In order to evaluate the impacts of parameter uncertainty and nonparametric uncertainty on the natural characteristics of a dual-rotor system, a nonparametric probabilistic method based on random matrix theory is proposed. In this paper, a nonparametric Riccati whole transfer model is derived based on the maximum entropy principle and the random matrix theory. It is used to model a dual-rotor system with nonparametric uncertainty, as well as to calculate the natural characteristics of the system. Furthermore, the impacts of parameter uncertainty and nonparametric uncertainty on the natural characteristics at the intermediate support element and at the disk-shaft element are discussed using numerical simulations, and the results are compared with related references. The results show that at the same level of uncertainties, the effect of nonparametric uncertainty is often more significant than that of parameter uncertainty. The effects of uncertainties also increase with the level of uncertainties. The results of this paper provide a theoretical basis for the design of uncertain dual-rotor and multi-rotor systems.

Superfine grinding, involving the fragmentation mechanism of wheat bran cell tissue, is being employed by milling industry. In order to determine the effect of wheat bran cell tissue on the fragmentation mechanism when using superfine grinding, a technical scheme of the nonlinear finite element numerical simulation method based on LS-DYNA is proposed in this paper. The physiological characteristics of wheat bran structural layers including outer pericarp, intermediate layer and aleurone layer are examined first, and then the mechanical properties of wheat bran structural layers and their effects on the super fine grinding process are analyzed. Secondly, the explicit time integration algorithm of LS-DYNA is introduced, and the application feasibility of LS-DYNA in the analysis of wheat bran superfine grinding mechanism is discussed. Finally, the specific application of LS-DYNA in the determination of grinding form and load, the selection and design of the grinding media and the selection of grinding temperature are discussed in detail in the process of superfine grinding for wheat bran cell tissue. The above research provides a theoretical basis for selecting and developing the equipment and technology suitable for wheat bran superfine grinding, and lays a theoretical foundation for enhancing the quality and efficiency of wheat bran superfine grinding.

The unbalanced magnetic pull (UMP) is one of the main vibration sources of the motorized spindle. A calculation model of UMP in a synchronous motorized spindle considering the magneto-thermal coupling is proposed in this paper. The finite element analysis models of the electromagnetic field and the temperature field of a motorized spindle are first established. Then a two-way coupling analysis method considering the effect of temperature variations on electromagnetic material properties of the motor is proposed. An experiment is conducted to verify the efficiency of this method. The thermal deformations of the spindle are calculated and used to analyze the air-gap variations between rotor and stator of the built-in motor. The 3D finite element electromagnetic model is adopted to calculate the UMP in the motorized spindle. The analysis results show that the eccentricity caused by thermal deformation can generate large UMP in the motorized spindle.

Effects of low temperature and washing on the vibration superfine grinding performance of wheat bran