Agricultural Tire Research Articles

Effect of surface roughness on tyre characteristics

Tyre characterisation is not a trivial or inexpensive exercise thus it is important to obtain representative measurements during tyre characterisation tests. Different test methods exist and vary from laboratory tests to outdoor tests on different surfaces. Each of the test surfaces have different surface roughness and will result in different tyre characteristics. This study compares friction coefficient measurements on dry non-deformable surfaces for laboratory test surfaces and outdoor test tracks on the same agricultural tyre with large lugs at two inflation pressures and three tread wear conditions. The influence of surface roughness on friction coefficient is investigated. The macrotexture and microtexture of multiple surfaces are measured and compared. The importance of measuring the microtexture of the outdoor test surface is noted. Static/Non-rolling tyre tests in a laboratory are compared to Static/Non-rolling tyre tests as well as Dynamic/Rolling tyres tests at an outdoor test facility. Excellent correlation is found between the Static vs. Dynamic and laboratory vs. outdoor tests results when the laboratory tests are conducted on a surface representing the outdoor surface.

A Simplified Approach to the Evaluation of the Influences of Key Factors on Agricultural Tractor Fuel Consumption during Heavy Drawbar Tasks under Field Conditions

The optimization of energy input on agricultural farms, such as through improved fuel consumption, is currently under investigation in agricultural mechanization research with the aim of achieving economic and environmental goals. In previous research, we developed a simplified algorithm focused on defining the most efficient tractor–implement combination considering the factors that most influence this aspect. The ASABE (American Society of Agricultural and Biological Engineers) equation for calculating the drawbar pull force was adopted to fit the results to the soil conditions. Agricultural tires of different sizes were tested at different pressure settings under field conditions to assess differences in drawbar force. The resulting algorithm underwent a linear regression analysis to achieve a simplified equation for assessing the optimal wheel-slip, mass, engine power, and tire pull force properties during drawbar works that result in optimal fuel consumption with a minimal tractor efficiency impairment. Using a specific probability density function, the Monte Carlo Simulation method introduced randomness into the input and runs a sufficiently large number of trials to identify the most probable output. The result is a simplified algorithm that can be used to investigate the effects of certain parameters on fuel consumption; however, it can be adapted to evaluate the effects of different implements, tires, engine settings, or fleet management methods on fuel consumption.

Agricultural tyre stiffness change as a function of tyre wear

Vehicle designers use tyre characteristic parameters to parameterize tyre models during the design phase of a vehicle to determine the ride comfort, handling and performance. Tyre data is mostly presented only for new tyres with 100% tread on them. Soft terrain traction and minimal compaction have always been major requirements for agricultural tyres, however agricultural vehicles are increasingly being used on asphalt/non-deformable terrain as commercial farms are ever increasing in size. As operational costs are always forced to a minimum, agricultural vehicles operate with tyres ranging from new to fully used condition ranging from 100% down to almost 0% tread on them. During the operational life of a tyre the tyre characteristics change as the tyre tread wears down. This study investigates the change in tyre characteristics on hard terrain with tyre wear at a single load condition, two different inflation pressures and three tread wear conditions. Significant trends are noted with dramatic changes in traction and tyre stiffnesses as the tyre wear changes.

Use of 3D scanning technique to determine tire deformation in static conditions

This paper presents an innovative digital method to analyse agricultural tire profiles based on pictures. From this method, we can conclude that the tire deformation is caused by the changes in vertical load and inflation pressure. The first stage in this method is 3D-scanning; the vertical cross-section is created from the obtained picture of the tested tire. From this cross-section, the deflection of the tire can be determined. Then, the horizontal cross-section is created - this operation allows determining the tire’s contact area at the highest vertical deformation. Obtained results can be useful to create the tire deformation characteristic. In turn, the contact pressure values can be determined (even through laboratory testing, without research in field conditions). The knowledge about contact pressure allows taking some actions to reduce soil compaction. In the description of the method, the radial tire was used, but the structure and equipment of the test bench allow the use of cross-ply tires with different dimensions.

