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Influence of Loading on the Near Field Based Passive Metamaterial in Structural Health Monitoring

V. G. M. ANNAMDAS, C. K. SOH

Abstract


The last decade had seen the rise in the smart structural health monitoring (smart SHM) techniques. A smart SHM technique is the process of adopting a smart damage detection and characterization strategy for monitoring engineering structures. These are executed by latest smart materials which are usually surface bonded or embedded inside structures. Recently, researchers of smart materials (fiber optics or piezo electrics, etc.) successfully adopted cabled and wireless smart SHM strategies. In all these strategies, the smart materials behave as an actuator or a sensor or as both in the presence of relevant input-output devices. However the advent of metamaterials has raised curiosity among the academia and military for its passive behavior. These materials are neither actuators nor sensors in true sense unlike smart materials but they are facilitators and specially designed patches or engraved on the surface of host structures to be monitored. These when subjected to input electromagnetic radiations alter the properties of the radiations but do not interfere or disturb the structure unlike smart materials. In the last few years, these were adopted as biosensors in life sciences such as chemistry, biology and medicine. They are being used as sensors or as enhancers to sensors for improving sensitivity of existing sensors in life sciences. These materials attracted military, air force and navy as they can be used as ‘shield devices’ and make invisibility of key vehicles/ installations a reality in another 10 years. Metamaterials are useful especially in today’s society which is suffering from terrorism and extremism where illusions can be created which can shield important infrastructures. However this paper presents the adaptation of these metamaterials for monitoring load on aluminum beams, which is the first of its kind in the world. Two types of experiments were performed for fixed-fixed and simply supported aluminum beams. In the first type, a circular metamaterial unit cell with input cable was attached on a probe using a cello tape, which was placed on the center of the simply supported beam. The next type comprised of a metamaterial attached to a form placed at a distance below the beam with fixed ends. In this second type, the metamaterial was not in contact with the probe or the structure under investigation. Both these strategies resulted in successful health monitoring signals that are transmitted during monitoring load in the range of 50 to 80N. Thus this new reusable metamaterial based SHM technique can be used in various load monitoring applications of civil, mechanical and aerospace engineering.

doi: 10.12783/SHM2015/81


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