institute of Aviation Motors (CIAM) as the leading scientific-research institute in the system of provision of the required dynamic and strength parameters of aircraft engines developed in the country is shown in the paper. Principles and traditions of the CIAM’s scientific strength school as applied to solving practical problems, establishing the causes of defects and working out specific certain recommendations on the basis of fundamental and engineering approaches are discussed. The fact that CIAM brings together engineers and researchers, as well as employees of industrial enterprises, universities, academic and branch institutes, research institutions of the Ministry of Defense and civil aviation, working in close contact with them, is a specific feature of the CIAM’s scientific strength school. The role of the outstanding scientists I. Sh. Neiman, S. V. Serencen, R. S. Kinasoshvili, I.A. Birger in the forming and development of the CIAM’s scientific strength school is also shown. A wide range of subjects dealing with the study of aircraft engine dynamics with an appropriate combination of theoretical, computational and experimental investigations in the area of creating and expanding the unique research-and-trial facilities for strength testing of engines and their assemblies and systems is noted. Much attention is given to conversion programs on ground-based application of gas-turbine engines including the development of Russian and International regulatory documents. Special emphasis is placed on close ties between the CIAM’s strength specialists with Samara’s aircraft engine manufacturers and the scientific strength school of CIAM and Samara’s aerospace cluster, as well as the outstanding role of academician N.D. Kuznetsov in the development and strengthening of these ties.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):9-23
views
Application of the invariant plastic flow theory for mathematical modeling of the processes of testing specimens under complex elastic-plastic deformation
Temis Y.M., Alkhimov D.A., Martynova A.D.
Abstract

The invariant plastic flow theory is applied for modeling the processes of testing thin-walled tubular steel specimens under complex elastic-plastic deformation. A software package for calculating simple and complex paths of deformation of thin-walled tubular specimens and analyzing the results obtained was developed for a model with translation and isotropic hardening, a combination of Kadashevich-Novozhilov and Arutyunyan-Vakulenko models. The errors arising in the course of numerical modeling of the deformation process beyond the elastic area are compensated by the correction algorithm that makes it possible to return to the loading hypersurface at each stage of calculation. A number of numerical experiments dealing with testing tubular steel 40Х16Н9Г2С specimens were conducted. The model parameters were chosen according to the data of repeated loading. The results of numerical stimulation of the processes of cyclical twist of the specimens, proportional loading, complex two-section and multi-section deformation paths, as well as the process of curvilinear deformation path in the form of concentric circles are presented. The observance of the principle of delay of vector and scalar properties is demonstrated, two-section deformation paths with different angles of fracture taken as an example. The numerical results are compared with the experimental data.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):24-36
views
Requirements for the order and the procedure of estimating structural strength characteristics of metal alloys for the main and critical parts of aviation gas turbine engines
Nozhnitsky Y.A., Kachanov E.B., Golubovskiy E.R., Kouevda V.K.
Abstract

Requirements of the technical regulations for the order and procedure of estimating structural strength of metal alloys used in critical and main parts of aviation engines in their certification are outlined in the paper. The scope of work to be carried out by the engine designer, the developer of the material/semi-finished product and the engine manufacturer to confirm the compliance with the mentioned requirements is described. The tasks to be solved at different stages of general and special qualification of the material are discussed. The spectrum of the main mechanical characteristics of alloys, including mono-crystal alloys, to be determined during the qualification tests is presented. The standards in accordance to which the tests are to be performed are mentioned. Relationships for the determination of the material characteristics to be used in estimating the strength and service life of engine parts are given. The requirements for the statistical processing of the results of investigating the structural strength of alloys are discussed, as well as the requirements for setting the values of the mechanical properties guaranteed in the delivery of materials/semi-finished products. The necessity to have data on possible presence of different defects in the main (critical for safe operation) engine parts is mentioned. The reference list includes principal technical regulations the requirements of which are to be met during special qualification of alloys used for the manufacture of the main and critical aviation engine parts.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):37-48
views
Application of the cyclic life additivity concept for the determination of service life of aero engine disks made from powder alloys
Tumanov N.V., Lavrentyeva M.A., Vorobyeva N.A., Kalashnikova A.I.
Abstract

