GB/T 23264-2020Brake lining assembly for electric power assist bicycles (English PDF)

3.1 Coefficient of friction

The ratio OF the friction force TO the normal force that is applied to the test piece.

3.2 Wear

6.1 Appearance quality inspection

Use methods of visual inspection and knocking to check the appearance quality.

6.2 Dimension measurement

Use a vernier caliper whose accuracy is 0.02 mm to measure the width and thickness.

6.3 Friction performance test

6.3.1 Test piece

6.3.1.1 Respectively prepare the two test pieces from the friction material of the two lining assemblies, or process with the same material according to the same process.

6.3.1.2 The size of the test piece is 25 mm × 25 mm; the allowable deviation is -0.2 mm ~ 0 mm.

6.3.1.3 The thickness of the test piece is 5 mm ~ 7 mm; the thickness difference between the two test pieces is less than 0.2 mm. If the thickness of the product is less than 5 mm, use its original thickness.

6.3.2 Equipment

6.3.2.1 Constant speed friction test machine: its performance and accuracy shall meet the requirements of JC/T 1065.

6.3.2.2 Micrometer: accuracy of 0.01 mm.

6.3.3 Test conditions

6.3.3.1 The test pressure (normal force) is 0.98 MPa.

6.3.3.2 The material of the disc of the test machine shall meet the requirements of JC/T 1065. Its surface shall be treated with abrasive paper whose particle size is P240 in JB/T 7498, so that the surface of the disc has no obvious scratches, rust, pits and other defects.

6.3.4 Test procedures

6.3.4.1 Respectively load the two test pieces into the two test piece support arms of the test machine.

6.3.4.2 Perform running-in of test pieces below 100 °C, until the contact surface reaches more than 95%. Use a micrometer whose accuracy is 0.01 mm to measure the thickness of the test piece; measure 5 points on each test piece; take the arithmetic average. The thickness measurement shall be performed after the test piece is cooled to room temperature.

6.3.4.3 When the test temperature is 100 °C, measure the friction force during the period when the disc rotates 5 000 revolutions. After the friction test, measure the thickness of the test piece according to 6.3.4.2.

6.3.4.4 At each test temperature of 150 °C, 200 °C, 250 °C, perform the same test according to 6.3.4.3. The highest test temperature of class-1 lining assembly is 200 °C; the highest test temperature of class-2 lining assembly is 250 °C. During each temperature test, the disc temperature shall rise to the specified test temperature within 1 500 revolutions. The temperature of the disc rises mainly by the friction heat of the test piece. When the specified test temperature is not reached within 1 500 revolutions, an auxiliary heating device can be used.

6.3.4.5 After the measurement of the highest test temperature is over, measure the friction force of the disc during 1 500 revolutions every time the temperature drops by 50°C from the highest test temperature, until it reaches 100 °C. The temperature drop from the previous stage to the next stage shall be completed within 500 revolutions.

6.3.4.6 After the test, visually inspect whether the test piece has cracks, bubbles, missing edges and corners, unevenness, warping, twisting, layering and other defects that affect the use, and whether the friction surface of the disc has obvious scratches and burning discoloration.

6.3.5 Calculation

6.3.5.1 The coefficient of friction of each test temperature is calculated according to Formula (1): […]