CENTER FOR NON DESTRUCTIVE EVALUATION

CNDE

UBIQUITOUS SENSING

Continuous Distributed Sensing using Fiber Optic Sensors:

The current state of the art for fiber optic sensing is the use of Fiber Bragg Grating and similar discrete sensing elements for localising the measurements. These techniques are now well known and applied in practical applications such as for structural health monitoring and process measurements. However, when faced with large volume of monitoring, the discrete approach becomes very limited in scope and increasing the number of discrete sensors becomes the limiting factor. Hence, continuous sensing will be the preferred solution where the sensing element is non-discrete and information anywhere along the length of the fiber can be obtained. Currently, continuous sensing is feasible using Rayleigh Scattering. This covers large volume, but with low resolution. Hence, it is necessary to explore new paradigms in fiber optic sensing techniques where large volume and higher resolution of measurement becomes feasible. In addition, the current sensors have an upper operational temperature range and increasing this operational temperature ranges will also be desirable.

Continuous Distributed Sensing using Ultrasonic Waveguide based Sensors

Ultrasonic waveguide sensing technologies are discrete in nature. The key advantage of this technique is the improved robustness as well as the temperature range of operations (-100 C to +1500 C). These sensors can measure process parameters such as ambient temperature, rheology of surrounding fluids, level and flow rate of fluids, etc. simultaneously using multiple guided wave modes. Using discrete sensor located along the length of the waveguide, it is feasible to obtain multiple measurements at different locations along the length of the waveguide. The CNDE at IITM is currently considered the leading group in the world in this technology and have an incubated company XYMA Analytics that is carrying this work into the commercial world with applications in high temperature measurements and structural health monitoring. The discrete nature of the measurements is again a limitation in the current technologies. Hence, it is envisaged in this work to explore phonon interaction mechanisms using ultrasonic wave-mixing approach for the isolation of information along the length of the waveguide. The phonon interactions are known to exist for ultrasonic waves, but have been explored to only a lesser extent with applications in the materials characterisation of materials. The CNDE at IITM along with National Metallurgical Laboratory in Jamshedpur has been working in this field over the past 5 years. The use of the phonon interactions for measurements of physical parameters and for health monitoring is a relatively new and unexplored field.

Hybrid Fiber-Optic & Ultrasonic Waveguide Techniques

The use of hybrid approach where the Ultrasonic Waveguides as a transmitter while employing Fiber-Optic sensing as a receiver unit will be explored and developed in this project. This is never been attempted before, but has several applications such as in explosive environment where remote transduction is necessary for safe interrogation of the components.

Structured Materials for Imaging