Gear Surface Research Articles

Research on the mechanism of magnetic flux concentrator in the gap-to-gap induction heating of wind power gear

Gear quality is one of the factors that determine the stability of the wind turbine. Electromagnetic heating is a green and efficient heating method, which has been used to heat wind power gears. Good mechanical properties could be obtained by induction hardening on the surface of wind power gears. And a uniform hardened layer along the tooth profile is needed. In this paper, research on the effect of the Magnetic Flux Concentrator (MFC) in gap-to-gap induction heating of wind power gear was carried out. The study and the experimental tests refer to the heat treatment of an inner gear ring of a wind turbine transmission of modulus m = 16 at frequency 6000 Hz. The calculated hardened depth is 3 mm inward from the side of the tooth profile, and reaches 2 mm at root of the tooth. The mechanism of the concentrator, and the relationship between MFC characteristics and the heating results are explored. The study found the heating time and quality could be significantly affected by the geometrical dimensions thickness "t", height "h" and material of the MFC. The Magnetocaloric Capacity "Mc" was proposed to describe the ability of the MFC to influence the heating process. The characteristics of the magnetic flux concentrator that affect the heating quality and efficiency are discussed. Meanwhile, this study found that the heating efficiency is related to the strength of the magnetic field in the MFC and the distribution of magnetic field lines. By adjusting t, h and the materials, the heating efficiency and quality could be significantly changed. The maximum temperature difference along the tooth contour was changed to 39.6%, and the average temperature was changed to 6%. When the relative permeability of the material is matched with the frequency, a better heating quality and higher speed could be obtained. The research provides a theoretical support for the precise control of the gap-by-gap induction heating of wind power gear, especially for quality control by the MFC.

Numerical Calculation Method of Meshing Stiffness for the Beveloid Gear considering the Effect of Surface Topography

The tooth surfaces of beveloid gears have different topography features due to machining methods, manufacturing accuracies, and surface wear, which will affect the contact state of the tooth surface, thereby affecting time-varying mesh stiffness between mating gear pairs. Therefore, a slice grouping method was proposed in this paper on the basis of potential energy to calculate the total meshing stiffness of beveloid gears with the surface topography. The method in this paper was verified by finite element method (FEM). Compared with the calculation results of this paper, the relative error is 5.9%, which demonstrated the feasibility and accuracy of the method in this paper. Then, the influence of parameters such as pressure angle, helix angle, pitch angle, tooth width, fractal dimension, and fractal roughness on meshing stiffness was investigated, of which results show that pressure angle, pitch angle, tooth width, and fractal dimension have an incremental impact on the mean value of mesh stiffness. However, the fluctuating value of mesh stiffness has also increased as the pressure angle, tooth width, and pitch cone angle increase. Both the helix angle and the fractal roughness have a depressive impact on the total stiffness. But the difference is that, with the increase of the helix angle, the fluctuation of meshing stiffness has been decreased. Conversely, with the increase of the fractal roughness, the fluctuation of meshing stiffness has been increased.

ПОВЫШЕНИЕ ТЕХНОЛОГИЧЕСКИХ ВОЗМОЖНОСТЕЙ МЕТОДА НЕПРЕРЫВНОГО ОБКАТНОГО ЗУБОШЛИФОВАНИЯ

The work purpose consists in the technological capacity updating of the method for cog-wheel continuous run-in gear grinding based on the purpose of efficient modes and characteristics of the worm disk. 
 The investigation methods are based on mathematical modeling and planning experiments. Machining aircraft cylindrical cog-wheels and special samples was carried out on modern NC machines, benches and plants with the use of up-to-date test equipment: coordinate inspection machine KIM R-100 “Klingelnberg”, profile meter MarSurf M300S “Mahr”, optical microscope Axiovert 400MAT “Zeiss”, electronic scanning microscope Tescan Mira3 “Tescan”, micro-hardness gage Micro Met 5104 “Buehler”, X-ray diffractometer Xstress Robot “Stresstech OY”, Barkhausen digital nose analyzer
 Rollscan 350 “StresstechOY”, plant APOON on the well-known and developed techniques. 
 The research results and novelty. Special strategy and cutting modes at the required characteristics of the combined polish-grinding worm allow ensuring gear profile roughness Ra=0.089 mkm keeping high accuracy of a ring gear (gear profile error Fa=1.6mkm) without gear honing thereby increasing productivity. The quality researches of gear surface layer give grounds for the application of the method for aircraft cog wheels.

