Tillage Forces Research Articles

Performance Evaluation of a Cicada-Inspired Subsoiling Tool Using DEM Simulations.

Subsoiling practice is an essential tillage practice in modern agriculture. Tillage forces and energy consumption during subsoiling are extremely high, which reduces the economic benefits of subsoiling technology. In this paper, a cicada-inspired biomimetic subsoiling tool (CIST) was designed to reduce the draught force during subsoiling. A soil-tool interaction model was developed using EDEM and validated using lab soil bin tests with sandy loam soil. The validated model was used to optimize the CIST and evaluate its performance by comparing it with a conventional chisel subsoiling tool (CCST) at various working depths (250-350 mm) and speeds (0.5-2.5 ms-1). Results showed that both simulated draught force and soil disturbance behaviors agreed well with those from lab soil bin tests, as indicated by relative errors of <6.1%. Compared with the CCST, the draught forces of the CIST can be reduced by 17.7% at various working depths and speeds; the design of the CIST obviously outperforms some previous biomimetic designs with largest draught force reduction of 7.29-12.8%. Soil surface flatness after subsoiling using the CIST was smoother at various depths than using the CCST. Soil loosening efficiencies of the CIST can be raised by 17.37% at various working speeds. Results from this study implied that the developed cicada-inspired subsoiling tool outperforms the conventional chisel subsoiling tool on aspects of soil disturbance behaviors, draught forces, and soil loosening efficiencies. This study can have implications for designing high-performance subsoiling tools with reduced draught forces and energy requirements, especially for the subsoiling tools working under sandy loam soil.

Simulation of Mouldboard Plough Soil Cutting Based on Smooth Particle Hydrodynamics Method and FEM–SPH Coupling Method

In the field of agricultural machinery, various empirical field tests are performed to measure the tillage force for precision tillage. However, the field test performance is costly and time-consuming, and there are many constraints on weather and field soil conditions; the utilization of simulation studies is required to overcome these shortcomings. As a result, the SPH method and the coupled FEM-SPH method are used in this paper to investigate the mouldboard plough–soil interaction. In this paper, the finite element software LS-DYNA was used to build the SPH model and the FEM-SPH coupling model of soil cutting, as well as to investigate the change in cutting resistance during the soil cutting process. The simulation results are compared with those of the experiments, and the curves of the simulation and experiment are in good agreement, which verifies the reliability of the model. The validated simulation model was used to investigate the effects of the cutting speed, depth of cut, inclination angle, and lifting angle of the mouldboard plough on cutting resistance. The simulation studies show that the SPH model takes 5 h and 2 min to compute, while the FEM-SPH coupled model takes 38 min; obviously, the computational efficiency of the FEM-SPH coupled model is higher. The relative errors between the SPH model and the experiment are 2.17% and 3.65%, respectively. The relative errors between the FEM-SPH coupled model and the experiment are 5.96% and 10.67%, respectively. Obviously, the SPH model has a higher computational accuracy. The average cutting resistances predicted by the SPH model and the FEM-SPH coupled model, respectively, were 349.48 N and 306.25 N; these resistances are useful for precision tillage. The cutting resistance increases with the increase in cutting speed and is quadratic; the cutting resistance increases with the increase in cutting depth and is quadratic; the horizontal cutting resistance and the combined cutting resistance increase with the increase in inclination angle, while the vertical cutting resistance remains essentially constant with the increase in inclination angle; the horizontal cutting resistance and combined cutting resistance increase as the lifting angle increases, while the vertical cutting resistance decreases as the lifting angle increases.

