Brake Squeal Analysis

Transcription

1 Brake Squeal Analysis João G. P. da Silva Fras-le Érico R. Fulco Fras-le Paulo E. D. Variante Fras-le Vagner do Nascimento - Master Fabiano N. Diesel - ESSS Daniel Boniatti - ESSS

2 Introduction Brake disc develop friction oscillations which are heard as brake squeal Typical brake assembly

3 Introduction There is three main categories of brake noise: Low frequency (100-1kHz) Groan and Moan noise Low frequency (1k 7kHz) Coupling of out of plane modes of rotor with bending modes of pads High frequency (8k 16kHz) Coupling of in plane modes of rotor with bending modes of pads

4 Disc CAD Model FEA Model Gray Cast Iron Young Modulus 110 GPa Poisson s Ratio 0.3 Mass Density 7800 kg/m³

5 Experimental x Numerical Results Disc 1273 Hz 2326 Hz 3115 Hz 1833 Hz 2584 Hz 3655 Hz

6 Friction Pad Friction Material Young Modulus 6 GPa Poisson s Ratio 0.2 Mass Density 1500 kg/m³ Structural Steel Young Modulus 210 GPa Poisson s Ratio 0.3 Mass Density 7700 kg/m³

7 Experimental x Numerical - Pad 4697 Hz 5768 Hz 9439 Hz Hz 2424 Hz 7890 Hz

8 Workbench Setup Geometry Pressure and Rotation Frequency [ K( u)]{ u} { F( u)} [ K] [ ] { } {0} i M 2 i i i

9 Workbench Setup T [ K ] [ M ]{ } {0} [ K T i ] [ K M i ] [ S N ] [ K L ] [ K C ] [ K SP ] Where: [K T ] is the tangent stiffness matrix; [K M ] is the material stiffness matrix; [S N ] is the stress stiffness matrix; [K L ] is the loading stiffness matrix; [K C ] is the contact stiffness matrix, and; [K SP ] is the spin softening matrix. F u K T

10 Boundary Condition X Displacement = 0 Y Displacement = 0 Z Displacement = 0 X Displacement = 0 Y Displacement = 0 Z Displacement = Free

11 Loading Force X = 0 Force Y = 0 Force Z = 100N

12 bonded contact Contact Pad/Disc friction contact esel,s,type,,tid cm,pad_1,elem allsel keyo,cid,16,0 rmodif,cid,33,1 APDL script to create a Component with the targets elements and to define the Squeal Damping setup

13 Static Analysis Setup nropt,unsym cmsel,s,pad_1 cmsel,a,pad_2 cm,e_pad,elem allsel APDL applied at the first load step to use Unsymmetric Newton-Raphson Method and to create Component with the targets elements of the Frictional Contact. cmrota,e_pad,,,1e-5 APDL applied at the second load step to define a rotation of the target elements Analysis with 2 load steps

14 Results Contact Status Contact status at the first load step Contact status at the last load step

15 Modal Analysis Setup Pre-stress from the last time of the Static Analysis T 2 [ K ] [ C] [ M]{ } {0} i i i i i j i Damped Frequency Calculating 200 modes using QRDamped Method Stability

16 Mode Stability Evolution of the real and imaginary part of eigenvalues versus the damping ratio (η1/ η2) and the friction coefficient ( ). Black surface is stable mode and white surface is unstable one. Reference: Sinou, Jean-Jacques and Jézéquel, Louis - Mode coupling instability in friction-induced vibrations and its dependency on system parameters including damping - European Journal of Mechanics - A/Solids, Volume 26, Issue 1, January-February 2007, Pages

17 Results Modes

18 Unstable Modes modo 04 modo 53 modo 42

19 Unstable Modes modo 69 modo 121 modo 106

20 Experimental Analysis Brake assembly of a test on the dynamometer Full scale brake dynamometer used in this study

21 Sound Pressure Level (db[a]) Numerical x Experimental Results Sound Pressure Level vs. Frequency for all Stops Above Threshold (70 db) Forward Reverse Drag Decel Frequency (Hz) Noise summary of the dynamometer test Predicted Unstable Mode Predicted Frequency Squealing Frequency (Experimental) % Error Hz Hz 4.29% Hz Hz 2.25%

22 Summary / Conclusions In this frequency range, the error is around 4%; The lower frequencies occurrences were not predicted by the numerical analysis, but this error can be attributed to the simplified assumptions on the modeling; Further work to include the fastening conditions, spider and caliper in the modeling will be addressed in the future

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