Dynamics of a powered disk in clay soil

Experiments were conducted with a single powered disk in a laboratory soil bin containing Bangkok clay soil with an average moisture content of 18% (db) and 1100 kPa cone index. The disk was 510 cm in diameter and 560 mm in radius of concavity. During the tests the disk angle was varied from 20° to 35°, ground speed from 1 to 3 km/h and rotational speed from 60 to 140 rpm. The working depth was kept constant at 12 cm. The vertical, horizontal and lateral reactions of the soil were measured by force transducers. The forward and rotational speeds were recorded. It was observed that disk angle, rotational speed and ground speed had significant effects on soil reactive forces and power requirement. With a small disk angle, low ground speed, and high rotational speed, the soil longitudinal reactive force was a pushing force and became a resistive one at larger disk angles and ground speeds. The soil transverse reactive force increased with an increase of rotational and ground speed but decreased with the increase of disk angle, whereas the vertical relative force increased only with the increase of ground speed but decreased with the increase of rotational speed and disk angle. It was found that the powered disk required the least power at a disk angle of 30° and rotational speed between 80 and 100 rpm. Increase in ground speed from 1 to 3 km/h increased the total power requirement by 31.8%. Upon driving the disk forward, the draft reduced considerably compared to that of the free-rolling disk. By driving the disk in the reverse direction, the draft reduced slightly. At a disk angle of 30°, rotational speed of 100 rpm, and ground speed of 3 km/h, the total power requirement of the forward-driven disk was 65% higher than that of the free-rolling disk. The predicted engine power of the forward-driven disk, however, was only 21% higher than that of the free-rolling one owing to the more efficient power transmission through the PTO, as opposed to the drawbar. The effects of reverse driving and free rolling of the disk were also studied.     

Effect of rotation direction of a rotary tiller on draft and power requirements in a Bangkok clay soil

Experiments were conducted in a Bangkok clay soil to evaluate the performance of a rotary tiller equipped with reverse or conventional blades. The conventional rotary tiller was equipped with C-type blades whereas the reverse-rotary tiller had new types of blades. Tests were conducted on wet land as well as in dry land. Tests were conducted at tractor forward speeds of 1.0, 1.5 and 2.0 km/h. A power-take-off (PTO) power consumed was calculated from the PTO torque and speed. The results indicated that the PTO power consumption was less for the reverse-rotary tiller compared to the conventional tiller for all passes and forward speeds. For both rotary tillers, power consumption decreased as the number of passes increased, whereas power consumption increased when the forward speed was increased. At all forward speeds, the power consumption was the highest during the first pass and lowest during the third pass. The maximum difference of PTO power requirement was after the first pass at 1.0 km/h forward speed. The reverse-rotary tiller consumed about 34% less PTO power under this condition.     

Effect of circumferential angle, lug spacing and slip on lug wheel forces

This study was conducted to investigate the effect of circumferential angle, lug spacing and wheel slip on forces produced by a cage wheel. Experiments were conducted in a laboratory soil bin having Bangkok Clay soil with 51% (d.b.) soil moisture content. Six ring-type loadcells were used to measure the soil horizontal, vertical and transverse reactions on the cage wheel lugs. The circumferential angle was varied from 0, 15, 30 to 45°. The lug spacing and wheel slip were varied from 20, 30 to 40° and 20, 35 to 50% respectively. All the force measurements were done at a constant 7 cm sinkage. The results showed that increasing circumferntial angle up to 45° can reduce variation in lug wheel forces, at the same time it had little effect on the mean pull and lift values. The side force was affected by the changes of circumferential angle. The 20° lug spacing not only gave the minimum variations but also maximum mean lug forces. The highest lug wheel forces occurred at 35% wheel slip.     

Embedded digital display and warning system of velocity ratio and wheel slip for tractor operated active tillage implements

A microcontroller-based embedded digital display and warning system was developed for measuring wheel slippage, velocity ratio, PTO torque, and draft requirement of active tillage machinery. The hardware system included magnetic pickup sensor for measuring the engine speed, load cells and amplifiers to measure and amplify the sensing unit signals of the draft, proximity sensors for wheel slip, and PTO torque transducer for measuring the torque requirement. It was provided with buzzers and LEDs to warn the operator, whenever slip and velocity ratio were not in the desired range based on the algorithm, for maximum fuel efficiency and tractive performance. It measured slippage, velocity ratio, torque and draft with a maximum absolute variation of 12.90%, 7.92%, 8.99% and 11.57%, respectively. The developed system can be easily adaptable to any combination of tractor and tillage implements, and guide the operator for better soil tilth with lesser energy input.     

