CHARACTERIZATION OF THE DYNAMIC PROPERTIES OF VISCOELASTIC ELEMENTS BY THE DIRECT STIFFNESS AND MASTER CURVE METHODOLOGIES .1. DESIGN OF LOAD FRAME AND FIXTURES

摘要

The theoretical foundations and principles governing the design of the test fixtures, including the load frame, for use in conjunction with the direct complex stiffness test method for the characterization of the dynamic properties of viscoelastic elements are presented. A graphical approach for facilitating the design and/or evaluation of the static stiffness and fundamental resonance frequency characteristics of the load frame is developed and its use illustrated. Based on an approximate analytical model of the complex stiffness test system comprising the load frame, force transducer, test sample end plates, connecting rods and a viscoelastic element, expressions are derived for correcting the inherent systematic errors in the measured complex stiffness of the viscoelastic element arising from the stiffness and inertia of these fixtures. It is shown that, for errors of less than 5% between the true complex stiffness of a viscoelastic element and the uncorrected measured stiffness, the stiffness of any of the test fixtures should be greater than the highest stiffness of the viscoelastic element by a factor of about 100, over the test frequency range. (C) 1995 Academic Press Limited [References: 17]