Influence of injection angle on oil splash of herringbone gear

Oil injection lubrication is a common lubrication method for aviation gear transmission. Due to the high-speed rotation of the gear, a part of the lubricating oil splashes off the gear surface after colliding with the gear surface. The amount of oil splashing under the oil injection condition affects the cooling effect of gear lubrication. In this paper, according to the characteristics of aviation herringbone gear injection lubrication, an oil splash calculation model of aviation herringbone gear injection lubrication is established by using advanced computational fluid dynamics theory and method, and the influence of different injection angles on oil splash is analyzed, which can provide theoretical guidance for the design of injection lubrication parameters.

Detection of cracks in green products of powder metallurgy by means of laser vibrometry

Cracking of green parts in powder metallurgy (PM) is a big concern in PM industry. Detection of cracks in green parts before sintering can prevent recycling of already sintered parts or production of defective ones. As opposed to sintered parts, where the presence of cracks is well revealed by impact spectroscopy, it is challenging for green parts. The reason is an extremely low mechanical quality factor of these parts composed of compacted but non-sintered metal powder particles. Low mechanical integrity of particles causes the absence of pronounced resonances of the parts. The aim of the study was to test a possibility to discerning healthy and cracked green parts using spectral characteristics of signals obtained by laser vibromery. Four similar green PM gear wheels made of steel powder were obtained from a PM manufacturing company, two of them were healthy and two with simulated cracks that appeared in the area of stress concentration between the hub and the disc. The experimental setup included a Polytec PSV-500 scanning laser vibrometer and a Bruel&Kjer vibration stand type 4824. Integrated spectrograms in the frequency range 50 – 3500 Hz were recorded upon a 95-point network on the gear surface at different vibration intensities proportionally graded in the range from 1 to 5. Comparison of the 3D (frequency-intensity-amplitude) vibration spectrograms showed that the defected specimens with cracks differed from the healthy ones in the following features: resonance frequency shift and/or splitting of resonances when the load changes. The study confirmed the principal possibility of cracks detection in green PM parts using laser vibrometry regardless the crack location in the part. The aim of further studies is to determine the sensitivity limit in terms of crack size.

Study on simulation and experiment of non-circular gear surface topography in ball end milling

The machining surface quality has an important influence on the meshing performance and life of non-circular gear transmission. According to the meshing principle of non-circular gear transmission, the coordinate system of non-circular gear tooth surface was established, and the tooth surface equation of non-circular gear was obtained. Combined with the tooth surface equation of non-circular gear, the cutting edge motion model of ball end milling cutter was established, and the milling locus equation of cutting edge under multiple factors was deduced. The surface topography of the non-circular gear was obtained by simulation calculation, and the influence of interval feed and feed per revolution on the residual height was analyzed. The non-circular gear solid parts were processed by five-axis CNC milling with a ball end milling cutter, and surface topography measurement experiment was carried out. The experimental results and simulation results were compared and analyzed. The analysis results show that the actual machined surface topography has a high coincidence with the theoretical simulation surface topography, which verifies the rationality of the theoretical method. This study has a certain guiding significance to improve the surface quality of non-circular gear in ball end milling.

Compensation Method for Inclination Errors in Measurement Results of Tooth Surface of Spiral Bevel Gear

The manufacturing error of spiral bevel gear tooth surface has a great influence on transmission efficiency and gear life. The error of the gear tooth surface needs to be measured accurately and fed back to the machine tool to adjust the parameters. When measuring the spiral bevel gear using a gear measuring machine, combined with the measurement theory of the tooth flank of spiral bevel gear, this paper proposed a method to compensate the inclination error in the measurement result precisely. Based on the iterative search method, a precision matching method for the theoretical and the measured tooth surface of the spiral bevel gear was designed to calculate the compensation results. The experimental results show that the inclination errors included in tooth surface measurement results reduced from more than 3 μm to less than 0.5 μm, and more than 70% of the errors are compensated by the proposed method. The accuracy of the measurement results improved significantly after compensation, and furthermore, it can provide a more accurate basis for the adjustment of machine tool parameters in the manufacturing process.

