Concepção, construção e analises preliminares das respostas em frequência de um gerador eletrodinâmico variável para testes modais em estruturas de Liga de Memória de Forma (LMF)

Abstract

Shape memory alloys (LMF) are increasingly being applied in various fields of study, research and industry. Higher education institutions and academic centers around the world have invested considerably in the development of this technol ogy and its applicability in the following industrial sectors: aerospace, robotics, automotive and biomedical. However, it is not enough to build several structured chemical models of these alloys, such as the "nitinol" that would be the Ni-Ti alloy (nickel 50% - titanium 50%), without testing them under cyclic loads and temper ature variation. Therefore, the electrodynamic vibrational tests are equipments that promote the tests of cyclic loads in the specimens in order to obtain results of structural fatigue, functional fatigue and analysis of the loss of capacity that the material has to undergo a reversible phase transformation. . The latter due to the gradual change due to the sum of slips and displacements at the molecular level. In this work, we describe the design, construction and preliminary analysis of the frequency responses of a cyclically varying electrodynamic equipment for appli cation of variable loading to specimens in LMF's. This device was constructed from a ferrite magnet under a fixed base. The coil connected to the central axis, in this case the actuator, by rotating the current direction promotes a magnetiza tion, making it a magnet. The fixation was made from support bases connected to three guides with compression springs attached to the actuator to facilitate the dynamics of the mechanism in alternating working directions. And at the end of the actuator was positioned an accelerometer. In the preliminary analysis, power was supplied to the system with a scan between 0Hz to 100Hz excitation fre quency. During real time data acquisition, FRF (frequency response function) was used by LabView®, thus generating the acceleration and displacement im ages in the response graphs.