| With the rapid development of automobile industry, the requirement of auto manufacturesand customers to automotives performance is increasing, so reducing the brake vibration andnoise has been an important issue to be solved. This paper solves brake noise numerically by themethods of complex eigenvalue, and do brake NVH test. The details as follows:(1) Large number of literatures on brake were read, the research background wassummarized, including development and work principle of vehicle brake, characteristics of brakenoise, overview of brake noise experimental research and brake noise mechanism, numericalanalysis method of brake noise, control strategy of brake noise. FE theory was introduced briefly,including elasticity assumptions, basic equation, analysis steps, analysis software. Then theory ofcomplex eigenvalue was described, and complex eigenvalue modal was derived, and advantagesand disadvantages of the three complex eigenvalue modal methods which are linearnon-prestressed modal analysis, partly nonlinear perturbation modal analysis, fully nonlinearperturbation modal analysis were compared.(2) The mathematical model disc brake multi-degree of freedom nonlinear vibration wasset up, and an A0class car of a joint venture was taken as study object, in ANSYS Workbenchthe finite element analysis model of brakes complex eigenvalues was established finally. AfterBrake noises of the model were resolved, change the friction coefficient between brake pads andbrake disc, the variation range of which was0.1~0.65. The result for recalculation of the modelshowed that there were almost unstable modes in each frequency segment of1kHz~15kHz,especially in the frequency segment of1k~2kHz and12k~13kHz real parts and negativedamping ratio of complex modes were large，modal stability was poor, the occurrence of brakenoise was high. However, we could make the determination that the brake NVH performancewas poor.(3) The brake structure was improved, to optimize brake NVH performance. Mufflershims were riveted on brake pad backplates, and RJ10sectorial chamfers along the brake radialdirection were made on brake pads, then finite element model of complex eigenvalues modalwas analyzed. According to comparing the previous results, the unstable modes quantity ofimproved brake was greatly reduced, and them were main in frequency range of3kHz~5kHzand13k~15kHz, moreover, real parts and negative damping ratio of complex modes weresignificantly reduced and modal stability was improved, ultimately the occurrence of brakenoises were lowered. The NVH performance was elevated dramatically.(4) In the LMS Dyno Giant7000NVH inertia brake NVH test bench NVH performance for the initial and updated brake were tested separately. The test results are consistent with theanalysis results basically. The initial brake has almost noises in each frequency segment of1kHz~16kHz, furthermore, the SPL(sound pressure level) of noise is particularly high, themaximum level of which can reach104.2dB(A), besides the occurrence of brake noises wasextremely high, which of greater than70dB(A) noise was54.85%. In particular，in the frequencysegment of12k~14kHz the SPL and occurrence of noise were specially high. Therefore, NVHperformance of initial brake was bad. The noise level of updated brake decreased obviously,because only a little noise was in the vicinity of the frequency of2kHz,4kHz and12kHz. Inaddition the SPL and occurrence of brake noises were significantly lowered. The highest levelwas83.19dB(A), and the noise occurrence more than70dB(A) was1.42%. So according to thetheory calculations and experiment it was proved that the updated brake had more excellentNVH performance.In summary, the study of this topic on brake noise theory and experiment could providereferences for brake design. |
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