Time-varying meshing stiffness calculation of an internal gear pair with small tooth number difference by considering the multi-tooth contact problem

Guangjian Wang,Qing Luo,Shuaidong Zou 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9

Due to the multiple tooth contact problem involving internal gear pair with small tooth number difference (IGPSTND), the existing analytical methods applied for standard spur or helix gear pairs to calculate the time-varying meshing stiffness (TVMS) are not suitable. In this paper, two methods are proposed for calculating the time-varying meshing stiffness in internal gear pairs with small tooth difference. In the first method, an analytical model is established by using the potential energy method, considering the clearance of initial contact tooth and the external load. The second method proposes the application of a hybrid finite elementanalytical method. The proposed two methods are validated by the application of the finite element method. By taking the results of finite element analysis as a comparative reference, the results show that the finite element - analytical method is closer to the reference results than the results obtained by the analytical method, and both methods are less computationally expensive than finite element analysis.

The occurrence mechanism and influencing factors of fault-slip rockburst

Kangyu Wang,Guangjian Liu,Zonglong Mu,Zhicheng Wang,Hao Zhou 한국지질과학협의회 2023 Geosciences Journal Vol.27 No.5

No method can simulate the stress wave generated by fault slip in the previous numerical simulation of fault-slip rockburst. As a result, the radiation characteristics cannot be simulated realistically, which causes the unclear mechanism of fault-slip rockburst. Therefore, the mechanical-parameter steepest descent method and static-dynamic analysis method were proposed. Taking the 7301 working faces of Zhaolou Coal Mine as the engineering background, the work analyzed the radiation characteristics of slip stress waves and the evolution characteristics of stress, cracks, and energy in the surrounding rocks of roadway in the process of rockburst. Besides, the influence law of fault geometric properties on rockburst was studied. (1) The mechanical-parameter steepest descent method based on the Mohr-Coulomb criterion could realistically simulate the stress waves generated by fault slip. (2) The fault-slip stress waves had the radiation characteristics of the P and S waves. The vibration velocity around the source was anisotropic, and the velocities of the P and S waves were 1,449 and 833 m/s, respectively. The simulation results were similar to real data. (3) The whole process of rockburst induced by fault slip was simulated. The process of fault-slip rockburst existed at the stable stage, initial rockburst stage, and full-scale rockburst stage. The number of tension cracks during the calm period was used as precursor information for rockburst. (4) The geometric characteristics of faults determined the radiation intensity and radiation area of the fault-slip stress waves, which significantly affected rockburst. The rockburst risk was higher in the roadway in the main radiation area of the S wave. Mechanical-parameter steepest descent, a numerical simulation method, provides a reference for simulating stress waves generated by fault slip. The results provide a basis for understanding the occurrence mechanism of fault slip rockburst and predicting the fault slip rockburst in real engineering.

Two-Sided Contact Mesh Stiffness and Transmission Error for a Type of Backlash-Compensated Conical Involute Gear Pair

Shuaidong Zou,Guangjian Wang,Yujiang Jiang 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.7

Both the drive- and back-side contact mesh stiff nesses (two-sided contact mesh stiff ness) for a new type of conical involute gear (NTCIG) is developed analytically. Instead of the conventional spring preload anti-backlash method, an active control strategy to eliminate the time-varying backlash is presented by adjusting the axial displacement of the driven gear. The dynamic transmission error (DTE) of the gear pair is calculated under different load excitations to analyze the differences between the drive- and back-side meshes under a time-varying backlash with anti-backlash conditions based on the NTCIG model with an eccentricity error. Considering the additional rotational angle caused by the anti-backlash and the differences from the two-sided contact, the theory of no-load transmission error for the NTCIG is modified by agreeing considerably well with the low component of the DTE. Moreover, the DTE curve under varying load excitations showed that the dynamics of the NTCIG improved considerably after backlash compensation. The drive- and back-side tooth meshes were analyzed according to the DTE of NTCIG with backlash control under various external excitations at different speeds and variable initial phases, frequencies, and amplitudes of the sinusoidal load.