Three-dimensional DEM tillage simulation: Validation of a suitable contact model for a sweep tool operating in cohesion and adhesion soil

Discrete element modelling (DEM) is widely used to estimate soil-tool interaction and tillage forces. To run an accurate simulation, it is essential to determine the appropriate DEM contact model and parameters. Although previous work has been introduced to determine the DEM contact model and parameters, the accuracy of numerical simulation is not high because of the soil differences when tillage tools operate in cohesion and adhesion soil in the middle and lower reaches of the Yangtze River in China. In this paper a Hertz-Mindlin with JKR Cohesion contact model and Linear Cohesion contact model were used to predict soil disturbance area and draft forces. The DEM parameters were determined using cone penetration, and uniaxial unconfined compression as an assisted test. The field experiment using sweep tool was used to validate the simulation results. A good agreement has been showed between simulation results and experiment results. Using verified model, the relative error for the predicted soil disturbance area at speeds of 0.50, 0.75 and 1.00 m/s were 5.3, 3.6 and 7.1 %, respectively. The maximum and average relative errors between simulated and measured draft forces were 6.98 and 3.91%, respectively. The effect of tillage depth and speed at soil disturbance area and draft forces were found which can provide some guidance for the selection of parameters during actual operation.

Performance Evaluation of Vertical Discs and Disc Coulters for Conservation Tillage in an Intensive Rice–Wheat Rotation System

As an advanced agricultural production technology, conservation tillage has been developed rapidly and adopted widely for many crops all over the world, but challenges remain with regard to dealing with excessive residues, especially for intensive rice–wheat rotation systems. Most studies to date have been based on a single type of tool and the indoor bin test to explore its performance. Accurate field test data on the tillage performance of different types of tools for conservation tillage are lacking in this area. In this study, five tillage tools were tested in a paddy field with plenty of crop residues to compare their performance. They were three vertical discs with plain disc (PD), notched disc (ND), and rippled disc (RD) and two disc coulters with plain disc coulter (PDC) and notched disc coulter (NDC). All five tools were tested using a specific field test rig at two different working depths of 70 and 100 mm. Tillage forces, straw cutting efficiency, soil disturbance width, and soil cutting depth were measured. The results showed that tool geometry and working depth had a significant impact on tillage performance. The vertical disc performed a higher average straw cutting efficiency, as well as lower tillage forces and lower soil disturbance width than the disc coulter. For straw handling and furrowing operations, RD had the highest straw cutting efficiency, moderate tillage force, and appropriate soil disturbance width among the five tools. For all five tools, the 100 mm working depth results in 40% higher draught force, 39% greater vertical force, and 18% higher straw cutting efficiency on average. For no-tillage seeding in the intensive rice–wheat rotation system, the RD would be a more suitable rotary tool for conservation tillage practice.

Prediction of Single Disc Seeding System Forces, Using a Semi-Analytical and Discrete Element Method (DEM) Considering Rotation Effects

Disc seeders are commonly used in no-till farming systems, and their performance evaluation generally rely on expensive and time-consuming field experiments. Mathematical models can help speed up force-related evaluations and improve the understanding of soil-disc interactions, to assist the performance optimisation processes. Previous analytical force prediction models of disc blades have not accounted for the free rotation aspect of the disc blade. This paper develops an analytical force prediction model from the wide blade failure theory adapted to suit rotating flat disc blades operating at different sweep and tilt angles and compares predictions with Discrete Element Method (DEM) simulations. To validate the two models, experiments were performed on a remoulded sandy soil condition using a rotating flat disc set at two tilt angles of 0° and 20°, and four sweep angles of 6, 26, 45 and 90° the 3-dimensional force components of draught, vertical and side forces were measured. Results showed a higher coefficient of determination (R2 = 0.95) was obtained with analytical model predictions compared to DEM predictions (R2 = 0.85) for their agreement with the test results. It was found that both the developed analytical approach and the DEM model can be used to predict tillage forces at different sweep and tilt angles acting on a rotating flat disc blade.

