Experimental Modal Analysis on Auto Brake Disk

As a high-speed rotating part, brake disk has a central symmetry property. For its brake friction surface, the vibration mode is mainly and evenly distributed along the circumference and the same radius. As combined with the other braking components, if some excitation is equal to natural frequency, mode is excited and then the self-deformation has strong vibration and noise in this case. Therefore, more attention is paid on the dynamic characteristics of brake disk during product design and development phase.
Modal analysis technique is a modern method to do dynamics analysis for parts and engineering structure system, which can solve many engineering problems. Testing and confirming the mode frequency and vibration mode is the important way to study and solve vibration and noise.


Note: this is not true picture of brake disk.
The testing engineer adopts AVANT MI-7008 data acquisition and signal analyzer with modal data acquisition software, which is from Hangzhou Econ Technologies Co., Ltd., and also uses a special modal impact hammer with a force transducer and a triaxial acceleration transducer, and then does modal test.
Considering the test conditions, now set 16 test points on its inside and outside layouts. Details as shown below
Geometry distribution Screenshot
Modal data acquisition:
Hardware parameters:
Choose a force transducer; Channel 1 is connected with an impact hammer for generating
excitation signals. Channel 2 and Channel 3 are connected with an acceleration transducer for receiving response signals.The test uses an ICP force transducer with 100mv/N sensitivity and an acceleration transducer with 100mv/g sensitivity.
Analysis parameters:
2000Hz Sampling frequency, 2048 sampling data, exponential average. operation mode:  Channel 1 is set to trigger with an impact hammer. 
Test points settings:
All test points’ motion direction, current test point;
Windowing settings:
Excitation Channel: force window; response Channel: exponential window
Figures of modal data acquisition interfaces
Excitation signals: X axis (horizontal direction) response signal
Y axis (horizontal tangent) response signal   Z axis (vertical direction) response signal


X axis FRF

Y axis FRF

Z axis FRF
Modal parameter identification
The engineer imports all recorded transfer function by using special modal identification software and gets all orders trial parameter including modal frequency, modal vibration mode, modal damping ratio and etc., from curve fitting identification.

 Figures of vibration mode
During the whole testing, AVANT MI-7008 data acquisition and signal analyzer shows its features of high reliability, high accuracy and easy-to-use. The engineer connects it with up-to-date ICP force transducer and an acceleration transducer, and uses modal data acquisition software to record data, and then import them to the offline software to get results and test reports, which can be finished in a short time.