Concepção e desenvolvimento de uma máquina multifuncional para testes eletro-termo-mecânicos de materiais com memória de forma.

Abstract

In this work it was accomplished the conception, assembly and tests of a multifunctional machine for eletro-thermomechanical characterization of shape memory alloys (SMA). The developed machine consists of the union of a hydraulic press with a thermal bath, a current source, and sensors of temperature, displacement and force, a data acquisition system, besides the mechanical adaptations for application of mechanical loading in the samples. Two operation manners were tested: A - thermal cycling with the sample submitted to constant uniaxial tensile load (dead weigh) and B - thermal cycling with the sample submitted to a constant central deflection in three points bending. In both operation manners, measures of electrical resistance were accomplished simultaneously with those of temperature, displacement and force. To validate the machine operating in the way A it was used an industrial sample of the Cu-14,0Al-4,0Ni (% weight) SMA, while for the way B a sample of the Ni-44,7Ti-5,9Cu (% in weight) SMA was used. This Ni-Ti-Cu SMA was obtained at laboratory by the Plasma Skull Push Pull (PSPP) technique. The validation tests demonstrated the good operation of the proposed equipment to determine the main properties of these functional materials, as the transformation temperatures, temperature hysteresis, shape memory effect under constant load and force generation under imposed deformation.