An approach to the estimation of cyclic life of aero engine disks made from powder alloys on the basis of the concept of cyclic durability additivity is proposed. Within the framework of this approach the durability of aero engine disks includes both the service life prior to low-cycle fatigue crack initiation and safe crack propagation life which is calculated as the crack stable growth period. Complex studies including the analysis of metallurgical defects in the areas of low-cycle fatigue crack initiation in disks of aircraft gas turbine engines, microfractographic reconstitution of crack kinetics and mathematical modeling of the disk stress-strain condition have been conducted. On the basis of these studies the connection between 1) the size, location and type of the defects, 2) the crack free life prior to low-cycle crack initiation caused by these defects, 3) the period of the crack growth and 4) the characteristics of stress-strain condition and the temperature of the disk in the area of crack initiation has been established. Comparative analysis of defects in granular nickel alloys produced by various technologies (for various maximum size of the grains) has been carried out. The maximum size of the defects and their number in a unit volume are shown to decrease considerably as the grain size decreases. The number of defects in critical areas of engine disks, however, remains quite large, even for the minimal size of the grains. The expedience of applying the deterministic approach for the calculation of disk survivability is shown.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):49-59
views
Modification of the starter turbine disk for blade containment certification tests
Karimbaev K.D., Sapronov D.V.
Abstract

The paper is related to gas turbine engine starter-generator blade containment tests. The starter turbine case is expected to contain a fragment resulting from rotor fracture with the maximal level of kinetic energy. It has been proved that one third of a rotor is a fragment with the maximal level of kinetic energy. It is possible to provide this type of fracture for rotors with central holes by special trimming. However, if the disc and the shaft are a one-piece structure formation of such a fragment seems to be a problem. This type of fracture is assumed to be impossible. The aim of this work is to specify the most energy-consuming fragment in the case of possible fracture and choose a way of conducting certification tests. The method presented in the paper is based on introducing a “weak link” –local thinning- in the area under the rim. It allows separating the rim and the blades with an admissible level of kinetic energy. Some proposals for certification tests are presented.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):60-64
views
Statistical estimation of load-bearing capacity of titanium alloy discs
Kutyrev V.V.
Abstract

The results of overspeed tests of titanium alloy model and full-scale discs are presented in the paper. The parameters of static distribution of the discs’ relative strength are determined for the discs destroyed according to the meridian pattern and the cylindrical pattern in samples of model and full-scale structures with and without holes in the casing. It is shown that in samples of model and full-scale discs with or without holes in the body in the case of fracture along the meridian section the average values of relative disc strength are equal, which indicates insignificant influence of the above- mentioned designs and presence of holes on the relative disc strength. In samples of discs with and without holes destroyed according to the cylindrical pattern the average values of relative disc strength are also equal, which testifies to insignificant influence of holes on the relative disc strength. In disc samples destroyed by the meridian pattern and the cylindrical pattern the average values of relative disc strength are not equal, which testifies to significant influence of the fracture pattern on the relative disc strength. The results can be used for predicting margins on the disc break-up rotation frequency.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):65-70
views
New possibilities of using spin rigs to provide gas turbine engine strength reliability
Nozhnitsky Y.A., Fedina Y.A., Shadrin D.V., Servetnik A.N., Baluev B.A., Kanachkin A.V., Lepeshkin A.R., Tomashev A.A., Chernyshev S.A.
Abstract

The main tasks of using spin rigs for carrying out certification, engineering and technological tests of gas turbine engine parts and assemblies are formulated. Specific design features of spin rigs are described in the paper. The main characteristics of the spin rigs used at CIAM are presented. The peculiarities of carrying out different tests using spin rigs and the main requirements for rigs are discussed. Examples of using spin rigs for carrying out tests are given. Examples of using the rigs are given, among them are tests intended to confirm the rotor load capacity or technological hardening of the rotor material; equivalent-cyclic tests to confirm the rotor life; investigation of the  vibration properties of rotating parts (optimization of structural damping of vibrations and specifying high-cycle fatigue of rotating blades, etc.); tests carried out to confirm the containment of rotor fragments in the engine casing and to determine the  rotor integrity under the impact of bird or other foreign objects sucked in the engine gas-air flow duct. The necessity of combining spin rig tests with calculations and physical investigations is shown. The main directions of updating spin rigs are considered. In particular, the necessity of developing rigs for different tests of engine fans with high bypass ratios; perfecting rigs and testing procedures for high-cycle fatigue investigations of rotating blades; producing the equipment for thermal cycling tests of rotor parts, especially parts made of composite or ceramic materials; investigation of vibrations in the conditions of rotor-stator contact; improvement of hardware and methods. 

