Master of Science in Mechanical Engineering (MSME)
Piezoelectric materials have seen a significant usage increase over the past decade. They have been found to be effective as either sensors or actuators in smart structure applications, which allows them to act more as an adaptive system rather than a passive system. Piezoelectric materials are very effective transducers which convert mechanical energy into electrical energy, known as the direct piezoelectric effect or they have the ability to convert electrical energy to mechanical energy, known as the converse piezoelectric effect. The absence of additional mechanical parts, its lightweight and high strength to weight ratio is what make piezoelectric materials so attractive for many applications. Many existing studies have focused on surface bonding or embedding piezoelectric actuators to straight structures but in recent years, piezoelectric actuator performance has been investigated for curved bream applications. The aim of this thesis is twofold; first, the performance of piezoelectric actuators and their capability to reduce strain and counter balance an external load for both a tensile configuration and a bending configuration is investigated. Secondly, the performance of the piezoelectric actuator on a curved beam structure when system parameters are varied will be investigated. An analytical model, FEM and experimental results are obtained and compared for the curved beam. It was shown that when the piezoelectric actuator is placed at the joint location, it is more effective for the tensile configuration rather than the bending configuration. For the bending actuation, it was experimentally shown that the most effective actuator placement on the composite beam was region 1 in order to recover the most strain due to the external load. Preload actuation deemed more effective compared to post load actuation for both the single lap joint and curved beam. It was also shown that the deflection of the curved beam increased as the length of the piezoelectric actuator was increased. An actuator with a length of 15 mm positioned near the beam’s free end, proved to be the best choice for the beam configuration selected. The analytical model provided the total deflection, including the x and y component, which can be calculated by knowing Fp, â1, â2 and â3 respectively. The location of the actuator, as well as its size can be changed with â1 and â2. By altering the system parameters, parametric studies can be conducted to find the optimal location and size of the actuator that will provide the greatest deflection and find the minimal voltage required by the actuator. Therefore by performing the parametric studies, optimization can be obtained by using the piezoelectric actuator to counterbalance the external force and return the free end to its initial position. If multiple actuators are available, this study will not only be able to return the free end to its initial position but multiple actuators can be placed along the beam in order to bring multiple points back to its initial position.
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Johnson, Calicia, "Effect of piezoelectric actuation on curved beams and single lap joints" (2011). LSU Master's Theses. 960.