Vol 11, No 1 (2025): 30.04.2025
Articles
Selection of the material grade and hardness of the working surface of the teeth of dynamically loaded gears
Abstract
The purpose of the study is to improve the design methods of gears. The problem, the solution of which the article is devoted to, is to establish functional dependencies between the hardness of the working surface of the gear teeth and operating conditions. The research methods are based on the theory of strength, Elasticity theories, Mechanics of contact interaction. The novelty of the work lies in the establishment of functional dependencies between the hardness of the working surface of the teeth and the basic initial data (power and rotation frequency of the gear); identification of the effect of the power and rotation frequency of the gear on the choice of hardness of the surface of the teeth. The results of the study - the overall dimensions of the spur cylindrical gear were carried out based on the contact strength condition; the ranges of the hardness values of the working surface of the teeth were determined; the functional dependencies between the given power, frequency of rotation and hardness of the surface of the teeth were established; a nomogram was constructed to determine the minimum value of the hardness of the working surface of the teeth, depending on the power and rotation frequency of the gear. The obtained results make it possible to determine the minimum hardness of the working surface of the teeth at given power and speed values and to choose the appropriate material and type of heat treatment for the design calculations of dynamically loaded gears.
7-13
Modeling of an automated system for correction of the tool center point displacement of an industrial robotic manipulator during the execution of technological operations along a complex curved contour
Abstract
The implementation of robotic systems significantly increases the productivity and safety of manufacturing processes. However, robotic manipulators do not always provide high precision in performing technological operations due to kinematic errors. The development of a correction system should take into account the specifics of the performed operations to ensure the required accuracy. This paper presents numerical modeling of a system for incremental forming based on the KUKA KR90 R2700 manipulator robot and the API Radian R-20 laser tracker integrated into the complex to improve the accuracy of positioning the tool center point of the manipulator robot. Additionally, a methodology for improving the positioning accuracy of the robot is proposed, a mathematical model of the robot control system is constructed, and the effectiveness of the selected methodology is evaluated.
14-26
Increasing the longevity of rotary bearings in gas turbine engines with air-fuel lubrication systems
Abstract
Turbojet engines with an air-fuel lubrication system are used in small-sized high-speed aircraft. In these engines, the cooling of rotary bearings is accomplished using air extracted from the compressor, while lubrication is provided by fuel drawn from the fuel pipeline. Under fuel lubrication, bearings operate under boundary friction conditions across a wide range of rotational frequencies and loads, which results in their limited longevity and reduced maintenance intervals for gas turbine engines (GTE). This study presents a computational analysis assessing the impact of bearing size, lubricant film temperature, rotational frequency, and axial load on the longevity of bearings lubricated and cooled by the air-fuel mixture. Methods to enhance the durability of rotary bearings in GTEs lubricated and cooled by the air-fuel mixture are delineated. The findings can be applied in the design of GTEs with air-fuel lubrication systems to extend the longevity of rotary bearings and consequently increase the maintenance intervals of the engines. The results obtained in the work are the product of the United Engine Corporation (UEC) activities.
27-39
Influence of forces of elastic pseudo-slippage of wheel pairs on the occurrence of shock pulses in the train
Abstract
The main issue in the operation of railway rolling stock is the safety of transportation of goods and passengers. This article highlights the impact of faults in chassis components on the stress-strain state (hereinafter referred to as SSS) of automatic coupler equipment. Studies of the stress-strain state of the automatic coupler under the influence of shock pulses arising depending on the speed of movement and the parameters of the track and the car were carried out.
40-50
Energy mathematical model of an aircraft power transfer unit
Abstract
The article proposes an energy mathematical model of an aircraft power transmission unit, as well as the results of experimental studies of a model power transmission unit at the “Diagnostics and Identification of Hydraulic Systems” stand of the Department of Applied Fluid Mechanics of the Federal State Budgetary Educational Institution of Higher Education UUNiT. The proposed mathematical model was verified with experiment, showing good consistency and sufficient reliability. The energy model of the data transmission unit is compared with existing and evaluated predictions for its application.
