Vibration energy harvesting is the transformation of vibration energy to electrical energy. The motivation of
this work is to use vibration energy harvesting to power wireless sensors that could be used in inaccessible or
hostile environments to transmit information for condition health monitoring. Although considerable work has
been done in the area of energy harvesting, there is still a demand for making a robust and small vibration
energy harvesters from random excitations in a real environment that can produce a reliable amount of energy.
Parametrically excited harvesters can have time-varying stiffness. Parametric amplification is used to tune
vibration energy harvesters to maximize energy gains at system superharmonics, often at twice the first natural
frequency. In this paper the parametrically excited harvester with cubic and cubic parametric nonlinearity is
introduced as a novel work. The advantages of having cubic and cubic nonlinearity are explained theoretically
and experimentally.
Ultrasonic guided wave technology is one of the more recent developments in the field of non-destructive evaluation. In contrast to conventional ultrasonic, this technology requires exposing only the areas where the transducers will be placed, hence requiring minimal insulation removal and excavation for buried pipes. This paper discusses how this technology can be used to detect defects in pipes under different conditions. Here the experiments were performed on small diameter pipes (<5 cm diameter); which were bare pipe, buried pipe and bitumen coated pipe. The results were gathered to see the effectiveness of this technology in detecting defects. Experiments were conducted using two dry coupled piezoelectric transducers, where one of them transmitted guided waves along the pipe and the other received them. The transducers produced tangential displacement, thereby generating the fundamental torsional mode T(0,1). In order to assess whether having multiple transducers has any effect on the resultant waveform, the receiving transducer was rotated around the circumference of the pipe.
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