## 1 Introduction  
Corn is one of the major food crops in China, and with the increase in planting area, the amount of corn straw resources as a by--product of agricultural production is also increasing, accounting for 42.87% of the total straw of the three major food crops [1]. In the process of achieving \"carbon peaking\" and \"carbon neutrality\", the potential use of maize straw is increasingly valued, playing a huge role in the manufacture of biofuels [2], livestock feed [3; 4; 5], soil nutrients [6; 7; 8], and composite materials [9; 10; 11], and straw cutting and shredding are prerequisites for the effective use of crop straws, from silking to shredding for field return [12; 13; 14]. The coarse fiber of corn straws at maturity formed, and the cutting process, requires a large cutting force to ensure that the shredded segments of corn straws meet the requirements [15], so the development of cutting and shredding equipment dedicated to corn straws to improve the shredding quality of corn straws is essential to promote the comprehensive utilization of corn straws. The discrete element method can reveal the interaction mechanism between cutting components and corn straw, which shows great advantages in designing and optimizing key components of the corn straw shredder [16]. The discrete element method is applied to the study of straw cutting and crushing, the difficulty is how to accurately establish the straw model and calibrate the parameter values. [PERSON] et al. [17] established multiple spherical particles with the same diameter and generated a discrete element model of straw by means of spherical particle stacking, and the resulting model was a rigid body; [PERSON] et al. [18] used the same spherical particles to build a discrete element model of round bale corn straw breaking and calibrated the contact parameters between materials using the stacking angle method; [PERSON] et al. [19] conducted a study on corn straw, straw node and inner flesh mixtures to the contact parameters were calibrated, and the discrete element models of straws, straw nodes, and inner flesh were developed separately by using the spherical particle stacking method. These studies considered corn straw as homogeneous material and used the same kind of particle spheres to build the discrete element model, which ignored the mechanical properties of the different structures of corn straw skin and inner flesh and the discrete element model could not be simulated for fragmentation. In order to ensure the accuracy of the discrete element model, some scholars selected different contact models to establish the discrete element model of crop straws: For example, [PERSON] et al. [20] used the Hertz-Mindlin with JKR model to establish the discrete element model for the epidermis and inner flesh of corn straws by combining mechanical tests and numerical models, and conducted straw baling tests; [PERSON] et al. [21] used the Hertz-Mindlin with JKR model to calibrate the parameters of the discrete element simulation model for dense forming of corn straw meal, and verified the availability of the relevant parameters through the corn straw meal mold hole compression test. The accuracy of the discrete element model was further improved by building separate discrete element models for different structures of corn straw (epidermis and inner flesh), but the method was mostly used for compression molding simulations. In order to explore more deeply the accuracy of the discrete element method to simulate corn straw crushing, [PERSON] [22], [PERSON] [23], [PERSON] [24], and [PERSON] [25] used the discrete element method Hertz-Mindlin with bonding to construct the corresponding straw models, respectively, which can reflect its relevant mechanical properties through bond rupture when subjected to external forces. Therefore, this model can be considered for discrete element modeling of corn straw fragmentation.