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):71-87
views
Experimental design of a device for bird strike bench tests of non-rotating fan blades
Shorr B.F., Matsarenko V.S., Serebryakov N.N.
Abstract

Requirements on the efficiency and safety of fan bird strike bench tests by throwing birds against non-rotating blades are discussed, including the requirements for providing the bird strike velocity, the installation of blades at the required angle of attack relative to the bird, the requirements for the strength of the parts of the device and its overhaulability.  Structural features of the device developed at CIAM are outlined in the paper. The device comprises two main parts: a disk model sector for blade installation and a rigid framework. The model disk can be turned relative to the framework and rigidly fixed in this position. The model disk sector is a solid part imitating part of the disk rim with shaped grooves for blade roots. The framework represents a set of supporting plates with peripheral slots for additional support using rolled section. Strength analysis of the device units operating under the action of heavy short-term impact loads is carried out by the results of finite-element 3D calculations. The device has been successfully used for bench tests during which large birds were being thrown against the block of three fan blades.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):88-98
views
Experimental determination of thermal-fatigue life of turbine blades with various coatings made of an advanced heat resistant nickel alloy
Bychkov N.G., Nozhnitsky Y.A., Khamidullin A.S., Pershin A.V., Avrutsky V.V.
Abstract

An original CIAM know-how for the experimental determination of thermal-fatigue life of parts of the gas-turbine engine hot section, including parts with heat-resistant and ceramic thermal barrier coatings, in the conditions of superficial uneven heating by high-frequency currents with continuous cooling of the parts at the preset air consumption is outlined in the paper.  The possibility of using high-frequency heating of the parts with coatings (including thermal protection coatings) for modeling superficial heating of full-scale parts of gas-turbine engines is shown on the basis of the tests of model samples with coatings controlling the temperature of the surface by means of a thermal imager. The method used makes it possible to simulate the thermal state of the part in the operating conditions. Temperature differences observed both over the surface and the thickness of a part create thermal stresses in the material, similar to those arising during the operation of the engine. If necessary, mechanical loads synchronized with changes in temperature, to simulate for example, the centrifugal force may be applied to the part. The article presents the results of experimental studies of thermal-fatigue life of rotor blades of the 1st stage of the turbine made of an advanced monocrystal alloy VZhM-5 without coating and with various protective coatings, conducted according in the regime Tmin↔Tmax = 350↔1050˚C.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):99-105
views
Research of the crack development process in a nickel heat-resistant alloyin the process of testing
Rozanov M.A.
Abstract

A method of direct observation of the process of low-cycle fatigue crack development during bend loading directly in the chamber of a scanning electronic microscope is described in the paper. It was found that the presence of slip bands near the apex of the crack is the determining factor of crack development in a specimen made of a nickel heat-resistant alloy with a monocrystalline structure. The fracture in the area of the crack apex was found to be of a brittle nature. In the case of crack propagation arrest before an obstacle an area of plastic deformation forms at some distance from the apex of the crack, with branches from the main crack.  Crystallographic orientation of the specimen was determined using the X-ray structure analysis and the Shmid factor was calculated for glide planes along which the fracture took place and secondary cracks were formed. The prevailing direction of the crack development was determined by slip systems with the value of Shmid factor maximum for the given conditions. It is shown that the described method of observation of the material structure and crack propagation under low-cycle fatigue makes it possible to obtain unique information about the fracture pattern and the impact of the material’s structure on its characteristics. The results can be used to determine the choice of the most favorable crystallographic orientation of the monocrystalline structure of the material of gas turbine engine blades relative to their geometry.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):106-113
views
Experimental studies of prototype models of bimetallic blisks of a high-temperature turbine with cooled blades for advanced gas turbine engines
Magerramova L.A., Stadnikov A.N.
Abstract

