Dynamic characterization of automotive exhaust isolators

Abstract

Different approaches to measure the dynamic stiffness and damping properties of several silicone and EPDM rubber automotive exhaust isolators were investigated in this research. Shaker excitation and electrohydraulic actuator methods were used to extract the dynamic properties, both under swept sine and random excitations. The shaker testing in the frequency domain using a frequency response function from linear theory produced good results, and the experimental set-up for this case is relatively inexpensive. The electrohydraulic excitation method, however, is more suitable for testing under low frequencies and large displacements. It is ideal to study the variations in stiffness and damping with frequency, displacement, temperature and preload. This study has confirmed that the stiffness and loss factor of the samples are highly dependent on preload and input force levels. It has also been shown that the stiffness and loss factor values are relatively insensitive to the manner in which the exhaust isolator is excited, whether it be with random, burst chirp or swept sine excitation. Of particular interest is the fact that stiffness and loss factor results are very similar between the electrohydraulic and shaker excitation, except at low frequencies.