Road vehicles - Brake linings - Compressive strain test method
1 Scope
This document specifies the principle, test equipment, technical requirements of test devices, sample preparation, test method, deflection compensation of test equipment, verification of test equipment with reference samples and test report of compressive strain test method for brake linings of road vehicles.
This document is applicable to measuring the compressive strain of brake lining disc brake pad assemblies and specimens cut from disc or drum friction materials.
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 and the following apply.
3.1
compressibility
C
change of thickness or deflection of the pad caused by uniaxial compressive load in the direction same as the compressive force and perpendicular to the friction surface when the maximum test pressure is reached in the last loading cycle
3.2
compressive strain
ε
ratio of the reduction in the thickness of the brake lining to the initial thickness in the direction of the friction surface and in the same direction as the compressive force due to the compressive load
3.3
net deflection
D
degree of bending or deformation of an object under pressure or load
3.4
friction material contact area
A0
area of friction material bearing the test load during the test
Note: It is recommended to consider grooves, chamfers, and any other features when determining A0.
3.5
hot compressibility
C400
compressibility when the pressure plate temperature is 400°C
3.6
heat conduction
TT
temperature-rise of the back plate of the brake pad assembly when the friction surface and the pressure plate are in contact for a specified time at a temperature of (400 ± 10)°C under a given pressure
Notes: The heat conduction is calculated using Equation (1):
TT=T3-T2 (1)
where,
T2——the Initial temperature of the back plate during high temperature test;
T3——the final temperature of the back plate during high temperature test.
3.7
thermal growth
dG
permanent change in specimen thickness when the friction surface and the pressure plate are in contact for a specified time at a temperature of (400 ± 10)°C under a given pressure, and then cooled to the room temperature
4 Symbols
The following symbols apply to this document (see Table 1).
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Principle
6 Test equipment
7 Technical requirements of test devices
8 Specimen preparation
9 Test methods
10 Deflection compensation of test equipment
11 Verification of test equipment with reference samples
12 Test report
Annex A (Informative) Test report forms