The traditional approach to designing turbine blisks based on the application of disk-blade pawl-coupling does not allow improving the design from the point of view of increasing the service life, reducing the wheel mass and improving the engine efficiency on the whole. This problem can be solved by using dissimilar materials in the integrated bimetallic wheel (blisk). Bimetallic blisk prototype models of a high-temperature turbine have been produced for strength durability research. The bimetallic blisk prototype model consists of one monocrystal cooled blade and a granulated Ni-based disk part. These elements are connected by the hot isostatic pressing (HIP) method. Capsular equipment is designed for producing the prototypes. It ensures the air tightness of the zone of joining of the blisk elements and preservation of the cooling lines in the blades during the HIP process.  Investigations of micro- and macrostructures of prototype joining zones have been carried out. High-cycle fatigue tests of bimetallic blisk prototype models have been carried out. It has been found that fatigue cracks originate in the blade material, whereas the zone of diffusion bonding of the two alloys in test conditions proved to be stronger than the blade material.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):114-121
views
Prospects of application of nanostructured heterophase polyfunctional composite materials in aero-engine manufacturing
Nizovtsev V.E., Klimov D.A., Bortnikov A.D., Nizovtsevа O.V.
Abstract

The article provides a brief overview of the features and applications of developed and investigated nanostructured superhard composite materials and coatings on their basis. The research carried out makes it possible to draw a conclusion of great prospects of using nanostructured composite materials on the basis of carbides, carbonitrides and diborides of transitional and refractory metals for aerospace objects. The use of new composite structural materials is the top priority in the area of improving technical and economic parameters of gas turbine engines. These materials are superior to traditional materials by their basic physical and mechanical properties several-fold. Numerous studies in this field indicate that the greatest progress in the development of new advanced structural composite materials can be expected on the way to creating materials based on polymeric, metallic, intermetallic, and ceramic matrices. At present, there is a distinct trend towards the creation of units and assemblies of multiple-start gas turbine engines and power plants with longer life and increased durability. Research in the area of using new-generation composite materials is carried out in almost all developed countries, primarily in the United States and Japan.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):122-127
views
Engineering design and experimental research of non-metallic parts and components of the hot section of the advanced gas turbine engine
Karimbayev T.D., Mezentsev M.A., Ezhov A.J.
Abstract

Technological and experimental research in support of creation of a high-temperature turbine nozzle unit made of diamond dust dispersion-hardened silicon carbide and the flame tube of a high-temperature combustion chamber made of carbon-fiber-reinforced-ray of ceramic composite material based on a ceramic polymer has been conducted. The studies demonstrated:

• technological capability of creating a composite structure of the nozzle made of super-hard diamond dust dispersion-hardened silicon carbide compatible with the mating metal turbine units;

• the results of testing the non-cooled flame tube made of carbon-fiber reinforced ceramic composite material based on a ceramic polymer.

The results will be used in the design, manufacture and tests of non-metallic components of combustion chambers and turbines of auxiliary power units, small-sized gas turbine engines and helicopter engines.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):128-138
views
Analysis of the possibility of using topology optimization in the design of uncooled turbine rotor blades
Vasilyev B.E., Magerramova L.A.
Abstract

This paper discusses a novel approach of gas turbine rotor blade design in order to take full advantage of rapidly developing additive manufacturing. It is necessary to implement new numerical optimization methods, such as topology optimization, in the design process in order to reduce weight by eliminating unnecessary material. As an example, topology optimization is conducted to find the optimal geometry of typical low-pressure turbine uncooled blade to ensure meeting the requirement of tuning out from the resonance frequencies of vibrations and obtaining minimum mass. As a result of optimization, potential weight reduction of 30% is obtained, while maintaining the blade profile. The check calculation results show the sufficiency of the safety margin values of the resulting blade design. In addition, the paper provides a description of the technological constraints of additive manufacturing and describes a possible method of the resulting blade manufacturing. The results indicate a potential of using topology optimization in the design of uncooled turbine rotor blades with regard to additive manufacturing in order to reduce weight and control natural vibration frequencies. The symbiosis of additive manufacturing and topology optimization will make it possible to use the full potential of both technologies.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):139-147
views
Early detection of vibration behaviour of aircraft engine multistage axial compressor in pre-surge states during rig testing
Khorikov A.A., Danilkin S.Y., Mazikina T.I.
Abstract