Effect of tine rake angle and aspect ratio on soil failure patterns in dry loam soil

Studies were conducted in a laboratory glass-sided soil bin with dry compact loam soil (c = 0.02 kPa, Φ = 20° and cone index 210 kPa) with the specific objective of observing the effect of flat tine rake angle and aspect ratio on soil failure patterns. The tine was moved in the soil in a quasi-static condition and soil failure patterns were observed through a glass window. Tine rake angles of 50°, 90° and 130° were used while aspect ratio effects were studied by varying both width and depth of the tine. Individual effects of width and depth were investigated by maintaining a constant aspect ratio of 2.0 but varying width and depth. Results obtained indicated that soil failure patterns are affected by tine design parameters. Soil failure patterns were observed to be of progressive shear type in all cases. For 50° rake angle tines, the patterns consisted of inclined shear lines starting from the tine tip and gradually moving upwards towards the horizontal soil surface, intersecting it at an average failure angle of 32°. In the case of 90° rake angle tines, the inclined shear surface was at a distance from the tine tip whereas, for 130° rake angle tines, prismatic-shaped stationary soil wedges were formed adjacent to the tine. Failure angles for the 90° and 130° rake angle tines were almost the same as those for 50° rake angle tines. The results of this study also indicated that aspect ratio alone cannot account for changes in soil failure patterns, their corresponding soil reactions, forward rupture or surcharge profiles. The effects are mainly due to the individual changes in width and depth. There were no distinct zones as described in the passive soil pressure theory. Soil failures were in regular cycles resulting in corresponding variations in the soil reactions on the tines.     

Analysis of the PTO load of a 75 kW agricultural tractor during rotary tillage and baler operation in Korean upland fields

In this paper, the PTO severeness of an agricultural tractor during rotary tillage and baler operation was analyzed. The S–N curves of the PTO driving gears were obtained through fatigue life test. To obtain the S–N curves of the PTO driving gears, the breakage time and rotational speed of the gears were measured through observation of the bending stress with changing torque. The torque acting on the PTO was measured and analyzed during rotary tillage and baler operation. Rotary tillage and baler operation were conducted at two ground speeds and two PTO rotational speeds at upland field sites with similar soil conditions, respectively. The load data were inverted to a load spectrum using rain-flow counting and SWT equations. Modified Miner’s rule was used to calculate the partial damage sum. The severeness was defined as the relative ratio of the damage sum. The results showed that the damage of the PTO increased when the ground speed or the PTO rotational speed increased. The effect of the PTO rotational speed on the severeness of the PTO was more significant than that of the ground speed. The severeness of the PTO of rotary tillage was greater than that of baler operation.     

Measurement of soil reaction forces on a single movable lug

In order to clarify characteristics of a new mechanism called a movable lug, a model of a single movable lug equipped with an L-shaped force transducer has been developed. The soil reaction forces (normal and tangential) on a flat single movable lug, a curved single movable lug and a fixed lug were measured on wet sandy loam soil in the laboratory soil bin test. These measured forces then were converted to lug pull and lift forces. The pull and lift forces obtained by the flat movable lug with 45° lug inclination angle and the curved movable lug were higher than those of the fixed lug. It was observed that the lift force of the fixed lug achieved its peak and dropped earlier than those of the movable lugs. However, the peaks of pull and lift forces of the flat and curved movable lugs were almost the same. The flat movable lug with 45° lug inclination angle generated a slightly higher peak of pull force than those with 30° and 60° lug inclination angles. However, the higher lug inclination angle produced, the lower peak of lift force. It was observed that the pull and lift forces increased as the sinkage increased. In contrast to the flat movable lug with 45° lug inclination angle, the curved movable lug produced greater lift force especially at high sinkage. The increase in lug slip from 5% to 25 and 50% caused an increase in the peaks of pull and lift forces. The soil moisture content affected the lug forces significantly.     

Improvement of a power tiller cage wheel for use in swampy peat soils

This study was aimed at investigating traction performance of a cage wheel for use in swampy peat soils in Indonesia. The tests were conducted in a soil bin filled with peat soil taken from the swampy areas. A set up was developed to measure tractive performance of a single cage wheel. Deep sinkage and high wheel slip were identified as the major problems of using the existing cage wheel design in swampy peat soils. The results revealed that increasing the lug angle from 15 to 35° and the length of lug improved the tractive performance of the cage wheel significantly, while increasing the number of lugs from 14 to 18 and width of lug did not improve the tractive performance significantly. A cage wheel with lug size 325×80 mm, 35° lug angle, 14 lugs (26° lug spacing), with 2 circumferential flat rings installed on the inner side of the lugs, out performed the other settings for use with power tillers in swampy peat soils.     

