<title>Removing effects of temperature changes from piezoelectric impedance-based qualitative health monitoring</title>

Abstract

A high frequency NDE technique has been under investigation at the Center for Intelligent Material Systems and Structures (CJMSS). Physical changes in the structure cause changes in the mechanical impedance. Due to the electromechanical coupling in piezoelectric materials, this change in structural mechanical impedance causes a change in the electrical impedance of the piezoelectric sensor. Hence, by monitoring the electrical impedance and comparing this to a baseline impedance measurement, we can determine when structural damage has either occurred or is imminent. However, there are still basic research issues that need thorough investigation before full-scale development and commercialization can take place. Included in these is the effect of temperature on this impedance based NDE technique. Since piezoelectric materials exhibit strong temperature dependency and change in temperature results in marked changes in the structural dynamic response, any variation that is associated with a change in temperature may be confused as damage. In this paper we analyze temperature effects on the electrical impedance of piezoelectric materials and the structures. We have used an empirical approach due to the complexity of the thermo-electrical-mechanical constitutive models for piezoelectric materials. Through the experimental investigations, it was found that a change in temperature modifies both the magnitude and phase of the electrical impedance of the piezoelectric sensors. A computer algorithm was developed which incorporates temperature compensation into our health monitoring applications. This compensation technique minimizes the effect of temperatures on the electrical impedance of piezoelectric sensors bonded on the structure, in the range from 80 to 1 60 degrees Fahrenheit. In this paper, we show how it is applied successfully to a bolted pipe structure.

Electromechanical impedance‐based ice detection of stay cables with temperature compensation

“…The conductance denotes the real part of the admittance. It is used in above equations because the imaginary part of the admittance is insensitive to the structural changes in some previous researches, and it is also proved in this study, which is shown in the following section. Additionally, , , , and σ G denote the corresponding means and standard deviations at the complete frequency range.…”

“…It is also experimentally shown that the mechanical properties of ice and the piezoelectric wafer depend on the temperature. With respect to the electrical characteristics, the piezoelectric coupling coefficients and the dielectric constant significantly vary with the temperature . There are positive correlations between the increases in aforementioned properties and the increases in the temperature.…”

“…Most of the aforementioned relationships between the temperature and the mechanical/electrical properties are known or are experimentally obtained for the involved materials although the analytical modeling of the temperature effects is significantly complicated for the complete system. The simple 1‐D model for the specific structure with simple boundary condition is investigated, and multivariate analysis methods are employed to remove the effects of temperature changes in most cases.…”

A Multi-scale Approach to Statistical and Model-based Structural Health Monitoring with Application to Embedded Sensing for Wind Energy

“…Although many materials exhibit a piezoelectric effect, including ceramics, composites, and polymers, the work in this dissertation is concerned with piezoceramic materials. Much of the theory supporting the use of piezoceramic materials for active sensing has been presented by Park, et al [83][84][85] and Bhalla, et al [86][87][88]. Impedance measurements as a method for structural health monitoring (SHM)…”

Avaliação da influência da temperatura no método de ISHM aplicado em eixos de material compósito de máquinas rotativas

“…Os autores concluíram que, além da faixa de frequência, existem limitaęões quanto a faixa de temperatura, que se for grande pode implicar em uma mă correspondência nas assinaturas. Estas limitaęões podem ser minimizadas utilizando mais de uma assinatura de impedąncia de baseline, obtendo um diagnóstico mais confiăvel Park et al (1998). propuseram uma técnica de compensaęćo para que a métrica de dano (RMSD) fosse estăvel quando a estrutura analisada fosse submetida a variaęões de temperatura, através do realinhamento das assinaturas de impedąncia medidas em diferentes temperaturas com a assinatura baseline.…”