In a simulation model of the process of corn straw crushing, its physical parameters and the model itself influence the accuracy of the numerical calculations of the discrete element method. This study attempts to improve the simulation accuracy of the crushing process and to find the optimal combination of parameters. Based on the Hertz-Mindlin with Bonding contact model, multiple particle replacement and bonding programs written using Visual Studio were imported through the application programming interface (API) of a discrete element method (DEM) model to establish three particle-bonding materials for a numerical simulation of the crushing process. Using results of mechanical corn stalk tests, DEM simulations of impact fracture, compression fracture, and bending fracture were conducted to determine the optimal combination of parameters. The resultant DEM-parameter combination led to simulation errors of 3.83%, 5.95%, and 7.86% in numerical simulations of impact fracture, bending fracture, and compression fracture of corn stalks, respectively. The performance of the corn stalk DEM using the proposed optimal parameter combination was validated using a 9RS-60 corn stalk crusher, revealing that the numerical simulation error was 8.77%. This study can improve the accuracy of the discrete element method in the simulation of the corn straw breaking process.

Low productivity and high electricity consumption are considered problems of the hammer mill, which is widely used in current feed production. In this paper, the mechanical properties of corn grain ground by a hammer mill were analysed, and the key factors affecting the performance of the hammer mill were determined. The single-factor experiment and three-factor, three-level quadratic regression orthogonal experiment were carried out with the spindle speed, corn grain moisture content and number of hammers as experimental factors and the productivity and electricity consumption per ton as evaluation indexes. The results showed that the order of influence on the productivity was spindle speed > corn grain moisture content > number of hammers and that the order of influence on the electricity consumption per ton was corn grain moisture content > spindle speed > number of hammers. The parameters were optimized based on the response surface method with the following results: the spindle speed was 4306 r/min, the corn grain moisture content was 10%, and the number of hammers was 24. The validation experiment was carried out with the optimal parameters’ combination. The productivity and electricity consumption per ton were 988.12 kg/h and 5.37 kW·h/t, respectively, which were consistent with the predicted results of the model.

Aiming at the problems of large vibrations and noise of a working stalk rubbing machine, this paper took the 9R-60 rubbing machine as the research object and used the B&K modal test system and the vibration test system to analyse the modal and no-load conditions of the whole machine. Through analysing modal test data, it was concluded that the first five natural frequencies of the machine were 95.262 Hz, 144.386 Hz, 288.198 Hz, 313.719 Hz and 326.140 Hz. The results showed that spindle rotation had a more significant effect on the vibration than the feed chain rotation; the maximum vibration acceleration occurred at the small motor frame at a spindle speed of 1700 r·min-1 and a feed chain speed of 0.65 m·s-1, which was 135.539 m·s-2. The distribution of the amplitude statistical characteristics of the vibration signals follows the normal distribution and belongs to the stationary random process. The vibration was a self-excited vibration of the rotating machinery caused by the rotation of the main shaft and a forced vibration excited by the rotation of the same shaft. The research provides a direction for further research on the vibration characteristics of the rubbing machine under load conditions, and provides a theoretical basis for the subsequent vibration reduction design.

To improve the working performance of hammer mill, cutting-edge hammer and oblique hammer were designed in this study. The advantages of new hammers were theoretically analyzed. The grinding process of corn grain with different hammers was studied by discrete element method (DEM) and experiments. Discrete element simulation results showed that under same rotor speed conditions, the cutting-edge hammer had highest bond-breaking efficiency in corn grain model. The oblique hammer could reduce the incident angle of corn grain and improve sieving efficiency. The motion trajectory of corn grain in grinding chamber was relatively dispersed and similar when using common hammer and cutting-edge hammer, and the motion trajectory was more concentrated when oblique hammer was used. The experimental results showed that both cutting-edge hammer and oblique hammer could improve the working performance of hammer mill. The productivity of hammer mill could be improved by using cutting-edge hammer, electricity consumption per ton and temperature rise of feed could be reduced by using oblique hammer, and the experimental results were consistent with simulation results and theoretical analysis results. The research results can provide references for the design of new hammer and the grinding process simulation of other agricultural materials.

Larger vibration and noise often exist in agricultural machinery due to the harsh working environment and high power. The rubbing machine is one of the indispensable pieces of equipment in the agriculture and livestock industry, and it is affected by the vibration of large constraints on its promotion and use. To reduce the vibration of the rubbing machine, the vibration characteristics of the spindle rotor were first analysed by modal simulation, thus determining the larger contributions to the spindle rotor vibration. Second, aluminium foam material was installed in the large deformation part of the spindle rotor. Its vibration reduction and energy absorption characteristics were used to optimise the vibration reduction design by increasing the damping. Third, a steel ball impact test was conducted to analyse the vibration characteristics of the optimised spindle rotor. The results show that the maximum impact accelerations were reduced by 28.4% and 64.75% in the axial and radial directions, respectively, and the impact energies were reduced by 67.3% and 90.65% in the axial and radial directions within 2 s of impact collision, respectively, indicating that the optimised spindle rotor damping increased significantly. In addition, the vibration reduction effect of the optimised rubbing machine was verified by a bench test. By measuring the change degree of the static component of the spindle rotor vibration, the axial, radial, and vertical vibrations of the spindle rotor were improved by 5.78%, 10.32%, and 23.96%, respectively. Therefore, optimising the spindle rotor with aluminium foam material can reduce the vibration generated during the impact of the material on the spindle rotor. The rubbing machine’s vibration, damping, and energy absorption were also realised in real working conditions.