The cutting of soil by narrow blades

The available models for predicting the forces acting on a narrow soil cutting blade have required separate measurements of the shape of the three-dimensional soil failure pattern ahead of the blade. It is proposed that a three-dimensional model consisting of straight line failure patterns in the soil can be used to predict both the draft forces and the volume of soil disturbed in front of a narrow blade. Limit equilibrium mechanics equations are written for the soil wedges in terms of an unknown angle of the failure zone and the theoretical draft force is minimized with respect to this angle. Force factors are thus found which are of the type to fit Reece's general earthmoving equation, but which vary with the width to depth ratio of the blade as well as with the rake angle of the blade and the friction angle of the soil. In addition the approximate geometry of the three-dimensional failure pattern in the soil is predicted for varying blade shapes and soil strengths. This allows the design of simple tools on the basis of their draft force requirements and their soil cutting efficiency. The draft force predictions and failure geometry calculations are shown to have considerable verification by experimental results.     

Experimental characterization of roughness parameters for fretting wear in spline couplings

Roughness parameters convey important information about the tribological properties of a material subjected to fretting conditions. They significantly affect the fretting life of the material. An experimental study has been conducted to characterize the variations in roughness parameters with respect to fretting wear and clearance in aero-engine spline couplings which are prone to angular misalignment. A dedicated test bench has been used to test spline couplings made of nitrogen hardened 42CrMo4 with crowned teeth. Tests were performed on samples of identical geometry and material under varying conditions of torque and misalignment angle between the hub and shaft of the coupling. Percentage differences in roughness parameters before and after the test have been characterized which showed symmetric variations, but interestingly mirrored in amplitudes for applied torques and misalignment angles. Even non linear variations behaved similarly for the most of the parameters. Both clearance and fretting wear were found to be in a direct relation with torque and misalignment angle. The parameters, namely peak count and mean height of the peaks have been found to be the most characteristic representation of fretting damage.     

Tractive performance and compaction effect of a road roller running on a weak sandy soil

This study aims to investigate the tractive performance of a two-axle, two-wheel vehicle with rear-wheel drive or brake and the compaction of a decomposed granite soil. The effects of traction or braking, the change of sinkage, the slip ratio of the front and rear roller, and the number of passes of the road roller were studied. A number of tests were conducted and the experimental data were compared with the theoretical analysis results. It was observed that the amount of sinkage on the front and rear roller took the minimum value when the front roller was in the unpowered rolling state and the slip ratio of the rear roller was almost zero. When the absolute value of the slip ratio of rear roller increased, the amount of sinkage on the front and rear rollers, the absolute value of the driven or braking force of the rear roller and the absolute value of effective tractive or braking effort of the road roller increased. When the front roller was in the unpowered rolling state and the rear roller was in the braking state at −5% skid, the compaction density of the soil was at a maximum.     

The universal earthmoving equation applied to chisel plough wings

This paper compares the results of tests which examined the effect of chisel plough wing geometry on tillage forces with those predicted by the Universal Earthmoving Equation as presented in E. McKyes' book Soil Cutting and Tillage, published by Elsevier (1985). The tests were conducted in the SAIT Tillage Test Track (an outside continous soil bin which contains a sandy loam soil) and in two field soild, one sandy loam and the other a red brown earth. The tests were conducted using a range of speeds from 5 to 15 km/h and at depths of 50 and 70 mm. The tests compared the effects of varying share wing width and rake angle. The comparison of the measured and predicted draft and vertical force responses showed a good correlation between the Universal Earthmoving Equation predictions and the measured width responses, but it did not always predict the correct rake angle responses.     

Soil disturbance and force mechanics of vibrating tillage tool

Experiments were conducted with vibrating tillage tools in a sandy loam soil. It was observed that during oscillating operation, initially draft increased slightly with an increase in forward speed but later it decreased. For the non-oscillating operation, draft increased continuously with increase in forward speed. The ratio of draft from oscillating to non-oscillating mode varied from 0.63 to 0.93. The total power required for oscillating operation was 41–45% more than the power required for non-oscillating operation. The soil surface was cracked due to tool motion showing the characteristics of lifting up of soil clods during the oscillating operation, whereas it showed the characteristics of soil flow during non-oscillating operation. The soil was pulverized more due to oscillating than non-oscillating operation. The reduction in dry bulk density of soil mass in the oscillating operation was about 70–270% more than that during the non-oscillating mode.     

The present state of force prediction models for rotary powered tillage tools

In the past, investigators of rotary tillage tools have concentrated their efforts in developing relationships between the power requirement and operational parameters of tillers. Many researchers have developed empirical force and torque prediction models without giving due consideration to the strength properties of soil. In the absence of proper soil-tool behaviour equations, the designers of rotary tools have relied on these empirical approaches. In recent years, the authors have proposed the first theoretical model for two-dimensional soil failure by a rotary powered blade. The presently available state-of-the-art ideas on rotary tilling force prediction models has been presented in this paper.     

