The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Thomas Keller - One of the best experts on this subject based on the ideXlab platform.
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Construction of modern wide, low-Inflation Pressure tyres per se does not affect soil stress
Soil and Tillage Research, 2020Co-Authors: Loraine Ten Damme, Thomas Keller, Matthias Stettler, François Pinet, Patrick Vervaet, Lars J. Munkholm, Mathieu LamandéAbstract:Abstract The interaction between rolling gear and soil is complex, but most important for the stress distribution in the soil profile. We explored the effect of three types of wide, low-Inflation Pressure tyres with similar dimensions on mean normal stress throughout the soil profile. We first tested the hypothesis that the stress is not affected by specific tyre-construction. Second, we tested the benefit of lowering the tyre Inflation Pressure to a minimum for the tyre with the lowest recommended Inflation Pressure. Finally, we tested the effect of tyres with similar tractive potential at different wheel loads, i.e. with a different weight-pull ratio. Stress measurements were made with Bolling probes at six positions simultaneously: both beneath the centreline (centre) and at 0.3 m lateral distance (+0.3 m) of the centreline of the wheel track, at 0.2, 0.4, and 0.6 m depth. The results revealed a very limited effect of tyre construction on mean normal stress. No differences were measured beneath the centre, and the differences at +0.3 m were found only at 0.2 m depth for the tyres at the rear axle. The effect of minimising tyre Inflation Pressure was limited to the upper parts of the soil profile for the measurements beneath the centre of the tyre (significant at 0.2 m depth and a trend at 0.4 m depth). Finally, our study did not reveal significant benefit of tyres with a lower wheel load while potentially having similar tractive performance, although the reduction of wheel load and associated lower Inflation Pressure potentially reduce stress in both top- and subsoil. The results emphasize that in order to reduce soil stress, tyre design and use should allow for a large contact area and low Inflation Pressure.
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modelling effects of tyre Inflation Pressure on the stress distribution near the soil tyre interface
Biosystems Engineering, 2008Co-Authors: Per Schjonning, Mathieu Lamandé, Johan Arvidsson, Frede Aakmann Togersen, Thomas KellerAbstract:Several investigations have shown that the distribution of vertical stress in soil just below a loaded tyre is not uniform. The stress distribution and the size and form of the tyre–soil interface are decisive for the stress propagation in the soil profile. We measured the distribution of vertical stress in the contact area for two radial-ply agricultural trailer tyres (650/65R30.5 and 800/50R34) loaded with ∼60 kN. The study took place on a sandy soil at a water content slightly less than field capacity. We tested the effect of three different Inflation Pressures (50, 100 and 240 kPa) in a randomised block design with three replicates. The vertical stress was measured with load cells located in 0.1 m soil depth. The vertical stress data were used also for identifying the soil area in contact with the tyre, i.e. the tyre footprint. A model (named FRIDA) is proposed that describes the tyre footprint by a super ellipse and the stress distribution by a combined exponential (perpendicular to the driving direction) and power-law (along the driving direction) function. The contact area doubled when the Inflation Pressure was reduced from 240 to 50 kPa. For both tyres, the measured peak stress increased significantly with tyre Inflation Pressure and was generally about 90 kPa higher than tyre Inflation Pressure. The model-fitted maximum stress was about 50 kPa higher than the Inflation Pressure. The 650/65R30.5 tyre displayed a longer footprint and a more uniform stress distribution in the driving direction and performed better at non-recommended Inflation Pressures than the 800/50R34. At the recommended Inflation Pressure, both tyres displayed a stress distribution across the width of the wheel that could be evaluated as optimal with regard to a minimised topsoil compaction. The suggested model seems very well suited for describing real stress distributions at the soil–tyre interface, but should be validated also with other tyres, wheel loads, and soil conditions. It has the potential to improve soil compaction models considerably and also for use to evaluate important features of tyres with scope to improve future designs.
