Search

Highlights IF and VF agricultural radial tires are capable of carrying a greater load at the same inflation pressure than a standard radial tire. For this MFWD tractor and central-fill planter, the rear tractor tire is the main source of soil compaction during planting. The peak soil stress for the rear tractor tire was greater for standard radial tire inflation pressures than for IF radial tire inflation pressures. Potential soil compaction is expected to be greater for standard radial tire inflation pressures than for IF radial tire inflation pressures. Abstract. New agricultural tire standards, designated as Increased Flexion (IF) and Very High Flexion (VF), have been introduced for agricultural machines that offer larger contact areas compared to the standard radial tire carrying the same axle load. Limited studies have been conducted on how the newly adopted IF tires and precision tire inflation pressure management systems affect soil compaction, fuel economy, and crop yield responses. This study aimed to investigate the effects of field and transport (road) tire inflation pressure settings of row-crop agricultural tractor and planter tires on soil compaction. A completely randomized design experiment was conducted at the Iowa State University farm at Boone, Iowa, for two tire inflation pressure levels on the dual front (Firestone IF 420/85R34) and dual rear (Firestone IF 480/80R50) tires on a John Deere 8310R MFWD tractor, as well as transport tires (Super single 445/50R22.5) on a John Deere DB60 central-fill planter. Soil compaction was measured using Stress State Transducers (SSTs) buried at 150 mm and 300 mm depths beneath the untrafficked soil surface. The soil cone index depth profile was measured at the tire centerline before and after the tractor and planter tire passes. After the tractor and planter tire passes, rut depth was also measured at the tire centerline. Peak octahedral normal stress (soct) and the corresponding octahedral shear stress (toct) values in soil were calculated from the SST data. The peak soct for the rear tractor tire was significantly greater for the Standard Radial Tire Pressures treatment than for the IF Radial Tire Pressures treatment. The tire inflation pressure treatment did not significantly affect the peak soct for the front tractor tire and the planter transport tire. For this tractor and planter configuration, soil stress results identify the rear tractor tires as the main source of soil compaction during planting. The Standard Radial Tire Pressures treatment caused significantly higher soil cone index and soil rut depth compared with the IF Radial Tire Pressures (P < 0.05). As indicated by soil stresses, potential soil compaction from the tractor and planter transport tires is expected to be greater for standard radial tire inflation pressures than for IF radial tire inflation pressures. Keywords: Increased Flexion (IF) radial tire, Soil compaction, Soil cone index, Soil stress state, Tire inflation pressure.

A discrete element method (DEM) calibration for a flexible wheat straw model for simulating direct shear test of wheat straw was investigated. The calibration process uses DEM simulated Design of Experiment (DOE) of a three-point bending test, DEM parameters initialised from previous cantilever beam test, and uniaxial compression test of wheat straw. Wheat straw samples from physiologically matured Winter wheat straw (Triticum aestivum) material were used to estimate shape of a flexible wheat straw model and to obtain material testing data. Using the DEM simulated DOE of a three-point bending test, a regression meta-model was established between particle contact Young's modulus, and bond Young's modulus and Poisson's ratio. An optimisation procedure that minimised a global error relative to the test data was utilised to determine the DEM parameters of particle contact Young's modulus, bond Young's modulus, and Poisson's ratio. From the three-point bending test of wheat straw (length of 55 mm, a diameter of 2.81 mm, and a thickness of 0.35 mm), and DOE based optimisation procedure, the DEM predicted Young's modulus of flexible wheat straw at a percent relative error (RE) of 3.11% compared to test data. Using the optimised DEM parameters of the flexible wheat straw model, the direct shear box test was simulated using the flexible fibre DEM model, as a validation experiment. DEM successfully simulated the direct shear behaviour of wheat straw from the ASTM laboratory direct shear box test, predicting wheat straw angle of internal friction (RE of 1.67%) and apparent cohesion close to zero.