Effects of non-smooth characteristics on bionic bulldozer blades in resistance reduction against soil

The phenomenon of soil adhesion occurs widely when terrain machines and construction machines work; this adhesion increases their working resistance. Bionics is one of the most effective methods to reduce resistance against soil. Several non-smooth convex form bulldozer blades were tested to study the effects of non-smooth characteristics on resistance reduction against soil. Under the same soil and test conditions, the draft forces of different non-smooth samples were obtained, and were lower than those of smooth samples. The sample with largest convex base diameter had the lowest draft force. The experiments with smooth and non-smooth samples were repeated to observe soil adhesion and test resistance. A minimum amount of soil adhered to the surface of the non-smooth sample, and the draft force varied smoothly. The smooth sample was different in soil adhesion and draft force.     

Design of a tool for injecting organic waste slurries in soil

The object of the study was to design a tool for the purpose of cutting, loosening and redepositing a sufficient soil volume to be mixed with a specified quantity of organic waste slurry such that the slurry would be completely covered. Laboratory tests were conducted to determine the best tool shape for this function and to minimize the draft force required in operation. The results of full scale field tests are also shown, including the comparison of draft force measurements with values predicted from mechanics theory.     

Steering forces on undriven, angled wheels

The steering forces at low speed and zero camber angle were measured on undriven, angled wheels using tyres with no tread. The forces were measured in a soil bin using a moist loam soil at different levels of compaction. It was found that the coefficient of side force relative to the wheel was related to slip angle by an exponential relationship. Coefficient of rolling resistance relative to the wheel was a linear function of slip angle in the region zero to 20° but was an irregular function of slip angle at higher angles. The effects of tyre size, load, inflation pressure and soil condition were modelled well using different versions of the tyre mobility number. The most successful version of mobility number was one which incorporated both soil cohesion and internal friction angle. The coefficients of the exponential and linear relationships mentioned above were predicted with varying degrees of success using mobility number.     

Tire slip-angle force measurements on winter surfaces

Tire lateral force data on winter surfaces cannot be obtained with the traditional laboratory test technique of an instrumented tire on a moving belt surface. Furthermore, changing snow and ice conditions can drastically change the tire/surface interaction. In this study the Cold Regions Research and Engineering Laboratory’s (CRREL’s) Instrumented Vehicle (CIV) was used in a unique configuration to measure tire lateral force versus slip-angle data on ice and snow at various temperatures, moisture contents, depths, and densities. The vehicle is instrumented to record longitudinal, lateral, and vertical force at the tire contact patch of each wheel as well as vehicle speed, tire speed, and front tire slip angle. The tests were conducted at the Keweenaw Research Center (KRC) in northern Michigan in February 2005 and March 2006. Tests were conducted on ice, packed snow from 0.50 to 0.58 g/cc, remixed snow depths of 2.5–20.3 cm at 0.43 to 0.48 g/cc and freshly fallen snow with depths of 0.5–17 cm at 0.07 to 0.23 g/cc. Surface air temperatures during testing ranged from −14 to 1.6 °C. The data collected show that peak lateral force and the shape of the lateral force versus slip-angle curve are related to snow properties and depths.     

Hysteresis in soil mechanical behavior

The performance of a vertical tine was investigated at various water contents during wetting and drying cycles in a clay-loam soil. Results showed that at a given water content the soil during the wetting cycle failed by fracture mode and offered relatively more draft. Soil during the drying cycle cracked, and when a tine was pushed through the soil, it failed along the cracks. This failure mode was referred to as preferential fracture. For a given water content, tine forces and soil shear strength properties were found to be greater during the wetting cycle than the drying cycle, which leads to the conclusion that there is a hysteresis effect in soil caused by drying stress induced by seasonal wetting and drying.     

直流磁场下销盘摩擦过程中的电磁感应力矩分析

为了研究磁场对材料摩擦磨损性能的影响,本文分析了直流磁场下销盘摩擦过程中的涡流和电磁感应力,并通过积分得到感应力矩的计算公式.在销盘0.1 mm间隙时检测了磁吸力和在不同试验条件下盘试样所受的感应力矩,利用试验数据对感应力矩公式中的修正系数进行了最小二乘法拟合,所得感应力矩公式的计算结果与不同电流和转速下的试验数据很好地吻合.在摩擦磨损过程中,可利用感应力矩公式计算出相应试验条件下盘所受的感应力矩,分析其对摩擦系数的影响.