Characteristics evaluation of brake linings for automobile - Small sample bench test method
1 Scope
This standard specifies the small sample bench test procedure for friction and wear performance and the levels and markings of friction coefficient of automobile brake linings (hereinafter referred to as "linings").
This standard is applicable to disc brake linings and drum brake linings for automobiles.
This standard is not applicable to parking brake linings.
2 Test apparatus
2.1 Functions of test apparatus
The test apparatus is a small sample bench test machine for friction materials as shown in Figure 1 and Figure 2. The test machine shall have the following functions:
a) Measuring the temperature of the brake drum;
b) Heating the brake drum;
c) Controlling the heating rate of the brake drum;
d) Cooling the brake drum only from the back side of the brake drum;
e) Controlling the cooling rate of the brake drum;
f) Measuring the friction force;
g) Measuring the rotating speed of the brake drum.
2.2 Temperature measuring device
The temperature measuring device shall be composed of welded thermocouple, alloy metal ring, silver-graphite brush and recorder with high input impedance.
The precision of temperature measuring system shall be full scale ±2%.
2.3 Friction force measuring system
The precision of friction force measuring system shall be full scale ±2%.
2.4 Brake drum
2.4.1 The precision of brake drum speed measuring system shall be full scale ±2%.
2.4.2 The temperature rise mode of the brake drum shall be adjusted as follows, and this state shall be maintained during the test:
The rotating speed of the brake drum shall be 417 r/min. Cool the brake drum from 149 ℃ to 93 ℃ with cooling air, then turn off the cooling air, and when the brake drum is naturally cooled to 82 ℃, turn on the heater, start timing and heat for 10 min. The temperature of brake drum shall rise to 221 ℃ ± 14 ℃ within 10 min.
The cooling mode of brake drum shall be adjusted as follows, and this state shall be maintained during the test:
The rotating speed of the brake drum shall be 417 r/min. Heat the brake drum to 371 ℃ with a heater, then turn off the heater and turn on the cooling air. When the temperature drops to 343 ℃, start timing and cool the brake drum for 10 min. The temperature of the brake drum shall be dropped to 93 ℃ ± 14 ℃ within 10 min.
2.4.3 The brake drum shall be made of pearlite cast iron with the Brinell hardness of 179 ~ 229, and the chemical composition content shall meet the following requirements:
Foreword i
1 Scope
2 Test apparatus
3 Preparations for test
4 Test steps
5 Result report
6 Levels and markings of friction coefficient
Annex A (Informative) Test data record table and data curve
Annex B (Informative) Product test result report format