Influence of running-in operating conditions on the steady-state torque loss of ground spur gears

The influence of gear running-in operating conditions on the steady-state efficiency of ground spur gears is not well established. However, it is accepted that less rough surfaces promote better efficiency. Five ground spur gears with similar surface finishing were submitted to two distinct test stages: (i) running-in stage and (ii) torque loss stage. During the running-in stage, five different running-in operating conditions were conducted to ascertain the influence of the load and temperature on the subsequent steady-state gear torque loss test. The mass loss and surface roughness parameters were influenced by the running-in operating conditions. However, different surface conditions after running-in had only a transient effect on the torque loss measured subsequently. So, the test campaign allow to conclude that even after a severe running-in operating condition, the gears surface still evolves in a significant way during the torque loss tests.

A compensation method for the eccentricity and inclination errors of spiral bevel gear based on improved ICP algorithm

Due to the manufacturing and assembly errors of the spiral bevel gear, the deviations between the measured tooth surface and its theoretical tooth surface will affect the measurement results of the tooth surface. After analyzing the tooth surface deviation of spiral bevel gear, this paper provided a compensation method to compensate the eccentricity and inclination errors by the registration of the theoretical and measured tooth surface. An improved iterative closest point (ICP) algorithm for the registration of the tooth surface was provided. The distance between the point in measured tooth surface and the nearest point in theoretical tooth surface is used to replace the minimum Euclidean distance, and the damping Gauss-Newton method is used to solve the geometric transformation matrix. Simulation experiments were carried out to verify the proposed compensation method. The compensation effect is over 93% for the concave tooth surface and over 89% for the convex tooth surface of the spiral bevel gear. The results also show that the improved ICP algorithm could compensate the eccentricity and inclination errors of the spiral bevel gear more precisely than the basic ICP algorithm.

ПІДВИЩЕННЯ НАДІЙНОСТІ СУДНОВИХ ЕНЕРГЕТИЧНИХ УСТАНОВОК ШЛЯХОМ УСУНЕННЯ НЕГАТИВНОГО ВПЛИВУ РОЗЦЕНТРОВОК ОСЕЙ З'ЄДНУВАЛЬНИХ ВАЛІВ

The influence of skew axes of the connecting shafts of marine aggregates on the efficiency and reliability of ship power plants is investigated. The reasons for the occurrence of centerings of axes of connecting shafts of marine aggregates are considered and their classification is offered. Failures of ship power plants are classified according to their impact on the efficiency of the installation (according to the consequences), according to the methods of their elimination, and by their nature and are divided into the groups according to the classes. It is shown that during operation, in the conditions of axial skew, traditional designs of the toothed clutch are characterized by non-uniform distribution of forces between pair of gears, which leads to their overload and, as a consequence, reduced load capacity, increased contact stresses, deterioration of lubrication surfaces of gears, increase in power consumption for friction, reduction of efficiency and deterioration of vibroacoustic characteristics due to shock load of gear. Ways to increase the efficiency of ship power plants by providing parameters of reliability of the main power plants by eliminating the negative impact of the centering axes of the connecting shafts of marine aggregates through the use of compensating devices are considered. It is proposed to use as compensating devices, the design of high-efficiency clutch, which in the conditions of axial skew, are characterized by a more uniform distribution of forces between pair of gears than existing ones, ie work almost as a perfect hinge. Regarding the proposed toothed couplings, a previously unknown objectively existing property of the toothed clutch operating at the skew of the axes of the connecting shafts is established, which is that under a certain nonlinear law changes in the generating side surfaces of the outer teeth evenly between all conjugate pairs of teeth. The use of a high-efficiency clutch in the ship power plants is considered and the basic and functional (structural) scheme of the main marine aggregate with a series connection of elements is made to assess the impact on reliability parameters.

Digital Twin-Driven Remaining Useful Life Prediction for Gear Performance Degradation: A Review

AbstractAs a transmission component, the gear has been obtained widespread attention. The remaining useful life (RUL) prediction of gear is critical to the prognostics health management (PHM) of gear transmission systems. The digital twin (DT) provides support for gear RUL prediction with the advantages of rich health information data and accurate health indicators (HI). This paper reviews digital twin-driven RUL prediction methods for gear performance degradation, from the view of digital twin-driven physical model-based and virtual model-based prediction method. From the view of the physical model-based one, it includes a prediction model based on gear crack, gear fatigue, gear surface scratch, gear tooth breakage, and gear permanent deformation. From the view of the digital twin-driven virtual model-based one, it includes non-deep learning methods and deep learning methods. Non-deep learning methods include the wiener process, gamma process, hidden Markov model (HMM), regression-based model, and proportional hazard model. Deep learning methods include deep neural networks (DNN), deep belief networks (DBN), convolutional neural networks (CNN), and recurrent neural networks (RNN). It mainly summarizes the performance degradation and life test of various models in gear and evaluates the advantages and disadvantages of various methods. In addition, it encourages future works.

