Levels Of Inflation Pressure Research Articles

Evaluation of the Changes in Dimensions of the Footprint of Agricultural Tires under Various Exploitation Conditions

This paper presents an innovative method to determine the impact of agricultural wheels on soil. The experiment was conducted under controlled conditions, and the parameters of the tire footprints on the soil were analyzed. The tested parameters were the width, length, and depth of the footprint, the cross-section area of the tire, and the area of the footprint. All parameters were determined using the 3D scanning method. Two types of tires, two levels of vertical load, and three levels of inflation pressure were used. The aim of the research was to demonstrate differences in changes in the footprint parameters as a result of changes in the operational parameters of the tires. It was found the bias-ply tire was less responsive to changes in the width and length of the footprint than the radial tire. Moreover, it was shown that radial and bias-ply tires achieved similar values for the footprint area but in the case of bias-ply tires, there was a much greater footprint depth. This means that the side parts of the footprint of bias-ply tires have a more vertical profile, so they carry the vertical loads to a lesser extent.

First Stabilize and then Gradually Recruit: A Paradigm Shift in Protective Mechanical Ventilation for Acute Lung Injury.

Acute respiratory distress syndrome (ARDS) is associated with a heterogeneous pattern of injury throughout the lung parenchyma that alters regional alveolar opening and collapse time constants. Such heterogeneity leads to atelectasis and repetitive alveolar collapse and expansion (RACE). The net effect is a progressive loss of lung volume with secondary ventilator-induced lung injury (VILI). Previous concepts of ARDS pathophysiology envisioned a two-compartment system: a small amount of normally aerated lung tissue in the non-dependent regions (termed "baby lung"); and a collapsed and edematous tissue in dependent regions. Based on such compartmentalization, two protective ventilation strategies have been developed: (1) a "protective lung approach" (PLA), designed to reduce overdistension in the remaining aerated compartment using a low tidal volume; and (2) an "open lung approach" (OLA), which first attempts to open the collapsed lung tissue over a short time frame (seconds or minutes) with an initial recruitment maneuver, and then stabilize newly recruited tissue using titrated positive end-expiratory pressure (PEEP). A more recent understanding of ARDS pathophysiology identifies regional alveolar instability and collapse (i.e., hidden micro-atelectasis) in both lung compartments as a primary VILI mechanism. Based on this understanding, we propose an alternative strategy to ventilating the injured lung, which we term a "stabilize lung approach" (SLA). The SLA is designed to immediately stabilize the lung and reduce RACE while gradually reopening collapsed tissue over hours or days. At the core of SLA is time-controlled adaptive ventilation (TCAV), a method to adjust the parameters of the airway pressure release ventilation (APRV) modality. Since the acutely injured lung at any given airway pressure requires more time for alveolar recruitment and less time for alveolar collapse, SLA adjusts inspiratory and expiratory durations and inflation pressure levels. The TCAV method SLA reverses the open first and stabilize second OLA method by: (i) immediately stabilizing lung tissue using a very brief exhalation time (≤0.5 s), so that alveoli simply do not have sufficient time to collapse. The exhalation duration is personalized and adaptive to individual respiratory mechanical properties (i.e., elastic recoil); and (ii) gradually recruiting collapsed lung tissue using an inflate and brake ratchet combined with an extended inspiratory duration (4-6 s) method. Translational animal studies, clinical statistical analysis, and case reports support the use of TCAV as an efficacious lung protective strategy.

Effect of Increased Deflection Tire Technology on Soil Compaction

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.

Evaluation of Agriculture Tires Deformation Using Innovative 3D Scanning Method

This study presents the results of research related to agriculture tire deformation under variable vertical load and inflation pressure. The research objects were two tires of the same size and different internal structures. Three levels of inflation pressure and five levels of vertical load were used. The loaded tire with each inflation pressure was scanned using the 3D scanner—the effect of this operation was a three-dimensional image of a tire part (near the place of contact with the surface). The next step was the creation of vertical and horizontal cross-sections of the tire profile, which allowed the analysis of tested parameters: profile height, location of the point of maximum tire deflection, the width of the tire profile, and the area of horizontal cross-sections. Finally, the mathematical model was formulated, describing contact areas of horizontal cross-sections as a function of the factors. Based on the conducted research, it was stated that an increase in vertical load caused reductions in both types of heights. Moreover, the width of tire profiles and the area of horizontal cross-sections increased due to the increase in vertical load (for bias-ply, increases were smaller than for radial tires). Similar changes were observed after the reduction of inflation pressure.