Relationship between the 3D Footprint of an Agricultural Tire and Drawbar Pull Using an Artificial Neural Network

HighlightsImprovement of tractor traction provides better field efficiency.Drawbar pull increased with tire footprint length.Drawbar pull decreased with increasing tire footprint volume and depth.3D footprint parameters, which the 2D footprint do not contain, affected the drawbar pull significantly.The ANN highlighted the relation adequately.Abstract.Improving the traction of an agricultural tractor on the field increases its working efficiency and capacity. Heavy work, like plowing, entails high levels of tire slip, which is directly related to power loss when the transmission of drawbar pull is required. Accordingly, it is possible to hypothesize that a tire with a higher traction capability could increase the working efficiency of the machine. The natural evolution for measuring the geometrical parameters of tires has led to the consideration of three-dimensional (3D) footprints since the distribution of the vertical stresses at the soil–tire interface may be highly non-uniform. In this study, the data acquired from 3D footprints of 10 sets of tires underwent processing along with the data from drawbar tests carried out with the same tires on soil terrain at different slip ratios. Subsequently, artificial intelligence multivariate methods based on artificial neural networks allowed traction prediction and verified the importance that the acquired geometrical parameters have on the measured drawbar pull. The study confirmed the correlation of the geometrical parameters of the 3D tire footprint with the drawbar pull and the results of the artificial intelligence modelling underlined the impact of these acquisitions. However, further work that considers various lug geometries is required to extend the generalizability of the studied methodology. Keywords: Field efficiency, Phenolic resin, Traction, Tractor.

Ground tyre rubber produced via ambient, cryogenic, and waterjet milling: the influence of milling method and particle size on the properties of SBR/NR/BR compounds for agricultural tyre treads

ABSTRACT The increasing number of scrapped tyres constitutes a global problem. One way of recycling them is to mill the rubber waste to produce ground tyre rubber (GTR), which is utilised as a component of fresh rubber compounds for manufacturing new tyres. This paper is focused on the characterisation and application of five grades of GTR produced via three methods: ambient, cryogenic, and waterjet milling. Each GTR was separated using sieves into five size fractions. Each fraction was mixed into a fresh rubber compound based on styrene–butadiene rubber (SBR), natural rubber (NR), and butadiene rubber (BR), designed for agricultural tyre tread. The higher Mooney viscosities of GTR-containing compounds indicate different processability while the curing properties changed only moderately. Smaller GTR particles result in better mechanical properties than larger ones. The waterjet milling process seems to be the most perspective.

Уточненная методика определения площади опорной поверхности шин современной сельскохозяйственной техники

It has been established that the predictive assessment of the level of impact on the soil of tractors and agricultural machines is based on the calculation of the specific pressure equal to the ratio of the vertical load to the propeller contact surface area. A mathematical model is proposed that has been developed based on the results of field tests of a large number of samples of agricultural tires. The adequacy of the model was assessed using the Nash-Sutcliffe efficiency coefficient.

Full-field and point strain measurement via the inner surface of a rolling large lug tyre

Vehicle safety and performance can be dramatically improved if force or friction measurement of the tyre-terrain interface is known. Since the tyre-terrain interface is responsible for the majority of forces acting on the vehicle, this region has received a lot of attention in vehicle dynamics. Direct measurement of the tyre-terrain interface is difficult since it is hidden by the tyre and terrain. A lot of research has been conducted on the inside of tyre using accelerometers or strain gauges with research more focussed on passenger car tyres and very little work performed on agricultural tyres with larger lugs. This study performs strain measurements using point measurement, from strain gauges, and full field measurement, using a stereo camera measurement system, of the inside of an agricultural tyre on a drum test rig during vertical and lateral loading. Results show similar trends when compared to results on passenger car tyres, however the mounting of the strain gauge relative to the lug is shown to play a large role in the developed strain. Linear relationships between the applied tyre force and strain were obtained in different direction with R2 values above 0.97.

Investigating the effect of farmyard manure on clay soil compactibility

One of the important factors that can control and decrease soil compaction is incorporation farmyard manure to the soil. It increases soil elasticity and soil tolerance to the imported load. To evaluate the farmyard manure effect on the soil compaction, it was incorporated in the clay soil at different rates of 0, 45, 60, and 90 Mg ha<sup>-1</sup>. Tests were conducted at different tire passes of 1, 6, 11 and 16 on the same track at three soil moisture contents of 8%, 11% and 14% (dry base); soil bulk density was measured at depths of 10, 20, and 30 cm. To evaluate soil compaction, cylindrical cores were employed to measure the soil bulk density. To assess soil behavior during the soil compaction process, three displacement transducers were placed in the soil in three coordinate directions of x, y and z. The soil volumetric change was measured using the transducers and soil sinkage was also measured. A single-wheel tester was used in a soil bin with a Barez 8.25-16 (8) P.R HLF agricultural tractor tire operated at a forward velocity of 0.8 m s<sup>-1</sup> under a vertical load of 4 kN and an inflation pressure of 300 kPa. Incorporating the farmyard manure noticeably decreased the final vertical and longitudinal displacement below the tire track, while the lateral displacement increased. Bulk density decrements of 14.7%, 9.7% and 6.3% were occurred via farmyard manure application rates of 90, 60 and 45 Mg ha<sup>-1</sup>, respectively. Maximum soil sinkage occurred at 14% moisture, 16 passes of tire and with no manure condition.

