QC/T 520-2019Scale sample test method for automotive friction materials (English PDF)

3.1 Equivalent friction radius

The radius of action of the friction resultant force of the friction pair.

3.2 Coefficient of friction

The ratio -- of the frictional force resisting the relative motion of two objects TO the normal pressure acting on the contacting surface of the two objects.

3.3 Friction work

The work done by friction.

3.4 Mass wear

The ratio -- of mass wear TO total average friction work, under specified conditions.

3.5 Volume wear

The ratio -- of the volumetric wear TO the total average friction work, under specified conditions.

3.6 Average braking torque

The ratio -- of the area covered by each braking torque versus time curve TO the effective braking time.

3.7 Friction torque stability coefficient

The ratio -- of the average braking torque to the maximum braking torque for each braking.

3.8 Area reducing scale ratio

The ratio -- of the total area of a single brake friction material TO the total area of a sample friction material.

3.9 Radius reducing scale ratio

The ratio -- of the equivalent friction radius of the brake TO the effective radius of the specimen.

[JB/T 5071-1991, definition 4.24, definition 4.25]

4.1 Test equipment

4.1.1 The performance indicators of the inertia brake testing machine shall meet the requirements of various tests.

4.5

4.5.2 Adjust the test equipment, to make it in normal working condition.

4.5.3 The specimen shall be installed on the fixed end. The gap with the test pair shall be adjusted to 0.4 mm ~ 0.6 mm. The test pair shall rotate during the test.

4.5.4 Before each test, the test inertia, brake speed, test specific pressure, brake temperature shall be adjusted, according to different vehicle models. All test parameters shall be input accurately.

4.5.5 The temperature of the friction surface is measured by a thermocouple, which is welded with "Nickle-aluminum-nickel-chromium". The thermocouple must be inserted along the effective radius of the specimen to a depth of 4 mm ~ 6 mm AND 0.5 mm away from the friction surface.

5.1 First run-in

The first run-in requirements are as follows:

a) Take the driving speed (Va) of the vehicle as 50 km/h; calculate the initial test speed (n0) according to formula (10);

b) Take the vehicle braking deceleration (a) as 3.0 m/s²; calculate the test specific pressure (P0) according to formula (12);

c) During the run-in process, the initial temperature of each braking shall not exceed 100 °C;

d) The number of braking shall be such that the contacting area of ring specimen is ground to reach above 90%, then stop run-in; however, the number of braking shall be not less than 10.

e) Record the pressure, torque, temperature, rotational speed during braking.

5.2 First measurement

The first measurement requires the following:

a) Use a micrometer, which has a precision 0.01 mm, to measure and record the thickness of the ring specimen and the marked three points of the test pair, to calculate the volume wear. If the mass wear needs to be calculated, use a balance, which has an accuracy of not less than 0.01 g, to measure and record the friction pair mass;

b) The friction pair shall be measured after cooling to room temperature.

5.3 The first friction torque test

The requirements for the first friction torque test are as follows:

a) For drum brake lining ring specimens, the vehicle speeds (Va) are respectively 50 km/h, 70 km/h, 90 km/h; for disc brake pad ring specimens, the vehicle speeds (Va) are respectively 80 km/h, 120 km/h, 160 km/h. Calculate the initial test speed (n0) according to formula (10);

b) Test specific pressure (P0) shall be 0.30 MPa, 0.40 MPa, 0.60 MPa, 0.80 MPa, 1.00 MPa, 1.20 MPa, respectively;

c) The braking cycle is based on the fact that the initial temperature of each braking does not exceed 100 °C;

d) Brake once at each test speed and each test specific pressure; each brake is from the initial test speed (n0) of the brake to the brake stop.

e) Record the pressure, torque, temperature, rotational speed during braking.

5.4 First recession and recovery test

5.4.1 Benchmark test

The benchmark test requirements are as follows:

a) Take the vehicle braking deceleration (a) as 4.5 m/s². Calculate the initial test speed (n0), according to formula (10). Calculate the test specific pressure (P0), according to formula (12). For drum brake lining ring specimens, the vehicle speed (Va) is 50 km/h and 70 km/h; for disc brake pad ring specimens, the vehicle speed (Va) is 80 km/h and 120 km/h. Braking is performed 3 times at each speed, as a baseline test in the fading test.

b) Record the pressure, torque, temperature, rotational speed during braking.

5.4.2 The first recession test

The requirements for the first recession test are as follows:

a) Calculate the initial test speed (n0), according to formula (10).

e) Record the pressure, torque, temperature, rotational speed during braking.

5.7 The second run-in test

It is carried out according to the provisions of 5.1, to apply 50 brakes.

5.8 The third friction torque test

It is carried out according to the provisions of 5.3.

5.9 The second measurement

It is carried out according to the provisions of 5.2.

5.10 Wear rate test

The wear rate test requirements are as follows:

a) Carry out three wear tests in total. Take the vehicle braking deceleration (a) as 3.0 m/s². Calculate the test specific pressure (P0), according to formula (12).

b) The first wear test: Calculate the initial test speed (n0) according to formula (10). For the drum brake lining ring specimen, take the vehicle speed (Va) as 50 km/h; for the disc brake pad ring specimen, take the vehicle speed (Va) as 80 km/h. The initial temperature of each braking is 80 °C ± 10 °C; apply 100 brakes. Each braking is from the initial braking test speed (n0) to the braking stop.

c) Carry out the third measurement, according to the requirements in 5.2.

d) The second wear test: Calculate the initial test speed (n0), according to the formula (10). For the ring specimen of the drum brake lining, the driving speed (Va) of the vehicle is taken as 70 km/h; for the ring specimen of the disc brake lining, the driving speed (Va) of the vehicle is taken as 120 km/h. The initial temperature of each braking is 120 °C ± 10 °C. Apply 60 brakes. Each braking is from the initial braking test speed (n0) to the braking stop.

e) Carry out the fourth measurement, according to the provisions of 5.2.

f) The third wear test: Calculate the initial test speed (n0), according to formula (10). For the drum brake lining ring specimen, take the vehicle speed (Va) as 90 km/h; for the disc brake pad ring specimen, take the vehicle speed (Va) as 160 km/h. The initial temperature of each brake is 150 °C ± 10 °C; apply 20 brakes. Each braking is from the initial braking test speed (n0) to the braking stop.