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

1. 12/20/2013
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. 12/20/2013
Tires on Soft Soil Study
Design of
experiment
Methodology
Tire
structure
Terramechanics
rig
Experiment
Modeling
Tire-soil
interaction
Simulations
Instrumentation
Results
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3. 12/20/2013
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
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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4. 12/20/2013
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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5. 12/20/2013
Additional Measurement Sensors
Fitted ultrasonic sensor to measure relative soil height
Steel Plate
Reference
az
45o
a
x
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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6. 12/20/2013
Methods of Soil Measurement
Cone Penetrometer Tests
6.5
kPa/mm
4.4
kPa/mm
Geotechnical lab tests by Schnabel Engineering
• California Bearing Ratio
• Standard Proctor Test
• Triaxial shear strength test
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7. 12/20/2013
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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8. 12/20/2013
Determination of Max Sinkage
ST
hinitial
M1
M2
P
h
W
undisturbed
soil surface max sinkage
Rdeformed
Rut
(Δz)
Δz=(h+Rdeformed )-hinital
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9. 12/20/2013
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
Parameter
No. of
Levels
Range
L1
L2
0 – 5 – 10 – 15 –
20 – 40 – 60 - 75 (or 90)
No. Slip
Load
Inflation Soil
Press. Comp.
1
All
L1
L1
L1
2
All
L2
L1
L1
3
All
L1
L2
L1
20 PSI
(1.38 bar)
4
All
L1
L1
L2
5
All
L2
L1
L2
6.5 ± 0.9
9kPa/mm
6
All
L2
L2
L1
7
All
L2
L2
L2
Slip %
8
Normal
load
2
5000 N
6000 N
Inflation
Pressure
2
29 PSI
(2 bar)
Compaction
Resistance
2
4.4 ± 0.4
kPa/mm
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10. 12/20/2013
Soil Deformation in
Full Range of Slip
0%
20 %
40 %
5%
60 %
10 %
90 %
15 %
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11. 12/20/2013
Individual Parameter Change
Parameter
Level
1
Level
2
Normal load (kN)
5
6
Inflation Pressure
(psi)
29
20
Cone Index
Gradient
(kPa/mm)
4.4
6.5
Lower inflation
pressure,
highest
drawbar pull
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12. 12/20/2013
Several Parameter Changes
Variation result of irregular
soil compaction
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13. 12/20/2013
Tire Sinkage Results
Lower inflation pressure
-> larger sinkage but
greater drawbar pull
Higher load -> greater
contact patch -> least
sinkage
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14. 12/20/2013
Main Effects and Interaction on
Drawbar Pull
High Slip DP coefficient
Peak DP coefficient
•
•
Inflation pressure has main
effect on peak drawbar pull
coefficient
Interaction of soil compaction is
evident with normal load and
inflation pressure
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15. 12/20/2013
Parameter Main Effects and
Interaction on Sinkage
Normal load has the
greatest effect on sinkage
Larger slope indicates a
greater degree of
interaction
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16. 12/20/2013
Conclusions
 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
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