GB/T 17469-2024 Characteristics evaluation of brake linings for automobile - Small sample bench test method
1 Scope
This document specifies the test equipment, test preparation, test procedure, result processing, friction coefficient classification and friction coefficient level marking and test report of the small sample bench test method for characteristics evaluation of brake linings for automobile.
This document applies to disc brake linings and drum brake linings for automobiles (hereinafter referred to as "linings")
This document does not apply to brake linings for parking brakes.
2 Normative references
The following documents contain requirements which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 5620 Road vehicles - Braking of automotive vehicles and their trailers - Vocabulary
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 5620 apply.
4 Test equipment
4.1 Test machine
See Figure 1 for the schematic diagram of a small sample bench test machine for friction materials. 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 of the drum;
e) controlling the cooling rate of the brake drum;
f) measuring the friction force;
g) measuring the rotational speed of the brake drum.
4.2 Temperature measurement system
4.2.1 The temperature measurement system shall be composed of welded thermocouples and measurement and recording devices that can meet the requirements of rotating temperature measurement.
4.2.2 The accuracy of the temperature measurement system is ±2% of the full scale.
4.3 Friction force measurement system
The accuracy of the friction measurement system is ±2% of the full scale and the deviation of the test load is ±2%.
4.4 Brake drum
The accuracy of the brake drum speed measurement system is ±2% of full scale.
4.4.1 The accuracy of the brake drum speed measurement system is ±2% of full scale.
4.4.2 The temperature rise of the brake drum is adjusted as follows and maintained in this state during the test: the rotation speed of the brake drum is 417 r/min, the brake drum is cooled from 149 °C to 93 °C with cooling air, and then the cooling air is turned off. When the cooling air is naturally cooled to 82 °C, the heater is turned on to start the timing, and the heating is carried out for 10 minutes. The temperature of the brake drum shall rise to 221 ℃ ± 14 ℃ in 10 minutes.
4.4.3 The temperature drop of the brake drum is adjusted as follows, and this state is maintained during the test: the rotation speed of the brake drum is 417 r/min, and the brake drum is heated to 371 °C with a heater, then the heater is turned off, the cooling air is turned on, and the timing is started when the temperature is reduced to 343 °C, and the cooling is carried out for 10 minutes. The temperature of the brake drum shall be reduced to 93 ℃ ± 14 ℃ within 10 minutes.
4.4.4 The material of the brake drum shall be pearlite cast iron, its chemical composition shall meet the requirements of Table 1, the Brinell hardness HBW shall be 179 ~ 229, and the size shall meet the requirements of Figure 2.
4.4.5 The brake drum shall be used within the range of inner diameter of 277.4 mm ~ 279.9 mm. There are three thermocouple installation positions as shown in Table 2, which are (2.55 ± 0.10) mm (position 1), (3.05 ± 0.10) mm (position 2) and (3.55 ± 0.10) mm (position 3) from the surface of the brake drum with an inner diameter of 277.4 mm respectively.
4.5 Other devices
Devices for measuring the thickness and mass of the sample as well as the height of the top of the fixture.
Contents Foreword i 1 Scope 2 Normative references 3 Terms and Definitions 4 Test equipment 5 Test equipment 6 Test step 7 Result processing 8 Friction coefficient classification and friction coefficient level marking 9 Test report Annex A (Informative) Test data record table and data graph Annex B (Informative) Report format of product test results
