Development of new technologies for the THz domain with applications on structural health monitoring

• Autor(a) principal: Pavia, João Pedro Calado Barradas Branco
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10071/18218
• topic: Frequency selective surfaces; Filters; Stress sensors; Sstructural health monitoring; terahertz; Informática aplicada à saúde; Equipamento de saúde; Processador de sinais; Radiação; Sensor; Sistemas de segurança

Structural health monitoring (SHM) plays a major role in industry and engineering today, as this methodology has completely changed the paradigm of how to assess the health status of structures. Previously, the methodology of reference, Non-Destructive Testing (NDT), consisted on conducting periodic inspections, made by specialized professionals that used external equipment. However, this method was quite expensive and time consuming. SHM systems are considered as an alternative to traditional methods, since these systems allow the continuous acquisition of the structural responses from the disturbances experienced by the structure. Through the measurement data, it will be possible to know the health condition of the structure and the existence of structural damages. Sensors represent a fundamental component of these systems, since they are responsible for the acquisition of data related to the health and integrity of the structures and they should be accessible, light and discrete, so as not to impose cost and weight on the structure and not to interfere with the structural resistance. Although the THz domain is a relatively new field of research in electromagnetic sensors, it is known that the use of frequency selective surfaces (FSSs) allows the creation of compact devices which can be easily integrated into the surface of the structures without harming its functionality and aesthetic appearance. The main goal of this dissertation is to study and numerically simulate stress sensors for the detection of THz radiation for applications in SHM, with high sensitivity and selectivity. Taylloring these characteristics to provide a good detection has been achieved through appropriate selection of materials and careful design of stress tunnable band pass filters for the THz domain. Numerical modelling of both the mechanical and electromagnetics, solving the elasticity equation and Maxwell’s equations, respectively, has been undertaken for two types of assembling of the devices using different thermoplastic polymers such as high-density polyethylene (HDPE) and polytetrafluoroethylene (PTFE). It was observed that two methodologies can be adopted to control the level of force applied to the sensors, namely through, the variation of the electric current and the positioning of the coil on the plunger.