Issue 42

M. Peron et alii, Frattura ed Integrità Strutturale, 42 (2017) 223-230; DOI: 10.3221/IGF-ESIS.42.24 223 Fracture assessment of magnetostrictive materials M. Peron, S.M.J. Razavi, F. Berto, J. Torgersen Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands vei 2b, 7491, Trondheim, Norway. mirco.peron@ntnu.no, javad.razavi@ntnu.no, filippo.berto@ntnu.no , jan.torgersen@ntnu.no M. Colussi Department of Engineering and Management, University of Padova, Stradella S. Nicola 3, 36100, Vicenza (Italy) A BSTRACT . Giant magnetostrictive materials are gaining interest in the field of smart material, especially the commercially known Terfenol-D, that is an alloy made out of iron, terbium and dysprosium (Tb 0.3 Dy 0.7 Fe 1.9 ). Since these smart materials are subjected to both mechanical loads and magnetic field during their industrial applications, an extensive characterization on the influence of a magnetic field and of defects on their fracture behavior is needed. Very few works can be found in literature about this topic and, thus, the purpose of this work is to partially fill this lack by means of three-point bending tests on single-edge pre-cracked Terfenol-D specimens. Failure loads have been measured at different loading rates and under magnetic fields of various intensities. Since giant magnetostrictive materials are very brittle, the strain energy density (SED) approach has been exploited by means of couple- field finite element analyses. SED has revealed itself as a robust parameters in the assessment of the magnetic field and loading rate effects on fracture resistance, allowing also to propose a relationship between the radius of the control volume and the loading-rate. K EYWORDS . Strain energy density; Fracture toughness; Loading rates; Magnetic field; Giant magnetostrictive materials; Terfenol-D . Citation: Peron, M., Razavi, S.M.J., Berto, F., Torgersen, J., Colussi, M., Fracture assessment of magnetostrictive materials, Frattura ed Integrità Strutturale, 42 (2017) 223-230. Received: 15.07.2017 Accepted: 17.08.2017 Published: 01.10.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION utomotive industry, avionics and robotics are constantly looking for innovations, especially in the field of sensors, actuators and energy harvesting devices where smart material, such as magnetostrictive materials, are widely exploited [1]. This kind of material can convert magnetic energy into kinetic energy, i.e. it exhibits deformation once an external magnetic field is applied, or the reverse, i.e. an applied force determines a magnetization change. Such industrial applications require remarkable elongation and high energy density capacity at room temperature, features widely A