Title page for ETD etd-04162007-093704


Type of Document Master's Thesis
Author Emmons, Shawn Glendon
URN etd-04162007-093704
Title Characterizing a Racing Damper’s Frequency Dependent Behavior with an Emphasis on High Frequency Inputs
Degree Master of Engineering
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Ahmadian, Mehdi Committee Chair
Ferris, John B. Committee Member
Southward, Steve C. Committee Member
Keywords
  • race damper
  • shock absorbers
  • high frequency characterization
Date of Defense 2007-04-05
Availability restricted
Abstract
As a racecar negotiates a track, it is subjected to many inputs at both high and low frequencies. These inputs come from the track surface, the motion of the body, and from aerodynamic disturbances. The damper’s ability to control these inputs leads to improved grip at the tires, which increases overall handling of the vehicle. Since dampers have always been assumed to be primarily velocity dependent, little work has gone into exploring damper’s frequency dependent nature. Therefore, this study evaluates the effect input frequency has on the damper’s output force.

Utilizing experimental testing, with a state of the art damper dynamometer, and computer simulation with a parametric damper model developed for this study, several inputs and key parameters are tested, and the damper’s frequency dependent nature starts to emerge. Constant peak velocity sinusoidal and sinusoidal sweep inputs are used for the experimental testing. The results show that as the input frequency is increased, the damper’s output force lissajou transitions from the characteristic shape of a damper’s lissajou to a shape characteristic of a spring’s lissajou. This change in the lissajou is linked to hysteretic effects, which includes the gas spring effect. Damper parameters that are suspected to contribute to the hysteretic effects are explored with computer simulation and additional experimental testing. The results from this show that fluid preparation, fluid type, initial gas pressure, and friction have a predictable effect on the damper’s output force.

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