Novel draught resistance sensing elements for measurement of drawbar power of agricultural machinery

Aim of study: To develop an instrumentation system comprising three force sensing elements to measure the draught resistance of any tillage and seeding tools during field operation by connecting one sensing element to each three-point linkage of the tractor.&#x0D; Area of study: Department of AgFE, Indian Institute of Technology, Kharagpur, India&#x0D; Material and methods: Commercial S-type transducers were packed laterally in between the curved plates perpendicular to the direction of travel in such a way that the magnitude of the imposed force decreased and its nature got reversed consequently during tillage force measurement. Finite element analysis was also performed on the proposed model of the sensing elements. The performance was evaluated on the basis of non-linearity, hysteresis, and non-repeatability. The data were validated with the draught values simultaneously recorded using instrumented three-point linkages of tractor.&#x0D; Main results: It offered good sensitivity and linearity during static calibration. The measurement capacity based on maximum applied load during static calibration was 10 kN with accuracy 93.40%. The low values of mean percentage error (9.03%), maximum absolute variation (17.43%), and root mean square error (0.51 kN) revealed good accuracy of the system. Validation was conducted by comparing the data for an offset type disk harrow with the model outputs of previous studies to assess its suitability for other soil working conditions, and the results were satisfactory.&#x0D; Research highlights: The advantages of this sensing device in the measurement of drawbar power are fewer changes in the hitching geometry, lower cost, and capability of quick hitching.

Wear Resistant Nanostructured Coating for Cultivator Shovels

In Indian economy agriculture plays a principal source of income. Primary and secondary operations such as ploughing are the basic actions and extensive usage of cultivators for secondary tillage operation causes wear of the shovels because they are subjected to high tillage forces. An ample amount of material is lost due to wear and abrasion. Therefore, control and prevention of wear of cultivator shovels are vitally important for agro applications because wear of critical components has an economic significance. In this work CrN coating is deposited over cultivator reversible shovels using the DC magnetron sputtering technique and the structure, morphological, hydrophobic and wear characteristics are determined. It is observed that the working life of the agricultural tool is increased up to a significant level by depositing the desired coating on the substrate.

Optimization design and performance study of a subsoiler underlying the tea garden subsoiling mechanism based on bionics and EDEM

Considering the problems of high tillage resistance, high energy consumption, and failure to break the plow pan in subsoiling caused by the high viscosity of tea garden soil, a new design method of a subsoiler underlying the subsoiling mechanism based on structural bionics and the discrete element method is proposed. Taking the largest toe of mole cricket's forefoot as the bionic object, the biological information of the contour of mole cricket's toe was extracted using the methods of image processing and reverse engineering, and the edges of its outer and inner contours were obtained. Combined with the structure of an existing subsoiler, initial point cloud data of a bionic subsoiling shovel were mapped by the methods of proportional amplification and rotation. Taking the minimum sum of outer and inner contour fitting errors as the optimal objective function and selecting high-order polynomial as the fitting function, the optimization model of the outer and inner contour point cloud fitting function was established. The optimal fitting function of the outer and inner contour point cloud was obtained, and the bionic subsoiler model was established based on these two optimal functions. In the study of the discrete element, four soil particle models were proposed based on the actual shape of the cohesive soil of a tea garden. Based on the principle of discrete elements and the agronomic requirements, a modeling method of the plow pan soil was proposed. First, the adjacent soil particles at the bottom were connected by bonding, and the soil with large porosity was squeezed by the preset force to form the plow pan soil. Then, six tillage layers were added above the plow to form a soil structure model of the tea garden. The bionic subsoiler was assembled into a four-bar subsoiling mechanism. The process of the subsoiling mechanism acting on the soil was analyzed by the co-simulation of ADAMS-EDEM and compared with the common subsoiler. The results showed that the bionic subsoiler, compared with the common subsoiler, reduced the tillage force in the horizontal direction by 16.34% and in the vertical direction by 24.53%, reduced energy consumption by 9.64%, increased the damage to the plow pan by 5.10%, and caused greater disturbance to the internal soil. The influence of different driving speeds on the tillage performance was studied, which provides a theoretical reference for the better selection of the working speed for subsoiling.

