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The most important cause of product damage during the harvesting process is the mechanical operations carried out during harvesting and transferring of agricultural products. Reducing the product w...

In this research, the interactions of a dual sideway-share subsurface tillage implement with soil were modeled by discrete element method (DEM) and evaluated in an indoor linear soil bin. Spherical particles with Hertz-Mindlin contact model and parallel bond between particles were used to simulate agricultural soil aggregates and their cohesive behaviors. In soil bin experiments, soil cutting resistance and soil disturbance characteristics resulting from the tillage tool operating at 0.25 m s−1 and 150 mm cutting depth, were measured. The calibration of bond stiffness was performed through comparing the draft forces of a simple soil engaging tool simulated with DEM and those estimated with an analytical tillage modeling results using a trial-and-error method. The ratio of soil bin measured vertical force to draft force was used in calibration of the most sensitive model parameter, particle shear modulus. Its calibrated value for a sandy clay loam soil was 50 MPa. The calibrated model was validated using the soil forces as well as the soil disturbance characteristics of the tool measured in the soil bin. When comparing the model to the experimental results, the relative error was −2.0% for the average draft force, 2.5% for the average vertical force, −7.7% for the average rupture distance, and 11.7% for the average disturbed area. Therefore, good correlations were achieved between the soil mechanical behaviors obtained by the experiments and the DEM simulations. It can be concluded that in DEM simulations of some tillage tools such as subsurface tillage implement, accurate predictions of the vertical forces as well as the draft forces, could be achieved by calibrating the particle shear modulus using the ratio of vertical force to the draft force applied to the tool.

A two-tine oscillatory subsoiler was developed at the University of South Australia for fracturing the compacted soil layers between grapevines using small tractors. As the soil forces exerted on the tines were unbalanced, the tillage forces, torque peaks through the power-take-off and the inertia of the tines transferred vibrations to the tractor and its driver. These vibrations currently prevent the commercial use of soil loosening settings that require the lowest engine power to be used.A simulation model is presented that calculates the dynamic behaviour of the tractor oscillating subsoiler system with the focus being on the vibrations at the tractor driver’s seat. The model considers the three oscillatory tillage phases of soil cutting, backing-off and catching-up, with positive and negative oscillation angles; tine inertia and the various tyre stiffness and damping parameters.The results of the simulation were compared to field measurements and a good correlation of both the magnitude of root mean square (RMS) acceleration and the response to change in the oscillatory tillage parameters of amplitude, frequency and oscillation angle were obtained. Refereed/Peer-reviewed

Based on the published benefits of oscillatory tillage, a subsoiler was developed at the University of South Australia, which had two deep working oscillatory tines and could be fitted with four shallow leading tines for increased loosening efficiency. A series of field trials were conducted in a sandy-loam soil to determine the most efficient setting of the tine’s oscillatory motion and to compare the effect of using straight or bentleg tines. The tines were oscillated with an amplitude at the tip of 69 mm and an oscillation angle of 278 using a forward speed of 3 km/h. The frequency of oscillation was varied from 1.9 to 8.8 Hz. Analysis showed that the underside of the oscillating tine pushed rearward on the soil during part of the oscillation cycle, this decreased the draft in comparison to rigid tillage from 25.8 to 9.3 kN. Increasing oscillation frequency, increasedthe PTO power requirement from 2.5 kW at 1.9 Hz to 26.3 kW at 8.8 Hz. The peaks and troughs in draft and torque were able to be aligned with the various phases of the oscillating tillage. An optimum oscillation frequency of 3.3 Hz (velocity ratio of 1.5) was observed for minimum power to operate the oscillating subsoiler. Whilst at this setting, the combined draft and PTO power was similar to the draft power of rigid tillage, but when considering the higher losses due to tractive efficiency and lower PTO power losses, the oscillating tillage would be expected to require around 27% less engine power than rigid tillage. Refereed/Peer-reviewed

A deep working oscillatory subsoiler was developed at the University of South Australia to be towed by a tractor (3 t and 70 kW) in a semi-mounted configuration. During use, the soil-tool interaction forces transferred too much vibration to the tractor when operating at the desired subsoiler settings. In order to reduce the tractor vibrations, the source of vibration was studied using the power spectral density method to correlate the tractor seat vibrations to machine operating parameters. It was found that tyre lug engagement and the engine speed did not have significant effect on tractor vibration. The soil-tool interaction of both soil cutting and compaction during the oscillating motion of the tine, combined with the torque peaks on the driveline from the power take-off to the tines, had the dominant effect on vibration.

In established Australian vineyards compacted soil either created naturally or by trafficking prevents root growth to desirable depths and restricts root systems from getting water and nutrients. This can reduce the life span and productivity of grapevines considerably over a period of years. To break up these compacted soil layers using small tractors a deep working oscillatory ripper was developed at the University of South Australia which had two deep working oscillating tines. One of the most important factors for the performance of this oscillatory ripper is the oscillation angle of the tines. To find the optimum oscillation angle a series of field tests were conducted in a sand-loam soil at six different oscillation angles. The tines oscillated at a frequency of 4.9 Hz and with amplitudes of between ±60 and 69 mm, with a nominal forward speed of 3 km/h. The trial results were quantified as draft requirement, power saving, power ratio, loosened area and amount of vibration on tractor seat. The greatest draft reduction of 50% was achieved for negative oscillation angles, where power ratio was less than 1. Power saving was significantly affected by changing oscillation angle. In general, vibration of the driver seat was higher for negative angles. In terms of performance −22.5° oscillation angle was the optimum for draft reduction and power saving, whereas the least vibration was obtained at an oscillation angle of +16° which was equal to Australian Standard threshold for 8 h continuous work. Refereed/Peer-reviewed