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soil stress as affected by wheel load and tyre Inflation Pressure
Soil & Tillage Research, 2007Co-Authors: Johan Arvidsson, Thomas KellerAbstract:Abstract The relative importance of wheel load and tyre Inflation Pressure on topsoil and subsoil stresses has long been disputed in soil compaction research. The objectives of the experiment presented here were to (1) measure maximum soil stresses and stress distribution in the topsoil for different wheel loads at the same recommended tyre Inflation Pressure; (2) measure soil stresses at different Inflation Pressures for the given wheel loads; and (3) measure subsoil stresses and compare measured and simulated values. Measurements were made with the wheel loads 11, 15 and 33 kN at Inflation Pressures of 70, 100 and 150 kPa. Topsoil stresses were measured at 10 cm depth with five stress sensors installed in disturbed soil, perpendicular to driving direction. Contact area was measured on a hard surface. Subsoil stresses were measured at 30, 50 and 70 cm depth with sensors installed in undisturbed soil. The mean ground contact Pressure could be approximated by the tyre Inflation Pressure (only) when the recommended Inflation Pressure was used. The maximum stress at 10 cm depth was considerably higher than the Inflation Pressure (39% on average) and also increased with increasing wheel load. While tyre Inflation Pressure had a large influence on soil stresses measured at 10 cm depth, it had very little influence in the subsoil (30 cm and deeper). In contrast, wheel load had a very large influence on subsoil stresses. Measured and simulated values agreed reasonably well in terms of relative differences between treatments, but the effect of Inflation Pressure on subsoil stresses was overestimated in the simulations. To reduce soil stresses exerted by tyres in agriculture, the results show the need to further study the distribution of stresses under tyres. For calculation of subsoil stresses, further validations of commonly used models for stress propagation are needed.
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technical solutions to reduce the risk of subsoil compaction effects of dual wheels tandem wheels and tyre Inflation Pressure on stress propagation in soil
Soil & Tillage Research, 2004Co-Authors: Thomas Keller, Johan ArvidssonAbstract:Abstract The use of heavy machinery is increasing in agriculture, which induces increased risks of subsoil compaction. Hence, there is a need for technical solutions that reduce the compaction risk at high total machine loads. Three field experiments were performed in order to study the effects of dual wheels, tandem wheels and tyre Inflation Pressure on stress propagation in soil. Vertical soil stress was measured at three different depths by installing probes into the soil horizontally from a dug pit. In one experiment, also the stress distribution below the tyre was measured. Beneath the dual wheels, vertical stresses at 0.15 and 0.3 m depth were lower between the two wheels than under the centre of each wheel, despite the gap between the wheels being small (0.1 m). At 0.5 m depth, vertical stress beneath the wheels was the same as between the two wheels. The stress interaction from the two wheels was weak, even in the subsoil. Accordingly, measured stresses at 0.3, 0.5 and 0.7 m depth were highest under the centre of each axle centre line of tandem wheels, and much lower between the axles. For a wheel load of 86 kN, tyre Inflation Pressure significantly affected stress at 0.3 m depth, but not at greater depths. Stress directly below the tyre, measured at 0.1 m depth, was unevenly distributed, both in driving direction and perpendicular to driving direction, and maximum stress was considerably higher than tyre Inflation Pressure. Calculations of vertical stress based on Boussinesq's equation for elastic materials agreed well with measurements. A parabolic or linear contact stress distribution (stress declines from the centre to the edge of the contact area) was a better approximation of the contact stress than a uniform stress distribution. The results demonstrate that stress in the soil at different depths is a function of the stress on the surface and the contact area, which in turn are functions of wheel load, wheel arrangement, tyre Inflation Pressure, contact stress distribution and soil conditions. Soil stress and soil compaction are a function of neither axle load nor total vehicle load. This is of great importance for practical purposes. Reducing wheel load, e.g. by using dual or tandem wheels, also allows tyre Inflation Pressure to be reduced. This reduces the risk of subsoil compaction.
Bahattin Tuncali - One of the best experts on this subject based on the ideXlab platform.
