GB/T 41062-2021 English PDF (GBT41062-2021)

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GB/T 41062-2021: Test method for thermal transport properties to friction materials and brakes
GB/T 41062-2021
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 43.040.40
CCS Q 69
Test method for thermal transport properties to friction
materials and brakes
ISSUED ON: DECEMBER 31, 2021
IMPLEMENTED ON: JULY 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3 
Introduction ... 4 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions... 6 
4 Test methods ... 6 
References ... 18 
Test method for thermal transport properties to friction
materials and brakes
WARNING – The personnel who uses this document shall have hands-on
experience in formal laboratory work. This document does not address all possible
security issues. It is the responsibility of the user to take appropriate safety and
health measures and to ensure compliance with the conditions which are set by the
relevant national regulations.
1 Scope
This document describes test methods for thermal diffusivity, specific heat, thermal
conductivity, and coefficient of thermal expansion to friction materials and brakes.
This document applies to the determination of thermal conductivity properties to disc
brake linings, drum brake linings and friction materials.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this
document and are indispensable for its application. For dated references, only the
version corresponding to that date is applicable to this document; for undated references,
the latest version (including all amendments) is applicable to this document.
GB/T 4339, Test methods for thermal expansion characteristic parameters of
metallic materials
GB/T 5620, Road vehicles - Vocabulary and definition for braking of automotive
vehicles and their trailers
GB/T 10295, Thermal insulation - Determination of steady-state thermal resistance
and related properties - Heat flow meter apparatus
GB/T 19466.4, Plastics - Differential scanning calorimetry(DSC) - Part 4:
Determination of specific heat capacity
GB/T 22588, Determination of thermal diffusivity or thermal conductivity by the
flash method
GB/T 32064, Determination of thermal conductivity and thermal diffusivity of
building materials: transient plane heat source method
3 Terms and definitions
Terms and definitions determined by GB/T 5620 and the following ones are applicable
to this document.
3.1
Thermal diffusivity
The rate of heat diffusion inside the friction material when the friction material is heated
or cooled.
Note: in square centimeters per second (cm2/s). The larger the thermal diffusivity, the
faster the temperature diffusion and heat flow through the material.
3.2
Specific heat
Cp
The heat absorbed or released by a unit mass of a substance when the temperature rises
or falls under the condition of constant pressure.
Note: in Joules per gram Celsius [J/(g·°C)].
3.3
Thermal conductivity
The time rate of heat flow per unit temperature gradient in the direction perpendicular
to the area, through the unit area, under stable conditions.
Note: in watts per meter kelvins [W/(m·K)].
4 Test methods
4.1 Determination method of thermal diffusivity
4.1.1 Method overview
The laser flash method is a method used to determine the thermal diffusivity. Expose a
test piece of known thickness to an intense laser or xenon flash lamp, to obtain a short
e) recording device;
f) host;
g) probe;
h) sample compartment;
i) thermostat.
4.1.3 Test piece
4.1.3.1 Flash method (method A)
4.1.3.1.1 The commonly used sample is a thin disk-shaped sample whose surface area
for receiving pulsed energy radiation is smaller than the energy beam spot. The typical
diameter of a test piece is 6 mm ~ 18 mm; the optimal thickness of a test piece depends
on the estimated thermal diffusivity; this thickness of test piece shall be selected to
ensure that the time required to reach the maximum temperature varies within 40 ms ~
200 ms. A thinner test piece shall be used for high temperature measurements, so as to
minimize the heat loss correction. The test piece shall be of sufficient thickness, so that
the to-be-tested material is more representative. The typical thickness of a test piece is
1 mm ~ 6 mm. Since the thermal diffusivity is proportional to the square of the thickness
of test piece, different thicknesses of test piece should be used in different temperature
ranges. The optimal thickness of test piece required for low temperature testing is
inconsistent with that required for high temperature testing.
4.1.3.1.2 Improperly selected thickness of test piece will not only cause unnecessary
test failures, but also be the main cause of test errors. Generally, a test piece with a
thickness of 2 mm ~ 3 mm can be selected at the beginning; then, the thickness of test
piece can be changed based on the obtained temperature recording curve (the signal
cannot be observed if the test piece is too thick).
4.1.3.1.3 The surface of the prepared test piece shall be flat and the parallel error shall
be within 0.5% of the thickness. There shall be no surface defects (sandish holes,
scratches, streaks) as they would seriously affect the test results.
4.1.3.2 Plane heat source method (method B)
4.1.3.2.1 The effective diameter of the test surface of the test piece shall not be less than
twice the diameter of the probe; the surface shall be flat, and the surface material and
density shall not be modified.
4.1.3.2.2 Block samples shall meet the requirements of 4.1.3.2.1, and can be prepared
into cylinders, cubes, etc. The thickness of the upper and lower samples shall be the
same, and the thickness should be greater than the diameter of the selected probe, but
not less than the radius of the probe.
4.1.3.2.3 Sheet samples shall meet the requirements of 4.1.3.2.1. During preparation,
the thickness of the upper and lower samples shall be the same, and the deviation shall
not be greater than 0.01 mm.
4.1.3.2.4 Film samples shall meet the requirements of 4.1.3.2.1. During preparation, the
thickness of the upper and lower samples shall be the same, and the deviation shall not
be greater than 0.001 mm.
4.1.3.2.5 The uniaxial anisotropy sample shall meet the requirements of 4.1.3.2.1.
During preparation, the test surface of the sample shall be parallel to the plane
determined by the x-axis and the y-axis.
4.1.3.2.6 Dry the sample to constant mass and adjust it to the test temperature; when
there are special requirements, the sample shall be adjusted according to the product
requirements.
4.1.4 Test procedure
4.1.4.1 The flash method (method A) shall be determined according to GB/T 22588.
4.1.4.2 The plane heat source method (method B) shall be determined according to
GB/T 32064.
4.1.5 Test report
The test report shall at least include the following information:
a) sample identification;
b) sample thickness;
c) test temperature;
d) thermal diffusivity, under the test temperature, that is calculated when X = 50%
(percentage of temperature rise), m2/s;
e) a statement related to the thermal diffusivity calculated for X = 25%, X = 75%
and X = 50%, or a comparison of the data at each temperature in the descending
part of the test curve with the theoretical model;
f) report of repeated test results at each temperature;
g) Whether the thermal expansion is corrected,...