51-61
Determination of additional stresses in the crankshaft of a reciprocating compressor caused by forced torsional vibrations at resonance point
Abstract
This paper presents the causes of torsional vibrations in a reciprocating compressor unit. The main stages of forced torsional vibration calculation are represented including plotting torque diagrams of the crankshaft, harmonic analysis of resulting torque, determination of torsional vibrations real amplitudes and additional shear stresses calculation caused by torsional vibrations at resonance point. Derivation of the mathematical equation for determining the real amplitudes of torsional vibrations is given in the article based on the equality of the works of external forces exciting torsional vibrations and forces damping the torsional vibrations.
62-77
Effect of different surface plastic deformation methods on high-cycle fatigue of notched specimens
Abstract
The paper presents a study of the effect of different surface hardening methods on the fatigue limit of a number of specimens. The following surface plastic deformation methods were used: pneumatic shot peening, hydro-shot peening, diamond burnishing, and roller rolling. The analyzed batches of circular cross-section specimens made of 30KhGSA, 12Kh18N10T, EI961, 45, and 20 steels with a stress concentrator in the form of a notch. The specimen diameter was 10 mm. It was found that diamond burnishing and roller rolling resulted in a greater increase in the fatigue limit of notched specimens. These hardening methods ensure a more complete distribution of compressive residual stresses along the depth of a non-propagating fatigue crack than with hydro-shot peening and pneumatic shot peening. With the same method of surface hardening, compressive residual stresses of greater magnitude are created in samples made of steels with a higher yield point than in samples with a lower yield point. Based on the results of this study, it was concluded that the criterion of average integral residual stresses should be used to assess the fatigue limit for surface-hardened notched samples. The criterion should be determined by the thickness of the dangerous section, equal to the critical depth of a non-propagating fatigue crack.
78-86
Automation of a test bench for studying the magnetic hysteresis of a damper based on multilayer magnetorheological elastomer
Abstract
The widespread use of electronic precision equipment necessitates research aimed at the development and improvement of vibration protection means. This study presents an investigation of a damper, the operating principle of which is based on the use of an "intelligent" material – a multilayer magnetorheological elastomer. The interest in such devices is due to their ability to adjust the elastic properties, sizes, and shapes of the working body by changing the external magnetic field, as well as the high load-bearing capacity of such devices. The effectiveness of active vibration isolation using the damper is determined by the quality of its transient processes, manufacturing technology, and the composition of the multilayer magnetorheological elastomer. The transient process time allows for determining the system's responsiveness, and consequently, the frequencies within which the device can operate effectively in active mode. The research results showed that the maximum transient process time was 106 ms, which corresponds to effective operation in the low-frequency range up to 9,5 Hz.
87-95
Determination flank clearance of gears of a planetary gearbox as a vibration source in a gas turbine engine using a standard tachometer signal
Abstract
It is demonstrated that the analysis of signals from the “standard” tachometric sensors of the input and output shafts of the GTE planetary gearbox enables assessing the toothed gearing backlash value in the “sun gear – pinion gears” pair. The possibility of identifying trends in the changes of high-frequency components that carry information on the technical condition of the gearbox is established. The results obtained significantly simplify the procedure for monitoring the technical condition of the gearbox by the studied parameter under operating conditions.
96-104
Analysis of vibration signals of micro-size aircraft engines based on joint time-frequency method
Abstract
As the current analysis technology for vibration signals cannot be a comprehensive study of the signal, which leads to the signal analysis not meeting the requirements of practical application, to more in-depth analysis of small engine vibration signals, the project team adopts time-frequency analysis technology to carry out specific work. By using LABVIEW2022 software programming, the application program based on the joint time-frequency method is realized to study the vibration signal of a small engine and determine the running state of the engine according to the corresponding results, to determine whether the engine performance is good. By using the STFT method, Gabor transform method, Wigner distribution method, CSD method, adaptive spectrum method, CWD method, MIF method, and MIB method, the corresponding programs are successfully used to realize the joint time-frequency analysis of such signals. The time-frequency analysis method mentioned above can achieve the expected effect.
105-117