Dynamic Characteristics of Rolling Agricultural Tire

Dynamic Characteristics of Rolling Agricultural Tire

OPERATIONAL PERFORMANCE OF AN AGRICULTURAL TRACTOR UNDER DIFFERENT TIRE INFLATION PRESSURES IN THE SUBSOILING OPERATION

For the agricultural tractor's best performance, it must be correctly adapted to the job. Among other factors, the adequacy of tire inflation pressure is one of the most important and may influence the operation's efficiency and productivity. This study aimed to evaluate an agricultural tractor's operational performance with different tire inflation pressures in the subsoiling operation. The study was carried out in an experimental area of the Agricultural Machinery and Mechanization Laboratory of the experimental farm “Água Limpa,” belonging to the University of Brasília. The experimental design used was in randomized blocks with the following values, 206.8 kPa (30 psi), 137.9 kPa (20 psi), and 68.9 kPa (10 psi), of inflation pressure for agricultural tractor tires. The mechanized set used was a tractor model TM7020 2WD MFWD pulling a subsoiler with five shanks, SPCR model, in a Latossolo Vermelho-Amarelo. The higher inflation pressure resulted in greater slippage, advance, hourly fuel consumption, and lower speed and operational field capacity.

DETERMINATION OF RATIONAL OPERATING MODES OF OPERATION OF TRACTOR AGRICULTURAL TIRES

The efficiency of wheeled agricultural tractors when performing traction technological operations is characterized by two aspects. The first of these is traction efficiency, which mainly depends on the coupling weight of the tractor and the perfection of its running system. Another aspect is environmental friendliness, which is determined by the level of compaction impact on the soil. In general, these aspects are oppositely directed. That is, an increase in traction efficiency requires an increase in the grip weight and, as a consequence, an increase in the radial load on the tires and the internal pressure in them. This leads to an increase in tire pressure on the ground and deterioration in their environmental performance. As a result of excessive soil compaction, the yield of agricultural crops is significantly reduced. To solve this problem, it is necessary to reduce the tire pressure on the ground, which can be achieved by reducing the grip weight or developing and introducing new innovative tire designs. But, even new innovative tire designs have corresponding limitations due to the radial load interval, internal pressure, travel speed and the amount of torque on the wheel. These restrictions form the area of possible operating modes of tractor tires, individual sections of which differ significantly in terms of traction efficiency and environmental friendliness. Within the limits of possible modes of operation of the tire, operating modes must be implemented in areas of high efficiency and environmental friendliness. The materials of this article are basic in the study and substantiation of rational operating modes of tractor agricultural tires, and also provide prerequisites for the formation of recommendations for improving the traction efficiency and environmental friendliness of wheeled tractors

Full-field strain measurements of the inside of an agricultural tyre using digital image correlation

This paper investigates strain measured on the inside of an agricultural tyre with large tread-blocks during a series of static tests using a novel measuring system. The full field strain measurements may be used in the development of a tyre which is capable of estimating tyre forces from strain measurements. The strain measurement system makes use of a calibrated stereo camera system on a mechanical stabilizing system that keeps the cameras pointed at the inside surface of the tyre in contact with the road while the wheel rotates. A static tyre test rig is used to displace the road surface relative to the tyre in the vertical and longitudinal direction. The large tread-blocks caused strain concentrations on the inner surface as the tyre deforms to comply with the road surface. Vertical and longitudinal tests each produce unique strain patterns in the contact patch region. Relationships between the applied forces and strain measurements were developed and showed that these relationships are near linear with R2 values above 0.97. The strain measurements also show that the location where strain gauges, for single point strain measurements, are placed inside the tyre is very important on large lugged tyres.

