T/CSAE 95-2018Tire Steady State Test Method of Combined Slip Property (English PDF)

4.1 Wheel geometry and tire coordinate system wheel Geometry and tire axis syste

4.1.1

Wheel center plane wheel plane the plane equidistant from the inner edges of the two sides of the wheel rim, the normal to which is the center line of rotation of the wheel.

[GB/T 12549, definition 4.1.1] (see Figure 1) 4.1.2 Wheel center wheel center the intersection of the center plane of the wheel and the centerline of the wheel's revolution.

[GB/T 12549, definition 4.1.1] (see Figure 1) 4.1.3 Tire grounding center T/CSAEXX-2018 the intersection of the intersection of the center plane of the wheel with the ground and the projection of the centerline of the wheel on the ground.

[GB/T 12549, definition 5.1.1] (see Figure 1) 4.1.4 Tire coordinate system (X, Y, Z) tire axis system (X, Y, Z) Right-handed rectangular coordinate system with the tire grounding center as the origin. The X axis is the intersection of the center plane of the wheel and the plane of the road, with the center of the wheel flat the direction of travel of the face is positive; the Z axis is the normal of the road plane, the upward is positive; the Y axis is in the road plane, and the direction is determined according to the right hand rule.

[GB/T 12549, definition 5.1.2] (see Figure 1)

Figure 1 tire coordinate system

4.1.5

Load radius (loading radius) loaded radius the distance from the center of the wheel to the grounding center of the tire.

The loading radius of a static tire under vertical load is a static loaded radius.

[GB/T 12549, definition 5.1.5] 4.1.6 Side angle slip angle the angle between the direction of travel of the tire grounding center and the X-axis of the tire coordinate system.

In the tire coordinate system, from the X axis to the direction of travel of the tire ground center, the right hand rule is used to determine the sign of the right and the negative.

[GB/T 12549, definition 5.1.3] (see Figure 1) T/CSAEXX-2018 4.1.7 Inclination angle (cab angle) the angle between the XZ plane of the tire coordinate system and the center plane of the wheel.

In the tire coordinate system, the XZ plane is turned to the center plane of the wheel, and its positive and negative signs are determined according to the right-hand rule.

[GB/T 12549, definition 5.1.8] (see Figure 1)

4.2 Tire rolling and slip characteristics Tire rolling characteristics and tire slip

4.2.1

Free rolling wheel

Rolling wheels with vertical loads but no driving or braking torque.

It is suitable for wheels that roll freely in a straight line, called straight free rolling tires.

A wheel that has a side angle or a non-linear motion with a camber angle.

4.2.2

Wheel rotation speed of free-rolling wheel the angular velocity of the free rolling wheel.

When the wheel is free to roll, it is called the wheel rotation speed of straight free-rolling.

Wheel)

4.2.3

Rolling radius

Under the specified test conditions, the distance the tire is moved from the grounding center of the tire for one week is the rolling circumference.

The value obtained by dividing the rolling circumference of the tire by 2pi is called the rolling radius.

4.2.3

Tire travel speed tire trajectory velocity the speed at which the ground center of the tire moves relative to the reference road surface.

Its component in the X direction of the tire coordinate system is called the tire longitudinal velocity, which is in the tire coordinate system Y direction.

The component is called the tire lateral velocity.

4.2.4

Tire longitudinal slip angular velocity the difference between the wheel rolling angular velocity under driving or braking conditions and the free rolling angular velocity of the wheel.

Note. The wheel rolling angular velocity and the wheel free rolling angular velocity should be measured under the same conditions of maintaining the longitudinal speed of the tire.

4.2.5

Tire longitudinal slip ratio T/CSAEXX-2018 the ratio of the longitudinal slip speed of the tire to the free rolling angular velocity of the wheel.

Among them, 0 is the wheel free rolling angular velocity, and is the wheel rolling angular velocity at any time.

4.3 Tire force and moment tire force and moment

4.3.1

Tire normal force (tire radial force) zF the component of the force acting on the tire along the Z-axis. The absolute value of the normal force of the tire, called the tire vertical load (tire vertical load) 4.3.2 Tire lateral force (tire lateral force) yF the component of the force acting on the tire along the Y-axis.

4.3.3

Tire longitudinal force the component of the force acting on the tire along the X-axis.

4.3.4

Tire overturning moment the moment vector on which the road surface acts on the tire causes the tire to rotate along the X axis.

4.3.5

Tire rolling moment (tire rolling moment) the moment vector on which the road surface acts on the tire causes the tire to rotate along the Y axis.

