GB/T 46581-2025Road vehicles — Brake lining friction materials — Test method for brake wear particle emission (English PDF)

3.1 NEDC brake cycle

The New European Driving Cycle brake cycle.

One cycle consists of four urban road modes and one expressway mode.

3.2 WLTP brake cycle

The World Light Vehicle Test Procedure brake cycle.

One cycle consists of 10 stages and 303 braking maneuvers, and a driving cycle of a total duration of 15,826 seconds.

3.3 Particulate size

The diameter of a spherical particle in aerodynamics that is equivalent to a density of 1,000 kg/m3.

3.4 Particulate concentration

The mass of suspended particulate matter per unit volume under the capture temperature and pressure conditions.

NOTE. generally, it is expressed as the quantity or mass of fine particles per unit volume or mass of gas or suspended in a liquid, depending on the type and size of the particulate matter.

3.5 Cascade impactor

A device that blows sample gas from a fine nozzle or slit towards a flat plate, causing particles to deposit on the flat plate through inertial force.

3.6 Brake emissions family

A collection of brakes designed to have similar emission characteristics, taking into account calipers, brake discs (drums), brake linings and other vehicle parameters.

3.7 Mass in running order

The total mass of the vehicle and its fuel tank when filled to at least 90% capacity, including the mass of the driver, fuel and fluids. With standard equipment installed in accordance with the manufacturer’s specifications, it also includes the mass of the vehicle body, driving cab, transmission, spare tire, and tools.

3.8 Aerosol

A dispersed system consisting of solid and/or liquid particles suspended in air.

3.9 Response time

The time difference between the start of a change in the measured value at a datum point and the measurement system response reaching 90% of the final reading.

NOTE. system response time (t90) consists of system delay time and system rise time. In this document, the inlet of the sampling nozzle is defined as the datum point.

3.10 Friction braking share coefficient

During a driving cycle, the ratio of the total energy absorbed by the full friction braking system to the change in the vehicle’s total kinetic energy during braking events (excluding road loads) in the same driving cycle.

3.11 Standard conditions

Conditions with a pressure of 101.325 kPa and a temperature of 273.15 K (i.e., 0 C).

3.12 Specific friction work

During a brake emission test, under a specified deceleration event, the actual friction work applied to the test brake.

5.1 Measurement Conditions

5.1.1 Brake components

5.2.2.2 Running-in

5.2.2.2.1 The final running-in speed is equivalent to full braking.

5.2.2.2.2 After running-in, use blast air to thoroughly remove wear particles from the brake linings and brake discs (drums), then, measure the thickness and mass.

5.2.2.2.3 After running-in, use air to purge the brake calipers and clamping tools to thoroughly remove wear particles. Simultaneously, use a waste cloth to remove wear particles inside the main duct of the wear particle capture device.

5.2.2.3 Wear particle measurement mode

5.2.2.3.1 One cycle of the wear particle measurement mode is shown in Table 3 (an equivalent mileage of 11 km), for a total of 30 cycles.

5.2.2.3.2 Replace one filter element every 10 cycles and measure the mass of the filter element.

If the mass of the filter element or the wear of the brake linings and brake discs (drums) is insufficient, the cycle shall be continued, until sufficient wear is achieved.

5.2.3 Measurement of wear particle mass

5.2.3.1 Filtration mass method

5.2.3.1.1 For the filtration mass method, a cascade impactor capable of achieving the fraction of particulate matter (PM10, PM2.5) is used. The diameter of the filter element shall be  47 mm (effective diameter 37 mm).

5.2.3.1.2 The PM2.5 emission (Ma) per 1 km per wheel travel is calculated by measuring the increment in filter element mass before and after the test. Ma is calculated in accordance with Formula (2). Where, Ma---the PM2.5 emission per 1 km per wheel travel, expressed in (mg/km);

Mb---the increment in filter element mass before and after the test, expressed in (mg);

Q2---the air suction volume of the capture device, expressed in (m3/min);

Q1---the flow rate in the main duct, expressed in (m3/min);

L---the total mileage under the wear particle measurement mode, expressed in (km).

