Simultaneous Identification of Vertical and Horizontal Complex Stiffness of Preloaded Rubber Mounts: Transformation of Frequency Response Functions and Decoupling of Degrees of Freedom

Abstract

Background

Rubber mounts are widely used to isolate vibrating components. Their complex stiffness characteristics, including dynamic stiffness and loss factors, are highly concerning in terms of vibration analysis and optimization. Rubber mounts show non-linear behavior with preload, leading to difficulty to predict their complex stiffness. Dynamic testing is generally necessary.

Objective

An approach to identify the complex stiffness of preloaded rubber mounts in both vertical and horizontal directions simultaneously is developed.

Methods

Tested Frequency Response Functions (FRF) of a mass suspended by rubber mounts are transformed to an FRF matrix of the mass center to decouple the Z Degrees of Freedom (DOF) and RZ DOF from other DOFs, which allows complex stiffness to be identified from the two decoupled DOFs. A software tool to implement automatically the FRF transformation and parameter identification is developed. An EPDM rubber mount is tested using the device and its complex stiffness is identified using the software to validate the proposed approach.

Results

The driving-point FRFs of the mass center calculated from the identified complex stiffness are very close to the corresponding FRFs determined from the test data. The comparison between the Finite-Element Analysis (FEA) results of the surficial FRFs and the test results shows good consistency as well. Therefore, the proposed approach and its supporting algorithm are validated.

Conclusion

the proposed approach allows for swift identification of high-accuracy complex stiffness of preloaded rubber mounts in both vertical and horizontal directions simultaneously.