experimental testing of an off-road tire in soft soil paper81437
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Corina Sandu, Scott Naranjo, Saied Taheri, Virginia Tech U.S. Army Quad Member: Dr. Paramsothy Jayakumar, TARDEC Industry Quad Members: Dr. Brant Ross, MotionPort, Mr. Daniel Christ, Michelin Americas Research CoTRANSCRIPT
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Experimental Testing Of An Off-road Tire In Soft Soil
Corina Sandu, Scott Naranjo,, Saied Taheri, Virginia
Tech
U.S. Army Quad Member: Dr. Paramsothy Jayakumar, TARDEC
Industry Quad Members: Dr. Brant Ross, MotionPort, Mr. Daniel
Christ, Michelin Americas Research Co
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2
Tires on Soft Soil Study
Modeling
Methodology
Tire structure
Tire-soil interaction
Simulations
Experiment
Design of experiment
Terramechanics rig
Instrumentation
Results
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Terramechanics Rig
Single wheel test rig for tire performance on various terrain
• Wheel slip controlled via two separate drive motors
• Measures forces and moments via wheel hub Kistler P 650 sensor
• Various terrain possibilities
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Fluid regulation via flow
• Can control response of system with air pressure
• Response time within 2.8 ms
• PI controller in LaVIEW provides controls
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Toe and Camber Adjustment
Linkages of different lengths adjust camber and toe
• Camber -8 to +80 in steps of 20
• Toe -25 to +250 in steps of 50
Designed for accuracy and robustness
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Additional Measurement Sensors
Fitted ultrasonic sensor to measure relative soil height
Steel Plate
Reference
45o
az
ax
25o
WITS - eight equidistant sensors used to estimate proper speed to maintain a slip ratio value and to estimate max sinkage
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Methods of Soil Measurement
Geotechnical lab tests by Schnabel Engineering
• California Bearing Ratio
• Standard Proctor Test
• Triaxial shear strength test
6.5 kPa/mm
4.4 kPa/mm
Cone Penetrometer Tests
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Silty Sand Preparation
• Versatile soil with a long range of low to high cohesiveness
• 5 stage soil preparation procedure per test run
• Insure soil consistency with Cone Penetrometer CP40 II
and taking samples for moisture content measurement
• Geotechnical lab data for soil
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Determination of Max Sinkage
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hinitial
Rdeformed
undisturbed
soil surface max sinkage (Δz)
h
Rut
P
M1
M2
ST
W
Δz=(h+Rdeformed )-hinital
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Design of Experiment
• Tire normal load and inflation pressure were chosen to
correlate with full-scale vehicle testing in South Africa
• Soil compaction resistance obtained through the repeatable
soil preparation procedure developed
• Test tire - LT235/85R-16 Michelin LTX A/T 2 E
No. Slip Load Inflation Press.
Soil Comp.
1 All L1 L1 L1
2 All L2 L1 L1
3 All L1 L2 L1
4 All L1 L1 L2
5 All L2 L1 L2
6 All L2 L2 L1
7 All L2 L2 L2
Parameter No. of Levels
Range
L1 L2
Slip % 8 0 – 5 – 10 – 15 –
20 – 40 – 60 - 75 (or 90)
Normal load
2 5000 N 6000 N
Inflation Pressure
2 29 PSI (2 bar)
20 PSI (1.38 bar)
Compaction Resistance
2 4.4 ± 0.4 kPa/mm
6.5 ± 0.9 kPa/mm 9
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Soil Deformation in
Full Range of Slip
0 % 20 %
5 %
40 %
10 %
15 %
60 %
90 %
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Individual Parameter Change
Lower inflation pressure, highest
drawbar pull
Parameter Level
1 Level
2
Normal load (kN) 5 6
Inflation Pressure (psi)
29 20
Cone Index Gradient (kPa/mm)
4.4 6.5
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Several Parameter Changes
Variation result of irregular soil compaction
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Tire Sinkage Results
Lower inflation pressure -> larger sinkage but greater drawbar pull
Higher load -> greater contact patch -> least
sinkage
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Main Effects and Interaction on
Drawbar Pull
• Inflation pressure has main
effect on peak drawbar pull
coefficient
• Interaction of soil compaction is
evident with normal load and
inflation pressure
Peak DP coefficient
High Slip DP coefficient
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Parameter Main Effects and
Interaction on Sinkage
Larger slope indicates a
greater degree of
interaction
Normal load has the
greatest effect on sinkage
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Conclusions
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Tire instrumented with wireless real-time deflection system
Normal load controller hardware installed, and required
software developed
Field scanners installed (used with other sensors for
sinkage measurements)
Various tests from design of experiment performed
Drawbar pull and sinkage data obtained for a large range of
slip ratio values
Interactions of various parameters on the drawbar pull and
sinkage were obtained
Data used to validate tire model developed at AVDL
concurrently with the experimental work