Investigation on cutting resistance characteristic of bucket wheel excavator using DEM and DOE methods

Abstract

As an important design parameter for bucket wheel excavator, the cutting resistance of the bucket wheel shows significant dynamic character and changes drastically under different work conditions. Therefore, this paper analyzes the trend of cutting resistance through a combination of discrete element method (DEM) and design of experiment (DOE). Firstly, the three-dimensional dynamic simulation of tool-particle cutting process is established using DEM. The accuracy of the DEM model is verified by the cutting resistance test. Based on DEM results, the cutting resistance, different flow regions and the contact normal stress distribution on the inside of the bucket were analyzed. Secondly, DOE method was used to analyze the changing regularity of the cutting resistance. With cutting speed, cohesion and particle size as variables, a total of 15 orthogonal working conditions were designed and simulated through DEM. Then, the response surface (RS) method is used to fit the original simulation results. The RS fitted results show that: (1) overall, the cutting resistance decreases as the particle size and cutting speed increase. A larger particle size will reduce the load weight of a single bucket by reducing the particle volume fraction, while a higher cutting speed will cause more particles to splash out of the bucket; (2) depending on different working conditions, the increasing of cohesion is able to increase the cutting resistance by increasing the cohesive force between particles, or reduce the cutting resistance through “big aggregates effect” which lowers the particle volume fraction.