Compression and Stress Relaxation Characteristics of Alfalfa during Rotary Compression

Jiajia Fang, Haijun Li, Jian Wang, Mingshao Yang, Zeying Zong, Yong Zhang


In order to reduce the power consumption of the round baler and improve the quality of the bale, the compression and relaxation characteristics of alfalfa were investigated with respect to moisture content, feeding speed, and steel roll speed. Experimental trials were performed by using a steel-roll fixed chamber round baler rotary compression test platform. Three moisture contents were prepared, 18%, 21%, and 24%. The feeding speeds were set at 1.11 m·s-1, 1.39 m·s-1, and 1.67 m·s-1, and the steel roll speeds were 106 r·min-1, 126 r·min-1, and 146r·min-1, respectively. The experimental data for these trails were collected and three compression models and a generalized Maxwell model were fitted to the pressure, density, or time data. The maximum compression pressure decreased with the increase of moisture content and increased with the increase of feeding speed, while the steel roll speed had no significant effect on the maximum compression pressure. The stress relaxation time decreased with the increase of moisture content, feeding speed and steel roll speed. The equilibrium stress decreased with the increase of the steel roll speed and moisture content and increased with the increase of the feeding speed. All compression models had a good fit for the experimental data.


Compression characteristics; Stress relaxation; Alfalfa; Large round baler; Rotary compression

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