Study on transmission error and torsional stiffness of RV reducer under wear

Ronghua Zhang,Jianxing Zhou,Zheng Wei 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.8

In order to discuss the influence of wear dynamic evolution on the degradation of core transmission performance, transmission error and meshing torsional stiffness of RV reducer, taking BX-40E reducer as the research object, based on Langkali-Nikraves contact force model and Archard wear theory, the wear coefficients with different position conditions were obtained through equivalent wear experiments. The RV transmission dynamic model considering wear, meshing stiffness, meshing force, meshing tooth pairs and transmission error linkage was established by using centralized parameter method and dynamic subsystem method. Compared with the traditional tooth profile wear simulation, which distribution and size of the wear depth curves were more and more different with wear dynamic evolution, theoretically concluded that the dynamic update of wear coefficient is necessary and correct for the accurate simulation of tooth surface wear. The transmission error shows a "double hump" distribution mapped to the wear depth of the tooth profile, and deteriorates with the wear accumulation. The equivalent torsional stiffness of cycloid pin teeth decreases piecewise approximately linearly due to wear. In the previous stage, the reduction rate is small because the tooth detachment first occurs at the tooth top and root, and the single tooth torsional stiffness near the tooth top and root is smaller. The research results provide a new idea and theoretical basis for improving the transmission accuracy, stability holding ability, wear reduction and life extension of RV reducer.

Dynamic characteristics of a planetary gear system based on contact status of the tooth surface

Ruibo Chen,Jianxing Zhou,Wenlei Sun 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.1

Studies on the planetary gear have attracted considerable attention because of its advantages, such as compactness, large torque-toweight ratio, vibrations, and high efficiency, which have resulted in its wide applications in industry, wind turbine, national defense, and aerospace fields. We have established a novel dynamic model of the planetary gear transmission by using Newton’s theory, in which some key factors such as time-variant meshing stiffness, phase relationships, and tooth contact characteristics are considered. The influences of gear axial tipping, operating conditions, and the meshing phase on the contact characteristics and the dynamic characteristics were researched systematically. It was found that the contact area of the tooth surface was moved due to the axial gear tipping, which obviously affected the meshing stiffness. With the increase in the inclination angle of the sun gear, the meshing stiffness decreases, which produces an evident influence on the high natural frequency in the planetary transmission system. In terms of the dynamic characteristics of the system, the component of rotating frequency appeared in the dynamic meshing force of the sun gear and the planetary gear. Moreover, the floating track of the center wheel varied significantly and exhibited an oval distribution as the inclination angle of the sun gear changed. When the inclination angle of the sun gear increased, the rotating frequency component increased significantly, but the other meshing frequency components remained unchanged; meanwhile, the deformation of the floating track also increased. If the inclination angle of the sun gear changes, the vibration state of the system and the collision impact could become more serious, and the lifetime of the planetary transmission system will reduce. Furthermore, when the load was increased, we found that the gear-tooth contact zone transformed from line contact to surface contact, the meshing stiffness increased, the effect of high natural frequency on the planetary transmission system became more evident, but its low-order natural frequency remained stable. With regard to the dynamic characteristics of the system, the components of the major frequency at the external gearing remained unchanged, but the rotation frequency of the sun gear and the meshing frequency amplitude increased linearly with the increase in load. In conclusion, the variation in the meshing stiffness of the planetary gear system had minor impact on the low-order natural frequency, but had a significant impact on the high natural frequency of the planetary transmission system due to the phase variation of the gear.

Low noise optimization of two-stage gearbox housing structure based on acoustic contribution analysis and topology optimization

Le Qi,Jianxing Zhou,Pengcheng Jin,Mingming Wang,Yongzheng Su,Hengyu Zhou,Guochun Liu,Lirui Song 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

In this paper, a rib layout optimization method that can efficiently reduce the radiated noise of gearboxes is proposed. Taking the secondary gearbox as the research object, the radiated noise of the housing is calculated using the FEM/BEM method, the process of determining the region with the maximum acoustic contribution is illustrated, and a topology optimization model that can reduce the air noise on the field points of the gearbox is established with the surface normal velocity of the region as the optimization target. The method is applied to add new noise reduction ribs on the surface of the gearbox. The results show that after combining the topology optimization with the acoustic contribution analysis, the sound pressure in the area with the highest sound pressure on the gearbox sound field is significantly reduced by adding new noise reduction ribs according to the optimization results.