Investigation on the relationship between macropits and wear particles in a gear fatigue process

Macropitting is one of the most common gear wear mechanisms, and monitoring its initiation and propagation is critical to ensure the safe operation of gearboxes. Wear debris analysis (WDA) is widely used to monitor and diagnose gear macropitting and its diagnostic capability relies on good understanding of the relationship between wear particle features and those of actual gear macropits. However, the study on this relationship has been impeded by on-going challenges in characterising gear macropits during the wear process. As a result, detailed experimental data of macropits and the quantitative relationships between wear particles and macropits evolving in the fatigue process are scarce.In order to address the above issues, this study examines macropits and wear particles generated on gear surfaces and their evolution in a gear fatigue process through employing a moulding method to obtain 38 batches of gear teeth moulds in the wear process. 2D characterisations of macropits on the moulds and sampled wear particles were conducted using optical microscopy. Qualitative and quantitative relationships between different features of macropits and wear particles were investigated. Results showed the concentration of wear particles had a similar trend to pitted area growth, yet with a delay. This behaviour was also found in 4 non-dimensional numerical features characterising the geometry of particles and pits. The results of this study provide further insight in the evolution of the fatigue process of gears and can assist in its monitoring.

Effects of rim thickness and drive side pressure angle on gear tooth root stress and fatigue crack propagation life

Gears are the most significant machine elements in power transmission systems. They are used in almost every area of the industry, such as small watches to wind turbines. During the power transmission, gears are subjected to high loads, even unstable conditions, high impact force can be seen. Due to these unexpected conditions, cracks can be seen on the gear surfaces. Moreover, these cracks can propagate, and tooth or body failures can be seen. The fatigue propagation life is related to the gear tooth root stress. If the root stresses decrease, the fatigue life of the gears will increase. In this study, standard and non-standard (asymmetric) gear geometries are formed for four different rim thicknesses and four different pressure angles to examine fatigue crack propagation life. Moreover, the effects of the rim thickness and drive side pressure angle on the root stress are investigated. The static stress analyses are carried out to determine the starting points of the cracks, and the maximum point of the stress is defined as the starting point of the cracks. Fatigue crack propagation analyzes are performed for gears whose crack starting points are determined. The static stress analyses are conducted in ANSYS Workbench; similarly, the fatigue propagation analysis is performed in ANSYS smart crack growth. In this way, the directions of the cracks are determined for different rim thicknesses and drive side pressure angles. Besides, the number of cycles and da/dN graphs is obtained for all cases depending on crack propagation. As a result of the study, maximum stress values were decreased by 66%. The fatigue propagation life was increased approximately fifteen times by using the maximum drive side pressure angle and optimum rim thickness.

Computerized Generation of Asymmetric Straight Bevel Gear

To carry out any type of analysis and study the gear drives, the primary steps include the graphical representation of the gear drive under consideration. In this study, the mathematical formulations of the tooth surface, tooth root surface, and tooth root transition surface of symmetric straight bevel gear were formulated based on the planning principle. The proposed modification has been done on the mathematical formulation of the symmetric tooth profile to consider the effect of asymmetric tooth profiles (which are characterized by different pressure angles on the loaded and unloaded sides). As a result of this study, a computer program based on the above mathematical formulation has been built to represent the final shape of symmetric and asymmetric teeth profiles of straight bevel gear for different design parameters.

Residual Stress Distribution Design for Gear Surfaces Based on Genetic Algorithm Optimization

The rolling contact fatigue of gear surfaces in a heavy loader gearbox is investigated under various working conditions using the critical plane-based multiaxial Fatemi–Socie criterion. The mechanism for residual stress to increase the fatigue initiation life is that the compressive residual stress has a negative normal component on the critical plane. Based on this mechanism, the genetic algorithm is used to search the optimum residual stress distribution that can maximize the fatigue initiation life for a wide range of working conditions. The optimum residual stress distribution is more effective in increasing the fatigue initiation life when the friction coefficient is larger than its critical value, above which the fatigue initiation moves from the subsurface to the surface. Finally, the effect on the fatigue initiation life when the residual stress distribution deviates from the optimum distribution is analyzed. A sound physical explanation for this effect is provided. This yields a useful guideline to design the residual stress distribution.