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4.3.6

Tire aligning torque the component of the moment vector acting on the tire on the tire causes the tire to rotate along the Z axis.

4.3.7

Wheel torque wheel torque the external moment acting on the tire relative to the axis of rotation of the wheel by the car.

If the torque causes the tire to generate a driving force, it is called a driving torque. If the torque makes the tire the braking force is called the braking torque.

4.4 Force and moment coefficients of force and moment

4.4.1

Tire longitudinal force coefficient the ratio of the longitudinal force of the tire to the vertical load.

4.4.2

Tire driving force coefficient the absolute value of the ratio of tire driving force to radial force.

4.4.3

Tire braking force coefficient the ratio of tire braking force to vertical load.

4.4.4

Tire longitudinal stiffness (tire braking/driving stiffness) the first derivative of the longitudinal force of the tire relative to the longitudinal slip.

The longitudinal stiffness of the tire is typically determined at zero offset, zero camber and zero longitudinal slip.

4.4.5

Tire longitudinal stiffness coefficient (tire braking/drive stiffness coefficient) tire longitudinal stiffness coefficient (tire braking/Driving stiffness coefficient) the ratio of the longitudinal stiffness of the tire to the vertical load of the tire.

4.4.6

Peak coefficient of driving adhesion the maximum value that the driving force coefficient can reach under the specified conditions of use.

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4.4.7

Peak coefficient of braking adhesion the maximum value that the braking force coefficient can reach under the specified conditions of use.

4.4.8

Drive coefficient of driving adhesion Under the specified conditions of use, the driving torque coefficient of the wheel in the idling state under the action of large driving torque.

4.4.9

Slide coefficient of braking adhesion the driving torque factor of the wheel in the emergency brake lock state under the specified conditions of use.

4.4.10

Ratio of driving peak friction coefficient to driving slip friction coefficient peak-to-slide ratio of driving adhesion the ratio of the peak friction coefficient of the tire to the slip friction coefficient under driving conditions.

4.4.11

Ratio of brake peak friction coefficient to brake slip friction coefficient peak-to-slide ratio of braking adhesion the ratio of the peak friction coefficient of the tire to the slip friction coefficient under braking conditions.

4.4.12

Tire longitudinal force load sensitivity the first derivative of the longitudinal force of the tire relative to the vertical load at any given longitudinal slip rate.

4.5 Steady state steady state

The combined force and moment of the external force and external moment of the tire and the inertial force and moment of inertia of the tire itself do not follow in the tire coordinate system.

The state of motion in which time changes.

4.6 Pressure inflation pressure

4.6.1

Cold inflation pressure the air pressure inside the tire under normal ambient temperature and the conditions of use do not change the tire pressure.

4.6.2

Warm inflation

Under certain conditions of use, the equilibrium air pressure achieved by the tire due to heat generated by exercise.

6.1 Ambient temperature requirements

The commonly used test environment temperature is 15 ° C ~ 27 ° C, and for special experimental research, users may set the ring according to their own needs.

Ambient temperature, but must ensure that the ambient temperature gradient changes within 1 hour is no more than 1 °C.

6.2 Test preparation

6.2.1 General

The test tires should be prepared for the necessary tests before the test, including the selection and storage of the test tires, the assembly and parking of the tire rims, refer to the determination of test conditions, the recording of necessary test information, and tire pre-run.

6.2.2 Selection and storage of test tires

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a) Selection of test tires the test of the longitudinal slip characteristics of the tire is more serious on the tire tread. If the test involves the replacement of multiple tires, to ensure the test Data comparability, should choose a wheel with similar production date, same batch, same storage environment, similar usage history and similar uniformity tire.

b) Storage of test tires Before the test, the tire should be placed in the area where the temperature does not exceed ±5 degrees of the ambient temperature of the equipment for at least 24 hours.

6.2.3 Assembly of tires and rims

a) Test rim size

The diameter and width of the test rim shall comply with the test requirements, and the rim flange profile shall conform to the T

b) Assembly of tires and rims when installing the tire on the rim, you need to follow standard installation procedures, such as those issued by the Rubber Manufacturer's Association.

quasi. At the same time, it is necessary to ensure that there are no damage, defects and impurities on the contact surface between the tire and the rim; it should not be excessively lubricated, otherwise it will cause the bead Slip; use a suitable adapter when necessary to ensure that the wheel assembly is installed smoothly on the shaft and that the steering center position is not changed.

c) Inflatable parking the assembled tires should be inflated to make them fully stable, usually for 3 hours.