5.2.3.1.3 The weighing range of the balance used to weigh the filter element shall be 0.1 g ~ 10 g. The appropriate accuracy shall be selected based on the amount of wear particle emission.

5.2.3.2 Light scattering particle mass concentration method

5.2.3.2.1 Although the light scattering particle mass concentration meter can measure particle mass concentration in real time, its accuracy varies depending on the type of particles measured.

Therefore, it needs to be used simultaneously with the filtration mass method. In this case, the measurement time needs to be matched with the filtration mass method, and a cascade impactor shall be installed during measurement.

5.2.3.2.2 The PM2.5 emission (Mc) obtained from the mass concentration is calculated using Formula (3). Where, Mc---the PM2.5 emission calculated based on mass concentration, expressed in (mg);

ts---the measurement start time;

te---the measurement end time;

rho---the mass concentration, expressed in (mg/m3);

Q3---the air suction volume of the light scattering particle mass concentration meter, expressed in (m3/s).

5.3 Test Report

The test report shall include at least the following contents.

— Before and after running and after the wear particle measurement mode is completed, the thickness and mass of brake linings and brake discs (drums);

— PM2.5 emissions Ma and Mc obtained through calculation;

— Braking torque, pressure, temperature, and rotation speed during the test;

— Temperature and relative humidity of the air in the main duct;

— Temperature and relative humidity of the test environment.

6.1 Brake Emissions Family

6.1.1 Original brake components and equivalent brake components

For original brake components and equivalent brake components, they belong to the same brake emissions family only if they share the following characteristic requirements.

a) Brake caliper type (floating or fixed, number and size of pistons, return element type);

b) Brake type. brake disc (friction surface, coating, single disc, double disc, ventilated, solid, size, mass, material formula) or brake drum (friction surface, simplex, duplex, size, mass, material formula);

c) Friction material type. disc lining (friction surface, size, shape, material, backing plate, material formula) or drum lining (friction surface, size, design, material, brake shoe, material formula);

d) Other characteristics affecting brake emissions (for example, new brake emission reduction systems).

6.1.2 Non-original interchangeable brake components and equivalent brake components

For non-original interchangeable brake components and equivalent brake components, they belong to the same brake emissions family only if they share the following characteristic requirements.

a) Brake caliper type (floating or fixed);

b) Axle where the brake is located;

c) Friction material formula;

d) For disc brakes. brake disc type (non-original interchangeable brake discs and equivalent brake discs are classified into families in accordance with Table 4); brake disc surface morphology (smooth and non-smooth); surface area of a single brake lining (PSA), divided into 10 levels in 10 cm2 increments;

e) For drum brakes. brake drum type (non-original interchangeable brake drums and equivalent brake drums are classified into families in accordance with Table 5);

diameter of brake drum (BDD), divided into 8 levels in 20 mm increments.

6.2.2.3.2 For single-point measurements, install the flow rate measuring device at the center of the duct. The upstream section of the flow rate measuring device shall be at least 5 times the inner diameter length of the duct, and the downstream section shall be at least 2 times the inner diameter length of the duct. The inner diameter of the duct in the flow rate measurement area may differ from the inner diameter of the sampling duct, but it shall be at least 35% of the sampling duct’s inner diameter. The installation of the flow rate measuring device shall not cause significant pressure changes (i.e., the pressure at the flow rate measuring device shall differ from the ambient pressure by within  1 kPa).

6.2.2.3.3 For multi-point measurements, install the flow rate measuring device perpendicular to the gas flow direction. The upstream section of the flow rate measuring device shall be at least 5 times the inner diameter length of the duct, and the downstream section shall be at least 2 times the inner diameter length of the duct. The inner diameter of the duct in the flow rate measurement area may differ from the inner diameter of the sampling duct, but it shall be at least 35% of the sampling duct’s inner diameter. The installation of the flow rate measuring device shall not cause significant pressure changes (i.e., the pressure at the flow rate measuring device shall differ from the ambient pressure by within  1 kPa).

