Temperature effects in EMI-based SHM: theoretical and experimental approaches

• Ano de defesa: 2025
• Autor(a) principal: Dias, Lorena Lopes [UNESP]
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Structural health monitoring; Electromechanical impedance; Temperature; Analytical model; Experimental tests; Monitoramento da integridade estrutural; Impedancia eletromecânica; Temperatura; Modelo analítico; Ensaios experimentais
• Link de acesso: https://hdl.handle.net/11449/313087; https://lattes.cnpq.br/0026374599165487; https://orcid.org/0000-0002-1870-6103

Structural Health Monitoring (SHM) is dedicated to the continuous assessment of structural conditions, aiming to detect damage at early stages and, consequently, ensure the functionality and safety of different structures. Among the various methodologies employed in SHM, the Electromechanical Impedance (EMI) technique stands out for its sensitivity to incipiente damage. Important findings have been achieved from experimental data, establishing this approach as the predominant one in the literature. However, theoretical analyses have also driven substantial advancements, demonstrating great potential. Despite this, the practical application of the EMI technique faces challenges due to its sensitivity to external conditions, such as temperature. Thermal variations induce changes in EMI signals, which can be mistakenly interpreted as damage, compromising the accuracy of structural diagnostics. To address this challenge, temperature compensation methods have been developed to minimize its influence on EMI signatures. In this context, the present thesis investigates the temperature effects on the EMI technique through two complementary approaches: theoretical and experimental. An analytical EMI model is developed to examine an Euler-Bernoulli beam with symmetrically coupled piezoelectric transducers. Three different dynamics are evaluated, i.e., longitudinal, flexural, and a combination of both. The study investigates both the influence of temperature variations and the presence of symmetric and asymmetric damages. The results exhibit strong similarity with experimental, particularly in peaks position. In addition, a temperature compensation technique is proposed through the incorporation of a new step involving the selection of the frequency range for computing damage detection indices, aiming to improve the detection accuracy. The methodology is demonstrated in an aluminum beam subjected to three different structural conditions: baseline (undamaged) and two types of damage. The obtained results confirm the effectiveness of the proposed approach in reducing false alarms during damage detection via EMI.