Note. If the tire has been assembled and filled in within 24 hours, there is no need to park it.

6.2.4 Determination of reference test conditions

The reference load of the tire is determined by the user based on the load index of the test tire and the actual vehicle load.

The reference pressure of the tire (specifically, the cold air pressure) is determined by the user based on the maximum air pressure of the test tire and the actual vehicle air pressure.

6.2.5 Test information record

The necessary test information should be recorded, including the following.

a) tire number

b) basic information about the tire, including size, pattern, brand, load index, speed level, maximum pressure

c) test rim size

d) inflation pressure

6.2.6 Pre-run

The tire should be pre-run before the formal test. The pre-run procedure can be designed by the user according to the test capability and working efficiency of the equipment, but be sure to achieve the following pre-run effects.

a) the internal residual stress of the tire due to packaging, storage and other factors has been eliminated;

b) the hysteresis force due to the viscoelasticity of the rubber material has been eliminated;

c) that the tyre has been brought to the required pre-run temperature;

d) There is no significant wear on the tread.

Note. If the test tire has been subjected to the same or similar pre-run procedure within 30 minutes, there is no need to repeat the pre-run.

6.3 Test

The test procedure for the steady-state composite characteristics of the tire should include the following steps.

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6.3.1 When the test starts, the tire should not be in contact with the road surface, and the sensor is cleared;

6.3.2 Start the test rig to move the test road in the specified direction and reach the required test speed;

6.3.3 Press the test tire against the road surface to achieve the vertical load required by the test. After the state is stable, proceed to the next step;

6.3.4 Bring the test tire to the specified side angle and roll angle, and proceed to the next step after the tire condition is stable;

6.3.5 Make the test tire produce longitudinal slip motion and reach the specified longitudinal slip ratio, after the longitudinal force is stabilized (for example, test tire rolling After 1.5 weeks, the test results of more than one week were continuously recorded, and the test under the longitudinal slip rate was completed;

6.3.6 Repeat the operation in 6.3.5 until all longitudinal slip ratio sequences have been completed;

6.3.7 Repeat the operations of 6.3.4 to 6.3.6 to complete other test sequences;

6.3.8 Repeat the operations of 6.3.3 to 6.3.7 until all vertical load sequences are completed;

6.3.9 Remove the load and disengage the tire from the test surface;

6.3.10 Stop testing the road surface.

Note. If the test involves multiple air pressure conditions, repeat the steps in 6.3.3 to 6.3.8 after adjusting the tire pressure to the target value.

7.1 Test data

For the test of steady-state longitudinal slip characteristics of tires, the following test data should be recorded.

a) tire longitudinal force ( );

b) tire lateral force (yF);

c) tire normal force (zF);

d) positive return torque (zM);

e) tipping moment (Mx);

f) wheel torque ( );

g) rolling moment ( )

h) tire travel speed (V)

i) loading radius ( )

j) Wheel speed ( )

k) yaw angle ();

l) roll angle ();

m) longitudinal slip ratio ( )

n) tire pressure ( );

o) Ambient temperature ( ) Note. The data unit of each variable is metric.

7.2 Data Processing

Filter, wild-point culling and averaging of a complete cycle of test data to obtain smooth tire force and moment characteristics line.

The steady-state test is sampled in a averaging manner. Before the formal sampling, the tire is stable for at least 2 turns, and then the tire is rotated.

The data of the circle is averaged. Taking into account the impact of tire uniformity on the test data, it is required to collect at least 32 points in one rotation of the tire.

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7.3 Indicator calculation

7.3.1 Drawing icons

For the test data processing, the following curve should be drawn.

a) plot the longitudinal force of the tire as a function of the longitudinal slip ratio;

b) plot the longitudinal force coefficient of the tire as a function of the longitudinal slip ratio;

c) Plot the longitudinal force load sensitivity of the tire as a function of the longitudinal slip ratio.

7.3.2 Calculation indicators

For test data processing, the following indicators should be calculated.

a) the longitudinal stiffness of the tire;

b) the longitudinal stiffness coefficient of the tire;

c) tire longitudinal force load sensitivity;

d) driving the peak friction coefficient;

e) braking peak friction coefficient;

f) driving slip friction coefficient;

g) brake slip coefficient of friction;

h) the ratio of the driving peak friction coefficient to the driving slip friction coefficient;

i) Ratio of brake peak friction coefficient to brake slip friction coefficient.