Made available in DSpace on 2022-04-28T19:46:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 The water retention curve (WRC) of arable soils from the southeastern United States at different levels of compaction (no compaction, and 10 and 20% increases in soil bulk density) was estimated using the van Genuchten–Mualem (VG) model. The VG water retention parameters of the noncompacted soils were obtained first by fitting measured soil hydraulic data. To construct the WRC of the compacted soils, gravimetric values of the permanent wilting point (θgw, 1,500 kPa) and the residual (θgr) water content were assumed to remain unchanged with compaction. The VG parameter α and exponent η after compaction were estimated using two approaches. In Approach 1, α and η were estimated from saturation, the permanent wilting point, and the residual water content. In Approach 2, the value of η was assumed to remain unchanged with compaction, which allowed α to be estimated immediately from the VG equation. Approach 2 was found to give slightly better agreement with measured data than Approach 1. The effect of compaction on the saturated hydraulic conductivity (Ks) was predicted using semitheoretical approaches and the VG-WRC function. HYDRUS-1D was further used to simulate vertical infiltration into a single-layered soil profile to determine the impact of compaction on the infiltration characteristics of the soils used in our analyses. Results showed that a 10–20% increase in soil bulk density, due to compaction, reduced cumulative infiltration (Ic) at time T = Tfinal (steady-state) by 55–82%, and the available water storage capacity by 3–49%, depending upon soil type. Univ. of Southern Queensland Centre for Agricultural Engineering CSIRO Agriculture and Food Black Mountain Science and Innovation Precinct Dep. of Earth Sciences Utrecht Univ. Center for Environmental Studies São Paulo State Univ. Dep. of Agricultural and Biosystems Engineering Iowa State Univ. Engineering Dep. Harper Adams Univ. Center for Environmental Studies São Paulo State Univ.

A novel approach to producing corn stover biomass feedstock has been investigated. In this approach, corn grain and stover are co-harvested at moisture contents much less than typical corn silage. The grain and stover are conserved together by anaerobic storage and fermentation and then separated before end use. When separated from the stover, the moist, fermented grain had physical characteristics that differ from typical low-moisture, unfermented grain. A comprehensive study was conducted to quantify the physical properties of this moist, fermented grain. Six corn kernel treatments, either fermented or unfermented, having different moisture contents, were used. Moist, fermented kernels (26 and 36% w.b. moisture content) increased in size during storage. The fermented kernels’ widths and thicknesses were 10% and 15% greater, respectively, and their volume was 28% greater than the dry kernels (15% w.b.). Dry basis particle density was 9% less for moist, fermented kernels. Additionally, the dry basis bulk density was 29% less, and the dry basis hopper-discharged mass flow rate was 36% less. Moist, fermented grain had significantly greater kernel-to-kernel coefficients of friction and angles of repose compared to relatively dry grain. The friction coefficient on four different surfaces was also significantly greater for fermented kernels. Fermented corn kernels had lower individual kernel rupture strengths than unfermented kernels. These physical differences must be considered when designing material handling and processing systems for moist, fermented corn grain.

HighlightsA mathematical model of soil reaction forces on a rotary tine tool was developed.Soil bin experiments using artificial soil enabled observation of soil failure due to soil-tine interaction.The model-predicted forces were similar to experimentally measured forces.Abstract. Understanding soil-tool interaction can enable better control of weeding tools to achieve higher weeding efficacy. The interaction between a vertical tine (mounted on a rotating disc) and soil was investigated using a mathematical model that estimated soil horizontal forces on the tine operating at different linear and rotational velocities. The kinematics associated with the linear and rotational velocities of the rotary tine tool were modeled, and the shearing and inertial forces were estimated. To evaluate model performance with different experimental factors, two sets of soil bin experiments were conducted using an artificial soil: with one tine to estimate model parameters and with two tines 180° apart. Experimental factors were longitudinal velocity (travel speed) at three levels (0.09, 0.29, and 0.5 m s-1) and speed ratio, i.e., the ratio of longitudinal velocity to peripheral velocity of the tines, at three levels (1, 1.5, and 2). Soil horizontal force and torque on the rotary tine tool were measured. A nonlinear least squares method was used to estimate model parameters from the experimental data, resulting in shearing force coefficients ranging from 2.9 to 37 N and inertial force coefficients ranging from 16 to 528 N s2 m-2. The variations in the shearing and inertial forces on the tine were due to differences in soil failure patterns among the treatments. The predicted longitudinal and tangential forces for two tines using the model showed trends that were similar to the forces measured in the experiment. However, the model overestimated the predicted forces because it did not account for the reduced force on a tine due to soil disturbance created by the other tine. Keywords: Soil-tine interaction, Weed control.

