GB/T 34007-2017Road vehicles—Brake lining friction materials—Drag test method for friction performance (English PDF)

3.1 Braking cycle

A braking process which consists of several braking runs, each braking operation consisting of 5 s braking and 10 s idling.

3.2 Constant pressure mode

The control method in which the pipeline pressure remains constant during braking.

3.3 Constant torque mode

The control method in which the braking torque remains constant during braking.

3.4 Initial brake rotor temperature

The temperature of the brake disc at the beginning of the first brake run of each braking cycle.

3.5 Maximum brake rotor temperature

The temperature exceeded by the brake disc is not allowed during each braking cycle.

5.1 Test type

The test type is divided into the original sample test and the sampling method test. The original sample test is to test the specimen of original size, the sampling method test is to prepare the specimen into the sample block of the specified size to perform test.

5.2 Test device for disc linings for categories M1, M2, N1, O1, O2, L vehicles

5.2.1 When performing the original sample test, the brake disc and brake caliper used in the test shall be the brake disc and brake caliper according to the drawings and technical documents.

5.2.2 When performing the sampling test, it shall install a fixed-type disc brake caliper on the test machine, the piston diameter is 36 mm. The distance between the center of the sample block and the center of the brake disc after installation is 116.5 mm.

5.3 Test devices for disc linings and drum linings for categories M3, N2, N3, O3, O4 vehicles

It shall install a fixed-type disc brake caliper on the test machine, which has a piston diameter of 60 mm. The distance between the center of the sample block and the center of the brake disc after installation is 108 mm.

6.1 Test procedure for disc linings for categories M1, M2, N1, O1, O2, L vehicles

6.1.1 Test preparation

6.1.1.1 Determination of test pressure and torque by original sample method

6.1.1.2 Determination of test pressure and torque by sampling method

The pressure per unit area of the friction surface of the sample block under constant pressure mode is 75 N/cm², the pressure of the brake pipeline is 0.89 MPa;

6.1.1.3 Treatment of the surface of brake disc

Before each test, the surface of the brake disc shall be treated by the sandpaper which has a grain size of P240 or finer in JB/T 7498, so that the surface of the brake disc has no obvious wear marks and rust; use a soft cloth and absolute ethanol to remove the dust and oil stains from the surface of the brake disc.

6.1.1.4 Preparation of specimen […]

6.1.2 Run-in of the lining or sample block

The lining or sample block shall be run-in before the formal test, until the contact area of the lining or sample block with the brake disc is not less than 80%.

6.1.3 Measurement of initial thickness and mass

Take out the linings or sample block that have been run-in, measure and record the thickness of each measurement point of each lining or sample block, accurate to 0.01 mm; weigh and record the mass of each lining or sample block, accurate to 0.01 g.

6.1.4 Test procedure

6.1.4.1 Test procedure at constant pressure mode

The test procedure at constant pressure mode is as shown in Table 1.

6.1.4.2 Test procedure at constant torque mode

The test procedure at constant torque mode is as shown in Table 2.

6.1.5 Measurement of final thickness and mass

Remove the lining or sample block after test, follow the requirements of 6.1.3 to measure and record the thickness and mass.

6.2 Test procedure for disc linings and drum linings for categories M3, N2, N3, O3, O4 vehicles

6.2.1 Test preparation

6.2.1.1 Determination of pressure

The pressure per unit area of the friction surface of the sample block is 75 N/cm² and the pressure of the brake lining is 1.17 MPa.

6.2.2 Run-in of sample block

The lining or sample block shall be run-in before the formal test, until the contact area of the sample block with the brake disc is not less than 80%. The surface temperature of the brake disc during running-in shall not exceed 200 °C.

The procedure for run-in of sample block is as shown in the test number 1 (run- in) in Table 3.

6.2.3 Measurement of initial thickness and mass

Take out the sample block that have been run-in, measure and record the thickness of each measurement point of each sample block, accurate to 0.01 mm; weigh and record the mass of each sample block, accurate to 0.01 g.

6.2.4 Test procedure

The test procedure is as shown in Table 3.

6.2.5 Measurement of final thickness and mass

Remove the lining after test, follow the requirements of 6.2.3 to measure and record the thickness and mass.

7.1 Collection of working friction coefficient

7.1.1 In the constant pressure mode, the collection point (µB) of the working friction coefficient is 1 s after each brake run, it is collected within the interval of ±1 s of this 1 s. The collection frequency is not less than 20 Hz, as shown in Figure 4.

7.1.2 In the constant torque mode, the collection point (µB) of the working friction coefficient is 1 s after the braking torque reaches 80% of the set value, it is collected within the interval of ±1 s of this 1 s. The collection frequency is not less than 20 Hz, as shown in Figure 5.

7.1.3 The working friction coefficient for each brake run is the average of the friction coefficients collected in the interval of (1 ± 0.1) s.

7.2 Collection point of minimum friction coefficient (µmin) and maximum friction coefficient (µmax)

7.2.1 In the constant pressure mode, the collection point of the minimum friction coefficient is the minimum value of the friction coefficient from the start of each brake run to the end of this brake run.

7.2.2 In the constant torque mode, the collection point of the minimum friction coefficient is the minimum value of the friction coefficient from the end of 0.5 s after the braking torque reaches 80% of the set value to the end of this brake time.

7.4 Method of determining the minimum friction coefficient and the maximum friction coefficient

The method of determining the minimum friction coefficient is to take the minimum value of the minimum friction coefficient as collected from each brake run [except for the test No.1 (run-in)] during the test.

7.5 Test report

The test report shall include basic information, test parameters, working friction coefficient, maximum friction coefficient, minimum friction coefficient, thickness wear record, weight wear record, surface condition of the lining and brake disc after the test, etc. […]