An Experimental–Numerical Approach for Modelling the Mechanical Behaviour of a Pneumatic Tyre for Agricultural Machines

The mechanical behaviour of an agricultural tyre is a matter of extreme interest as it is related to the comfort of operators, to the adherence of agricultural machines, and to the compaction of agricultural soil. Moreover, the deformability of the tyres plays a fundamental role in vehicle stability in terms of side rollover. The behaviour of a loaded tyre during its deformation is complex, due to the combined contributions of the carcass components, the tread rubber and the air contained within it. Therefore, this study proposes an experimental–numerical approach for the mechanical characterization of agricultural tyres based on real-scale experiments and matches these results with a finite-element (FE) model. The tyre flattening in the elastic field has been described using two coefficients (Young’s modulus “E”, Poisson’s ratio “ν”), whose values have been identified with an iterative FEM procedure. The proposed approach was applied to two different tyres (420/85 R24 and 460/85 R34), each one inflated at two different pressures (1.0 bar and 1.6 bar). Young’s modulus was appreciated to be highly variable with the inflation pressure “p” of the tyres. Furthermore, the response surface methodology was applied to find two mathematical regression models, useful for studying the variations of the tyre footprint dimensions according to the type of tyre. This simple approach can be applied in other simulations without suffering any loss of accuracy in the description of the phenomenon.

Motion resistance measurements on large lug tyres

Motion resistance of tyres directly contribute to the operational costs of all vehicles. Advances in the design and simulation of large off-road vehicles (construction, mining, agriculture etc.) have increased the need for accurate models of large off-road tyres. Vehicle OEMs use coast down and drawbar pull tests to determine the motion resistance of tyres used. Drum test rigs and motion resistance test trailers can also be used to determine motion resistance. Most research on motion resistance to date have been conducted on passenger car tyres with on-road truck tyres coming into focus. Motion resistance studies on agricultural tyres traversing over deformable terrain have been conducted in the past. However as more off-road vehicle are being used on-road OEMs of off-road vehicle are infesting in motion resistance measurements on non-deformable terrain. This paper compares different methods used to measure the motion resistance of a large lug tyre, as used in agricultural applications, on non-deformable terrain. Some basic considerations that need to be taken into account are the very low longitudinal forces that need to be measured compared to the large vertical load carried by the tyre and tyre operating conditions.

Prediction of energy dissipation of off-road vehicles using smoothed-particle hydrodynamics techniques

This paper studies the energy dissipated during experimental and simulated procedures for the pressure-sinkage and shear-strength test. These tests are performed using a clayey-loam soil and modelled as smoothed-particle hydrodynamics (SPH) technique in Visual Environment's Pam-Crash software. The hydrodynamic elastic plastic material is used to define the equation of state for the clayey-loam soil. The soil is modelled at five different levels of compaction to represent multi-pass of a tyre over soil. The soil calibration is performed using the pressure-sinkage and direct shear-strength test and validated using experimental data from a soil bin facility. The energy dissipation is calculated using the soil sinkage values at every pass of wheel. Finally, the results of experimental and simulation dissipation energy are discussed and the effect of the tyre multi-pass on dissipated energy is investigated and presented. This research will further continue to model an agricultural FEA tyre over the clayey-loam soil to compute tyre performance and interaction characteristics.

Specifics of certification of agricultural tires with maximum consideration of their operating conditions

The problems of product quality and competitiveness are typical in the modern world. The international market constantly demands the improvement of the performance properties of automobiles, tractors, agricultural machinery and other types of mobile vehicles. At the same time, they can not be increased without significant improving of the tire performance characteristics. Pneumatic tires are among the critical units of mobile vehicles that have a significant impact on the following performance properties; therefore, as a complex product, they were included in the list of approval in accordance with Regulation No 106 for agricultural vehicles and their trailers. The purpose of the research was to develop recommendations for improving the methodology of conducting certification tests of agricultural tires aimed at improving product quality. The article discusses the methods of certification and approval of tires for agricultural vehicles and their trailers. The drawbacks of the method of certification of agricultural tires using the method of automobile ones are analyzed. It is proposed to supplement the certification with test methods developed in the Russian Federation that are as close as possible to the operating conditions of agricultural vehicles and tires of traction machines. The experience of work of “Bridgestone” and “Michelin” companies in the Russian Federation is presented. The absence of a national tire certification system in Russia influence in many cases vehicle breakdowns, which lead to downtime, as well as to the occurrence of accidents. In case of serious accidents in transport, when there is insufficient clarity of the causes of the accident or it is clear that the accident is related to tire failure, the victims initiate legal proceedings against the manufacturers, involving the payment of monetary compensation. At the same time, mass production defects are usually hidden behind the losses of consumers. To improve the quality of agricultural tires, it is proposed to revise UN/ECE Regulation No 106 as close as possible to operating conditions, as well as to create an independent accredited tire center.

