Experimental Study of Load-Deflection and Creep Characteristics of Compressed Rubber Components for Vibration Control Devices

Abstract

Elastomeric (rubber-like) materials are extensively used in various machine design applications, especially for flexible elements of vibration/shock/noise control devices and of power transmission couplings. In order to have high performance characteristics, such elements should accommodate large static and dynamic loads and/or large deflections in a limited size. In many applications high damping, low creep and substantial nonlinearity of the load-deflection characteristic are required. Since these specifications are contradictory, they are frequently impossible to satisfy just by selecting special rubber blends. The paper describes some results of an experimental study of geometric shape influence on the above specifications. It is demonstrated that for unbonded rubber flexible elements of a cylindrical shape loaded in a radial direction, a desirable nonlinear load-deflection characteristic can be naturally obtained (e.g., so-called “constant natural frequency” characteristic for vibration isolators), and creep rate can be significantly reduced as compared with conventional shapes of bonded rubber elements loaded in compression. This can lead to increased permissible deformations and/or loads on a flexible element, and/or to possibility of using rubber blends having higher damping (which is usually associated with higher creep rates). During the course of the research, an accelerated creep test technique has been developed which allows to use state-of-the-art servohydraulic testing machines for creep evaluation. It was also demonstrated that two definitions of the relative creep rate being used in the literature are not equivalent. More consistent results are obtained using the initial (free) height of the specimen (vs the deformation after 1 min of loading) as a reference dimension.