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Controlled hypotension and minimal Inflation Pressure: a new approach for pneumatic tourniquet application in upper limb surgery.
Anesthesia and analgesia, 2003Co-Authors: Bahattin Tuncali, Ayse Karci, Abdul Kadir Bacakoglu, Ahmet EkinAbstract:UNLABELLED Minimal Inflation Pressures are recommended for limb surgery to eliminate complications attributable to high Inflation Pressures with the pneumatic tourniquets. We applied controlled hypotension and a minimal Inflation Pressure (CHAMIP) technique to provide a bloodless surgical field. Thirty-six patients scheduled for upper extremity surgery were randomized equally to receive either normotensive anesthesia and conventional Inflation Pressures or controlled hypotension (systolic arterial blood Pressure of 80-100 mm Hg and mean arterial blood Pressure >60 mm Hg) and minimum Inflation Pressures. Anesthesia was induced with propofol IV bolus and remifentanil IV continuous infusion and maintained with propofol and remifentanil IV continuous infusion. To determine the minimal Inflation Pressure, the digital plethysmograph was applied to the second finger at the side of the operation and the tourniquet was inflated slowly until the arterial pulsations disappeared on the oscilloscope. A bloodless surgical field was obtained in almost all patients, even though systolic arterial blood Pressures (100-138 mm Hg versus 80-100 mm Hg) and applied tourniquet Inflation Pressures (270 mm Hg versus 110-140 mm Hg) were significantly lower in the hypotensive group. No complications associated with controlled hypotension were encountered. In conclusion, CHAMIP may be a safe and reliable method for upper extremity surgery performed with pneumatic tourniquets. IMPLICATIONS Pneumatic tourniquets are associated with adverse effects resulting from high Inflation Pressures. Therefore, minimal Inflation Pressures are recommended in extremity surgery. To reach real minimal Inflation Pressure the patient's blood Pressure must be reduced. We used controlled hypotension with remifentanil and propofol to reach minimal Inflation Pressures.
Mohammad Gholami - One of the best experts on this subject based on the ideXlab platform.
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Modeling of bias-ply tire deflection based on section width, Inflation Pressure, vertical load and rotational speed.
2014Co-Authors: Kamran Rafiee, Majid Rashidi, Mohammad GholamiAbstract:This study was conducted to model deflection ( ) of bias-ply tire based on section width (b), Inflation Pressure (P), vertical load (W) and rotational speed (N). For this purpose, deflection of three bias-ply tires with different section width were measured at three levels of Inflation Pressure, four levels of vertical load and six levels of rotational speed. In order to model deflection based on section width, Inflation Pressure, vertical load and rotational speed, a four-variable linear regression model was suggested and all the data were subjected to regression analysis. The statistical results of study indicated that the four-variable linear regression model = 16.526 + 0.0182 b - 0.3667 P + 0.0356 W - 0.0050 N with R = 0.952147 may be suggested to predict deflection 2 of bias-ply tire based on section width, Inflation Pressure, vertical load and rotational speed for a limited range of bias-ply tire sizes.
