Walnut shell breaking is an important aspect of post-harvest processing. However, shell-breaking results differ significantly from ideal uniaxial compression results. In this paper, the effect of multipoint loading on the walnut shell-breaking mechanism by combining FDEM with cohesive elements was investigated. The model for walnuts was created using micro-X-ray CT scans and experimental data. Simulation parameters describing mechanical properties were calibrated through modeling the uniaxial compression experiment. The loading point locations were quantitatively described in terms of top and azimuthal angles. The results show that the crack ex-tension rate increases with the number of loading points and the singularity value, and the maximum value of the four-point loading speed is about 450 m/s. The number of cracks is only related to the number of loading points and is not related to the location of the loading point. In addition, three loading methods are proposed, and the fastest crack propagation rate is achieved when the azimuthal angle of four-point loading is 0, 150, 180, and 330, respectively. These findings may serve as a theoretical foundation for studying shell crushing.

Construction method of quantitative evaluation model for the maturity of Korla fragrant pear

For a fast and accurate evaluation of the values of damaged fragrant pears, a prediction method of the damage degree of Korla fragrant pears was proposed. To study variation laws of damages of fragrant pears under different volumes of squeezing deformation, the partial least squares regression (PLSR), the generalised regression neural network (GRNN) and the adaptive neural fuzzy inference system (ANFIS) were chosen to predict the damage degree of fragrant pears and establish the optimal prediction model. The results demonstrated that with the increase of ripeness or deformation value, the damage degree of fragrant pears increases gradually. For performance comparison of prediction models based on PLSR, GRNN and ANFIS, it was found that the trained PLSR, GRNN and ANFIS can all predict the damage degree of Korla fragrant pears. The ANFIS, which inputs the membership function of dsigmf (R² = 0.9979, RMSE = 46.6) and psigmf (R² = 0.9979, RMSE = 46.6), achieves the best performance. Research results can provide theoretical references to the evaluation of the commodity value of damaged fragrant pears, quality grading of fragrant pears and design of the picking machine.

This study designed two levels of quantitative fertilizer distribution to investigate precision fertilization applications in orchards in South Xinjiang, China, which have vast rows and narrow plant spaces. The machine comprised a base frame, a ditching device, a fertilizing apparatus and an earth-covering device. The design parameters of the flow stabilization screw, conveyor screw and single-ring fertilizer quantity were summarised using theoretical analysis. The single-ring fertilizer quantity of the conveyor screw was verified via an experiment by combining EDEM software. Three-factor and three-level Box–Behnken tests were conducted using the spiral rotation speed of the conveyor, advancing of the speed and the opening degree of fertilizer outlet as the test factors and using the coefficient of variation (CV) of uniformity as the test index—thus obtaining the optimal working parameters. The simulation test results revealed that the single-ring fertilizer quantity of the fertilizing apparatus was 145.6 g, fulfilling the design requirements. The prototype testing results showed that the CV of uniformity was 6.521% when the spiral rotation speed of the conveyor, the opening degree of the fertilizer outlet and the advancing speed were 66 RPM, 42% and 2.7 km/h—thus meeting the needs of precision fertilization operations. The two designed levels of the quantitative fertilizer distributors were applied to fertilization processes in orchards with wide-row spaces and narrow plant spaces in South Xinjiang, China and were able to effectively carry out the precision fertilization applications. These data could also provide references for the optimization of spiral quantitative fertilizer distributors.