Abstract
The longitudinal axial flow threshing cylinder of the full feeding rice combine harvester is widely used in China and works with violent vibration. To explore the source of the excitation affecting the vibration and to reduce the vibration, a finite element modal analysis and multipoint input and multipoint output (MIMO) modal test were performed to solve the natural vibration characteristics. By analyzing the excitation frequency, we concluded that the main reason for the resonance was the coupling between the rotation frequency of the threshing cylinder and the first natural frequency. To avoid the influence of resonance and realize a lightweight design, we proposed a combination of size optimization and topology optimization. The second rotation orthogonal combination test was designed to analyze the first natural frequency, maximum stress, and maximum deformation of the threshing cylinder, and the threshing cylinder was reconstructed as a central symmetrical structure to balance the rotational inertia force. The field experiment results showed that the amplitudes of the optimized threshing cylinder were significantly lower than those of the original threshing cylinder. This study provides ideas for solving the vibration characteristics of rotating parts and provides an important reference for the design of vibration reduction and weight reduction of key parts in the field of agricultural machinery.
Highlights
The threshing cylinder is an important working part installed in combine harvesters, which has the functions of threshing, conveying, and separating stalks [1]
In analyzing the specific structure of a threshing cylinder, we proposed a combination of size optimization and topology optimization to improve the first natural frequency of the threshing cylinder to avoid the range of excitation frequency
To combine the two methods of size optimization and topology optimization to achieve the best performance of a threshing cylinder, two factors and five levels of a quadratic rotation orthogonal combination test scheme were designed, in which the separation bar was hollow with different diameters, and the fixed plate was topologically optimized by deleting different mass fraction materials
Summary
The threshing cylinder is an important working part installed in combine harvesters, which has the functions of threshing, conveying, and separating stalks [1]. The vibration problem has become a bottleneck that affects the progress of the combine harvester in the direction of high efficiency, reliability, and comfort, and most of the traditional studies are mainly focused on optimizing the static working parts, and rarely involve the optimal design of the rotating parts. The natural frequencies and excitation frequencies of the threshing cylinder were analyzed by resonance analysis, and an optimal scheme for changing the natural frequency was obtained by a quadratic rotation orthogonal combination test by combining size optimization and topology optimization. This study can provide the basis for obtaining the vibration characteristics of the structure and can provide an important reference for vibration reduction and weight reduction of the key components in the field of agricultural machinery
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