Purdue University Purdue e-pubs Publications of the Ray W. Herrick Laboratories School of Mechanical Engineering 9-2011 Influence of the Cavity Mode on Tire Surface Vibration J Stuart Bolton Purdue University, bolton@purdue.edu Wonhong Choi Follow this and additional works at: http://docs.lib.purdue.edu/herrick Bolton, J Stuart and Choi, Wonhong, "Influence of the Cavity Mode on Tire Surface Vibration" (2011). Publications of the Ray W. Herrick Laboratories. Paper 32. http://docs.lib.purdue.edu/herrick/32 This document has been made available through Purdue e-pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional information.
Influence of the cavity mode on tire i surface f vibration 2011.09.04 Won Hong Choi J. Stuart Bolton Herrick Laboratories Purdue University 1
Introduction of Tire Noise Tire Noise Structure Air borne borne noise Airborne noise Waves Mechanical Aerodynamic Driving Force vibration phenomena Effective sound radiation when wave propagation speed is greater than sound speed (331 m/s) /) Tire cavity noise dominant source of cabin noise in 200 Hz to 300 Hz range The effect of interior acoustic mode on tire surface vibration (hence, on sound radiation) will be discussed Structur al Waves 2
Finite Element Model Generating Geometry 205/70R14 slick tire Basic sampled nodal set : 1 21 (adopted from the work of Kim) Downscale to create nodes in inner space Duplicate in the circumferential direction 3
Mesh of Undeformed Tire 205/70R14 slick tire Treadband Sidewall Air cavity Rim Front View Element size : 2 [cm] < λ min / 6 4 Isometric View
Boundary conditions and Load Fixed boundary condition on the rim Inflated tire with an increase of air density and corresponding tension on the surface 1 N normal, nodal force at a driving point Harmonic analysis : 0 to 1000 Hz with an increment of 2 Hz 5
Comparison of point input reactance of undeformed tire Im / u Reactance : Driving Po int f Stiffness like behavior : jk / Verification of stationary tire 6
Map of vibration response vs. frequency and angle for uninflated tire Response symmetric about 0 deg. Thin, horizontal feature at 200, 400, 600, 800 Hz Response on sidewall F 7
Map of vibration response vs. frequency and angle for inflated tire Increase on cut on frequency Difficult in differentiating features on response 8
Wave number frequency plot for uninflated tire First acoustic mode c f 200Hz d d m c 331m/s, speed of sound d m 0.54 m, mean diameter 9
Wave number frequency plot for inflated tire Increase on both cut on frequency and phase speed Position of acoustical mode unchanged 10
Comparison of results with and without air cavity Acoustical Modes 11
Effect of Spatial Distribution of Input Force Point force Force over a large area 12
Map of radial velocity vs.. frequency and angle for a point force and force over a large area 13
Wave number frequency plots for a point force and force over a large area 14 Acoustical features become clearer
Wave number filtering 1 Wave number frequency response at the first acoustic mode, 206 Hz was selected Force over Large area 15
Wave number filtering 2 Structural feature Acoustical feature Highlight the surface motion due to the first acoustic mode Hann window applied to eliminate higher wave number component at 206 [Hz] 16
Map of radial surface velocity Dipole like vibration pattern 17
Dipole model for tire in free space r 1 P (r, θ) Dipole model for the tire in free space r 2 P( r, ) j 0cQk 4 r 1 j 0cQk 4 r 2 18
Linear Quadrupole Model r 1 P (r, θ) r 2 Linear quadrupole model on the reflecting surface r 3 r 4 Ground P( r, ) j 0cQk 4 r 1 j 0cQk 4 r 2 j 0cQk 4 r 3 j 0cQk 4 r 4 19
Experimental Setup Six ICP microphones 235/70R15 tire 20
Data analysis procedure Acquire data Edit individual drops Fourier transform High pass filter Plotsoundpressure level at the first acoustic mode 21
Experimental Result 1 Result for all five cases with the theoretical prediction 22
Experimental Result 2 Result averaged in five cases with the theoretical prediction Good agreement except at the location the closest to the ground 23
Conclusion Structural and acoustical waves of the tire could be identified based on their phase speed Evidence of the interaction between the structural and acousticalresponse was found The dipole like sound radiation pattern of the acoustical mode was confirmed dby wave number fl filtering and acoustical measurement 24