Microstructures and magnetic phase transformations in shape memory alloy polyurethane polymer composites for acoustic applications

Abstract

This thesis deals with the research work carried out on Smart Materials, newlineone of the multifunctional materials used as sensors and actuators. newlineFerromagnetic Shape Memory Alloy (FSMA) is one of the classes of Smart newlineMaterials in which the characteristics, large power stroke output and frequency newlineresponse can be enhanced by applying magnetic field which leads to the newlineMagnetic Field-Induced Strain (MFIS). These properties possessed by the newlineFSMA demanded that these alloys can be used as actuators and sensors. This newlinethesis primarily consists of seven chapters which discuss the salient features newlineand the new technological developments of the FSMA.The basic properties of newlinethe Ni-Mn-Ga alloys have been analysed using the traditional characterization newlinetechniques. The effect of Mn substitution on both the martensite and the newlinemagnetic transition of the stoichiometeric FSMA Ni-Mn-Ga alloys has been newlinestudied. The studies confirm that the Mn substitution induces the crystal newlinestructure from highly ordered austenite cubic structure to martensite newlineorthorhombic, the martensite transformation temperature increases and the newlineCurie transition temperature decreases with the increase of Mn content in place newlineof Ga. newlineA custom-made experiment has been designed to determine the newlinemagneto-thermo-mechanical properties of Ni-Mn-Ga/PU polymer composites. newlineThe sample Ni-Mn-Ga/PU, used was fixed between a commercial piezo stack newlineactuator and two PZT stress sensors. The longitudinal stress waves passed newlinethrough the test samples are received by the PZT sensor. The test samples used newlinein the investigations are pure PU, Ni-Mn-Ga/PU, Ni-Mn-Ga single crystals and newlineTerfenol-D. The piezo actuation generates the tensile and compressive waves newlinein the samples. newline