Application of a quasi-static stalk bending analysis to the dynamic response of rice and wheat stalks gathered by a combine harvester reel

Horizontal and vertical reaction forces of rice and wheat stalks gathered by a combine harvester reel were measured by the experiment system, newly developed in order to clarify dynamic response of the crop stalks related to the gathering performance and to discuss the application of a quasi-static stalk bending analysis to the determination of the reaction force of crop stalks under dynamic loading conditions. The experiment was conducted under five different loading speeds, and the effect of the loading speed on the reaction force was investigated. As the loading speed increased, the horizontal force had a large positive peak value, while the vertical force involved the change in the force direction and had a negative peak value, depending on the initial deflection shape of crop stalks. Thus, the results simulated by the stalk bending analysis involved a large amount of error, and limitations of the analytical method were identified. The experimental results were examined in terms of acceleration at the loading point during the gathering operation. The location of a positive peak in the horizontal reaction force and a negative peak in the vertical one coincided with that of the negative peak in the horizontal acceleration and the positive peak in the vertical one, respectively. These results indicated that the peak values under high loading speeds were due to the effect of the inertial force of the crop stalks. Further, the error in the simulated results under high loading speeds was investigated in terms of the direction of the acceleration force determined by the difference between the simulated and measured values. The direction of the acceleration force coincided with the loading direction during the gathering operation, and the error was shown to be the force required for the accelerated motion.