Automatic adjustment of tire inflation pressure through an intelligent CTIS: Effects on the vehicle lateral dynamic behavior

The paper investigates the effect of tire inflation pressure on the lateral dynamics of a passenger car, and presents a possible control-oriented methodology aimed at adapting tire pressure to the current vehicle loading condition targeting a reference characteristic. Starting from the tire characteristics at several inflation pressure levels, the paper investigates the effect of changing selectively tire pressure on each of the two axles, through theoretical calculation of the curvature gain based on the computation of the derivatives of stability, and compares the obtained sensitivity to the results of a multibody simulation model validated through on-track tests. Finally, the work presents a possible algorithm that could be implemented on-board vehicle ECU to provide, for the current loading condition of the vehicle, a tire pressure combination that targets a specific lateral dynamics characteristic. The algorithm is intended as part of the control logic of an intelligent Central Tire Inflation System (CTIS) able to adjust automatically tire pressure according to the actual vehicle working conditions.

Relationships among the contact patch length and width, the tire deflection and the rolling resistance of a free-running wheel in a soil bin facility

Qualitative and quantitative analysis of contact patch length-rolling resistance, contact patch width-rolling resistance and tire deflection-rolling resistance at different wheel load and inflation pressure levels is presented. The experiments were planned in a randomized block design and were conducted in the controlled conditions provided by a soil bin environment utilizing a well-equipped single wheel-tester of Urmia University, Iran. The image processing technique was used for determination of the contact patch length and contact patch width. Analysis of covariance was used to evaluate the correlations. The highest values of contact length and width and tire deflection occurred at the highest wheel load and lowest tire inflation pressure. Contact patch width is a polynomial (order 2) function of wheel load while there is a linear relationship between tire contact length and wheel load as well as between tire deflection and wheel load. Correlations were developed for the evaluation of contact patch length-rolling resistance, contact patch width-rolling resistance and tire deflection-rolling resistance. It is concluded that the variables studied have a significant effect on rolling resistance.

Study on the variation characteristics of vertical equivalent damping ratio of tire–soil system using semi-empirical model

Prediction and determination of the damping ratio of a tire–soil system is very important to the design of the suspension system of the tractor. With this aim, a test rig was designed and developed to measure the vertical equivalent damping ratio of tire–soil system using Free-Vibration Logarithmic Decay Method. The test was performed with three kinds of tractor tire using a combination of five inflation pressure levels, three soil depths and four soil moisture contents in the paddy soil. The results revealed that the vertical equivalent damping ratio of tire–soil increases with the increase in soil depth and decreases with the increase in tire inflation pressure. It also increases with relative increase in soil moisture contents (observed at 37.9%, 48.8% and 66.7% soil moisture content) then decreases as soil moisture content is too high (observed at 77.4% soil moisture content). So, it is concluded that the vertical equivalent damping ratio of tire–soil system is evidently dependent on tire inflation pressure, soil moisture content and soil depth. These have to be noticed and used in design parameters of tractor suspension system.

Pressures and Timing of Intermittent Pneumatic Compression Devices for Efficient Tissue Fluid and Lymph Flow in Limbs with Lymphedema

Pneumatic compression of tissues with lymph stasis is, aside from the manual massage, a commonly used therapeutic modality in limb lymphedema. A number of pneumatic devices have been constructed. There is lack of reports of comparative studies determining inflation pressure levels, inflation/deflation cycle times, and total pumping times. We tried to answer the question how high compression pressure and how long compression timing should be applied to the limb soft tissues to reach tissue fluid (TF) head pressure above 30 mmHg, necessary to initiate proximal flow. TF pressures were measured subcutaneously during intermittent pneumatic compression in the lymphedematous limbs stage II to IV. Pressures of 50, 80, and 120 mmHg and timing 5, 20, and 50 sec were applied. a) the TF head pressures were lower than those in inflated chambers, b) inflation time of 5 and 20 sec was not long enough to generate TF head pressures above 30 mmHg, even if the compression pressures were as high as 120 mmHg, c) the 50 sec timing allowed to reach head pressures above 30 mmHg; however, they remained always lower than in the compression chamber, d) TF head pressures differed at various levels of the limb depending on the soft tissue mass, e) deflation of the inflated whole sleeve for 5 and 20 sec was followed by high end pressures, whereas that of 50 sec brought about pressure drop to 0, facilitating refilling with TF of the distal parts of the massaged limb. Our observations point to the necessity of applying high pressures and compression times over 50 sec, to generate effective TF pressures and provide enough time for creating TF flow. Short inflation times generate TF pressures as in one-chamber devices that preclude its effectiveness compared to the multi-chamber devices.

