SAE J2598:2020 pdf free
SAE J2598:2020 pdf free.Automotive Disc Brake Pad Natural Frequency and Damping Test
This document separates the measurement procedures to obtain the brake pad natural frequencies and that required to obtain the loss factors. The reason for this separation is that in the development of this procedure significant differences were found in the repeatability of the results for these two measurements between different testers. The result is that highly accurate and consistent natural frequency data can be obtained with less rigorous measurement system and procedure requirements. This measurement procedure is presented in Part A.
The more rigorous loss factor measurement procedure is presented in Part B. It is important to note that although the requirements for this measurement are more stringent, there is still greater variability in the loss factor results. The magnitude of this variability will be discussed in some details in Part B.
The preferred measurement setup is shown in Figure 1. This configuration shows the use of a microphone for the response measurement and an impact hammer for excitation. The same setup can be used with an accelerometer. One may use equivalent non contacting measurements such as laser doppler vibrometer, if the results can be shown to be equivalent.The pad is placed on a piece of foam, with the friction material facing down. However, the measurement can also be done with the friction material facing up.
To be sure that the lower three natural frequencies and their corresponding loss factors are measured, it is necessary to excite both torsional and bending modes. The lowest three natural frequencies may then be selected from these results with high confidence.
Figures 2 to 4 show three suggested measurement configurations. Using all three of these combinations of force input and response locations, one can be confident of that the lowest three natural frequencies will be measured.SAE J2598 pdf free download.
