GB/T 11834-2023Friction linings for industrial and agricultural machines (English PDF)

4.1 Classification

Friction linings are classified into three categories according to their materials and manufacturing processes. The classification and codes are specified in Table 1.

4.2 Designation

The designation of friction linings shall consist of the product's intended use, a reference to this document, classification code, and product dimensions.

Example 1: A Class 2 brake band with a width of 100 mm and a thickness of 4 mm shall be designated as: Brake band GB/T 11834-ZD2-100×4.

Example 2: A Class 3 clutch plate with an outer diameter of 380 mm, an inner diameter of 202 mm, and a thickness of 10 mm shall be designated as: Clutch plate GB/T 11834-LP3-380×202×10.

5.1 Appearance quality

5.1.1 Whether or not the surface of the friction linings is processed shall be agreed upon by the supplier and the buyer.

5.1.2 The friction linings shall be of uniform material and shall not have defects such as cracks, bubbles, delamination, missing edges, chipped corners, warping, or burrs.

5.3 Friction performance

5.3.1 The small sample bench test results of Class 1 and Class 2 friction linings shall meet the following requirements:

-- The coefficient of friction at the normal temperature µnormal temperature shall not be less than 0.25 and shall meet the stated grade;

-- The coefficient of friction at the high temperature µhigh temperature shall not be less than 0.25 and shall meet the stated grade;

-- The coefficient of friction at any point in the second decline temperature range of 93°C~288°C and the second recovery temperature range of 149°C~93°C in the five tests shall not be less than 0.15; the difference between the coefficient of friction at each temperature point and the average value of the five tests shall not exceed 20%.

5.3.2 The drag test results of the friction performance of Class 3 friction linings shall meet the following requirements:

-- The operational coefficient of friction µoperation shall be within ±15% of the appointed coefficient of friction;

-- After the test, the friction linings shall show no delamination or chipping.

5.4 Relative density deviation

The relative density deviation of friction lining samples manufactured with the same friction material formulation and the same manufacturing process shall be less than 5%.

5.5 Softening property

The softening property applies to Class 1 friction linings. This also applies when the buyer requires Class 2 and Class 3 brake bands with a thickness not exceeding 6.5 mm to have softening property. After the softening property test, the surface of the friction lining shall not have any cracks.

5.6 Bending performance

The bending strength and maximum strain of the friction linings used for clutch plates shall conform to the provisions of Table 5.

5.7 Shear strength

The shear strength of ZP2 and ZP3 bonded friction linings at the normal temperature of (23±5) °C shall not be less than 2.5 MPa.

The shear strength of ZP2 and ZP3 bonded friction linings at the high temperature of (300±10) °C shall not be less than 1.5 MPa.

5.8 Limits of harmful components

5.8.1 The friction linings shall not contain asbestos.

5.8.2 Other harmful elements in the friction linings shall meet the limits specified in Table 6.

6.1 Appearance quality

Check by visual inspection.

6.2 Dimensional deviation

The width and thickness of friction linings used for brake pads and brake bands, and the inner and outer diameters of friction linings used for clutch plates shall be measured using a vernier caliper with an accuracy of 0.02 mm. The thickness of friction linings used for clutch plates shall be measured using a micrometer with an accuracy of 0.01 mm. The measuring instruments used for the measurement of other dimensions shall be agreed upon by the supplier and the buyer.

6.3 Friction performance

6.3.1 Small sample bench test

The small sample bench test for Class 1 and Class 2 friction linings shall be carried out in accordance with the provisions of GB/T 17469. […]

6.3.2 Drag test for friction performance