The Critical Cutting Speed for Cane Stubble Stems and Optimization of Deep Vertical Rotary Tillage Blade

Abstract

When performing deep vertical rotary tillage (DVRT) in sugarcane stubble fields, the weakly supported soil condition (broken-soil state) results in insufficient fragmentation of cane stubble stems during cutting.

This study developed a coupled FEM-DEM simulation model of the stem-soil-blade system under weak soil support conditions. The model was used to evaluate three common DVRT blades: the large bending angle blade (LBAB), the horizontal rotary tillage universal blade (HRTUB), and the stubble shredding blade (SSB), along with their rectangular and serrated extensions. The analysis focused on the influence of blade geometry and structural parameters on critical cutting speed (CCS) and maximum cutting force (MCF). Geometric parameters of the HRTUB-Circular Sawtooth (CS) configuration, which demonstrated optimal cutting performance, were then optimized. Experimental results showed that with blade edge thicknesses of 1–3 mm, the average CCS values for LBAB, HRTUB, and SSB reached 12.8 m/s, 12.7 m/s, and 12.8 m/s, respectively, while the average MCF measurements were 322.2 N, 323.4 N, and 327.1 N. When implementing HRTUB-CS blades with a 1.5 mm edge thickness under optimized tooth parameters (8 mm pitch and 0.6 height-to-pitch ratio), CCS decreased to 7.9 m/s and MCF decreased to 226.1 N. These values represented reductions of 31.3%, 30.7%, and 33.1% for CCS, and 23.1%, 23.5%, and 24% for MCF compared to LBAB, HRTUB, and SSB, respectively. These findings provide valuable insights for optimizing DVRT cutters and offer methodological references for other mechanical stubble return operations.