Search Results (40)

To address surface quality defects caused by traditional mechanical polishing of gears, such as machining scratches and large surface waviness, this study proposes a novel immersed chemical-mechanical polishing (CMP) process for gear finishing. Numerical simulations were conducted in FLUENT to analyze the gear surface stress distribution and polishing fluid flow trajectories under different process conditions. The Euler–Euler method and RNG k–ε turbulence model were used to optimize process parameters and clarify the formation mechanism of ultra-smooth tooth surfaces. Experimental results for spiral bevel gears show that the proposed immersed CMP process effectively improves surface quality. The tooth profile roughness was reduced from Ra 1.531 μm to 0.509 μm, and surface scratches were significantly alleviated. These results confirm the feasibility and effectiveness of the proposed process. This study provides a reliable approach for efficient and precision polishing of complex-structured gears and extends the application of CMP technology to non-planar mechanical components. Full article

The meshing contact performance of spiral bevel gears is critical for transmission accuracy and service life but is inevitably influenced by manufacturing deviations. Existing tooth contact analysis (TCA) and lubrication-related studies for spiral bevel gears are mostly based on ideal theoretical tooth surfaces, failing to reflect the actual meshing state of as-machined gears with inherent machining deviations, and have poor robustness for complex deviated spatial surfaces. To accurately assess the actual meshing state, this paper proposes a novel contact performance analysis method based on a high-precision digital tooth surface reconstructed from one-dimensional probe measurement data. Unlike traditional TCA methods that rely on complex principal curvature calculations, this approach eliminates the mounting distance parameter by simplifying the meshing coordinate system, and employs a variable-radius cylindrical cutting method combined with a binary search algorithm to determine the instantaneous contact ellipse, effectively reducing computational complexity and improving solution robustness for deviated tooth surfaces. Experimental validation demonstrates that the digital tooth surface achieves a reconstruction accuracy of 2.6 × 10⁻⁵ mm. Furthermore, the method accurately predicts the contact pattern location and transmission error, with a discrepancy of only 4.7% compared to theoretical design values, which is highly consistent with the no-load rolling test results. This study confirms that the proposed method effectively reflects the actual meshing condition of machined gears, providing a practical theoretical foundation for the high-quality manufacturing and control of spiral bevel gears. Meanwhile, the high-fidelity contact characteristics of as-machined tooth surfaces output by this method can provide reliable input boundaries for thermoelastohydrodynamic lubrication (TEHL) simulation, friction loss prediction and anti-scuffing design of spiral bevel gears considering machining deviations. Full article

To extend the time between the overhauls of helicopters, a novel collaborative methodology that takes into account uncertain misalignment errors by considering the shape and performance of the gear is built. Firstly, the digital characteristics of contact patterns, such as the reference point and direction angle, are extracted. Secondly, an optimization model calculates the equivalent misalignment by minimizing deviations in the reference point and direction angle between two contact patterns. This equivalent misalignment accounts for uncertainty misalignment errors introduced by complex gear support deformation. Thirdly, the ease-off is utilized to derive the pinion target surface that can sustain meshing performance under an equivalent misalignment, similar to the original gear in real conditions. This way it integrates with the optimization theory for flank reconstruction to redesign the pinion surface. Simulations reveal that the critical digital characteristics of the contact path on the original gear under the equivalent misalignment mirror those of the original gear in real conditions. Moreover, the surface parameters of the redesigned pinion result in an identical surface under a different equivalent misalignment, maintaining similar contact and dynamic performance. This proposed collaborative design approach, considering the shape and performance while accounting for uncertain misalignment errors through ease-off, greatly improves the gear transmission behavior. Full article

The combined reducer consisting of spiral bevel gear pair and planetary gear train is widely used in the aerospace field, and its dynamic performance seriously affects the fatigue life of the gears. However, there has been little research on the dynamic performance analysis of the combined gear reducer. In this paper, the coupling multibody dynamic models of spiral bevel gear pair and planetary gear train with and without bearing modules are established based on ADAMS software, respectively, and the influence of bearings on the dynamic performance of the coupling system is studied, and the analysis results are verified by experiments. The results demonstrate that the flexible bearings in the coupled system will induce a pronounced shaft swing that amplifies the combined reducer vibration. Because of the displacement of the sun gear, the meshing force of the planetary gear train fluctuates periodically at low frequency, which increases the maximum dynamic meshing force and is not conducive to its fatigue life. This low-frequency fluctuation can be greatly reduced by introducing additional bearings. In addition, dynamic testing confirms vibration spectral components include obvious shaft rotation frequencies except gear meshing frequencies, verifying the modeling accuracy and analytical methodology. Full article

