A bioinspired tooth plate structures imitating convex structures on the head and body surfaces of dung beetles was presented and analysed using the discrete element method. Simulation results showed that compared with the regular tooth plates without bionic structures, the bionic crushing tooth plate offers a better performance and higher efficiency in crushing wet attapulgite clay. Based on the simulation results, a two-stage crushing machine was designed, produced, and validated through experiments. Experimental results confirmed that the developed crushing equipment with the bioinspired convex structures can effectively crush the attapulgite clay with high moisture content, which cannot be crushed by existing crushers due to the adhesion of the wet clay particles to the tooth plate surfaces. The produced crushing equipment has been applied for processing the attapulgite clay in China, and the design idea can be applied to develop other equipment for crushing rare earth minerals with high moisture content.

： As a new precision transmission system, the anti-backlash roller enveloping hourglass worm gear has been increasingly used in robot joint design, packaging production line, and CNC (computer numerical control) machine tools. In spite of that, a general theory used to analyze the classic single and double roller transmissions principles still remain uncovered. To solve this problem, unified engagement equation, induced normal curvature, lubrication angle, autorotation angle, entrainment velocity, helix angle and contact line equation are established for the first time and numerically investigated by utilizing Matlab code. The difference between the single-roller enveloping hourglass worm and the double-roller enveloping hourglass worm in terms of their transmission principle and transmission performance are theoretically clarified. Transmission efficiency experimental tests are conducted for both two roller enveloping hourglass worms. The results of our studies show that there is no significant difference between the two roller enveloping hourglass worms regarding their transmission efficiency. The anti-backlash single-roller enveloping hourglass worm (ASEHW) gear enjoy more advantages with respect to above key technical indicators than the anti-backlash double-roller enveloping hour glass worm (ADEHW) gear. In addition, the ASEHW gear are easier to fabricate, install, and calibrate compared with its counterpart. However, when eliminating gear backlash is taken into account, the ADEHW gears are more auto-adjustable. This study will laid a theoretical foundation for promoting the application of the anti-backlash roller enveloping hourglass worm gears and improving its related performance.

In gear transmission, temperature rise has a non-negligible impact on the accuracy, noise and transmission efficiency. However, there is no relevant research on the temperature rise of the anti-backlash single-roller enveloping hourglass worm (ASEHW) gear. To solve this problem, based on tribology principle and Hertz contact theory, the thermal power calculation method of the ASEHW gear was proposed for the first time and thermal analysis was carried out by Ansys software. The bulk temperature of the ASEHW gear under four different rotating speed (300 r/min, 600 r/min, 900 r/min, 1200 r/min) is calculated. The main factors causing temperature rise of the ASEHW gear are analyzed theoretically. Meanwhile, an experimental study is performed to verify the simulation results and validate the theory methods. The theory presented in this paper provides a solution for the thermal power calculation of ASEHW gear. This research provides a theoretical basis for further optimization of ASEHW gear.

Anti-backlash roller enveloping hourglass worm gear drives, as a new precision transmission system, has been extensively applied in robot joint design, and CNC (computer numerical control) machine tools. However, tooth profiles of the roller enveloping hourglass worms are spatial complex surfaces and very difficult to machine. The meshing and transmission properties such type of worm gear drive are especially sensitive to the errors in machining the tooth profiles of such worms. Thus, in order to improve the accuracy in machining their tooth profile surfaces and reduce the surface roughness, barriers to achieve precision machining of these complex surfaces have to be overcome. In the present study, an equation of grinding contact line for the roller enveloping hourglass worm gear drives with seven critical error parameters was for the first time established based on modern theory of gear meshing. Influence of each error parameter on the grinding contact line was decided through numerical analysis. Also, in order to find the best relationship between the grinding speed and the grinding feed rage, real contact patterns between the grinding rod and the machined worm tooth surface at different grinding speeds were observed using a metallurgical microscope and compared with the theoretical contact pattern calculated from the developed line of contact equation. Based on the obtained results, an innovative grinding method that can offset the loss of radius of the grinding rod was developed and a grinding process under the optimal rotational speed was presented. The proposed grinding process was then applied to generate the complex helical surface of a high precision roller enveloping hourglass worm. Outcomes of this study formed a profound theoretical and practical background for manufacturing and machining of the roller enveloping hourglass worm gear drives.

In this study, the moving particle semi-implicit (MPS) method is employed for numerical simulation of flow field in gearbox of high-speed railway trains so as to understand the lubrication mechanism and mode in the gearbox during high-speed operation. A high-fidelity 3D model for a high-speed train gearbox under actual working conditions is created for the first time. RecurDyn and ParticleWorks co-simulation is conducted to acquire the flow field distribution in the gearbox under the coupling of multi-fields and to calculate the churning losses. Effects of key parameters including rotation speed, viscosity, and immersion depth on the churning power losses of the gearbox are investigated to determine their influences on the lubrication performance of the gearbox. Those results form a theoretical base for futuristic optimization of the high-speed train gearboxes.

This paper proposes a single-roller enveloping hourglass worm gear design and verifies its advantages compared to the existing double-roller worm gear system and the conventional worm gear set. Our hypothesis is that the single-roller worm gear with appropriate configurations and parametric values can eliminate the backlash in mating gear transmission while maintaining advantages of the double-roller worm gears. Also, the self rotation of the rollers when they are in the worm tooth space (TS) will help the gear system to avoid jamming and gear tooth scuffing/seizing problems caused by zero backlash and thermal expansion. In order to test that hypothesis, a mathematical model for the single-roller enveloping hourglass worm gear is developed, which includes a gear engagement equation and a tooth profile equation. Using that model, a parametric study is conducted to inspect the influences of center distance, roller radius, transmission ratio, and the radius of base circle on the worm gear meshing characteristics. It is found that the most effective way in eliminating the backlash is to adjust the roller radius and the radius of base circle. Finally, a single-roller enveloping hourglass worm gear set is manufactured and scanned to generate a 3D computer model. That model is compared with a theoretical model calculated from the developed mathematical model. Comparison results show that both models match very well, which verifies the accuracy of the developed mathematical model and our initial hypothesis that it is possible to achieve transmissions with zero backlash by adjusting the design parameters.

The new precision transmission system-Anti-backlash roller enveloping hourglass worm gears are now widely employed in many industrial sectors such as robot joint design, packaging production line, and CNC (computer numerical control) machine tools. Therefore, it is of great interest to have knowledge of their corresponding transmission principles that are seldom discussed in the literature. Using the theories of differential geometry and gear meshing, the objective of this paper is to analyze and compare meshing characteristics of anti-backlash single- and double-roller enveloping hourglass worm gears in terms of their transmission principle, engagement equation, induced normal curvature, lubrication angle, autorotation angle, entrainment velocity, helix angle, and distribution of contact curves. The major differences between these two roller enveloping hourglass worms are theoretically investigated in this work. Our results show that the anti-backlash single-roller enveloping hourglass worm (ASEHW) gears provide better performance with respect to gear meshing and transmission than the anti-backlash double-roller enveloping hourglass worm (ADEHW) gears. In addition, compared with the ADEHW gears, the ASEHW gears are easier to fabricate, install, and calibrate. However, the ADEHW gears are more auto-adjustable in eliminating gear backlash. Our study puts forward a theoretical background for futuristic design, application, and promotion of the anti-backlash roller enveloping hourglass worm gears.