SAE J3175-2024 汽车摩擦材料摩擦材料规范化的弹性常数制动片

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For more information on this standard, visit

https://www.sae.org/standards/content/J3175_202412/

SURFACE VEHICLE

STANDARD

J3175™

DEC2024

Issued 2019-11

Reaffirmed 2024-12

Superseding J3175 NOV2019

Road Vehicles - Friction Materials - Finished Brake Pad

Normalized Elastic Constant of Friction Material

RATIONALE

Measurement of variations in elastic properties because of raw materials, internal cracks, or other factors can be useful for

quality control. Elastic properties are also important for lining characterization. The purpose of this test procedure is to

evaluate the normalized elastic constant of friction material on a finished brake pad.

SAE J3175 has been reaffirmed to comply with the SAE Five-Year Review policy.

1. SCOPE

This SAE standard specifies a method for testing and measuring a normalized elastic constant of brake pad assemblies

using ultrasound. This document applies to disc brake pad assemblies and its coupons or segments used in road vehicles.

2. REFERENCES

2.1 Applicable Documents

The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the

latest issue of SAE publications shall apply.

2.1.1 SAE Publications

Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA

and Canada) or +1 724-776-4970 (outside USA), www.sae.org.

SAE J380 Specific Gravity of Friction Material

SAE J2725 Road Vehicles - Friction Materials - Elastic Properties Measurements

3. DEFINITIONS

3.1 NORMALIZED ELASTIC CONSTANT OF FRICTION MATERIAL (NECFM)

A measure of the elastic constant (C44) independent of friction material density.

C44 can be referred to from SAE J2725.

3.2 ULTRASONIC MODES

Shear wave/ultrasonic wave mode where the direction of wave propagation is perpendicular to the friction surface of a brake

pad.

SAE INTERNATIONAL J3175™ DEC2024 Page 2 of 9

3.3 COORDINATE SYSTEM DEFINITION

See Figure 1.

Figure 1 - Coordinate system

4. SYMBOLS

Dfriction Friction thickness (Dtotal - Dplate), in meters (m)

Dplate Constant, nominal pressure plate design thickness, in meters (m)

Dtotal Overall thickness of pad at given measurement point, in meters (m)

NECFM Normalized Elastic Constant of Friction Material, in pascals (Pa)

Tsmeasured Transit time when measuring calibration steel block, in seconds (s)

Tsoffset System delay (Tsmeasured - Tsstandard), in seconds (s)

Tsplate transit time through pressure plate (Dplate / Vsplate), in seconds (s)

Tstotal Transit time through brake pad, in seconds (s)

Tsstandard Constant (known transit time through certified calibration block), in seconds (s)

Tsfriction Measured transit time through friction material (Tstotal - Tsoffset - Tsplate), in seconds (s)

Vsfriction Velocity of shear wave in friction, in milliseconds (ms)

Vsplate Constant (3228), velocity through standard pressure plate, in milliseconds (ms)

ρnormalized 1, in kilograms per cubic meter (kg/m³)

SAE INTERNATIONAL J3175™ DEC2024 Page 3 of 9

5. EQUIPMENT

The test equipment needs to be capable of meeting the specifications indicated on Table 1.

Table 1 - Minimum test system capabilities and specifications

Parameter

Minimum requirement or capability

Micrometer (or other means of measuring pad

thickness)

±0.03 mm.

Ultrasonic pulse signal generator

Repeated pulses equal to or less than 0.2 µs in width and of sufficient

amplitude to generate an averaged waveform with defined peaks and

valleys at the receiver output.

Waveform digitizer and display

Acquisition sampling rate at least 50 MHz, ability to display waveforms

in real-time, have automatic or manual peak detection, signal averaging

(50 times minimum), and automatic time-of-

flight measurement

capability. Timing precision of ±10 nanoseconds.

Coupling load fixture

The coupling load test fixture must be capable of supplying and

monitoring up to 1000 N (220 pounds

) of compressive load to the

samples and of maintaining the polarization of the ultrasonic sensors

to better than ±5 degrees. The precision of the load fixture should be

±20 N (5 pounds

). For shear wave transducers, the direction of

polarization as is indicated on the sensors. The fixture must allow for

rotation of each sensor (about the propagation direction) to ensure that

the polarization of the sensors are co-linear.

Ultrasonic shear sensors (N=2)

The shear wave transducers must be linearly polarized with

polarization clearly marked. They must operate with a center frequency

in the range from 1 to 5 MHz and have a 10 dB bandwidth greater than

80%, and have an active piezoelectric element.

Optional: Software for waveform analysis and

obtaining friction time-of-flight (T

friction)

Propagation timing standard (calibration block)

With known shear wave transit time of ±5 nanoseconds.

Sensor concentricity relative to each other

Less than 0.5 mm.

5.1 Facilities

Test facility capable of maintaining test equipment.

5.2 Test stand verification

Verify the measurement capability of the test stand using with the following items:

a. Appropriate checklists to verify features, functionality, and specifications (full scales, accuracies, sampling rates, etc.).

b. Gage repeatability and reproducibility study with at least ten preselected brake pads and at least three operators, with

three repeats each.

5.3 Test Stand Condition

All test equipment, fixtures, and samples shall be inspected prior to use. Nicks, burs, corrosion, or contamination on any

contacting surfaces can cause variation in the test equipment that can exceed the intended measurement capability of the

test procedure.

5.4 Calibration

a. Because of triggering delays in the instrumentation and propagation delays in the piezoelectric sensors, it is necessary

to calibrate the system using a test sample where the propagation time is known or measured independently. A

propagation timing standard with known shear waves must be accurate to ±0.2 µs. Stainless steel is recommended for

calibration due to its uniform physiochemical properties. The calibration block whose transit time for shear waves has

been measured independently should be used and should be 15 to 26 mm in thickness.

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标签： #汽车 #材料规范 #材料

摘要：

本文档详解SAE J3175-2024标准，该标准由国际自动机工程师学会发布，专门针对汽车摩擦材料领域，重点规范了制动片弹性常数的标准化测试方法与定义。作为最新的2024年修订版本，该标准旨在统一汽车制动系统中摩擦材料的弹性模量、剪切模量等关键力学参数的测量与报告流程，解决行业因测试方法差异导致的数据不可比问题。通过引入规范化的弹性常数测定方法，本标准有助于摩擦材料制造商、制动片生产商及整车厂在设计阶段更精准地预测刹车片的压缩性、回弹性及热变形行为，从而提升制动系统的NVH（噪声、振动与平顺性）

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