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Method for judging spring effect of commercial vehicle equipped with air suspension
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QC/T 1224-2025: Method for judging spring effect of commercial vehicle equipped with air suspension
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/QCT1224-2025
QC
AUTOMOTIVE INDUSTRY STANDARD
ICS 43.020
CCS T 04
Method for Judging Spring Effect of Commercial Vehicle
Equipped with Air Suspension
Issued on: MAY 9, 2025
Implemented on: DECEMBER 1, 2025
Issued by. Ministry of Industry and Information Technology of the People’s
Republic of China
Table of Contents
Foreword... 3
1 Scope... 4
2 Normative References... 4
3 Terms and Definitions... 4
4 Judgment Technical Requirements... 5
5 Vehicle Test Methods for Natural Frequency and Damping Ratio... 6
Appendix A (Informative) Calculation Results of Air Spring Load Ratio... 9
Appendix B (Informative) Test Results Record of Air Suspension Natural Frequency
and Damping Ratio... 10
Bibliography... 12
Method for Judging Spring Effect of Commercial Vehicle
Equipped with Air Suspension
1 Scope
This Document specifies the technical requirements for judging the vibration reduction effect
of commercial vehicles equipped with air suspension, as well as the vehicle test methods for
natural frequency and damping ratio.
This Document applies to M2, M3, N2, N3, O3, and O4 category vehicles equipped with rear axle
air suspension; other vehicles shall refer to this Document for guidance.
2 Normative References
The provisions in following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
GB 1589 Limits of dimensions, axle load and masses for motor vehicles, trailers and
combination vehicles
GB/T 3730.2 Road vehicle – Masses - Vocabulary and codes
GB/T 34591 Terms of air suspension for commercial vehicle
3 Terms and Definitions
For the purposes of this Document, the terms and definitions given in GB 1589, GB/T 3730.2,
GB/T 34591 and the following apply.
3.1 Damping ratio
The ratio of the actual damping coefficient to the critical damping coefficient.
[SOURCE. GB/T 2298-2010, 3.96]
3.2 Sprung mass
The mass of the load above the suspension elastic elements, that is, the mass of the load borne
by the suspension.
[SOURCE. GB/T 12549-2013, 6.2.2]
3.3 Air spring load ratio
The ratio of the mass carried by the air spring in the suspension to the sprung mass.
4 Judgment Technical Requirements
4.1 When all axles (or axle groups) of a vehicle are under maximum permissible axle load, the
vibration reduction effect of all rear axles equipped with air suspension in M2 and M3 category
vehicles shall meet the requirements of 4.3, 4.4, and 4.6.Failure to meet these requirements
shall result in the vehicle not being considered as equipped with air suspension.
4.2 When all axles (or axle groups) of a vehicle are under maximum permissible axle load, the
vibration reduction effect of all rear axles equipped with air suspension in N2, N3, O3, and O4
category vehicles shall meet the requirements of 4.3 to 4.6.Failure to meet these requirements
shall result in the vehicle not being considered as equipped with air suspension.
4.3 When all axles (or axle groups) of a vehicle are under maximum permissible axle load, the
air spring load ratio shall be no less than 50%. The air spring load ratio is calculated according
to Formula (1). For axle groups, the air spring load ratio of each axle shall be calculated
separately, and the calculation results shall be recorded with reference to Appendix A.
Where.
η – air spring load ratio, in %;
ma – air spring load capacity, in kg;
m – sprung mass, in kg.
4.4 The natural frequency of the air suspension shall be no greater than 2.0 Hz.
4.5 The damping ratio of the air suspension shall be no less than 0.2.
4.6 The ratio of the damping ratio of the air suspension without damper to that with damper
shall be no greater than 50%.
5 Vehicle Test Methods for Natural Frequency and Damping
Ratio
5.1 Test Vehicle
5.1.1 The air suspension condition shall meet the vehicle manufacturer's technical requirements.
5.1.2 The tire tread depth shall be at least 50% of the original tread depth; and the tire inflation
pressure shall meet the vehicle design technical requirements, with an error not exceeding ±3%
of the specified inflation pressure.
5.1.3 The axles (groups) shall be under maximum permissible axle load.
5.2 Road conditions
The test road shall be a straight, firm asphalt or concrete surface; dry and flat; with a
longitudinal slope not exceeding 1%; uniform unevenness without abrupt changes; and a road
length no less than the minimum road length required for the test data collection time.
5.3 Wind speed
Wind speed shall not exceed 5 m/s.
5.4 Test instruments
5.4.1 Test instruments include accelerometers, data acquisition devices, etc.; suitable for impact
measurement, and with stable and reliable performance.
5.4.2 The sampling frequency of the test instruments shall be no less than 100 Hz.
5.5 Test apparatus
The test shall use rigid, hard wedge-shaped bumps or other similar devices. The height (H) of
the device shall be 80 mm to 85 mm (see Figure 1). The lateral width of the device shall ensure
that all wheels of the test vehicle axle (group) are placed on it.
Figure 1 – Schematic diagram of wedge-shaped bump
Wheel
5.6 Test procedure and data processing
5.6.1 Install an accelerometer at the corresponding position on the frame (or bus body) above
each test axle.
5.6.2 Select the appropriate number of test devices of the same height based on the number of
axles equipped with air suspension on the vehicle.
5.6.3 Drive the wheels of the test axle (group) onto the test device, brake the vehicle, shift to
neutral, and stop the engine (or electric motor).
5.6.4 Start the free vibration acceleration recording device.
5.6.5 Release the brakes; and the vehicle moves along the wedge-shaped bump under gravity;
with all wheels of the test axle (group) simultaneously falling from the test device. If using
other similar devices, all wheels of the test axle (group) shall fall from the test device
simultaneously. The wheels shall not touch the test device after landing.
5.6.6 Stop recording free vibration acceleration when the vehicle comes to a stop.
5.6.7 The test data is low-pass filtered with a cutoff frequency of 5 Hz and fitted to form a free
vibration decay curve (see Figure 2). The curve shall be complete and without abnormalities.
The time interval and peak value of the first and second suspension compression states of the
vibration decay curve are read; and the natural frequency and damping ratio of the air
suspension are calculated according to Formulae (2) and (3).
Where.
f - natural frequency of the suspension sprung mass, in Hz;
T - time interval between the first and second suspension compression peaks, in s;
ζ - air suspension damping ratio;
A1 - first suspension compression peak, in m/s²;
A2 - second suspension compression peak, in m/s².
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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