Surge is a dangerous aero-elastic phenomenon. When surge occurs a shock wave originates in the gas path of the compressor, which damages individual elements of the compressor, as well as the test beds for measuring the parameters of the workflow. Therefore, early diagnostics of pre-surge states of multistage axial compressors of modern aircraft engines characterized by extremely high aerodynamic loading and small radial clearances between the rotor and the stator is an urgent task. The paper presents the results of the analysis of dynamic processes that take place during throttling of aircraft engine multistage compressors in test bed conditions.  Diagnostic features of the pre-surge state of the compressor were revealed in the signals from strain gauges mounted on the blades, and the signals from sensors of static pressure pulsations installed in the compressor housing. The research was carried out using up-to-date methods of processing and analysis of the signals of dynamic processes based on the fast Fourier transform and wavelet analysis using a 3D representation of the results of the study. The results of the study indicate the possibility of early diagnosis of surge, and also show that several forms of axial vibrations and their respective acoustic frequencies depending on the size of connected masses may occur in the case of loss of gas dynamic stability. The developed methods and means are proposed to be used for the creation of automated systems for preventing surge in compressor rig testing to determine the gas dynamic stability margin.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):148-159
views
Dynamic behaviour of high- bypass- ratio turbofan carbon fiber-reinforced plastic blade ubder unsteady airloads
Buyukli T.V., Fedorchenko Y.P., Shorstov V.A.
Abstract

The dynamic behavior of vibrating blades of an advanced high- bypass- ratio turbojet engine wide-chord fan under unsteady air loads has been researched. Unsteady air loads occur because of the flow around the impeller situated in the air inlet in the case of strong crosswind. These loads affect the blade dynamic behavior and could lead to increasing of the blade vibration amplitude and the stress in the blades. Blade dynamic behavior is investigated on the basis of 3D high-level gas-dynamic and finite-element models. The gas-dynamic model takes into account unsteady viscous 3D air flows. The strength model takes into account geometrical non-linearity and anisotropy of the composite material. The Cobra software package developed at CIAM and based on Godunov’s method is used for aerodynamic research and obtaining unsteady aerodynamic loads. The ANSYS package of finite-element analysis is used to solve the mechanical problem. The paper deals with both forced vibrations of a blade under given cyclic aerodynamic loads and vibrations with account for the fluid-structure interaction (FSI) of the structure and the flow of titanium and carbon-fiber-reinforced blades. The results of investigations have been compared. The differences between the results of solving the task of forced vibrations and vibrations with FSI, as well as the differences between the results obtained for blades of the same configuration but made of different materials are presented.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):160-170
views
Calculation and experimental investigations on the efficiency of various ways of vibration damping of jet engine parts
Shorr B.F., Serebryakov N.N., Stadnikov A.N., Shadrin D.C., Rudenok E.S., Kanackin A.V., Bortnikov A.D.
Abstract

The results of investigations in experimental and computational estimation of the efficiency of engine part vibration damping using different ways of damping carried out at CIAM are presented. Vibration tests have been carried out on a dynamic simulator for a turbine stage with dampers of various masses. The damper with the optimal mass and stiffness is specified according to the results of blade strain-gaging. The possibility of efficient damping of compressor blade vibration using thin damping coatings is shown. A method of damping a fan blade without a root platform is presented. The efficiency of the method proposed has been analyzed and experimentally confirmed using a plate imitating the fan blade. The possibility of active damping of gas turbine engine part vibrations using piezoelectric elements has been considered, and the potential efficiency of the method has been experimentally confirmed. Reducing resonant stresses in a thin titanium plate is an example of applying the method.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):171-182
views
Experimental and theoretical study of vibration bifurcations in aviation transmission gears
Dorofeyev V.L., Golovanov V.V., Ghukasyan S.G., Dorofeyev D.V., Storchak V.G., Afanasyev I.A.
Abstract

Tooth gearings are used in transmission systems of aviation engines to carry the torque from the engine to the accessories. Various forces occur in the course of loading their teeth. The cogwheels making up a part of the transmission system of the aviation engine consist of elements affected both by the rigid and soft restoring forces. Spasmodic change of rigidity in the case of changing the number of engaged couples of teeth causes parametric vibrations of cogwheels. It follows from this that transmission is not only a nonlinear, but also a parametric oscillatory system. The maximum amplitude is not realized when passing the resonance in the case of quick changes of the rotation frequency. Two different values of fluctuation can be registered in the steady-state regime for identical values of the rotation frequency. This duality is called bifurcation. Bifurcations of vibrations can be quite often observed in aviation transmission gears. The existence of bifurcation of vibrations in aviation transmission gears is theoretically proved and the pilot study confirming theoretical conclusions about the existence of bifurcation of oscillatory processes in tooth gearings is described in the paper. Bifurcation parameters are determined.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):183-192
views
Dynamic modelling of non-linear vibrations in cylindrical tooth gearing of aircraft drive systems
Kalinin D.V., Temis J.M.
Abstract