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Modeling of Radial-Ply Tire Rolling Resistance Based on Tire Dimensions, Inflation Pressure and Vertical Load
American-Eurasian Journal of Agricultural and Environmental Science, 2014Co-Authors: Mohammad Mohammadi, Majid Rashidi, Mohammad GholamiAbstract:This study was conducted to model rolling resistance (R) of radial-ply tire based on tire dimensions, viz., section width (b) and/or overall unloaded diameter (d), Inflation Pressure (P) and vertical load (W). For this purpose, rolling resistance of three radial-ply tires with different section width and/or overall unloaded diameter were measured at three levels of Inflation Pressure and four levels of vertical load. In order to model rolling resistance based on dimensions, Inflation Pressure and vertical load, seven multiple-variable regression models were suggested and all the data were subjected to regression analysis. The statistical results of study revealed that the multiple-variable regression model R = - 0.17827 + 0.00465 d - 0.00168 P + 0.03161 W with R = 0.976 may 2
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Modeling of Rolling Resistance for Bias-Ply Tire Based on Tire Dimensions, Inflation Pressure and Vertical Load
2014Co-Authors: Majid Rashidi, Mohammad Gholami, Mohammad Mohammadi, Ali Hajiaghaei, Mohsen AlikhaniAbstract:This study was conducted to model rolling resistance (R) of bias-ply tire based on tire dimensions, viz., section width (b) and overall unloaded diameter (d), Inflation Pressure (P) and vertical load (W). For this purpose, rolling resistance of three bias-ply tires with different section width and/or overall unloaded diameter were measured at three levels of Inflation Pressure and four levels of vertical load. In order to model rolling resistance based on dimensions, Inflation Pressure and vertical load, seven multiple-variable regression models were suggested and all the data were subjected to regression analysis. The statistical results of study revealed that the multiple-variable regression model R = - 0.09986 - 0.00985 b + 0.00639 d - 0.00124 P + 0.04003 W with R = 0.9817 may be suggested to predict rolling resistance of bias-ply tire based on tire dimensions 2 (section width and overall unloaded diameter), Inflation Pressure and vertical load for a limited range of tire sizes. However, experimental verification of this model is necessary before the model can be recommended for wider use.
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Modeling of Bias-Ply Tire Deflection Based on Tire Dimensions, Inflation Pressure, Vertical Load and Rotational Speed
2014Co-Authors: Kamran Rafiee, Majid Rashidi, Mohammad Gholami, Parham Fatehirad, Siamak Akhtarkavian, Babak JaberinasabAbstract:This study was conducted to model deflection ( ) of bias-ply tire based on tire dimensions, viz., section width (b) and overall unloaded diameter (d), Inflation Pressure (P), vertical load (W) and rotational speed (N). For this purpose, deflection of three bias-ply tires with different section width and overall unloaded diameter were measured at three levels of Inflation Pressure, four levels of vertical load and six levels of rotational speed. In order to model deflection based on dimensions, Inflation Pressure, vertical load and rotational speed, seven multiple-variable linear regression models were suggested and all the data were subjected to regression analysis. The statistical results of study indicated that the five-variable linear regression model = 16.602 + 0.0203 b - 0.0006 d - 0.3667 P + 0.0356 W - 0.0050 N with R = 0.952152 may be suggested to 2 predict deflection of bias-ply tire based on section width, overall unloaded diameter, Inflation Pressure, vertical load and rotational speed for a limited range of bias-ply tire sizes. However, experimental verification of this model is necessary before the model can be suggested for wider use.
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Modeling of Deflection for Radial-Ply Tire Based on Tire Dimensions, Inflation Pressure, Vertical Load and Rotational Speed
2014Co-Authors: Parham Fatehirad, Kamran Rafiee, Majid Rashidi, Mohammad Gholami, Babak Jaberinasab, Siamak AkhtarkavianAbstract:This study was conducted to model deflection ( ) of radial-ply tire based on tire dimensions, viz., section width (b) and overall unloaded diameter (d), Inflation Pressure (P), vertical load (W) and rotational speed (N). For this purpose, deflection of three radial-ply tires with different section width and overall unloaded diameter were measured at three levels of Inflation Pressure, four levels of vertical load and six levels of rotational speed. In order to model deflection based on dimensions, Inflation Pressure, vertical load and rotational speed, seven multiple-variable linear regression models were suggested and all the data were subjected to regression analysis. The statistical results of study indicated that the five-variable linear regression model = 178.12 + 0.3354 b - 0.3800 d - 0.3788 P + 0.0651 W - 0.0019 N with R = 0.9777 may be suggested to 2 predict deflection of radial-ply tire based on section width, overall unloaded diameter, Inflation Pressure, vertical load and rotational speed for a limited range of radial-ply tire sizes. However, experimental verification of this model is necessary before the model can be suggested for wider use.