Computational and experimental assessment of the influence of ultra-low pressure tires of mobile power equipment on soil

The article describes a method for determining the maximum pressures in contact of an ultra-low pressure tire with deformable soil: with low bearing capacity using the example of a thin-walled tire 1020x420-18 of the Bel-79 model. In the current practice of determining the effect of pneumatic tires on the soil, the method of determining the contact area of a tire on an undeformable flat bearing surface is used. By dividing the load on the tire by the obtained contact area, multiplied by correction factors, the maximum tire pressure on the soil is obtained. By comparing the maximum pressure obtained in the tire contact with the non-deformable bearing surface with the permissible pressure, the correspondence of tractor and agricultural tires to operating conditions on soils with a certain moisture and hardness is evaluated. But this method of assessment is unacceptable for tires of low and ultra-low pressure due to significant deformation of the tire and soil: in contact and, therefore, a larger contact area and lower values of maximum and average pressure on the soil. Therefore, the novelty of the work is an experimental assessment of the impact on the soil of tires of low and ultra-low pressure on deformable soil. The method includes the experimental determination of the dependence of tire and ground deformations on air pressure in a tire and load, as well as the dependence of the contact area sizes on deformable soil on tire and ground deformations. The contact areas and the coefficients of the uneven distribution of pressure in the contact according to the average values and shapes of the diagrams determine the maximum pressure in the contact of the tire with deformable soil. As a result, the curves of the dependences of maximum pressures in contact on air pressures and loads on deformable soil for low and ultra-low pressure tires were obtained for the first time. The dependences of maximum pressures in contact on air pressure at fixed loads can be a kind of passport for thin-walled tires, similar to the traction characteristics of tractor tires and the traction and speed characteristics of automobile tires. The results obtained make it possible to determine with high accuracy the operating conditions of high-traffic vehicles on low and ultra-low pressure tires.

Determination of the maximum pressure on the soil of agricultural tires with different ballasting methods of tractor

The theoretical analysis of the maximum pressure on the soil of tractor tires with different methods of tractor ballasting is presented. The mathematical model of an empty and liquid ballasted agricultural tire is presented. Problem. As the standards of the running systems of mobile agricultural machinery on the soil limit the maximum pressure of wheeled tractors on the soil, there is a contradiction between high traction efficiency and harmful effects on the environment. The goal of the research is to perform a comparative analysis of the maximum tire pressure on the soil with two methods of increasing the tractor's weight: by installing cast iron ballast and filling the tires with ballast liquid. In solving the final goal, a methodology that provided the analytiсal methods for evaluating the effect of the tire filling with ballast fluid on its stiffness, load capacity and the area of contact area with the soil, is used. As a result it has been found that the tire stiffness increases by 3.5–5.5% when filled with 75% and practically does not change when filled with 40% by liquid ballasting. Cast iron ballasting is a versatile way to increase tractor weight, with maximum soil pressure 4.5–6.5% lower than tire liquid filling. Options for 75% and 40% liquid ballast for the use of water and calcium chloride solution as ballast liquid are considered. The originality of the work is to determine the maximum pressure on the soil of the agricultural tire ballasted with liquid and to compare it with traditional cast iron ballasting by the level of maximum pressure on the topsoil. The practical value of the work is, at the stage of designing or upgrading the wheeled tractor, to provide recommendations on possible method of the tractor ballasting, taking into account the agro–environmental requirements for maximum soil pressure.

Development of an HLFS agricultural tire model using FEA technique

This paper proposes a new high lug farm service (HLFS) agricultural tire size 220/70B16 tread design used for off-road agricultural operation. The HLFS tire is modeled using finite element analysis (FEA) technique in Visual Environment’s Pam-Crash software. The HLFS tire is designed using a combination of different materials including the Mooney–Rivlin material for tread. The Mooney–Rivlin material is an hyper-elastic material and it accurately resembles the mechanics and behavior of rubber used in tires. The FEA tire model is then validated against manufacturer’s provided data for several tire characteristics including radial, lateral, and tangential stiffness. This research will further continue to investigate the HLFS tire performance over clayey loam for different operating conditions.