This study investigates the wear performance of 20CrMnTi steel, a commonly used material for spiral bevel gears, after heat treatment, with a focus on the microstructural evolution and wear behavior in both the surface and gradient direction of the carburized layer. The results show that the microstructure composition in the gradient direction of the carburized layer gradually transitions from martensite and residual austenite to a martensite–bainite mixed structure, and eventually transforms to fully bainitic in the matrix. With the extension of carburizing time, both the effective carburized layer depth and the hardened layer depth significantly increase. Wear track morphology analysis reveals that the wear track depth gradually becomes shallower and narrower, and the wear rate increases significantly with increasing load. However, the friction coefficient shows little sensitivity to changes in carburizing time and load. Further investigations show that as the carburized layer depth increases, the carbon concentration and hardness of the samples gradually decrease, resulting in an increase in the average wear rate and a progressive worsening of wear severity. After the wear tests, different depths of plowing grooves, spalling, and fish-scale-like features were observed in the wear regions. Additionally, with the increase in load and carburized layer depth, both the width and depth of the wear tracks significantly increased. The research results provide a theoretical basis for optimizing the surface carburizing process of 20CrMnTi steel and improving its wear resistance. Full article

Compared to spiral bevel gear drives with localized conjugation, line contact spiral bevel gears possess a significantly larger meshing area, theoretically achieving full tooth surface contact and substantially enhancing load capacity. To accurately support the root strength calculation and parameter design of line contact spiral bevel gear drives, this paper presents a theoretical analysis and experimental study of the root bending stress of gear pairs. First, based on the analysis of the meshing characteristics of line contact spiral bevel gear pairs, the load distribution along the contact lines is investigated. Using the slicing method, the load distribution characteristics along the contact line are obtained, and the load sharing among multiple tooth pairs during meshing is further studied. Then, by applying a cantilever beam bending stress model, the root bending stress on such a gear drive is calculated. A root bending moment distribution model is proposed based on the characteristics of the line load distribution previously obtained, from which a formula for calculating root bending stress is derived. Finally, static-condition experiments are conducted to test the root bending stress. The accuracy of the proposed calculation method is verified through experimental testing and finite element analysis. The results of this study provide a foundation for designing lightweight and high-power-density spiral bevel gear drives. Full article

Spiral bevel gears are used in a wide range of industries, such as automotive and aerospace, to transfer power between intersecting axes. However, a certain level of vibration is always present in the systems, primarily due to the complex dynamic forces generated during the meshing of the gear teeth affected by the tooth profile. To address these challenges, this research developed a comprehensive dynamic model with eight degrees of freedom, capturing both translational and rotational movements of the system’s components. The study focused on evaluating the effects of two different tooth profile modifications, namely topology and flank modifications, on the vibration characteristics of the system. The system comprised a spiral bevel gear pair with mesh stiffness in forward rotation. The results highlighted that optimizing the tooth profile and minimizing tooth surface deviation significantly reduce vibration amplitudes and improve dynamic stability. These findings not only enhance the performance and lifespan of spiral bevel gears but also provide a robust foundation for the design and optimization of advanced gear systems in industrial applications, ensuring higher efficiency and reliability. In this paper, it was observed that some modifications led to a 68% reduction in vibration levels. Additionally, three modifications helped improve the vibrational behavior of the system, preventing chaotic behavior, which can lead to system failure, and transforming the system’s behavior into periodic motion. Full article

This paper investigates the special phenomenon that the practical immersed depth of a spiral bevel gear as the driving gear under splash lubrication is significantly less than the static depth. To quantify the practical immersion depth, a computational fluid dynamics (CFD) approach integrated with image processing techniques is utilized to determine the dynamic immersion depth and the associated churning power loss. First, a theoretical method is developed to estimate the churning losses of the bevel gear by replacing the static immersion depth with the practical dynamic immersion depth. Subsequently, the CFD method, which incorporates the overset mesh technique and the volume-of-fluid (VOF) method, is employed to simulate the gear churning phenomenon. Meanwhile, the dynamic immersion depth is determined through image processing techniques that analyze the oil distribution characteristics in the splash-lubricated bevel gear. Finally, experimental results obtained from a dedicated lubrication test rig are favorably compared with the numerical results, confirming that the practical dynamic immersion depth is an accurate and effective parameter for calculating power losses. Full article

Thermal effect is an important cause of gear system engineering failure. Spiral bevel gears are widely used in helicopter transmissions, but scuffing often occurs during operation. Tooth surface body temperature is an important factor influencing scuffing in scuffing standards. A thermal dynamic model of spiral bevel gear transmission was developed based on varying tooth body temperatures under different oil spray conditions. Vibration acceleration experiments were conducted using a dedicated scuffing test rig. The results indicate that higher oil spray temperatures intensify vibrations, with a 24.3% increase in the maximum variance of vibration acceleration. Mesh frequency and stiffness decrease, increasing the likelihood of tooth surface failures such as scuffing. Accurate monitoring of tooth body temperature is critical to ensuring the reliable operation of spiral bevel gears in helicopter transmissions. Full article

Spiral bevel gears are extensively employed in mechanical transmissions; however, they are prone to adhesive wear when operating under high-speed and heavy-load conditions. Research indicates that the tooth surface roughness of gears significantly influences the friction and wear of the meshing gears. The present study delves into the origins of tooth surface roughness through the integration of the W-M function and fractal theory. Utilizing an involute helical gear with surface roughness for tooth cutting, a three-dimensional model is established with roughened tooth surfaces. This paper introduces an approach to developing three-dimensional gear models with roughness and applies the finite element method to perform thermodynamic analysis on gears exhibiting diverse levels of surface roughness. The thermal analysis of gears with varying degrees of roughness was conducted using the finite element method. Comparative analysis of the results under specific operating conditions elucidated the impact of roughness on tooth surface temperature rise. In order to validate the simulation model, an experimental test platform for spiral bevel gears of identical size was established. This model integrates tooth surface roughness with thermodynamic analysis, allowing for the rapid assessment of tooth surface temperature rise under different machining conditions, and reducing the cost of validating predicted tooth surface load-carrying capacity. Full article