Weed seed burial as affected by mouldboard design parameters, ploughing depth and speed: DEM simulations and experimental validation

Discrete element method (DEM) was employed to model and optimise the weed seed burial and tillage forces as affected by mouldboard design parameters (i.e. the cutting angle (ε), the setting of the share angle (θs), the curvature parameter (q)), ploughing depth and speed. Several mouldboards were designed with combinations of ε at 40°, 45°, 50° and 60°, θs at 25°, 35°, 45° and 55° and q at 20, 22, 24 and 30. A total of 64 DEM simulations were performed and the resulting percentage of weed seed burial and tillage forces were analysed. Optimisation of mouldboard design parameters was performed using the response surface methodology (RSM). The optimal combination resulted in ε = 32.3°, θs = 47.8°, and q = 28.2. Then, the combined influence of ploughing depth and speed was investigated and the values of 0.3 m and 1 ms−1 were selected as the best combination to achieve maximum weed seed burial. For validation of the simulation results, a full scale mouldboard plough was tested in the field with blue-coloured polyethylene pellets as a layer of weed seed on the topsoil. Comparison of the measured and predicted weed seed burial below the critical burial depth (i.e. 0.15 m) showed the simulated percentage of weed seed burial within bounds of ±15% of the measured values with R2 of 0.93. As a conclusion, DEM can be a useful tool to optimise the design of tillage tools to improve the effectiveness of tillage.

3D FINITE ELEMENT ANALYSIS OF THE TILLAGE AND STRAW CUTTING PERFORMANCE OF A CURVED-EDGED TOOTHED DISC

The management of crop residues together with compacted soil under intensive farming systems requires highly efficient and well-adapted tools. The performance assessment of such tools requires proper definition of their technical designs as well as the tool-induced soil-straw dynamic interactions. Few studies have characterized the performance of toothed discs based on their design considerations and mechanical responses. This study evaluated the tillage forces, structural strength, straw-cutting performance, and tillage-depth uniformity of a curved-edged toothed disc in comparison to a straight-edged toothed disc. The design of the curved-toothed disc was inspired by the arc-shaped structure of the mole-rat's claw. 3D finite element analysis (FEA) was used to simulate the discs’ interactions with soil and straw. Field experiments were conducted to validate the FEA results. It was revealed that the curved disc reduced the tillage forces by up to 22.8%, and significantly reduced the stresses on the tool. The disc also achieved uniform tillage depths and improved the straw-cutting efficacy by up to 26.31%. Bionic curved cutting-profiles on toothed discs thus provide a structurally enhanced, energy-efficient option for effectively managing crop residues and improving seeding performance in no-till conservation farming.

Study on the reduction of soil adhesion and tillage force of bionic cutter teeth in secondary soil crushing

Fine breakage of topsoil blocks in a seedbed has an important impact on operation quality of planting and harvesting mechanisation. Structure and material of the cutter teeth are one of the key elements in fine topsoil breaking. In order to improve the tillage performance of crushing cutter teeth, a bionic cutter teeth prototype inspired by the badger claw toe is proposed. In addition, the surface of the cutter teeth was modified by anti-adhesion material coating. The simulation model was established in ANSYS/LS-DYNA software and simulated soil cutting process was analysed. The results showed that cutter teeth with bionic structure could effectively reduce the average cutting resistance, cutting stress, soil energy, and maximum cutting resistance, obtaining soil cutting effect. By employing Fourier transform infrared spectroscopy (FTIR), water contact angle combined with abrasion resistance tests, mixed polytetrafluoroethylene (PTFE) and fluorosilicone acrylic acid (FAA) resin coatings after sintering were found to combine well with the cutter teeth. When the coating thickness was 10 μm, the tillage force was the lowest, and the abrasion resistance was the highest, which resulted in best comprehensive performance of cutter teeth. Scanning electron microscope (SEM) images indicated that the coating material can protect the surface and prevent abrasion. Field test results also proved that uncoated and coated bionic cutter teeth had lower energy consumption and soil adhesion, especially for the coated bionic cutter with 10 μm thickness. The results of this study could provide an important reference for designing a more efficient rotating tillage tools. • A bionic cutter teeth prototype inspired by the badger claw toes. • Bionic structure achieved fine crushing and improved tillage performance. • Mixed PTFE and FAA coating protected cutter teeth surface and prevented abrasion. • Bionic structure and coating had superimposed effect on anti-adhesion/resistance.