Measuring lung water: Ex vivo validation of multi‐image gradient echo MRI

To validate a fast gradient echo sequence for rapid (9 s) quantitative imaging of lung water. Eleven excised pig lungs were imaged with a fast GRE sequence in triplicate, in the sagittal plane at 2 levels of inflation pressure (5 and 15 cm H(2) O), an intervention that alters T(2) *, but not total lung water. Images were acquired alternating between two closely-spaced echoes and data were fit (voxel-by-voxel) to a single exponential to determine T(2) * and water content, and compared with gravimetric measurements of total water. T(2) * averaged 1.08 ± 0.02 ms at 5 cm H(2) O and 1.02 ± 0.02 ms at 15 cm H(2) O (P < 0.05). The measure was reliable (R(2) = 0.99), with an average mean error of 1.8%. There was a significant linear relationship between the two measures of water content: The regression equations for the relationship were y = 0.92x + 19 (R(2) = 0.94), and y = 1.04x + 4 (R(2) = 0.96), for 5 and 15 cm H(2) O inflation pressure respectively. Y-intercepts were not statistically different from zero (P = 0.86). The multi-echo GRE sequence is a reliable and valid technique to assess water content in the lung. This technique enables rapid assessment of lung water, which is advantageous for in vivo studies.

Impact behavior modeling of motorcycle front wheel-tire assembly

Experiments were conducted to investigate the influence of certain parameters that affect the impact response of the motorcycle front wheel-tire assembly under various impact conditions. Impact tests were conducted according to 2ν5 − 1 fractional factorial design using a pendulum impact test apparatus with impact speed, impact mass, tire inflation pressure level, striker geometry, and impact location as design factors. Significant factors influencing the response of the wheel-tire assembly were identified. Coefficients for each factor were also determined, and empirical models were then developed for each response. An analysis indicates that the developed models fit well within the experimental ranges of the respective factors. However, for several interaction effects, the models become unrealistic, whereby they give certain deformation values when approaching zero impact mass and/or zero impact velocity. This is not consistent with the mechanics of the physical world, as there should not be any significant deformation when delivered impact energy is small enough. Efforts have been made in developing better models to resolve the inconsistency and to include a wider range, especially considering the case of the lower limit of experimental factors, which are an impact mass of 51.18 kg and/or an impact velocity of 3 m s−1 (10.8 km/h) down to zero. The minimum amount of impact energy required to produce the onset of observable deformation on the wheel was incorporated in the development of new models. Finally, the present models have been developed not only to cover the lower regions but also to range up to the upper limits of the factors, which are an impact mass of 101.33 kg and an impact velocity of 6 m s−1 (21.6 km/h).

Performance prediction of animal drawn vehicle tyres in sand

Four animal drawn vehicle (ADV) tyres of 5.00–19, 6.00–19, 7.00–19 and 8.00–19 sizes were tested in sand under various but controlled conditions in an indoor soil bin. A tyre test carriage with four-bar parallel linkage was developed for accommodating a single wheel of different sizes. Performance tests were conducted at five levels of inflation pressure and load. The sand compaction level was varied in the range of 3.4–4.5 MPa/m and forward speed of the test carriage was maintained at 3.1 km/h. Performance of the tyres 7.00–19 and 8.00–19 was identical and offered less rolling resistance as compared to other tyres. However, their use in camel carts may not be recommended beyond the payload of 6 kN on single wheel with inflation pressure and sand compaction range of 172–379 kPa and 3.4 –4.5 MPa/m, respectively. Based on the experimental results, empirical models were developed to predict the performance of tyres. The accuracy of prediction of the developed empirical models was compared with that of existing semi-empirical approaches. Model with sand mobility number considered relatively simple and convenient to use in the field and yields reasonably good prediction for rolling resistance and sinkage.