The results of modeling nonlinear parametric vibrations in aircraft tooth gears are presented in the paper.  Resonance vibration with loss of tooth contact is analyzed.  A lumped-parameter dynamic model of cylindrical gears is investigated using the results of gear stiffness modeling obtained from a finite element model for simulating elastic-damping connection for each step during one phase of mesh. Parametric vibrations of a system with base excitation due to variable mesh stiffness and non-linear effects determined by modeling the conditions of loss of tooth contact are studied. It is shown that the maximal level of dynamic loads does not exceed a limit value determined by the presence of discontinuous vibrations in the system. A number of parametric studies are presented to demonstrate the influence of major gear contact ratio on the resultant dynamic behavior. The results obtained by the numerical simulation of steady-state responses of two different pairs of spur gears are in satisfactory agreement with the experimental results. 

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):193-202
views
Calculation of the performance of a coulomb friction damper of a crown bevel gear wheel for different forms of resonant oscillations
Kozharinov E.V., Temis J.M.
Abstract

Different designs of a Coulomb friction damper used to decrease the amplitude of bevel gear resonance oscillations and existing approaches to the modeling of variable-structure dry-friction systems are discussed in the paper. A parametric 3-d finite-element model of contact “bevel gear - plate damper” interaction has been developed. Natural frequencies of the system have been determined for different contact parameters. A set of amplitude-frequency curves of the “damper-wheel” system under consideration has been constructed for different values of damper pre-pressure. The work of the constraining force for the oscillation period has been calculated. By estimating the period-average number of sliding elements basic operating in the relative slip mode the principal modes of a Coulomb friction damper operation – with continuous and instant relative stops – are studied. The influence of the damper pre-pressure value on the relative amplitude of different forms of resonance oscillations is analyzed. A conclusion has been made on the basis of the calculation results that applying a Coulomb friction damper is an efficient way of reducing the amplitude of resonance oscillations of the bevel gear.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):203-212
views
Diagnostic methods and tools for condition-based maintenance of aircraft drives
Golovanov V.V., Vasilenko V.G., Zemskov A.A., Panov S.S., Emelianova A.A.
Abstract

The helicopter ground-airborne health and usage monitoring system (HUMS) presented in the paper illustrates the basic methods of determining the technical condition of aircraft drives by a set of signals received in operation. These algorithms can be realized using the kinematic scheme of a rotor unit with information about the number of teeth in gears, the number of splines in spline connections, the design parameters of the bearings as well as the presence of synchronization signals that are recorded in parallel with vibration signals. The presented methodology for the estimation of vibration parameters of multi-shaft units takes into account the fluctuation of specific frequencies in the real operating conditions of the gearbox. Hardware requirements are formed on the basis of vibration models of gears and gearboxes. The operating frequency envelope of vibration sensors is to include specific frequencies of all gears, spline connections and rolling bearings. The dynamic range is determined based on the vibration activity of the gearbox and units in the places where the sensors are installed. The requirements to the equipment of data accumulation and pretreatment are presented and validated. A method of balancing helicopter classical and coaxial rotors is presented.  The method is based on the analysis of the effect of varying the values of the adjustment parameters of rotor blades (balance weight, assembly swash plate, tab angle) on the values of amplitudes of vibration harmonic components. The main goals of the support center concerning the technical condition of helicopter drives and its cooperation with the operator are stated.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):213-221
views
Tribodiagnostics of aircraft reduction gear elements
Shabalinskaia L.A., Golovanov V.V., Bubnova E.S., Milinis L.V., Prodanov E.S.
Abstract