Development of a dual sideway-share subsurface tillage implement: Part 2. Effect of tool geometry on tillage forces and soil disturbance characteristics

Simulation of tillage tool-soil interactions provides opportunities to accelerate new equipment design and evaluate its performance. The dual bent blade subsurface tillage implement which its performance has been evaluated in the field, is a new conservation tillage tool deserving its soil cutting efficiency to be improved by optimizing its geometry using discrete element method (DEM) modeling. In order to achieve this objective, the effect of share size (5.9, 7.6, 11.3, 16.8, 22.6 and 28.2 cm), rake angle (7.5°, 15°, 25°, 30°, 35° and 40°), tilt angle (10°, 20°, 25°, 30°, 35° and 40°), and shank rake angle (45°, 60°, 75°, 90° and 97.5°) of the tool plowing at 150 mm depth, on soil cutting forces and soil disturbance characteristics were investigated using the validated DEM model developed in part 1 of this study. Results showed that the draft and vertical forces increased with increasing share size, while the specific resistance (SR) decreased. With increasing share rake angle, the draft force, SR, upward vertical force and the degree of soil pulverization increased. The minimum SR of the tool was at the tilt angle of 20°. But at this tilt angle, the uniformity of the cutting-depth for a long share-size was low, due to greater lateral bending of the share. As the rake angle of the shank decreased, the draft and vertical upward forces decreased. DEM simulation results showed that an efficient non-inversion tillage implement design can be achieved by developing a dual sideway-share subsurface tillage tool having a total cutting width of 53 cm with the rake and tilt angles of 15° and 10°, respectively, and attached to a 75°-rake-angle shank and plowing 150 mm deep in a sandy clay loam soil.

Evaluation of bentleg and straight narrow point openers in cohesive soil

The bentleg opener was developed to overcome the high soil disturbance caused by straight narrow point openers, with the original evaluation conducted on sandy soils. A bentleg furrow opener was compared to narrow point openers with varying rake angles (45° and 90°) and cutting edge cross-sections (blunt, and single- and double-side chamfers) for soil disturbance, tillage forces, and soil aggregate break down in Black Vertosol (Vertisol in the USDA Soil Taxonomy), a highly cohesive soil relative to sandy soils used previously. Whereas the 45° rake angle caused greater soil disturbance, produced larger soil aggregates, and reduced draught and vertical force requirements, all openers with 90° rake angle (blunt and chamfered openers) had a shallow critical depth (44–46 mm) and caused smearing. Contrary to previous findings in sandy soil, both single and double side chamfering of opener cutting edge had no significant effect on soil movement, furrow width, and furrow cross-sectional area. However, greater soil movement was observed on the chamfered side of the single-side chamfered opener than the non-chamfered side. The chamfers significantly reduced draught and vertical forces and produced smaller soil aggregates. The bentleg opener loosened soil to the furrow bottom but caused the least soil movement out of the furrow and formed a ridge in the middle of the furrow, which resulted in the highest furrow backfill. It also encountered a downward vertical force which assisted penetration and had a greater proportion of aggregates within the optimum range (1.18 and 9.5 mm). The bentleg opener, thus, shows potential for improved seed covering and satisfactory performance at operating speeds above 8 km h−1.

