چكيده به لاتين
Shape memory alloys (SMA) exhibit shape memory effect (SME), allowing the alloy which is upon a cyclic thermal loading to return to its original shape after heating beyond the transformation temperature. Piezoelectric materials (PM) also have the ability to convert mechanical strain into electrical voltage or current. In this work, a thermal energy harvesting structure is analyzed numerically. The structure is a composite cantilever beam, comprising of two or three layers, i.e., SMA, PM and shape memory polymer (SMP). The beam is subjected to different fluctuating temperature ranges, and then we obtain results about energy harvesting performance such as phase transformation strain, output voltage and stress. In this regard, the effect of pre-strain and two types of SMAs, i.e., one-way and two-way SMAs are compared with each other in a particular thermal loading. Moreover, the effect of SMA thickness layer on output voltage has been investigated. Regarding the results, we conclude that for larger pre-strains, the higher the maximum temperature is applied, the greater piezoelectric voltage and higher phase transformation strains are derived. But for a small pre-strain (0.2%), no phase transformation and no output voltage is observed. Furthermore, it is concluded that in a thermal loading by using two-way SMAs, electrical potential can be derived without any pre-strain, and in this situation, increasing the thickness of SMA can rise output voltage remarkably. Furthermore, in a situation in which polyvinylidene fluoride (PVDF) is used, output voltage is 4 times higher than using PZT as piezoelectric. In addition, when shape memory polymer is coupled with piezoelectric, using PVDF can induce voltage about 33 V which is 11 times higher than using PZT in such configuration. Finally, a configuration in which shape memory effect of SMA and SMP and piezoelectric effect are combined with each other is studied. Results from this configuration show that output voltage is higher than another.
