This paper describes research into the performance of a hydraulic automotive damper at frequencies up to 500 Hz. A review of published literature found little information on damper behaviour above 30 Hz. Design of vehicles for low levels of noise, vibration, and harshness (NVH) requires attention to these higher frequencies. The high-frequency force-velocity behaviour of a monotube damper was measured. Excitations included two-frequency inputs and a random input. In addition to traditional data analysis methods, techniques based on the wavelet transform were used. The results indicate that friction and hydraulic valve flow at near-zero velocity are important mechanisms in determining high-frequency force generation. Another significant mechanism is the transition between notch (leakage) flow and disc valve flow.
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