Ahmet Ekin - One of the best experts on this subject based on the ideXlab platform.
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Controlled hypotension and minimal Inflation Pressure: a new approach for pneumatic tourniquet application in upper limb surgery.
Anesthesia and analgesia, 2003Co-Authors: Bahattin Tuncali, Ayse Karci, Abdul Kadir Bacakoglu, Ahmet EkinAbstract:UNLABELLED Minimal Inflation Pressures are recommended for limb surgery to eliminate complications attributable to high Inflation Pressures with the pneumatic tourniquets. We applied controlled hypotension and a minimal Inflation Pressure (CHAMIP) technique to provide a bloodless surgical field. Thirty-six patients scheduled for upper extremity surgery were randomized equally to receive either normotensive anesthesia and conventional Inflation Pressures or controlled hypotension (systolic arterial blood Pressure of 80-100 mm Hg and mean arterial blood Pressure >60 mm Hg) and minimum Inflation Pressures. Anesthesia was induced with propofol IV bolus and remifentanil IV continuous infusion and maintained with propofol and remifentanil IV continuous infusion. To determine the minimal Inflation Pressure, the digital plethysmograph was applied to the second finger at the side of the operation and the tourniquet was inflated slowly until the arterial pulsations disappeared on the oscilloscope. A bloodless surgical field was obtained in almost all patients, even though systolic arterial blood Pressures (100-138 mm Hg versus 80-100 mm Hg) and applied tourniquet Inflation Pressures (270 mm Hg versus 110-140 mm Hg) were significantly lower in the hypotensive group. No complications associated with controlled hypotension were encountered. In conclusion, CHAMIP may be a safe and reliable method for upper extremity surgery performed with pneumatic tourniquets. IMPLICATIONS Pneumatic tourniquets are associated with adverse effects resulting from high Inflation Pressures. Therefore, minimal Inflation Pressures are recommended in extremity surgery. To reach real minimal Inflation Pressure the patient's blood Pressure must be reduced. We used controlled hypotension with remifentanil and propofol to reach minimal Inflation Pressures.
Majid Rashidi - One of the best experts on this subject based on the ideXlab platform.
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Modeling of bias-ply tire deflection based on section width, Inflation Pressure, vertical load and rotational speed.
2014Co-Authors: Kamran Rafiee, Majid Rashidi, Mohammad GholamiAbstract:This study was conducted to model deflection ( ) of bias-ply tire based on section width (b), Inflation Pressure (P), vertical load (W) and rotational speed (N). For this purpose, deflection of three bias-ply tires with different section width were measured at three levels of Inflation Pressure, four levels of vertical load and six levels of rotational speed. In order to model deflection based on section width, Inflation Pressure, vertical load and rotational speed, a four-variable linear regression model was suggested and all the data were subjected to regression analysis. The statistical results of study indicated that the four-variable linear regression model = 16.526 + 0.0182 b - 0.3667 P + 0.0356 W - 0.0050 N with R = 0.952147 may be suggested to predict deflection 2 of bias-ply tire based on section width, Inflation Pressure, vertical load and rotational speed for a limited range of bias-ply tire sizes.
