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Three Dimensional Modeling of Energy Harvester System using Magnetic Shape Memory Alloys

Mehrabi, Mohammad Mahdi | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51728 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Sayyadi, Hassan; Hoviat Talab, Maryam
  7. Abstract:
  8. Magnetic shape memory alloys (MSMAs) are a new kind of smart materials which are great alternatives for energy harvesting systems due to some unmatched characteristics such as reversible large strain, high cycle fatigue and fast time response. In this work, an energy harvesting system using MSMA is studied. For this goal, a 3-D thermodynamic-based MSMA model is applied for predicting magnetomechanical behavior of the MSMA sample which is used in the energy harvester system. Since demagnetization effect, which has a great influence on the model’s outputs, has been neglected in the selected MSMA model, a new approach is presented for inserting demagnetization coefficients, regarding to the considerations of the problem and the loading type, and it is shown that this approach has an appropriate performance for the specific magneto-mechanical loading of this problem, and it can be used for further simulations of the project. Energy harvesting is performed via embedding the MSMA specimen in the air gap of a magnetic core and exerting mechanical loading with the presence of bias magnetic field. In order to reduce the need of the bias magnetic field and enhance the efficiency of the system, an elastic layer is placed in the air gap between the specimen and the core, thus it can cooperate with the bias magnetic field to fulfill the reversing mechanism of the alloy specimen, and it leads to an increase in the harvesting system efficiency. The results depict the most harvested power of the system is obtained in 0.4 Tesla bias magnetic field, in which the specimen reaches magnetic saturation. Then, the system response in different strain rate of the input is investigated, and it is shown that while the output RMS voltage is increased with the increase of the loading strain rate, the RMS power measures show a different behavior, as they rise till 20 1/s strain rate , and then decrease. In addition, the system output is studied in 2-D applied mechanical loading, and it is illustrated that, when the phase difference between the two mechanical loads in two directions is 0, the most voltage and power are harvested. Further more, inserting dynamic effect, which is due to the increase of the mechanical loading frequency, demonstrate that up to 100 Hz frequency no sensible change is seen in the model output, but in higher frequencies, the dynamic effect of the mechanical loading is evident, as in 400 Hz frequency, RMS voltage is 12% less than its measure obtained from the modeling without considering the dynamic effect
  9. Keywords:
  10. Magnetic Shape Memory Alloys (MSMA) ; Energy Harvesting ; Bias Magnetic Field ; Magnetic Circuit ; Martensite Variants Returning Mechanism

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