Search

Crawler combine harvesters are mostly used in paddy field operation in South China. The field operation load is complex and variable, which leads to fatigue fracture and other accidents of gearboxes under the impact of variable loads and seriously affects the trouble-free working time of the whole machine. In order to solve the problem of high fault rate of gearboxes of crawler combine harvesters, the single HST hydro-mechanical differential steering gearbox developed by the team is taken as the test object, this study designs and builds the gearbox assembly fatigue test bench, and then carries out the fatigue test of differential steering gearboxes. The test results show that the test bench can well test the comprehensive working performance and durability of differential steering gearboxes, and has advantages of simple structure, convenient installation, etc. This is of great significance to study the fatigue damage rule of differential steering gearboxes, optimize and improve the mechanical structure of gearboxes and reduce the fault rate of its internal parts in the future.

Strong impacts and vibrations exist in various structures of rice combine harvesters in harvesting, so the bolt connection structure on the harvesters is prone to loosening and failure, which would further affect the service life and working efficiency of the working device and structure. In this paper, based on the vibration signal acquisition experiment on the bolt and connection structure of the vibrating screen on the harvester, failure feature identification is studied. According to the sensitivity analysis results and the primary extraction of the time-frequency feature, most features have limitations on the identification of failure features of vibrating screen bolts. Therefore, based on the establishment of a high-dimensional feature matrix and multivariate fusion feature matrix, the validity of the feature set was verified based on the whale optimization algorithm. And then, based on the SVM method and high-dimensional mapping of the kernel functions, the high-dimensional feature matrix is trained by the LIBSVM classification decision model. The identify success rates of time domain feature matrix A, frequency domain feature matrix B, WOA-VMD energy entropy matrix C, and normalized multivariate fusion feature matrix G are 64.44%, 74.44%, 81.11%, and more than 90%, respectively, which can reflect the applicability of the failure state identification of the normalized multivariate fusion feature matrix. This paper provided a theoretical basis for the identification of a harvester bolt failure feature. [ABSTRACT FROM AUTHOR]

The bolts and connections of each working part of a rice combine harvester can suffer from severe instantaneous impacts and alternating loads, and these strong impacts and loads cause instantaneous fracture and fatigue failure of the bolt face and even the loosening, detachment, and fracture of the bolt. The main vibration directions and the most complex vibration parts of the bolts and connections in the main working parts of a combine harvester under time-variable multiload excitation were obtained through the analysis of response signals in terms of time-domain and frequency–domain characteristics via a vibration response experiment. This study revealed that the random peak value of the vibrating screen is 12.5622, which is the severe impact and collision standard. For the vibrating screen, the local peak in the 4-Y direction was the main load of the destroying bolt connection (the impact reached 60.57 m/s2, 96.91 m/s2) and the vibration energy intensity in the 4-Z direction was mainly concentrated at 12.42 m/s2, which is the maximum vibration energy value in the three directions (the peak vibration value reached 109~115.68 m/s2), so the bolted connections of the vibrating screen are the most vulnerable to destruction. Therefore, a kinetic model and a microscopic response model of a vibrating screen were established via the centralized mass method to explore the kinetic response characteristics of bolted structures subjected to multiple excitation loads, thus providing a mathematical model for identifying the features of bolted connections based on static characteristics. [ABSTRACT FROM AUTHOR]

In the rainy season, which often has uncertain rainfall, crawler combine harvesters have difficulty traversing wet and soft rice fields. A large amount of clay is often accumulated on the track surfaces, resulting in frequent slipping and sinking, which greatly affects the operational performance and harvesting efficiency of crawler combine harvesters. To address this issue, this paper proposes a high-traction track grouser based on the structure of an ostrich's foot sole. First, a traction force mathematical model is constructed to analyze the interaction between a track grouser and wet and soft rice fields, and parameter optimization is conducted. Then, the bionic information of a dung beetle's non-smooth body surface is extracted, and the surface of the track is designed with biomimetic convex hull patterns based on the geometric similarity principle and adhesive experiments. Finally, the analysis results indicate that the optimized track grouser significantly improved the traction of the track in wet and soft rice fields. For the track plate with a bionic desorption convex hull pattern, a convex hull diameter of 6 mm, convex hull spacing of 8.25 mm, and convex hull height of 3 mm led to good adhesion reduction and desorption effects in wet and soft soil. [ABSTRACT FROM AUTHOR]