Meshing Contact Impact Properties of Circular Arc Tooth Trace Cylindrical Gear Based on Rotating Knife Dish Milling Process

Taking the circular arc tooth trace (CATT) cylindrical gear as a research object, in order to obtain the CATT cylindrical gear’s meshing contact impact properties, the meshing contact impact hypothesis of the CATT cylindrical gear was put forward based on the contact dynamics theory and gear transmission physical model, and the gear mesh contact impact model was set up further. The finite element solution algorithm for solving the impact problem was given. Then, the accurate 3D model was set up based on the gear tooth surface equation, and the finite element analysis models of the meshing contact impact with different impact positions were established further. The model was to study the distribution rule of the gear surface meshing contact impact stress and relationship between the impact velocity, impact position, and the impact stress. Moreover, the reason for the maximum impact stresses distribution rule of primary and secondary impact tooth surface was discussed. Research result shows the driven wheel dangerous areas of gear root impact are the gear top of the primary impact tooth surface and the gear root of the secondary impact tooth surface; the driven wheel dangerous areas of gear top impact are the gear root of the primary impact tooth surface and gear top of the secondary impact tooth surface; the driven wheel dangerous areas of pitch circle are the gear root and pitch circle of secondary impact tooth surface; and impact velocity and impact position have a major influence on the impact stress. The study results provide a theoretical basis for the dynamic design and industrial application of CATT cylindrical gears.

Supply channels in planetary rotary hydraulic and pneumatic machines with central wheel wave numbers different by unit

The physical criteria limiting the size of the channels, including the conditions excluding the fl ow of the medium between adjacent cameras "under the satellite", are considered. The comparison of the variants of the channels execution is carried out: in the end wall of the epicycle; in the end wall of the sun gear; in the cylindrical toothed surface of the sun gear. The design criteria that characterize the relative sizes of the channels have been refi ned. For any planetary rotary machines with the number of waves N of the epicycle, which exceeds the number of waves M of the sun gear by two (N – M = 2), the channels should be located at the ends of the epicycle, but with N – M = 1, the relative cross-sections of the channels in the cylindrical toothed surface of the sun gear are much larger than in the end wall of the epicycle, therefore, for a planetary rotary machines with a low pressure of the medium, for example, vacuum pumps, it is advisable to make the channels in the cylindrical toothed surface of the sun gear.

Parametric optimization of drilling on IS 10,343 Gr. 2A carbon steel by Taguchi method: A case study

In this study, the effect of cutting parameters of the drilling such as spindle speed and feed on the gear shifter's inner surface, a product of “Shree Chamunda Engineering Works” was investigated to improve surface finish and productivity. The experimental study was conducted on the gear shifter made of IS 10,343 Gr. 2A as per the L9 orthogonal array of Taguchi method to determine optimal drilling parameters. Analysis of Variance (ANOVA) was also performed to determine the significant effect of the response and the percentage contribution of individual parameters over the response. A confirmation test was carried out to validate the test results. The results revealed that the 3.006% reduction in the rejection of the gear shifter had been observed with suggested optimum process parameters.

激光熔覆与淬火再制造QT700球墨铸铁齿轮熔覆层的组织与性能

激光熔覆与淬火再制造QT700球墨铸铁齿轮熔覆层的组织与性能

Application of an unstructured overset method for predicting the gear windage power losses

Enhancing the efficiency of gear systems is of significance to reduce fuel consumption and overall weight. Windage power losses become prevailing in high-speed gear systems, such as aero-engine applications. To avoid the shortages and limitations of commonly used methods (e.g. negative volume in dynamic mesh method and one moving object in sliding meshing method), this paper describes an unstructured overset computational fluid dynamics technology to simulate the airflow pattern in a gearbox and calculate the windage losses. A disk, a spur gear and a helical gear, spinning in the air at rotational speed up to 7200 r/min are studied respectively, the windage power losses obtained by the numerical method show good agreement with experimental data and analytical findings in the open literature. Meanwhile, the associated deceleration torques exerted by pressure and viscous forces on spinning gear surfaces are also determined. Furthermore, the overset method facilitates to estimate the windage losses of a non-meshing gear pair. The results of this paper indicate that the overset method can accurately predict the windage power losses and provide a new route to investigate the flow pattern surrounding the gears. This method can serve as an effective tool for engineering applications in the future.