Analysis and experiments of potato impact damage during the process of bagging and unloading

High potato damage and peeling rates have been caused by the potato loading and unloading bag device. It is also unclear on the impact damage. In this study, a potato loading and unloading bag device test bench was constructed to reduce and prevent losses. Two aspects were mainly taken to optimize the structure: the potato collection device and the unloading device. A mechanical structure was adopted with the dual buffering of buffer rollers and limiting rollers, in order to reduce the impact damage of potatoes during bagging; Furthermore, two limiting rollers of "gather caching and separate bagging" mode were used to achieve uninterrupted harvesting for the high bagging efficiency; The lifting slide of the bag unloading device adopted the technology of "gradually decreasing with weight" to control the drop height of potatoes during bagging within a specific range, thus avoiding damage that caused by excessive drop height of potatoes. The position of the buffer roller was adjusted to determine the optimal movement trajectory of the potato, and then minimize the damage during potato bagging. The severity of the impact between potatoes and buffer rollers was evaluated to calculate the maximum contact stress. The main parameters of key components were then determined, according to the main structure and working principle of the device. The impact theory was analyzed during potato bagging. The key influencing factors were clarified on the potato skin damage. RecurDyn and EDEM were coupled to simulate the stress situation of potatoes under roller buffering and non-roller buffering states. The maximum collision contact force of potato blocks with roller buffering was reduced to 263.566 N, compared to those without roller buffering. Taking the conveying speed, buffer roller diameter, and feeding amount as the experimental factors, while the potato damage rate and skin breakage rate as evaluation indicators, a three-factor three-level orthogonal experiment was conducted using Box-Behnken neutral combination design function in Design-Expert. Variance analysis was also performed to analyze the impact of the interaction of various experimental factors on the evaluation indicators using the response surface method (RSM). The working parameters were optimized to determine the optimal values of each parameter, according to actual working conditions. A series of experiments were conducted to verify using an electronic potato impact detector. The results showed that the potato damage rate and skin breaking rate were 0.82% and 1.14%, respectively, when the conveying speed was 0.96 m/s, the diameter of the buffer roller was 83mm, and the feeding amount was 26 t/h. The peak impact acceleration was smaller than the critical damage threshold of potato impact acceleration. At the same time, the impact acceleration at the last point was much smaller than the initial one. The relative errors between the measured and the theoretical values after parameter optimization were 4.06% and 0.4%, respectively. The intensity of the potato impact decreased in a manner like wave, where the impact weakened gradually. Therefore, the potato bagging and unloading device achieved the expected goal of potato collecting and reducing loss. Field experiments showed that the potato damage rates were 0.97%, 1.32%, and 1.58%, respectively, and the skin breaking rates were 1.34%, 1.53%, and 1.87%, respectively, when the harvesting speeds were 0.6, 0.8, and 1.0 m/s, respectively. The high performance was all met the national standards.