The dynamic stiffness properties of automotive hydraulic bushings exhibit significant amplitude sensitivity which cannot be captured by linear time-invariant models. Quasi-linear and nonlinear models are therefore proposed with focus on the amplitude sensitivity in magnitude and loss angle spectra (up to 50 Hz). Since the model parameters of a production bushing are unknown, dynamic stiffness tests and laboratory experiments are utilized to extract model parameters. Nonlinear compliance and resistance elements are incorporated, including their interactions in order to improve amplitude sensitive predictions. New solution approximations for the new system equations (containing both nonlinear compliance and resistance elements) refine the multi-term harmonic balance term method. Quasi-linear models yield excellent accuracy but lack the ability to predict trends in amplitude sensitivity since they rely on available dynamic stiffness measurements. Nonlinear models containing both nonlinear resistance and compliance elements yield superior predictions to those of prior models (with a single resistance or compliance nonlinearity), while also providing more physical insight. Suggestion for further work is briefly mentioned.

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.

This article addresses the frequency dependent properties of elastomeric vibration isolators in the context of lumped parameter models with fractional damping elements. A mass is placed between two fractional calculus Kelvin-Voigt elements to develop a minimal order system for the example case of a conventional elastomeric bushing typical of automotive suspension systems. Model parameters are acquired from measured dynamic stiffness spectra and a finite element model. The minimal order system model accurately predicts dynamic stiffness in both broadband resonant behavior as well as the lower-frequency regime that is controlled by damping. For transient response analysis, an inverse Laplace transform of the dynamic stiffness spectrum is taken via the Residue Theorem. Since the fractional calculus based solution is given in terms of problematic integrals, a new time-frequency domain estimation technique is proposed which approximates time-domain responses for a class of transient excitation functions. The approximation error is quantified and found to be reasonably small, and

No abstract

No abstract