Effects of loading conditions on cracks of corn stalk and power consumption of machine

Abstract: Because high moisture content of the new-harvested corn stalks in northern China, drying process is long under natural conditions in which limit instantaneous harvesting and bundling. Fracturing and laceration on corn stalks need to be adjusted for rapid drying of corn stalks and to overcome bundle below. In order to design corn stalk adjusting material device, two single factor experiments were designed according to loading forms including single-point direct pressure and three-point bending in this study. Each experiment included four levels as: internode and short axis, internode and long axis, node and short axis and node and long axis. Impacts of loading forms (single-point direct pressure and three-point bending), loading positions (internode and node) and loading directions (long axis and short axis) on the cracks, load and power consumption of corn stalks with the same moisture content were investigated based on single factor experiment design scheme during compression process. The results indicated that four main cracks were produced on the rind of corn stalks under two loading forms on the axial during the compression process. Four main cracks of each corn stalks showed up, down, left and right symmetrical distribution, a number of small cracks were also produced. The main cracks gradually extended with the increasing of the displacements. When the displacements reached 18 mm for the internode compression samples, the main cracks extended to the vicinity of the node, and continuously reached to compression. The main cracks then stopped expanding due to the constraints of the node. The main cracks extended to the entire length of the sample for the node compression samples, the depth of all cracks were equal to the epidermis thickness of the sample. This study showed that length and depth of the main cracks of two loading forms were the same, so the best adjusting ending displacement was set to 18 mm. With the same loading positions and loading directions, the displacements of main cracks produced by three-point bending and single-point direct pressure were similar, but the load and power consumption of two loading forms were different. Load and power consumption of three-point bending were lower than single-point direct pressure. With the same loading positions，loading directions and the displacements, load and power consumption of two loading forms from big to small were node and short axis, node and long axis, internode and short axis and internode and long axis. Load and power consumption of three-point bending were lower than single-point direct pressure. In the initial stage of compression, there was no significant difference in the average value of load and power consumption between single-point direct pressure and three-point bending. With increasing the displacements, the difference of load and power consumption between single-point direct pressure and three-point bending was gradually expanded. When the displacement reached the best adjusting ending point (18 mm), the average value of load of three-point bending significantly reduced about 55.5% more than single-point direct pressure (α=0.05). The average value of power consumption of three-point bending was reduced about 25.5% more than single-point direct pressure (α=0.05). These results provided the basis for designing corn stalk harvesting and adjusting device.