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Table 1 - Soil constituents
and its measured properties
Item
Sand (%)
Silt (%)
Clay (%)
Bulk density (kg/m3
Cohesion (kPa)
Frictional angle (°)
Cone index (kPa)
)
Value
34.3
22.2
22.2
2360
4.8
32
700
Materials and Methods
Soil and tire interaction can be investigated in the field or under
controlled conditions. In the field conditions, due to the
presence of related parameters, a more realistic simulation of
phenomena occurs. On the other hand, due to the unpredictability
and variation of some of these parameters, there may
be significant errors in field data acquisition and the validity
of the results may be affected. Soil and tire experiments under
controlled conditions are commonly presented in the form of
single-wheel testers (SWT) that are carried out in soil storage
environments. These environments can control soil and wheel
variables.
Soil Bin Facility
A soil bin testing facility was utilized with the aim of providing
a controlled environment to achieve soil and tire interaction.
Mechanical soil properties are given in Table 1.
A three-phase electromotor
of 30 hp
(MOTOGEN Corporation)
was used to supply
the carriage movement in
the soil bin length using a
chain system encompassing
the single wheel tester
moving on rails. To measure
traversing tire rolling
resistance, four S-shape
load cells (Bongshin Model
DBBP) containing capacity
of 200 kg, sensitivity of
0.1 kg, and frequency of
80 Hz were calibrated and
placed in appropriate positions
horizontally in a
parallel pattern to connect
the L-shape frame and single
wheel tester. Measuring
the forces on the wheel in
two horizontal and vertical
dimensions in dynamic
conditions has been used
32
in various other research. To provide load variable levels, a
Bongshin model DBBP load cell (S-shape) with the capacity of
two tons, sensitivity of 0.1 kg, and frequency of 80 Hz was calibrated
and placed vertically between a power bolt and tester
hub (Fig. 2).
To provide various velocities of carriage movement, a
SV 220IS5-2 NO, 380 V, 30 hp model of LG inverter (brand LS)
with frequency range of 0 to 50 Hz and step of 0.01 Hz was
used to control the rotational speed of the engine. To move the
drive wheel, an electromotor of 7.5 hp (MOTOGEN Corporation)
was used. Furthermore, a main inverter was installed
to allow changes in the rotational output speed. This inverter
had the capacity to adjust braking and starting acceleration
of the electromotor. By means of the display panel in front of
each inverter and related settings menu, changes could be applied
(Fig. 3).
Stress Gauges
In this system, a profile with a standard dimension of 120×120
mm was used as a frame. Five stress sensing elements were
installed in the central line of the profile longitudinally. Each
element of stress sensor was composed of a 100 kg load cell
with a measurement precision of 0.1 kg (Bongshin Model
DBBP) and a circular T- shape link connected to it. To prevent
any lateral deviations of this link and movement in the vertical
direction, its head was passed through a 10 mm thick MDF
board. The other end of the load cells was tightened to the front
of the profile. In addition, to function properly and prevent the
introduction of fine particles into the space behind the links,
the plate was covered with a special coating of thin transparent
plastic before placing the system in deep soil. By placing this
Fig. 2. The system of soil bin along with equipment for data acquisition.
IEEE Instrumentation & Measurement Magazine
October 2021
Instrumentation & Measurement Magazine 24-7

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