In this paper, we propose a novel gradient index metamaterial lens to focus elastic wave energy in polymer pipes. We investigate multi-mode focusing of guided ultrasonic waves in a poly-vinyl chloride (PVC) pipe by designing and integrating an embedded gradient index (GRIN) lens within the pipe wall. The metamaterial lens is composed of equally spaced cylindrical brass inserts embedded into the pipe wall. All the inserts are of same height which is equal to the half-thickness of the pipe. Insert diameters are varied in circumferential direction to realize hyperbolic secant distribution of refractive index around the circumference of pipe. We explore focusing of three pipe wave modes commonly used for guided wave inspection of pipelines namely, L(0,2), L(0,1) and T(0,1), using a single lens design. We further verify the lens performance through numerical simulations estimating the amplification of wave energy in focal regions of the GRIN lens for these three modes. We also estimate attenuation of guided waves propagating in PVC pipe through experimental measurements.

Pipelines for oil distribution may affect the environment when natural disasters such as landslides and earthquakes damage the infrastructures. Besides natural causes, illegal extraction of oil from the pipelines can produce significant environmental damage and sometimes loss of lives from explosions. During the spill, the fuel flow of the main stream theoretically reduces, but this variation is within the normal flow fluctuation and so it is not possible to detect this illegal activity using fuel flow measurements. Transducers based on Fiber Bragg Grating (FBG) sensors are very attractive for pipeline monitoring. In two previous works we proposed a new transducer for increasing the sensitivity of FBG sensors to detect illegal activities on the pipelines (drilling). In fact FBG sensors attached directly on the surface of the pipe are not capable to detect strain variations induced by a drill. This paper reports an update on the experimental results obtained on a real size pipeline and a theoretical study aimed to explain why a surface attached sensor does not work.

Oil and gas infrastructures may be exposed to landslides, earthquakes, corrosion and fatigue, and to damage from thefts or vandalism, leading to leakage and failure with serious economic and ecologic consequences. For this reason, an increasing interest in applied research on monitoring and protecting pipelines (for fuel, oil and natural gas transportation) arises. Aimed at the mitigation of catastrophic effects of human and natural damage, the present paper proposes a smart real-time Structural Health Monitoring (SHM) system capable to control structural integrity continuously, focusing on the issue of spillage for thefts of fuels which are not detectable, in real-time, by the existing monitoring systems. The system consists of a smart-pipeline containing a health monitoring integrated measurement chain, i.e. an enhanced Fiber Bragg Gratings-based fiber optics neural network on the pipes, for displacement and acceleration monitoring (gathering many other different measurements such as: ground motion, permanent ground displacement, pipeline temperature, pipeline deformation, leakage, etc.). Specifically, the ability to measure these characteristics at hundreds of points along a single fiber and the great accuracy of each point of measure, are particularly interesting for the monitoring of structures such as pipelines in order to detect hazardous and unauthorized intrusion and damage.

Structural health monitoring (SHM) and condition based maintenance (CBM) are keys to shifting the paradigm from schedule based maintenance to cost effective operation and maintenance of reliable systems. Continuous comb transducer strips have the potential to generate ultrasonic guided waves for structural health monitoring of plate and shell structures (pipelines, pressure vessels, storage tanks, airframes). A theoretically driven approach, based on the application of wave mechanics principles, is used to research and design a network of strip sensor. Fibrous piezoelectric composites are considered for the comb elements, widely expanding the design space of these elements to include fiber orientation and volume fraction in addition to size, configuration, and location of the electrodes. Piezoelectric and mechanical properties for these innovative sensor designs are estimated through micromechanical modeling. Specifically, micromechanics enables us to consider different fiber orientations and constituent properties and provides the composite properties for input to finite element analysis of wave propagation. Finite element simulations of ultrasonic guided wave generation and propagation using Abaqus Explicit-Standard Co-Simulation are conducted in order to design the sensory system.