Influences of mechanical contact on damage evaluation with electromechanical impedance technique

Abstract

The mechanical contact during material mechanical damage evaluation with electromechanical impedance technique was investigated, and the influencing factors, such as the times of in situ contact, contact stress, and area, were studied. The resonance frequency shift Df of electrical impedance signature was regarded as the damage identification index. Results show that the influence of mechanical contact on damage evaluation could not be neglected. With increasing times of in situ contact, the characteristic resonant peak shifted leftward gradually due to the resulted superficial indentations, and the Df value was in the order of 10 22 -10 21 kHz for each mechanical clamping. The evolution direction of the resonance peak with contact stress was reversed, and the Df value was about 10 21 -10 0 kHz. The order was equal or even more serious against that of the early-stage mechanical damage. The relationship between the Df value and the contact area, however, was elusive because of the combined effects of indentation damage and the compressive stress. Simulation experiments were conducted accordingly, and the abnormality was discussed. The quantitative results were compared between the steel and the Al alloy, and the variation with material property was demonstrated. Effective precautions to avoid the influence of mechanical contact were proposed.

Optimization of lamb wave parameters in mechanical damage evaluation of Z2CN18.12N welding joint

“…Accordingly, the propagation behavior of the Lamb wave would be influenced. In the previous work, the influence of mechanical contact on the mechanical impedance of the host structure has been confirmed during the mechanical damage evaluation with EMI technique [4] . The intrinsic reasons for these two situations are similar to each other.…”

“…It is significant to study the damage behavior and develop the damage evaluation and monitoring technology to prevent unexpected disasters. Some research work have been conducted and several methods have been developed, such as electro-mechanical impedance (EMI) [3,4] , Lamb wave [5] , eddy current [6] , and metal magnetic memory [7] . Each has some particular applications, and the characteristics might vary from each other.…”

Influence of Parameter Variation on Electromechanical Admittance Spectrum of a Multiple Degree of Freedom System

“…In this study, the parameters of Component 1 are unchanged, while the parameters of Component 2 are allowed to vary arbitrarily. This model represents a wide range of applications in EMI technique, such as variation of steel member's boundary conditions [8] and an embedded aluminum rod to monitor concrete strength gain [9]. The mechanical impedance of Component 1 and Component 2 can be derived as…”