The paper is devoted to the tribodiagnostics of the technical condition of aircraft reduction gear elements (exemplified by the aircraft gear box). The following methods of testing the parameters of wear products are used: atomic-emission spectroscopy (ASTM D 6595-00), ferrography (ASTM D7690 – 11), dispersion and morphological analysis (ASTM D – 6786 – 002).  Experimental and design increased and admissible-limit values of concentrations of wear product  elements and particles in the lubricant oil have been determined by statistical analysis of 120 lubricant samples selected in the process of rig testing of ten gears of five  KSA-33M  accessory gear boxes. Statistical analysis of the samples has been carried out to determine the maximum permissible, increased and normal values of diagnostic parameters of wear and to carry out their standardization. As a result, design values of increased concentration (IC) and maximum permissible concentration (MPC) of wear elements and particles in the lubricant oil of the KSA-33M accessory gear box have been found. A method of tribodiagnostics of components of the KSA-33M accessory gear box has been developed on the basis of the research carried out and the data obtained earlier. The method makes it possible to assess the technical condition of the part without its disassembly and removal from the aircraft, and, in case of any deviations from the norm, to predict its running hours before the state of emergency.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):222-227
views
Ways of increasing the reliability and service life of bearing assemblies of modern gas-turbine engines and gears
Petrov N.I., Lavrentyev Y.L.
Abstract

Problems connected with ensuring reliability and service life of bearing assemblies of helicopter gas-turbine engines and accessory gearboxes have a significant place within the framework of ensuring reliability of the latter. The experience of operating the existing aviation gas-turbines and gearboxes, as well as the experience of creating new types of structures, shows that determination and establishment of the service life of the main and most loaded parts that include bearing assemblies is one of the first-priority problems facing producers of aviation gas-turbine engines and gears. The paper demonstrates an attempt to analyze the main problems which are at the bottom of shorter service life and lower reliability of domestic aviation bearings as compared to bearings made by foreign manufacturers. The scope of work to ensure the reliability of bearing assemblies in aerospace products is specified, proposals for solving the existing problems are put forward. Experimental methods of confirming the service life of bearings are outlined.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):228-237
views
Method of investigating the elastohydrodynamic contact in slide bearings with compressible and incompressible lubrication
Temis M.J.
Abstract

An algorithm of solving the problem of elastohydrodynamic contact is presented in the paper. It is used to calculate characteristics of journal and thrust bearings with oil or gas lubrication. The algorithm is based on simultaneous solution of the problem of lubrication flow in the gap created by the bearing sliding surfaces and the problem of specifying the change in the gap shape due to the shift of position and deformations of sliding surfaces caused by lubrication pressure in the gap. Modifications of Reynolds equation describing incompressible (oil) and compressible (gas) lubrication flow in journal and thrust bearing are used for the calculation of bearing characteristics. The finite-element method is used to solve the Reynolds equation. Lagrange multipliers are used to ensure closedness of the rectangular region for a journal bearing.  A step-by-step process with error self-correction at each step is applied for solving the nonlinear Reynolds equation for compressible lubrication. The shape of the gap in bearings with incompressible lubrication is defined by calculating the equilibrium pad position in a bearing taking into account the deformations of siding surfaces and bearing parts under the action of lubrication pressure. The shape of the gap in gas bearings is defined by the deformations of elastic foils. These deformations are calculated when solving the problem of deformation and contact interaction of the foils with each other and with the bearing housing under the action of lubrication pressure. The presented method of calculation of elastohydrodynamic contact in slide bearings allows taking into account the design features of physical products for the analysis of rotor supports characteristics.

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):238-249
views
Research of hydrodynamic processes in the lubrication system of gas turbine engines
Gulienko A.I., Shchurovskiy Y.M.
Abstract

A lubrication system with supply and scavenge oil gear pumps with electric drives is the subject of research. The features of the workflow in lubrication system units are analyzed and the possibility of applying a homogeneous model for the description of a fine-dispersed air-oil mixture is evaluated. The principle of construction of a mathematical model of a lubrication system based on dynamic equations of the typical processes in the nodes – the flow of the two-phase mixture, mixing of the air and liquid flows, filling cavities of gear pairs in the suction zone of the pump is outlined. The developed mathematical model is verified by comparing the calculated and experimental processes. 

VESTNIK of Samara University. Aerospace and Mechanical Engineering. 2015;14(3-1):250-261
views

This website uses cookies

You consent to our cookies if you continue to use our website.

About Cookies