## 1 Introduction  
In the context of the national potato as a staple food strategy, the scale of potato cultivation in China has increased [1] and the demand for mechanized potato harvesting has increased accordingly, and the potato-soil separation stage effect is one of the important criteria to measure the performance of harvesting machines. Nowadays, oscillating separation screens are widely used in potato harvesters because of their simple structure and high efficiency in potato-soil separation. However, the current research on oscillating sieves mainly focuses on reducing potato damage and improving the rate of bright potatoes, while little research has been reported on the crushing characteristics of the soil during separation. In the process of potato-soil separation, soil crushing and potato skin damage are contradictory: the more significant the soil crushing, the more serious the potato damage. Therefore, it is necessary to analyze soil crushing characteristics in order to obtain reasonable parameters for the oscillating sieve, so that potato-soil separation is maximized and potato damage is reduced. The analysis of soil forces and motion in the actual harvesting process is too complex, and there are many limitations in conducting experiments, making it difficult to conduct in-depth research. In 1971, the discrete element method (DEM) was first applied by [PERSON]. Nowadays, DEM is widely used in agriculture [2]. It provides a new method to investigate soil motion and fragmentation characteristics and can simulate the actual working conditions and visually reflect the soil motion and force situation, which is conducive to efficient and convenient analysis. However, due to the diversity of soil types, the physical parameters of soil in different regions are very different. In order to ensure the accuracy of the parameters used in the simulation model, the physical parameters of the soil need to be calibrated. In the discrete element simulation, density, Poisson's ratio, elastic modulus, static friction coefficient, rolling friction coefficient, and collision restitution coefficient are the parameters set in the model [3]. Some of the parameters are simple to measure whilst others are quite complicated. The complexity depends mostly on the accuracy of the shape and size of the model particles and if the DEM model established by direct measurement parameters exhibits the same bulk characteristics as the real situation [4]. Particle size often has to be increased because of limitations in computation [5] and the particle shape cannot always be accurately characterized. Thus, even if the parameter values can be directly and precisely measured, it does not mean that the simulation will show the same level of accuracy at a bulk level. Therefore, some methods should be adopted to calibrate the simulation parameters [3]. Applications for the calibration of parameters for materials such as coal dust, manure, fertilizer. and soil have been reported by a large number of national and international authors. [PERSON] et al. [6] calibrated coal dust particles and [PERSON] [7] calibrated parameters for pig manure particles using, these material particles are similar to soil particles and are all bulk materials. In order to save computing time in modeling and simulation, they used spherical particles of equal diameter with a magnification of 10-50 times the size instead of fine particles, as did [PERSON] [8], [PERSON] [9], and [PERSON] [10], who used soil particles with radii of 1, 5, and 8 mm, respectively, for their discrete element simulations. [PERSON] [11] and [PERSON] et al. [12] used the JKR (Johnso-Kendall-Roberts) surface energy to simulate the surface adhesion of materials with different moisture contents. When the JKR value and the particle radius are the same, it indicates that the material has medium moisture content at this time. The larger the JKR value, the higher the moisture content and when the JKR is 0 the moisture content is also 0 and the material is dry at this time. [PERSON] et al.