Discrete element method (DEM) simulation to improve performance of a mouldboard skimmer

Historically, most mouldboard plough research has been focused on improving the performance of the mouldboard itself, with very little focus on other plough components such as the skimmer. The skimmer is a critical additional component of the overall mouldboard plough which affects its performance in the field. The skimmer has a significant effect on the ability of the plough to bury topsoil and surface residues and there is a need to understand the effect of speed, depth and critical working angles on both forces and soil movement. Soil bin and analytical studies by Saunders (2002) investigated the potential to improve soil-skimmer interaction. Recent studies have shown that discrete element method (DEM) has the potential to predict both tillage forces and soil movement of tillage implements. In this study experimental and analytical work carried out by Saunders (2002) was replicated using a DEM simulation. A good correlation was obtained between the measured and predicted draught (R2 = 0.9) forces, furrow area (R2 = 0.68) and maximum soil throw (R2 = 0.77) while a fair correlation was obtained between measured and predicted and vertical forces (R2 = 0.5). It was also found that better draught force prediction can be obtained using DEM than with an analytical method. Results of the study showed that DEM has potential to accurately model tillage forces and soil movement and guide improvements to skimmer working angles.

Tillage force and disturbance characteristics of different geometric-shaped subsoilers via DEM

With the increased use of agricultural machinery in field operations, soil compaction has become increasingly severe, and the plough pan has become deeper. Subsoiling is an excellent way to address this problem. However, it is limited by high energy consumption, which is closely related to tillage force. To investigate the effect of the geometric shape of shanks and tines on tillage force and soil disturbance in loam, a layered soil model in accordance with the actual conditions was established and five different subsoilers were simulated via discrete element modeling. The results indicated that the shank impacted soil disturbance and tine impacted tillage force. The draft force of curved shank and chisel tine was 8% less than that of the straight shank and sweep tine. The straight shank and sweep tine produced a larger furrow profile and a higher furrow width. The subsoiler with curved shank and chisel tine (C-C) exhibited the lowest specific resistance (12.87, 17.52, 19.46 and 21.18 kN/m2 in the 30, 35, 40 and 45 cm tillage depth, respectively) considering the draft force and soil disturbance characteristics. Hence, these results will facilitate in the selection of a suitable subsoiler and design of new subsoilers with lower energy consumption requirements for loam areas worldwide.

STRUCTURA GENERALA A FORŢEI DE TRACŢIUNE, CONSECINŢE ÎN CERCETĂRILE EXPERIMENTALE ŞI APLICATIVE

The empirical and theoretical estimation of the draft force of agricultural machinery for soil tillage, has been the target of scientific research for about one hundred years. The results obtained so far may seem contradictory or divergent. The article presents the results of some research on the usual calculation formulas of the draft force of agricultural machines for soil tillage. Although apparently these formulas are different, analyzing the structure of the formula, we find cohesion and coherence embodied in a simple generalization and easy to use both theoretical and experimental. Moreover, the formulas are convertible between them, the two languages used for their definition (the mechanics of deformable solids and that of the phenomenological description), are only different forms of expression for the same phenomenon. Another problem that is addressed in the research whose results are presented in this article is that of highlighting the dependence of the draft force on the tool speed (in the field) of the soil tillage machine. Exposure is complemented by an algorithm that highlights the dependence of the draft force on the tillage tool speed. Also like a consequences of the draft tillage force structure, finally, a third problem addressed in these researches and whose results and perspectives are given in this paper is that of optimizing the working processes of agricultural machinery for soil tillage. The treatment of the problem starts from the hypothesis of the most general formula of the traction resistance force and proposes some ways to solve the optimal problem.

Simulation of tillage forces and furrow profile during soil-mouldboard plough interaction using discrete element modelling

The mouldboard plough has a complex shape and its development has mainly relied on resource intensive and time consuming empirical or semi empirical methods. However, if the mouldboard plough to soil interaction can be simulated, improved and more energy efficient mouldboard ploughs can be designed without performing field tests which may only be undertaken at certain times of the year. In this study the interaction between the soil and a mouldboard plough was simulated using discrete element method (DEM) and results were compared to experimental test and analytical draught force results and furrow profile measurement. It was found that draught and vertical tillage forces can be predicted within 1.9–16.6% and 0.3–21.5% of the total cutting forces, respectively. This shows that DEM can predict draught forces better than analytical method which predicted draught forces within 3.6–44.4% of the total cutting forces. The comparison of the furrow profile area results also showed that DEM can predict the furrow profile area within 0.8–16.5% of the measured furrow profile area. Results of the study proved that DEM has the potential to predict soil-mouldboard plough interaction with a reasonable accuracy.

