Experimental and Numerical Activities on Damage Detection Using Magnetostrictive Actuators and Statistical Analysis

Abstract

The purpose of this work is to present the formulation of a new experimental procedure to employ in problems of damage analysis of structural elements. The proposed method is based on the acquisition and comparison of Frequency Response Functions (FRFs) of the monitored structure before and after damage occurred. Structural damages modify the dynamic behaviour of the structure and consequently its FRFs making possible calculation of a representative “Damage Index.” The experimental activity was carried on using two prototypes of magnetostrictive actuators developed within the European Commission funded project named MADAVIC (Magnetostrictive Actuators for Damage Analysis and VIbration Control). Three kinds of damages have been simulated on two beam-like structures: little mass disturbances, partial cuts of the beam sections and constraint yielding. Two expressions of damage indices were calculated and analysed. The main target of the work was to assess the reliability of the damage identification by using a “repetitiveness index.” This index is related to the lowest measurable damage extension and the statistical t-test, in order to verify if each calculated index was really representative of a structural damage, rather than of unforeseen differences between the FRFs. A simple Finite Element Model (F.E.M.) of the second test-article has also been developed for numerically simulating the experimental tests and comparing the corresponding results.