The complex mechanical system of a rice combine harvester not only has various excitation sources, but also, the vibration transmission path between each working device and the vibration contribution characteristics to the frame are not clear, so it is difficult to perform a reduction vibration design for the sharp vibration of the rice combine harvester frame. Therefore, based on the comparison and improvement of multiple classical transfer path analysis methods, this paper analyzed the vibration transfer characteristics and transfer characteristics of each harvester by the discrete time matrix method and operating path method. In the Experimental section, through the vibration characteristic experiment firstly, this paper obtained the power spectrum variation and the most needed optimized path in the transmission path of each device under each operating condition. Secondly, through frame simulation analysis under the exciting force, we obtained the vibration damping areas that needs to be optimized. Finally, the damping optimization experiment connected with the vibration characteristic experiment, and the excitation force simulation analysis was performed. The results of the damping optimization experiment displayed that the maximum change value of the vibration acceleration of the cutting table decreased from 7.862 m·s−2 to 3.522 m·s−2, decreasing by 55.2%, and the peak amplitude of the multipoint test in the cab was 5.4, 5.3, 1.7 and 2.0 μm, respectively, which was significantly reduced, so the optimization effect was significant. This study provides theoretical support for the vibration reduction optimization of a rice combine harvester frame. [ABSTRACT FROM AUTHOR]

As a multi-source vibration machine, the complex vibration of the combine harvester has caused many effects on various components. In this paper, the dynamic response of the plate and shell on the combine harvester is studied, and the influence of various factors on the vibration of the plate and shell is determined. The structure of the plate and shell is optimized, and the scheme of structural optimization that replaces the finite element model with the surrogate model is developed. The structure is designed with Latin hypercube design (LHD), the model of response surface is generated based on the Kriging model, and then the parameters are optimized by a multi-objective genetic algorithm (MOGA). It is realized that the first-order natural frequency of the plate is increased by 14.6% under the same mass, avoiding the resonance range of the main excitation of the machine. At the same time, its dynamic response under the multi-point force is also greatly decreased by 62.4%. [ABSTRACT FROM AUTHOR]

When rice stalk is impacted by the threshing bars during threshing process, the grain is separated but the rice stalk is also damaged. Damage of the rice stalk not only increases the energy consumption of process, but also results in small parts of the rice stalk being mixed with the grain increasing the difficulty of grain cleaning. The states of rice stalk before and after threshing were investigated by analysing the state response of rice stalks under the reaction of the threshing bars. The structural damage of rice stalks was analysed by comparing the relationship between the threshing force and the reaction tensile force, the bending force, and the pressing force during threshing. Damage modes were observed from the microstructure of rice stalks and rice leaves. The results showed that during rice stalk threshing, the force of the threshing bar was between 36.4 N and 121.0 N. Single rice grain and multiple grains are threshed, hollow stalks, stalk node and leaves are pressed damage and stalk root and stalk nodes maybe tensile damaged in threshing process. The microstructure of rice stalk following threshing was destroyed. The thin-walled tissues were completely deformed and the original structure was not visible. The main connections between the rice leaves were interrupted and flat, completely losing the normal shape of the original leaves. The research results revealed the level of the reaction force and microstructure damage of rice stalks. • Threshing force and reaction force reveals damaged distribution of rice stalk. • Rice stalk damage modes were obtained from microstructure after threshing. • Rice stalk is damaged during the process of grain threshing and separated. [ABSTRACT FROM AUTHOR]

