Application analysis of restoring force surface method, detection of non-symmetrical pretension of cylindrical test-specimens

In classical linear dynamics, the modal analysis or transfer function measurement gives a very good bases to understand dynamics of structures, however, in other cases nonlinear testing methods - like Restoring Force Surface (RFS) method - can be used to detect nonlinear characteristics. RFS works with a pushplate-structure-pushplate measurement setup, where inappropriate preparation of the setup, e.g. uneven pretension, may cause highly erroneous results. A detailed analysis is described in this paper for RFS measurement of cylindrical samples, where evaluation was made in the first compression resonance. Beside presenting the measurement principles, the non-uniform pretension as well as other influencing effects are detailed, and an optimized way of execution is proposed for this measurement method.