6.2.2.3.4 A calibrated flow rate measuring device shall be used to measure and record the standard-condition cooling air flow rate. To ensure accurate calculation of the standard- condition cooling air flow rate, the temperature sensor at the flow rate measurement location shall have a measurement accuracy of  1 C, and the pressure sensor shall have a measurement accuracy of  0.4 kPa.

6.2.2.3.5 If a high efficiency particulate air filter is used to prevent contamination of the flow rate measuring device, the high efficiency particulate air filter shall be installed at least 5 times the duct’s inner diameter upstream of the flow rate measuring device, and the pressure drop shall be continuously monitored. If necessary, the gas flow rate measurement value shall be corrected. The model of the high efficiency particulate air filter shall be selected in accordance with the requirements of the flow rate measuring device.

6.2.2.3.6 The cooling air flow rate shall remain constant throughout the entire brake emission test. Once the set value (Qset) for the cooling air flow rate is determined, it shall be the same and constant throughout the brake emission test.

6.2.2.3.7 Before the test, a leak check shall be performed on the duct system and brake chamber.

Set the cooling air flow rate to Qset, and after the flow rate stabilizes, continue measuring for at least 2 minutes. If the measured average flow rate is within  5% of Qset, continue the test; if it exceeds this range, stop the test, check the flow rate measuring device and troubleshoot the leak source, and retest after the problem is resolved.

6.2.2.3.8 Use the measured cooling air flow rate and the inner diameter of the sampling duct, and in accordance with Formula (4), calculate the corresponding instantaneous cooling air velocity at the sampling duct. Where, U---the instantaneous cooling air velocity, expressed in (km/h);

Q---the cooling air flow rate, expressed in (m3/h);

di---the inner diameter of the sampling duct, expressed in (mm).

6.2.2.4 Cooling air cleanliness

The cooling air entering the test system shall be filtered through a high efficiency particulate air filter (not lower than Grade-G35 specified in GB/T 13554-2020). If a filter (charcoal, activated carbon, or equivalent device) for removing volatile organic compounds is required, it shall be installed upstream of the high efficiency particulate air filter.

6.2.3 Background particulate matter

6.2.3.1 General requirements

6.2.3.1.1 Background particulate matter concentration is expressed by PN, and it is calibrated and reported based on TPN10 and SPN10 under standard conditions.

6.2.3.1.2 Before background particulate matter calibration, the particle number counter (PNC) shall be zero-point verified as follows. in accordance with the equipment manufacturer’s specifications, install an appropriate filter at the PNC inlet and record the PN concentration.

The PNC inlet reading shall be  0.2 particles/cm3. After removing the filter, the PNC shall show an increase in the measured concentration, which shall return to  0.2 particles/cm3after replacing the filter.

6.2.3.2 System-level background particulate matter calibration

6.2.3.2.1 After the test equipment has been installed, debugged, undergone major maintenance, or when there are signs of system faults, system-level background particulate matter calibration shall be performed.

6.2.3.2.2 Without installing brake clamps or any brake components in the brake chamber, under the minimum particulate concentration reduction factor (PCRF) setting, measure TPN10 and SPN10.

6.2.3.2.3 The minimum and maximum cooling air operating flow rates shall be used. 5 minutes after the cooling air has stabilized, background particulate matter calibration shall begin.

6.2.3.2.4 During background particulate matter calibration, a single nozzle may be used for the sampling of TPN10 and SPN10.

6.2.3.2.5 Background particulate matter calibration shall continue, until the background concentration stabilizes. If, under standard conditions, the 5-minute moving average values of TPN10 and SPN10 (continuously measured at a frequency of 1 Hz) after PCRF correction are ......