Empirical model for impact response of motorcycle front spoked wheel-tyre assembly

An experimental study on the response of the motorcycle front wheel-tyre assembly in a frontal impact was conducted. A topological approach was employed whereby the post-impact projected deformation area of the wheel was selected as the response variable. Design factors included in the design of experiment were impact speed (S), impact mass (M), inflation pressure level of the tyre (P), contact geometry of the striker (G), and the offset distance of the impact location from the axle (D). A 2v5-1 fractional factorial design with four replications was applied. Statistical software, Minitab version 13, was employed in the experimental design and data analysis. The impact tests were conducted using the in-house developed pendulum impact test rig. A factorial analysis was performed to identify the significant factors influencing the responses of the wheel-tyre assembly. It was found that the influential effects for the response, excluding the torn-off cases, are the main effects S, M, P, and D, and interaction effects SM and PG. On the other hand, for the response including the torn-off cases, the main effects are the same but the interaction effects are slightly different, namely SM, MD, MG, and PG. These factors were then incorporated in the establishment of the empirical models for predicting the impact response of the wheel-tyre assembly. Regression analysis was also carried out to evaluate the yielded empirical models. Curves demonstrating the behaviour of the wheel under various impact conditions investigated were generated based on the empirical models. A comparison was also made with the findings where maximum residual crush was the response variable.

A study on radial directional natural frequency and damping ratio in a vehicle tire

The measurement of radial directional natural frequency and damping ratio in a vehicle tire has been studied. Natural frequencies and damping ratios in the radial direction of various tires, from passenger car tires to truck bus tires, are reported. The radial direction modal parameters of tires subjected to different levels of inflation pressure, have been determined by using a frequency response function method. To obtain the theoretical natural frequency and mode shape, the plane vibration of a tire has been modeled as though it were that of a circular beam. By using the Tielking method that is based on Hamilton’s principle, theoretical results have been determined by considering the rotational velocity, tangential and radial stiffness, radial directional velocity and tension force which is due to tire inflation pressure. The results show that experimental conditions can be considered as the parameters that shift the natural frequency and damping ratio.

Experimental study on energy absorption characteristics of motorcycle front wheel—tyre assembly in frontal impact

This article presents a study on the frontal impact properties of the motorcycle front wheel—tyre assembly using squared change of velocity and dissipated impact energy as response variables. The laboratory-scaled impact tests were performed on the wheel—tyre assemblies using pendulum impact test apparatus according to a 25−1 V fractional factorial design with four replicates. Five parameters that are included in the experiment were impact speed (S), impact mass (M), tyre inflation pressure level (P), contact geometry of striker (G) and offset distance of impact location from axle (D). The test specimen used in the study was a spoked wheel of size 1.40 × 17. Minitab has been employed to support the entire experimental process. The collected experimental data were organized, and factorial analysis was performed. The significant factors influencing the impact responses of the wheel—tyre assembly were identified, which are S, M, P, D, SM and SD. The associated empirical models were then established and presented, followed by the factorial plots for the respective significant factors. The curves demonstrating the impact response of the wheel—tyre assembly under various impact conditions were generated from the developed models to illustrate the impact response of the wheel—tyre assembly under various impact conditions within the experimental region. Comparison was made to the values of dissipated energy predicted by the developed model and the values of impact energy from fundamental kinetic energy equation, and it was found that the model is consistent with the physical condition within the experimental region.

An experimental study of deformation behaviour of motorcycle front wheel-tyre assembly under frontal impact loading

Experiments were conducted to study the deformation behaviour of front wheel-tyre assembly of a motorcycle when subjected to frontal impact loading. Impact tests were conducted using an in-house developed pendulum impact test apparatus. Statistical software, Minitab version 13, was employed to support the entire experimental process. Some of the parameters that influence response of the motorcycle in a frontal crash, viz., impact speed, impact mass, inflation pressure level of the tyre, contact geometry of the striker and offset distance of impact location from the axle were varied during the experiments. A 2 V 5 - 1 fractional factorial design was incorporated in the experimental investigation and is described in detail. Experimental results are presented in terms of the maximum residual crush sustained by the wheel, normalized area of deformation and dissipated impact energy. Regression analysis to relate the impact energy to maximum residual crush and normalized area of deformation was then performed. It was found that the deformation of the wheel-tyre assembly is well correlated to the dissipated impact energy. Factorial analysis was also performed to investigate the effect of individual parameters on response of the assembly. These are presented in factorial plots, followed by a brief discussion.