HighlightsSimulation of uniaxial compression was performed with flexible fibers modeled in DEM.Bond-specific DEM parameters were found to be sensitive in uniaxial compression.A calibration technique that is not plunger-dependent is shown and validated.Abstract. To accurately simulate a discrete element method (DEM) model, the material properties must be calibrated to reproduce bulk material behavior. In this study, a method was developed to calibrate DEM parameters for bulk fibrous materials using uniaxial compression. Wheat straw was cut to 100.2 mm lengths. A 227 mm diameter cylindrical container was loosely filled with the cut straw. The material was pre-compressed to 1 kPa. A plunger (50, 150, or 225 mm diameter) was then lowered onto the compressed straw at a rate of 15 mm s-1. This experimental procedure was simulated using a DEM model for different material properties to generate a simulated design of experiment (DOE). The simulated plunger had a travel rate of 40 mm s-1. The contact Young’s modulus, bond Young’s modulus, and particle-to-particle friction DEM parameters were found to be statistically significant in the prediction of normal forces on the plunger in the uniaxial compression test. The DEM calibration procedure was used to approximate the mean laboratory results of wheat straw compression with root mean square (RMS) percent errors of 3.77%, 3.02%, and 13.90% for the 50, 150, and 225 mm plungers, respectively. Keywords: Calibration, DEM, DOE, Flexible DEM particle, Uniaxial compression, Wheat straw.

Variations in the moisture content (MC) of grains strongly influence machine performance analysis during crop harvesting and post-harvest grain handling operations. For experimental or numerical methods such as discrete element method (DEM) technique to include the effect of MC on physical and mechanical properties, comprehensive study was conducted to investigate the effect of maize MC on single kernel properties and bulk grain dynamic responses, which have relevance for DEM crop model calibration. Individual kernel properties of shape, size, coefficient of restitution, and stiffness, and bulk material responses of bulk density, angle of repose, direct shear test (angle of internal friction, apparent cohesion), hopper flowability, and grain-machine interaction (GMI) impact plate forces responses were measured on maize samples at 11%, 16%, and 26% MC levels. At individual particle responses of coefficient of restitution and stiffness, maize kernels at MC of 26% had significantly the lowest values compared to the values at the other MC (11% and 16%). Increasing maize MC reduced the hopper discharge flowability by 20% and GMI impact plate forces by 25%. Significant effects of MC on the material behaviours should be considered for calibration of DEM maize models.

Limited studies have been conducted to establish scaling relationships of soil reaction forces and length scales of bulldozer blades using the Discrete Element Method (DEM) technique. With a DEM-based similitude scaling law, performance of industry-scale blades can be predicted at reduced simulation efforts provided a calibrated and validated DEM soil model is developed. DEM material properties were developed to match soil cone penetration testing. The objectives of the study were to develop a DEM soil model for Norfolk sandy loam soil, establish a scaled relationship of soil reaction forces to bulldozer blade length scales (n = 0.24, n = 0.14, n = 0.10, and n = 0.05), and validate the DEM-predicted soil reaction forces on the scaled bulldozer blades to the Norfolk sandy loam soil bin data. Using 3D-scanned and reconstructed DEM soil aggregate shapes, Design of Experiment (DOE) of soil cone penetration testing was used to develop a soil model and a soil-bulldozer blade simulation. A power fit best approximated the relationship between the DEM-predicted soil horizontal forces and the bulldozer blade length scale (n) (R2 = 0.9976). DEM prediction of soil horizontal forces on the bulldozer blades explained the Norfolk sandy loam soil data with a linear regression fit (R2 = 0.9965 and slope = 0.9634).

A method to calculate the local damping coefficient and the bond Young's modulus of a flexible fibre for use in the discrete element method (DEM) was proposed and validated. Segments of harvested wheat straw were clamped on one end while the other end was deflected a set distance, released, and allowed to vibrate freely. This cantilever beam motion was captured by a high-speed camera (960 fps). The red-band of the images were isolated and used to calculate the x-section height (mm) along the stem in time. This data was then fit to a non-linear function, which conforms to beam theory. The global bond damping coefficient, as a function of x-section height, was then calculated and found to be in the range of −0.5 to −0.2. The cantilever beam experiment was then repeated in the DEM software LIGGGHTS, where the wheat straw was modelled as a single line of spheres connected by stiff-flexible bonds. A design of experiment (DOE) was ran varying bond Young's modulus and local bond damping, to determine the linear relationships with the global bond damping coefficient and the frequency of oscillation of the DEM particle respectively. With the proposed method the DEM local bond damping coefficient and the DEM bond Young's modulus were calibrated with relative errors of 0.9% and 1.8% respectively to laboratory estimated values. Utilising the linear relationships found from the DEM simulations, the bond Young's modulus was found to be in the range of 0.42–4.84 GPa.

