Design parameter optimization for tillage blade of crank-type rotavators considering strength and weight

This study conducted design parameter optimization for tillage blade of a crank-type rotavator (45 kW rated power, eight blades). Load, stress, and mass of the blade were obtained from field tests and a commercial program, and design parameter optimization was carried out with them. Selected design parameters were the heights of front and rear ribs, and thickness of the blade. And objective function was minimizing the mass of the blade. Optimization for the nominal tillage blade was conducted considering two different cases of thickness profile: constant thickness of tillage blade in the length direction and inclined thickness. In addition, it was conducted in two different cases of safety factor to consider the changes of tillage load depending on the soil characteristics: higher safety factor on the stress than the nominal tillage blade and lower safety factor. From the results of the optimization for the nominal tillage blade, the mass of the blade reduced by 3.2% under the same safety factor condition. And results of the optimizations with various conditions showed that higher safety factor increased the mass of the blade. The inclined blade also increased the mass of the blade to have the same safety factor. The results of the sensitivity analysis provided that the design parameter affected most on the stress and mass of the blade was thickness of the blade. Therefore, determining appropriate safety factor and thickness of the blade is important in designing the tillage blade. Design parameters of this study do not affect on the surface area of the blade, which is the important influence factor for the tillage performance. Thus, the process used in this study will contribute to the design of tillage blade in minimizing the mass while having similar tillage performance. Further studies on optimization of the shape of the frame and optimization of geometrical structure of the blade will be needed.