Mechanical properties of soil-engaging components interacted with ultrasonic vibration in agricultural machinery

Reducing the resistance of soil-engaging components can greatly contribute to the energy saving for a higher performance of agricultural machinery in modern agriculture. In this study, a motion theoretical model was constructed to investigate the mechanical properties of the soil-engaging components that interacted with the ultrasonic high-frequency vibration in agricultural machinery. A novel device with ultrasonic vibration was also developed to excite the key soil-engaging components, thereby reducing the operating resistance, high-power supporting power, and the impact on soil compaction. Specifically, the device was composed of the ultrasonic generator, transducer, horn, and soil blade. A systematic analysis was made on the contact separation and impact fragmentation in the interaction between the soil-engaging component with high-frequency vibration and soil. A blade with high-frequency vibration was utilized to produce the vibration impact with the small amplitude, but there was a great acceleration to the soil. Once the vibration speed was greater than the forward speed, the contact time between the blade and the soil was reduced significantly in this case. A theoretic analysis was then implemented to explore the specific mechanism for the soil crushing and resistance reduction of the soil-engaging component with ultrasonic vibration. A soil tank test system was designed to evaluate the performance of soil-engaging components with ultrasonic vibration. Some parameters were also optimized for the operating resistance and soil crushing characteristics of soil contacting parts with ultrasonic high-frequency vibration. The test results showed that the operating resistance of the soil-engaging component under the excitation of ultrasonic vibration was significantly lower than that under the non-vibration state. Furthermore, the greater the soil hardness was, the higher the operating resistance reduction rate was. The reduction rate of operating resistance increased from 22% to 43%, when the soil hardness increased from 1 to 4 MPa. Alternatively, the reduction rate of resistance was greater than before, as the moisture content decreased in the range of soil moisture content of 15%-30%. Once the soil moisture content exceeded 30%, the reduction rate of operating resistance increased slightly, with the increase of soil moisture content. Correspondingly, the fluctuation stability of instantaneous operating resistance was improved for a stronger soil crushing, due to the impact fragmentation and energy transfer of the soil-engaging component under the excitation of ultrasonic high-frequency vibration to the soil. In addition, the resistance fluctuation was averaged by the standard deviation of operating resistance, where the soil fragmentation was calculated by the soil particle size. Once the soil hardness was 1 MPa, the fluctuation stability of working resistance was not significantly improved in the soil-engaging component. The reduction rate of operating resistance increased significantly in the fluctuation, with the increase of soil hardness. The standard deviations for the reduction rate of operating resistance were 37.1% and 54.3%, respectively, when the values of soil hardness were 2.5 and 4 MPa. More importantly, the distribution of soil particles was tended to the direction of small size after the action of ultrasonic vibrating on the soil-engaging component, compared with that without vibration. This finding can provide strong technical support to the potential application of soil-engaging components under ultrasonic vibration with high frequency and low amplitude in agricultural machinery.