Tillage tools are subject to friction and low-stress abrasive wear processes with the potential deterioration of the desired soil quality, loss of mechanical weed efficacy, and downtime for replacing worn tools. Limited experimental methods exist to quantify investigate the effect of wear-resistant coatings on shape parameters of soil-engaging tools. ASTM standard sand/rubber wheel abrasion and pin-on-disk tests are not able to simulate wear characteristics of the complex shape of the tillage tools. Even though the tribology of tillage tools can be realistic from field tests, tillage wear tests under field conditions are expensive and often challenging to generate repeatable engineering data due to variable soil conditions in the field. A technique that simulated tillage wear of cultivator sweep in a circular soil bin filled with abrasive gravel medium and moisture condition was developed and applied to quantify the wear characteristics of cultivator sweeps with and without hardfaced edges. The hardfaced cultivator sweep had a cemented carbide chip applied to the bottom cutting edge and front tip sections of a standard cultivator sweep according to a proprietary CADEN Edge welding process. The CADEN Edge hardfaced sweeps showed improved wear performance 1.7 times and 3.5 times on mass and shape (sweep length and sweep wing cutting width) dimensions, respectively, compared with the un-hardened standard sweep. The results implied hardfaced cultivator sweep with cemented carbide chips provide potential in maintaining tillage productivity and the desired soil quality for seed-bed preparation.

A 762‐mm‐diameter pipe 1,886 km long was installed to transfer crude oil in the USA from North Dakota to Illinois. To investigate the impact of construction and restoration practices on long‐term soil productivity and crop yield, vertical soil stresses induced by a Caterpillar (CAT) pipe liner PL 87 (475 kN vehicle load) and semi‐trailer truck (8.9 kN axle load) were studied in a farm field. Soil properties (bulk density and cone penetration resistance) were measured on field zones within the right‐of‐way (ROW) classified according to construction machine trafficking and subsoil tillage (300‐mm‐depth tillage and 450‐mm‐depth tillage in two repeated passes) treatments. At 200 mm depth from the subsoiled surface, the magnitude of peak vertical soil stress from trafficking by the semi‐truck trailer and CAT pipe liner PL 87 was 133 kPa. The peak vertical soil stress at 400 mm soil depth appeared to be influenced by vehicle weight, where the Caterpillar pipe liner PL 87 created soil compaction a magnitude of 1.5 greater than from the semi‐trailer truck. Results from the soil bulk density and soil cone penetration resistance measurements also showed the ROW zones had significantly higher soil compaction than adjacent unaffected corn planted fields. Tillage to 450 mm depth alleviated the deep soil compaction better than the 300‐mm‐depth tillage as measured by soil cone penetration resistance within the ROW zones and the unaffected zone. These results could be incorporated into agricultural mitigation plans in ROW construction utilities to minimize soil and crop damage.

Simulation of tool-to-soil interaction provides opportunities to accelerate new equipment design and evaluate performance of tillage tools. Simulation based evaluation of worn tillage tools performance on soil flow has not been done. Discrete Element Modelling (DEM) has a potential to simulate worn tool to soil interaction problems, where worn tools CAD can be generated using 3D scanning. The DEM parameters of Hertz-Mindlin with Parallel Bond model were calibrated to match draft force and soil failure zone measured from a tool bar moving at 0.22 m/s and 38 mm cutting depth. The draft force and soil forward failure zone were predicted at 7% and 24% relative errors compared to measured values, respectively. Using the optimized DEM soil model, the interaction of three 3D reconstructed sweeps (new sweep, carbide treated-worn, untreated-worn) with soil were simulated to compare their geometric wear dimensional loss, performance on soil forces and soil flow. Results showed that the carbide treated-worn sweep had similar soil draft force and soil forward failure distance as the new sweep. The untreated-worn sweep showed lower vertical force (less suction) and its wing induced soil failure zone (front and lateral) showed poor soil tilth quality compared with the carbide treated-worn sweep and the new sweep.

Due to the importance of planting depth on yield potential, we need to measure planting depth to improve planting depth accuracy. A number of pressure-based active planter depth control systems are commercially available. These systems actively control downward pressure on the planter units based on a target pressure setting. The necessary target pressure can change significantly depending on spatial and temporal conditions. However, precision planters are not equipped with subsurface sensors that enable detection and quantification of corn seed depth. The primary objective of this review was to evaluate nondestructive sensing technologies that may be used for corn seed detection, thereby enabling determination of planting depth in a closed trench. The sensors were reviewed in terms of their suitability for the application, operational requirements, and sensor advantages and limitations for soil subsurface detection. Ground Penetrating Radar (GPR) was recommended as a viable candidate for corn seed depth sensing but there is no single technique that can be conclusively identified as the best technology. A limitation of the available systems is that they do not provide a way to close loop control planting depth. A possible solution could be using sensor-based closed loop controls in respect to the planting depth. These could significantly improve the accuracy of pressure-based active control systems, and significantly improve the potential yield and economic benefits of planter depth control systems.