Overview
Automotive brake systems are susceptible to frictionally induced dynamic instabilities which can result in brake squeal whereby the brake generates an audible monotone frequency of high amplitude. Dynamic instability can be related to the coefficient of friction between the brake pad and brake disc with coupling between the pad and disc resulting in both in-plane and out-of-plane vibration. Out-of-plane vibration of the brake disc is generally accepted to cause brake squeal, with one ofthe disc diametral modes of vibration being excited to generate a squeal frequency which is slightly lower than that ofthe excited mode; a typical example of which is shown in Figure 1.
Many different techniques are involved in the analysis of brake squeal including modal analysis, dynamometer and vehicle testing and numerical modelling. During this assignment you will explore the use of modal analysis and dynamic modelling in the prediction of brake squeal.
Task 1: Experimental Modal Analysis
Shared with you excel sheets for this You will be provided with an automotive brake disc for which you are required to undertake experimental modal analysis to identify its natural frequencies and modal damping for the modes in the range of 0—20 kHz. You will work in groups to undertake the measurements, appendix. but the results and analysis must be completed individually.
Task 2: Finite Element Modellin
You will be provided with a CAE model of the brake disc which has the material properties shown in Table 1. Using finite element analysis (FEA) predict the free-free natural frequencies in the range of 1-20,000 Hz and compare to the measured values that have been provided to you. Investigate and explain any differences in the correlation between the predicted and measured values.
Task 3: Simulink Modelling
Develop a 4-degree offreedom Simulink model of the system shown in Figure 2 to predict both pad and disc vibration. The model represents a single pad acting on a brake disc with frictional sliding between the two bodies. A normal load, N, is generated by the piston force acting on the brake pad. The pad and disc stiffness and damping coefficients are obtained from modal analysis details can be found in the Appendix for reference only.
Analyse the resultant vibration and comment on the results. Data for the disc shown in Table 2 based upon your particular configuration will be available on Canvas, whilst the material properties of the pad can be found in Table 3.
