Discrete element method (DEM) simulation is an important method to analyze the interaction relationship between materials and equipment, and to develop machinery and/or equipment. However, it is necessary to input specific simulation parameters when establishing a DEM simulation model. In this study, the interval values were measured through angle of repose tests of fallen jujube fruit (FJF), and the simulation angle of repose tests for FJF were established with EDEM software (DEM Solutions Ltd. Edinburgh, Scotland, UK). Then, the Plackett-Burman design, steepest ascent search experiment, and center composite design experimental methods were utilized to obtain the specific values of the simulation parameters from the interval values. The results showed that significant influencing factors in the simulation angle of repose include the Poisson’s ratio, the static friction coefficient between FJF, and the static friction coefficient between FJF and the steel plate, for which the optimal values were 0.248, 0.480, and 0.309, respectively. The angle of repose tests’ results showed that the error was 0.53% between the simulation angle of repose (29.69°) and the angle of repose (29.85°). In addition, the flow rate test results showed that the average error was 5.84% between the physical and simulation tests. This indicated that the calibrated parameters were accurate and reliable, and that the simulation model can accurately represent the physical tests. Consequently, this study provides an EDEM model of FJF that was essential in designing machinery and equipment through the EDEM simulation method.

Low working efficiency is an important reason for the limited application of the traditional aspirated-air type jujube fruit pickup machine. In this study, a provoke-suction type harvester for ground jujube fruit (PSH) was designed, based on the principle of negative pressure suction after shoveling the jujube fruit mechanically. The main working parameters were analyzed and the structures of the key devices were designed. Then, a three-factor and three-level Box–Behnken method was used to evaluate the performance of the PSH. The results showed that the pickup rate, impurity rate, and working efficiency were 99.36%, 5.63%, and 1672.3 kg∙h−1, respectively; as the forward speed, provoke teeth buried depth, and airflow velocity were 0.21 kg∙h−1, 74 mm, and 26.4 kg∙h−1, respectively. Furthermore, the verification results showed that the pickup rate, impurity rate, and working efficiency were 98.05%, 5.97%, and 1591.2 kg∙h−1, respectively, moreover, the relative errors were 1.32%, 6.04%, and 4.85%, respectively, indicating that the parameter optimization model can accurately predict the test results. The working efficiency of the PSH was significantly improved compared with the traditional aspirated-air type jujube fruit pickup machine. This research can provide a reference for the development of the jujube fruit pickup machine.

No abstract

HighlightsA quadratic orthogonal rotation combination design was used to test the influences of four factors.The significant influence of each factor was obtained using the analysis of variance method.Interactions of the factors were analyzed using the response surface method.Abstract. To provide a theoretical basis for the design of harvesting and processing machinery for Glycyrrhiza glabra stems and for energy conservation during processing, the bending characteristics of G. glabra stems were studied. The comprehensive influences of four factors (loading position diameter, loading speed, span, and moisture content) on the bending characteristics of G. glabra stems were tested using a quadratic orthogonal rotation combination design. The results indicated that the single factors loading position diameter and span had a significant influence on the bending characteristics of G. glabra stems. In addition, as the loading position diameter increased, the maximum bending force and bending energy of G. glabra stems tended to increase, while the bending stress tended to decrease. As the span increased, the maximum bending force and bending energy of G. glabra stems tended to decrease, while the bending stress tended to increase. As the moisture content increased, the maximum bending force and bending stress of G. glabra stems tended to decrease, while the influence on bending energy was not significant. The loading speed had no influence on the bending characteristics of G. glabra stems. The interaction between loading position diameter and span had a significant influence on the maximum bending force and bending energy, and the interactions between loading position diameter and moisture content and between loading speed and span had a significant influence on the maximum bending stress. This study on the bending characteristics of G. glabra stems can provide a theoretical basis for the design of harvesting and processing equipment and for the pretreatment of G. glabra stems. Keywords: Bending characteristics, Licorice, Loading position, Loading speed, Moisture content, Span.