An Engineering Review of the Farm Tractor's Evolution to a Dominant Design

This paper explains the origin and merits of the dominant farm tractor design, which has endured since the 1940s. Understanding the origins and rationale for this dominant design enables engineers to appreciate its merits, and understand its drawbacks, which could be addressed in future designs. Additionally, the methods used in this paper to study tractor evolution are applicable to the study of other products with a longstanding dominant design. Two themes are covered in this paper: first, the historical context that directed the farm tractor's design evolution is presented; and second, a terramechanics-based tractor model is used to analyze why the dominant design is conducive to good performance. The prominent characteristics of the dominant tractor design are its weight distribution, wheel layout, tool location, and construction. Its weight distribution maximizes drawbar pull by placing 70 to 80% of the total vehicle weight on the rear wheels. Shifting the weight forward reduces pulling force while shifting it backward produces a negligible increase in pulling capacity while dangerously increasing the risk of upending the tractor. The tractor has four wheels arranged in a rectangular pattern—the rear wheels are driven while the front ones are usually idle. Rear wheels are of large diameter to increase ground clearance and tractive efficiency. Front wheels are of small diameter to allow for a large steering angle despite a narrow track width. A narrow track width reduces the space required for making a U-turn at field ends and improves access to farm spaces. Inline front and rear wheels are desirable for ease of driving between rows and to best harness soil compaction. Attaching implements behind the rear axle leverages tillage forces to increase maximum drawbar pull and enables using large tools. The tractor's crankcase and transmission housing are structural components—this reduces mass and manufacturing complexity.

Simulating the effect of rake angle on narrow opener performance with the discrete element method

Narrow openers are widely used in Australia to place seed and fertiliser into furrows under no-tillage seeding operations, but excessive soil disturbance often limits their performance. The discrete element method (DEM) and a hysteretic spring contact model can be used to model soil-tool interactions, although previous work has been limited in its evaluation of soil disturbance. A new approach was used to evaluate soil disturbance in DEM simulations using a voidage grid binning technique to identify loosened soil after tillage and therefore paralleling soil bin and field testing methodologies. The effect of opener rake angle (35–90°) was simulated and compared to previous soil bin studies in a sandy loam soil predicting furrow profile parameters loosened area, ridge height, dip area, furrow backfill and lateral soil throw with relative errors of 9%, 16%, 14%, 0.8%, and 9%, respectively. Soil layer mixing trends also followed those measured in soil bin experiments-low rake angle openers moving deep soil up the furrow profile and maximising the furrow mixing effect. Additionally, predicted soil failure (critical depth and forward rupture ratio m) and tillage force rake trends followed those expected from classic empirical based soil mechanics studies. DEM predicted approximately a twofold draught penalty with increasing rake angle as well as a vertical force transition at 71°–closely matching trends consistently reported in literature. The approach followed demonstrated an improved potential for DEM simulations to optimise the performance of narrow openers.

Comparison of the discrete element and finite element methods to model the interaction of soil and tool cutting edge

Soil tillage is an energy intensive operation and design improvements that reduce forces have been pursued for many different tools. Due to the high cost of prototyping and testing, computer modelling has been adopted to design tillage equipment. In order to model soil-tool interaction two methods namely; finite element method (FEM) and discrete element method (DEM) have been used. Fielke (1994 and 1996) found that for shallow working low rake angle tools the cutting edge geometry of a tillage tool has a major effect on tillage forces and soil movement. FEM modelling of the tests was also carried out in Fielke (1999) . In this paper the experimental work of Fielke (1994) was simulated using DEM techniques and the results were compared to both the measured data and FEM predicted results. The results of the study showed that better vertical force prediction was obtained using DEM whereas forward soil movements below the tillage depth were simulated more accurately using FEM. This can be attributed to the larger size of particles used in DEM simulation than needed to pass around the cutting edge. It was also shown that DEM can be used to accurately predict soil failure planes.