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Modeling of Radial-Ply Tire Rolling Resistance Based on Tire Dimensions, Inflation Pressure and Vertical Load
American-Eurasian Journal of Agricultural and Environmental Science, 2014Co-Authors: Mohammad Mohammadi, Majid Rashidi, Mohammad GholamiAbstract:This study was conducted to model rolling resistance (R) of radial-ply tire based on tire dimensions, viz., section width (b) and/or overall unloaded diameter (d), Inflation Pressure (P) and vertical load (W). For this purpose, rolling resistance of three radial-ply tires with different section width and/or overall unloaded diameter were measured at three levels of Inflation Pressure and four levels of vertical load. In order to model rolling resistance based on dimensions, Inflation Pressure and vertical load, seven multiple-variable regression models were suggested and all the data were subjected to regression analysis. The statistical results of study revealed that the multiple-variable regression model R = - 0.17827 + 0.00465 d - 0.00168 P + 0.03161 W with R = 0.976 may 2
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Modeling of Rolling Resistance for Bias-Ply Tire Based on Tire Dimensions, Inflation Pressure and Vertical Load
2014Co-Authors: Majid Rashidi, Mohammad Gholami, Mohammad Mohammadi, Ali Hajiaghaei, Mohsen AlikhaniAbstract:This study was conducted to model rolling resistance (R) of bias-ply tire based on tire dimensions, viz., section width (b) and overall unloaded diameter (d), Inflation Pressure (P) and vertical load (W). For this purpose, rolling resistance of three bias-ply tires with different section width and/or overall unloaded diameter were measured at three levels of Inflation Pressure and four levels of vertical load. In order to model rolling resistance based on dimensions, Inflation Pressure and vertical load, seven multiple-variable regression models were suggested and all the data were subjected to regression analysis. The statistical results of study revealed that the multiple-variable regression model R = - 0.09986 - 0.00985 b + 0.00639 d - 0.00124 P + 0.04003 W with R = 0.9817 may be suggested to predict rolling resistance of bias-ply tire based on tire dimensions 2 (section width and overall unloaded diameter), Inflation Pressure and vertical load for a limited range of tire sizes. However, experimental verification of this model is necessary before the model can be recommended for wider use.
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Modeling of Bias-Ply Tire Deflection Based on Tire Dimensions, Inflation Pressure, Vertical Load and Rotational Speed
2014Co-Authors: Kamran Rafiee, Majid Rashidi, Mohammad Gholami, Parham Fatehirad, Siamak Akhtarkavian, Babak JaberinasabAbstract:This study was conducted to model deflection ( ) of bias-ply tire based on tire dimensions, viz., section width (b) and overall unloaded diameter (d), Inflation Pressure (P), vertical load (W) and rotational speed (N). For this purpose, deflection of three bias-ply tires with different section width and overall unloaded diameter were measured at three levels of Inflation Pressure, four levels of vertical load and six levels of rotational speed. In order to model deflection based on dimensions, Inflation Pressure, vertical load and rotational speed, seven multiple-variable linear regression models were suggested and all the data were subjected to regression analysis. The statistical results of study indicated that the five-variable linear regression model = 16.602 + 0.0203 b - 0.0006 d - 0.3667 P + 0.0356 W - 0.0050 N with R = 0.952152 may be suggested to 2 predict deflection of bias-ply tire based on section width, overall unloaded diameter, Inflation Pressure, vertical load and rotational speed for a limited range of bias-ply tire sizes. However, experimental verification of this model is necessary before the model can be suggested for wider use.
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Modeling of Deflection for Radial-Ply Tire Based on Tire Dimensions, Inflation Pressure, Vertical Load and Rotational Speed
2014Co-Authors: Parham Fatehirad, Kamran Rafiee, Majid Rashidi, Mohammad Gholami, Babak Jaberinasab, Siamak AkhtarkavianAbstract:This study was conducted to model deflection ( ) of radial-ply tire based on tire dimensions, viz., section width (b) and overall unloaded diameter (d), Inflation Pressure (P), vertical load (W) and rotational speed (N). For this purpose, deflection of three radial-ply tires with different section width and overall unloaded diameter were measured at three levels of Inflation Pressure, four levels of vertical load and six levels of rotational speed. In order to model deflection based on dimensions, Inflation Pressure, vertical load and rotational speed, seven multiple-variable linear regression models were suggested and all the data were subjected to regression analysis. The statistical results of study indicated that the five-variable linear regression model = 178.12 + 0.3354 b - 0.3800 d - 0.3788 P + 0.0651 W - 0.0019 N with R = 0.9777 may be suggested to 2 predict deflection of radial-ply tire based on section width, overall unloaded diameter, Inflation Pressure, vertical load and rotational speed for a limited range of radial-ply tire sizes. However, experimental verification of this model is necessary before the model can be suggested for wider use.