Soil stress state orientation beneath a tire at various loads and inflation pressures

Stress state transducers (SSTs) were used to determine the orientation of the major principal stress, σ 1, in soil beneath the centeline of an 18.4R38 radial-ply R-1 drive tire operated at 10% slip. Two soils, a sandy loam and a clay loam, were each prepared twice to obtain two density profiles. One profile of each soil had a hardpan and the soil above the hardpan was loose. The soil in the second profile was loosely tilled. The stress state was determined at a depth of 358 mm in the sandy loam and 241 mm in the clay loam soil. The tire was operated at two dynamic loads (13.2 and 25.3 kN), each at two levels of inflation pressure (41 and 124 kPa). When the orientation of σ 1 was determined directly beneath the axle, the mean angles of tilt in the direction of travel ranged from 6 to 23 degrees from vertical. Inflation pressure did not significantly affect the angle when the dynamic load was 13.2 kN in the sandy loam soil, and neither inflation pressure nor dynamic load significantly affected the angle in the clay loam soil. When the dynamic load was 25.3 kN in the sandy loam soil, the orientation of the major principal stress determined directly beneath the axle was tilted significantly more in the direction of travel when the tire was at 41 kPa inflation pressure than when at 124 kPa. These changes in stress orientation demonstrate the importance of measuring the complete stress state in soil, rather than stresses along only one line of action. The changing orientation of σ 1 as the tire passes over the soil indicates the soil undergoes kneading and supports future investigation of the contribution of changes in stress orientation to soil compaction.

HIGH-INFLATION PRESSURE AND POSITIVE END-EXPIRATORY: Injurious to the Lung? Yes

There is a growing body of evidence suggesting that high levels of inflation pressure and high levels of PEEP may be injurious to lung tissue and other organ systems. Limiting peak alveolar pressures below 35 cm H2O may help in avoiding these injuries. The findings have led to the development of a lung-protective strategy that is based on physiologic parameters. This strategy, often using permissive hypercapnia and pressure-limited modes of ventilation, may gain widespread use in the near future. If this strategy reduces barotrauma, a reduction in the length of time on mechanical ventilation and mortality rates can be anticipated. At our center we routinely initiate mechanical ventilation in patients with acute lung injury, using tidal volumes of approximately 6 mL/kg. This may be decreased further if peak alveolar pressures exceed 30 to 35 cm H2O. PEEP is added to maximize alveolar recruitment and oxygenation. Optimal PEEP is located at the inflection point of the respiratory compliance curve. Usually a PEEP of 8 to 12 cm H2O is sufficient. Although we usually initiate mechanical ventilation with a volume-cycled mode, we are not hesitant to switch rapidly to a pressure-limited mode if results are unsatisfactory. We believe that more attention to the potential harmful effects of pressure and volume on lung architecture may result in further improvement of survival in patients with acute respiratory failure.

Traction prediction using soil parameters obtained with an instrumented analog device

A fully instrumented device capable of measuring soil sinkage and shear parameters developed at the Agricultural Engineering Department, University of California, Davis was employed to conduct in situ sinkage and shear tests in a tilled and a farm, dry, Yolo loam soil. Similar tests were also conducted in a tilled, moist Yolo loam soil. An 18.4R38 tire was tested at different levels of inflation pressure and axle loads in these soil conditions. Soil parameters obtained using the instrumented device were related to the traction prediction equation parameters using traction mechanics, principle of conservation of energy and dimensional analysis.

Determination of dynamic three-dimensional soil-tyre contact profile

A technique for measuring the dynamic three-dimensional contact profile between a tyre and deformable soil has been developed. The method involves measuring incremental lateral arc lengths of the profile at discrete locations along the contact length and fitting the coefficients of a model of soil deformation at the soil-tyre interface to the experimental data using a nonlinear constrained optimization algorithm (SUMT). Two representations of the measured contact area were compared: (i) the two-dimensional surface which is the union of all points on the original undeformed soil surface which undergo deformation by the tyre; (ii) the final three-dimensional deformed surface. Contact area measurements were made for two different sized tyres at two levels of inflation pressure, dynamic load and slip in two different soil conditions. The contact width, length and area predicted by the technique were compared with corresponding values for static contact between a tyre and a rigid surface.

Performance of Log-Skidder Tires

ABSTRACT THE performance of three different sizes of log-skidder tires was compared at two travel reduction and two inflation pressure levels. Results indicated that when log-skidder tires are operated on dry soil conditions there is little effect on performance due to tire size. Inflation pressure should be set at the minimum recommended level for a particular tire load.