Vibroindentation tests for the determination of time-dependent mechanical properties

This paper is dedicated to the problem of nondestructive testing for determination of time-dependent mechanical properties of various materials. A new method, which is referred to as an adaptive contact impedance evaluation (ACIE) with respect to time, is considered herein. It is based on mechanical contact impedance evaluation (MCIE) at the local contact area between a piezoactive sensor and a specimen. The MCIA concept is based on the vibrational analysis of the motion response of a material or structure to a controlled excitation in the indentation. The opportunity of using vibroindentation tests to extract time-dependent flow property information was undertaken. These tests can be applied to various specimen geometries including small volume specimens. The fraction of specimens "damaged" in the test is small thereby enabling repeated or subsequent testing. Indentation creep and load-time measurements have been performed by using combined piezoelectric-magnetostrictive transducer. Composite transducers, consisting both piezoelectric and/or magneto strictive materials with sectioned electrodes as well as divided winding coils and exploiting both direct and inverse piezoelectric and magnetostrictive effects were applied. These smart ACIE sensors are standing wave resonance devices and their design is based on changing modes and types of resonance vibrations in order to match contact impedance associated with different engineering materials. Dynamic response obtained from the experimental sensor highly correlates with time-varying mechanical and theological parameters.