The Experimental Research on Gear Eccentricity Error of Backlash-Compensation Gear Device Based on Transmission Error

Li Yu,Guangjian Wang,Shuaidong Zou 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.1

Backlash compensation is a research focus in precision gear transmission, and eccentricity error is the main factor which leads to transmission error(TE) with large period and periodically variable backlash in gear transmission, therefore, the eccentricity of gear has to be considered in anti-backlash. Firstly, the dual-eccentricity model for calculating the transmission error caused by eccentricity errors of gears is presented based on external parallel-axes gear transmission. Then, the tests are carried out at different input speed and initial starts for acquiring transmission error of the designed backlash compensation device, and the eccentricity error of the gear is identified from the testing data of transmission error by curve fitting based on the calculation model. Both the value and phase of the fitting eccentricity error are well coincident with the calculating model. Finally, the fast Fourier transform (FFT) is also employed to analyze the value of the eccentricity error. The results of the FFT are closed to the fitting values. The work is helpful for obtaining the eccentricity error of gear from the testing results of transmission error, which is useful for forecasting the TE caused by eccentricity error and provides important reference for backlash compensation and control.

Two Typical Synoptic‑Scale Weather Patterns of Dust Events over the Tibetan Plateau

Xingya Feng,Rui Mao,Dao‑Yi Gong,Guangjian Wu,Cuicui Shi,Guohao Liang,Yufei Wang 한국기상학회 2023 Asia-Pacific Journal of Atmospheric Sciences Vol.59 No.4

Synoptic-scale weather systems play dominant roles in inducing high tropospheric dust over the Tibetan Plateau (TP). However, few studies have summarized the typical synoptic-scale weather patterns when high tropospheric dust occursover the TP, as well as the difference between the distribution and transport methods of dust under weather patterns. Basedon dust optical depth (DOD) from remote sensing data and reanalysis data during 2000 to 2019, two typical synoptic-scaleweather patterns (T1 and T2) in the middle troposphere in association with high DOD in spring over the TP were obtainedby using the self-organizing map (SOM) clustering method. The results show that the T1 features a deep trough over theAltai Mountains and the westerly wind increases over the TP. As a result, dust is transported from the Taklimakan Desertand Qaidam Basin to the upper troposphere and extends to the TP and northern China. T2 shows a low-pressure system overthe western TP and decreased westerly winds over the TP, resulting in dust from the Taklimakan Desert, Qaidam Basin, andwestern TP to downstream areas. T1 (T2) contributes more to DOD over the eastern (western) TP. Therefore, we believe thata small increase (decrease) in DOD in the western (eastern) part of the TP from 2000 to 2019 may be related to an increase(decrease) in the occurrence of the T2 (T1). This work may provide a new possibility for projecting dust transport and itsinfluence on tropospheric dust over the TP.

Nanocomposites of Polypropylene and Halloysite Nanotubes Prepared by a Novel Vane Mixer

Xiaochun Yin,Sai Li,Liang Wang,Guangjian He,Zhitao Yang 한국고분자학회 2017 폴리머 Vol.41 No.2

Halloysite nanotubes (HNTs) were used to prepare polypropylene (PP) nanocomposites through a novel vane mixer. The effects of melt blend time and halloysite content on properties of composites were investigated. SEM analysis was performed to show that HNTs were well dispersed in PP matrix with the increase of mixing time. DSC showed both the degree of crystallinity and crystallization temperature increased due to the introduction of HNTs into PP, which indicating a potential nucleation effect induced by the nanotubes. TGA illustrated that the presence of HNTs had two opposite effects on the thermal behavior. A surface catalytic action of the halloysite speeded up thermal degradation of PP. However, this effect was reduced with improved HNTs dispersion. Rheological investigations revealed that rheological properties were significantly increased by the addition of low fraction of halloysite to PP. The 2 wt% HNTs nanocomposites reached maximum tensile strength because HNTs dispersed evenly in PP.