Research on dynamic characteristics and radiation noise of a helicopter main reducer based on finite element and boundary element method

Jingqi Zhang,Jianxing Zhou,Shengnan Wang,Haiwei Wang,Feng-xia Lu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

In order to solve the problem of radiation noise of helicopter reducer with symmetrical structure, a simulation method is proposed to predict the noise of gearbox of a helicopter reducer from steady dynamic response to the acoustic radiation calculation. Primarily, taking the influence of time-varying stiffness into consideration, the lumped mass model of gear-rotorbearing system is established. The dynamic load of transmission system is solved by NewMark-β method, which is regarded as excitation of the gearbox. Then finite element model of housing is established, the radiated noise of the housing is predict by finite element and boundary element method, the influence of multi-source excitation on the radiated noise of the gearbox is analyzed. Finally, the radiated noise of the reducer under different working conditions is explored. All conclusions of this research could provide theoretical reference for vibration and noise reduction of helicopter reducer.

Study on the coupling relationship between wear and dynamics under steady uniform temperature field of planetary gear system

Ning Dong,Jianxing Zhou,Ruiting Tong,Quanwei Cui,Yiyi Kong,Junshang Feng,Shichen Xiao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.12

Wear of tooth profiles and thermal deformation caused by temperature changes are difficult to avoid in gear systems and have important effects on the performance, even to failure. In this paper, a dynamic wear prediction model with coupled thermal deformation and wear is proposed to study the interaction between wear and dynamics of planetary gear system under temperature field, accounting for the effect of temperature on material properties. The system's performance under different wear cycles and temperatures is analyzed. The results show that the difference in the structure makes the curve shape of the thermal deformation error for the external and internal gear pairs completely different, which in turn affects the dynamic response. The distribution and the degree of fluctuation of tooth profile wear depth change as the mesh cycle increases. The early wear is beneficial to the system's uniform load performance and vibration, and the performance decreases as the wear increases, but the external and internal gear pairs are affected by wear to a different extent. The thermal deformation and wear errors have competing or facilitating mechanisms depending on the temperature difference and the degree of wear.

Study on wear evolution of spur gears considering dynamic meshing stiffness

Ning Dong,Quanwei Cui,Jianxing Zhou,Ruiting Tong,Haiwei Wang,Feng-xia Lu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.7

Wear is an inevitable phenomenon in gear systems and has a great impact on performance and longevity. In view of the fact that the actual variation of meshing stiffness in the double teeth contact region and the nonlinear relationship between meshing stiffness and force are ignored in previous wear prediction studies, a new method with loss-of-lubrication is proposed in this study. A translational-torsional dynamic model is developed for the coupling effect between wear and dynamic characteristics of external spur gears. To obtain more precise dynamic responses, the meshing stiffness and force are coupled with tooth wear, taking into account the structural coupling effect and nonlinear contact. The tooth surface is then discretized, and a wear model is developed based on Archard wear equation, in which the average pressure is used for the engaging point. Experiments and numerical simulations are carried out to analyze the wear pattern and the interaction between wear and dynamic responses. The results show that the progressive wear process is self-adaptive. Meanwhile, the area with the largest wear depth moves slightly from the dedendum and addendum to the pitch line as the wear cycle increases. When the wear depth is at the level of the tooth profile deviation, the influence of wear on meshing stiffness is very small within the single tooth contact region. However, there is a significant decrease in the stiffness of the double teeth contact, and this decrease is related to the wear cycle and torque. At the initial wear phase, as the load increases, the fluctuation of the wear depth within the engaging-in region intensifies and the overall wear depth increases. With the increment of rotate speed, the engaging-in impact makes the fluctuant area of wear depth become larger.

Constructing all-in-one graphene-based supercapacitors for electrochemical energy storage via interface integration strategy

Zhu Yucan,Peng Long,Chen Song,Feng Yuchao,Xia Jianxing,Wang Wei,Chen Liang,Yin Hong,Zhou Minjie,Hou Zhaohui 한국탄소학회 2023 Carbon Letters Vol.33 No.3

With the rapid development of flexible wearable electronic products, flexible all graphene-based supercapacitors (FGSCs) with reduced graphene oxide rGO//graphene oxide (GO)//rGO structure have attracted substantial attention due to their unique structures and energy storage mechanism. However, restricted by design idea and preparation technology, improvement of capacitance performance for the FGSCs is not obvious recently. Herein, we demonstrate that an interface integration strategy of constructing the high-performance FGSCs with compact structure. Hydroquinone (HQ)-modified rGO (HQ-rGO) films (electrode materials) and sulfuric acid-intercalated GO films (electrolyte/separator) are assembled into the FGSCs utilizing hydrogen bonding and capillary contractility. The HQ further improves the electrochemical capacitance of electrode materials. The synergistic effect of the hydrogen bonding and capillary contractility guarantees compact and stable structure of the device. The resulting FGSCs exhibit an excellent areal capacitance of 804.6 mF cm−2 (@2 mA cm−2) and 441 mF cm−2 (@30 mA cm−2), and their highest energy and power densities can achieve 109.5 μWh cm−2 and 21,060 μW cm−2, respectively. These performances are superior to other all-in-one graphene-based SCs reported. Therefore, the construction technology of the FGSCs is a promising for developing all graphene-based SCs with high-performance.