Operating parameters such as threshing cylinder speed, concave clearance and bar spacing are the most important factors that influence the power consumption of threshing apparatus and grain loss ratio during the threshing process. In order to obtain rice threshing optimal operating parameters, investigations were conducted on the longitudinal axial threshing apparatus test bench of combine harvester. The threshing power consumption and grain loss ratio of longitudinal axial threshing apparatus were measured at the different combination of cylinder speed, concave clearance and bar spacing. Rice threshing experiment results were analyzed by carrying out regression analysis and the significance of regression effects assessing. The confidence interval of the optimal operating parameters was used to control the performance of threshing and separation process, and the optimal variables of the longitudinal axial threshing apparatus were predicted in advance and tested soon afterwards. When the total grain loss ratio was controlled within less than 0.33% and the threshing power consumption was less than 46.36 kW with a confidence of 0.95, the confidence interval of the best cylinder speed was 772.61-905.74 r/min, the best confidence interval of concave clearance was 22.18-37.93 mm, and the best confidence interval of bar spacing was 104.96-170.17 mm. The results showed that the best threshing cylinder speed was 839 r/min, the best concave clearance was 30 mm and the best bar spacing was 138 mm. These operating parameters can reduce the energy requirements of threshing process and also can lead to low grain loss. [ABSTRACT FROM AUTHOR]

In order to optimize the length of longitudinal-flow threshing cylinder of combine harvester, in this paper the length-adjustable longitudinal-flow threshing cylinder was designed and used to conduct rice threshing and separating performance experiments. The grain distribution rules and distribution equation under the grid concave were developed. The length of longitudinal-flow threshing cylinder was optimized by calculating the optimal deflector helical angle of cylinder cover. The optimal length of the longitudinal-flow threshing cylinder was used to conduct rice threshing and separation performance confirmatory test. The result showed that when the feeding rate was 7 kg/s, adapted deflector helical angle of 7.64°, the optimal length of the longitudinal-flow threshing cylinder was 3 159.77 mm, and then the un-separated grain loss ratio could be controlled at the range from 0.2 % to 0.3%. The verification test result was about 0.29%. This study may provide a basis and method for design the length of longitudinal- flow threshing cylinder of combine harvester. [ABSTRACT FROM AUTHOR]

When a rice combine harvester operates in the field, its frame vibrates significantly under multi-source excitation forces which can cause complex vibration and structural deformation. The vibration response of combine harvester frame under multi-source excitation was deduced. Based on the multi-source excitation of combine harvester, the chassis frame and the threshing frame were assembled into a complete combine harvester frame, which was used to analyse the constraint modal characteristics and its internal connection. A dynamic model of the combine harvester frame as a 7-degrees of freedom rigid body was developed to obtain modal shape and frequency. The excitation parameters of the dynamic model and its vibration response were developed in MATLAB. Vibration response of rice combine harvester frame was tested to verify the dynamic model. By comparing the independent modal frequency of the chassis frame and threshing frame with that of the complete combine harvester frame, the constant modal frequency of complete combine was shown to be directly related to the independent modal frequency of the chassis frame and the threshing frame. The amplitude of signal simulated by the vibration model of combine harvester frame was consistent with the measured amplitude of the frame, which verified the validity of the dynamic model. The six orders constant modal frequencies of the combine harvester frame were within the operating frequency range that could cause complex vibration coupling and resonance. Vibration response of rice combine harvester frame under multi-source excitation could provide a reference for further improvements in the combine harvester frames. • Split and binding constrained modal was used to analyze combine harvester frame. • Dynamic model of combine harvester frame was analyzed under Multi-source excitation. • Constrained modal shapes were used to analyze vibration response of harvesting state. • Constrained modal response was obtained with Multi-source frequency acted on frame. [ABSTRACT FROM AUTHOR]