Construction and Analysis of a Discrete Element Model for Calculating Friction Resistance of the Typical Rotary Blades.

The measurement of friction resistance on rotary blades presents challenges, and the characteristics of friction resistance for different parts of rotary blades remains uncertain. To tackle these problems, a model that based on Coulomb's friction law combined with the DEM method was proposed to calculate the friction resistance. The three typical rotary blades were selected, including IT-type blade (ITTB), L-type blade (LTB), and J-type blade (JTB), as the research objects. Each rotary blade was divided into six parts, namely P1, P2, P3, P4, P5, and P6, based on their lengthwise, curved, the sidelong part, and both inner and outer sides. The simulation parameters of the soil model were calibrated by the cone penetration test, and the friction resistance calculation model was verified by the flat plate sliding friction test. Finally, the discrete element model of blade-soil was adopted to quantitatively and visually analyze the friction resistance characteristics and variation for different parts of rotary blades. The results showed the penetration resistance of simulated and measured were in excellent match, with a relative error of 4.26 %. The relative error between the simulated and physical results for friction resistance was 4.70 %, which illustrated the accuracy of the friction resistance calculation model. The analysis of the friction resistance revealed that different parts presented different variation, relating to their structural characteristics. For the three typical rotary blades, the friction resistance for the P2, P4, and P6 on the inner side were greater than that of the corresponding P1, P3, and P5 on the outer side. The sum of the average friction resistance of P4 in the curved part and P6 in the sidelong part accounted for more than 50 %, and the sum of the average friction resistance per unit area accounted for more than 60 %. However, the total area proportions of P4 and P6 in ITTB, LTB, and JTB were 16.15 %, 26.13 %, and 17.30 %, respectively, bearing most of the friction resistance in a smaller area. Therefore, it is possible to optimize the design and surface treatment for the curved and sidelong parts to achieve the effect of reducing resistance and wear. This study provides a new technical reference regarding the optimized design for different parts of rotary blades to achieve targeted resistance and wear reduction.