Dynamic Analysis of Hydraulic Bushings with Measured Nonlinear Compliance Parameters

Abstract

Hydraulic bushings with amplitude sensitive and spectrally varying properties are commonly used in automotive suspension. However, scientific investigation of their dynamic properties has been mostly limited to linear system based theory, which cannot capture the significant amplitude dependence exhibited by the devices. This paper extends prior literature by introducing a nonlinear fluid compliance term for reduced-order bushing models. Quasi-linear models developed from step sine tests on an elastomeric test machine can predict amplitude dependence trends, but offer limited insight into the physics of the system. A bench experiment focusing on the compliance parameter isolated from other system properties yields additional understanding and a more precise characterization. Amplitude dependence predictions are improved in numerical simulations of the system while using the experimentally determined nonlinear compliance parameter, expanding the capabilities of reduced-order hydraulic bushing models.

Harmonic amplitude dependent dynamic stiffness of hydraulic bushings: Alternate nonlinear models and experimental validation

“…al. [18] proposed a new experiment to measure the fluid compliance of hydraulic bushing pumping chambers using pressurized air so that only a single fluid is present in the chambers. Finite element models are utilized in other studies [7][8][9]17] to computationally determine the fluid compliance.…”

“…Hydraulic elastomeric devices are often employed in automotive powertrain and suspension systems because of their unique dynamic properties, leading to both vibration isolation and motion control [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. These properties are achieved by an internal fluid system working in tandem with the elastomeric structure of a bushing.…”

“…These properties are achieved by an internal fluid system working in tandem with the elastomeric structure of a bushing. Despite some similarities with hydraulic engine mounts that have been extensively studied [1][2][3][4][5][6][7][8][9], the behavior of hydraulic bushings is quite different and merits its own in-depth studies [10][11][12][13][14][15][16][17][18]. Prior, though limited, investigations of these devices have largely focused on simpler transfer function type formulations based on the linear time-invariant (LTI) system theory [10][11][12][13][14][15][16].…”

“…Chai et al [13][14][15][16] further developed the linear models for frequency and time domain characteristics for a laboratory bushing device and even introduced a nonlinear fluid resistance term [17]. Fredette et al [18] recently developed a new laboratory experiment to measure the nonlinear fluid compliance of hydraulic bushing pumping chambers.…”

“…Under harmonic excitation, hydraulic bushings exhibit significant amplitude dependent behavior [10,11,[14][15][16][17][18], which cannot be described by the linear time-invariant system theory.…”