This paper presents an innovative and comprehensive methodology for loaded tooth contact analysis (LTCA) of spiral bevel gears, integrating ease-off surface computation with high-precision virtual generating tooth surfaces. The methodology integrates an error-sensitivity analysis model with a semi-analytical LTCA model for spiral bevel gears based on ease-off surfaces, developed using a Universal Generation Model. By leveraging sophisticated corrections in the machining process, the desired ease-off surfaces are obtained, ensuring the accuracy of the generated tooth surfaces. This simulation ensures minimal errors between theoretical and virtual generating tooth surfaces, providing a reliable basis for LTCA. The LTCA model is formulated using CNC-generated tooth surfaces, focusing on misalignments such as pinion offset, adjustment errors, and angular position errors along the pinion and gear axis. The feasibility and effectiveness of the proposed method are verified through comparisons with LTCA software analysis results, demonstrating its high accuracy in predicting the impact of misalignments on contact patterns and load distribution. This integrated approach offers significant advancements in the design and analysis of spiral bevel gears, providing a robust tool for predicting and analyzing gear performance under various misalignment conditions. The combined methodology enhances the reliability and accuracy of LTCA, ensuring optimal performance and durability of spiral bevel gears in practical applications. Full article

To enhance the static and dynamic performance of the grinding wheel spindle system, with the gear grinding machine (YKF2060) as the research object, a static mechanics model of the spindle system was established based on Castigliano’s theorem, taking into account the equivalent effect of the triple-point contact ball bearing at the front end of the spindle. Meanwhile, based on the overall transfer matrix method, a dynamic model of the main spindle–eccentric shaft dual-rotor system was established, taking into account the effects of shear deformation and gyroscopic moments. On this basis, the effect of the spindle span, the front and rear overhang of the eccentric shaft, and the bearing stiffness on the static stiffness and first-order critical speed of the system was analyzed. Finally, static stiffness experiments, modal tests, and finite element simulation models were conducted to verify the static and dynamic models. The results show that the stiffness of the front outer bearing has the greatest influence on the static and dynamic performance of the system, while the stiffness of the rear inner bearing has the least influence. The relative errors of the static stiffness and the first two natural frequencies between static stiffness experiments, modal tests, and finite element simulation models are less than 10%, and the mode shapes match well. The established static and dynamic model can effectively reflect both the static and dynamic characteristics of the spindle system. Full article

Spiral bevel gear drives are widely used in mechanical transmission devices due to their compact structure, smooth transmission, and cost-effectiveness. With the continuous improvement in mechanical product quality, higher and higher requirements are set for the precision, smoothness, and power density of gear transmission devices. Chatter can lead to poor workpiece surface finish on spiral bevel gears, excessive tool wear, and even damage to machine tools. Therefore, the effective prediction of milling chatter during the processing of spiral bevel gears is essential. Regenerative chatter is one of the most fundamental types of vibration in machining processes. This paper presents an improved fully discrete algorithm for predicting the stability of time-delayed cutting in the milling process of spiral bevel gears. The method is validated using single- and double-degree-of-freedom models, demonstrating its accuracy and computational efficiency. The results show that the proposed method improves computational efficiency while ensuring accuracy. Full article

A vectorized analytical model for the cutting dynamics in the spiral bevel gear face hobbing process has been developed, which is based on machine tool kinematics and vibration vectorization. The structural modal parameters of the cutter head spindle system are obtained through experimental modal analysis with hammer impact testing. The analytical model is utilized to simulate the generation of simulated vibration acceleration signals during spiral bevel gear hobbing. A wavelet threshold denoising method is applied to process the simulated vibration signals of the spiral bevel gear face hobbing with added white noise. Signal processing methods, including short-time Fourier transform are employed for time-domain analysis, frequency-domain analysis, and time–frequency-domain analysis of measured signals and simulated signals, thereby extracting the corresponding statistical features. In addition to the results of the experimental modal analysis, the causes of chatter in spiral bevel gear hobbing are discussed in detail, revealing that the main factor is cutter head vibration in the Y direction of the Hunan ZDCY CNC EQUIPMENT YKA2260 machine tool used in this research. The error in the time-domain characteristic parameters between simulated signals and measured vibration acceleration signals is within 15%, with a difference of 3.5% in spectral peak values. The predicted tooth surface morphology from simulation matches the actual morphology on the workpiece, comprehensively validating the reliability of the cutting dynamics model for the spiral bevel gear face hobbing process. Another conclusion drawn from numerical simulation experiments is that the amount of tooth surface waviness of the spiral bevel gears is the ratio of tool chatter frequency to cutting fundamental frequency. Full article