Shape memory alloy wire actuators can be used in combination with compliant structures to attain desired force and displacement capabilities. The wires can be placed inside a matrix, as in composite, or outside the material connected at different points on the structure. In the latter case, the offset of the wire and the location of the points decides the overall deformation of the structure. In this article we study the effects of offset distance, and the number of points, called attachments, where the shape memory alloy wire is connected to a host beam. First the characteristic curve of the shape memory alloy wire actuator is derived from a constrained recovery model. Then the response of a beam model, undergoing large deflection due to follower forces, is superposed with the characteristic curve to obtain the maximum beam deformation. It is found that there exists a particular offset, called optimum offset, for which the deformation of the host is maximum. Moreover, the ratio of stress and change in strain in the shape memory alloy corresponding to the optimum offset, attains a particular value, irrespective of the flexural rigidities of the beam. Furthermore, it has been observed that for a set of beams that have flexural rigidity less than a particular value, the deformation increases with number of attachments. However, for the beams that have flexural rigidity more than that particular value, the deformation remains almost unaltered with number of attachments. These numerical results are also supported qualitatively by the experimental observations.
Finite element analysis is conducted on a barium calcium zirconate titanate (BCZT) material to investigate its energy harvesting performance at different porosities. Porosities are gradually increased to 25% in steps of 5. BCZT piezoceramics attached to a host cantilever beam in unimorph configuration and subjected to base vibration are considered for the present study. Both and modes are considered. Power is harvested using a load resistance optimized with the structure's natural frequency of vibration. Up to a certain porosity level, an increase in voltage and power is observed in the system. An increment in voltage by ≈95% in mode and ≈119% in mode is observed at 10% porosity. Power increased by 50% in mode and by 53% in mode at 5% porosity compared with the nonporous material.
Finite element studies have been conducted on the ( )( ) Ba Ca Ti Zr O 0.85 0.15 0.9 0.1 3 (BCTZ) material fabricated at different sintering temperatures. BCTZ materials calcined at 1300 C for two hours and sintered at four different temperatures viz. 1520 C, 1530 C, 1540 C and 1550 C for two hours were considered. The structure was subjected to base vibration and its dynamic effect was studied. Sensing, energy harvesting and actuation capabilities of the system was studied. It was observed that BCTZ material sintered at 1540 C o demonstrated maximum values for sensing voltage, actuation displacement and harvested energy. Actuator displacement was measured in terms of tip displacement of the cantilever beam. Compared to BCTZ material sintered at 1520 C o for two hours, sensing voltage increased by about 81% in d 31 mode and 30% in d 33 mode. Similarly, harvested power increased by about 238% in d 31 mode and 60% in d 33 mode. Actuation displacement in d 31 mode was found to be more than that in d 33 mode. It was observed that fabrication method has a profound effect on the material which can enhance the energy harvesting and sensing capabilities.
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