Effect of magnetic field on mechanical properties in Permendur

Young modulus of magnetostrictive materials such as Permendur are changed by altering the external magnetic field. This phenomenon is called δ. E effect. In this paper, it has been experimentally shown that the shear modulus in Permendur is also changed in such a way that the ratio between Young modulus and shear modulus is not constant in different magnetic fields. Thus, Poisson ratio of it is also changed in different magnetic fields. Acoustic pulse-echo method is exploited to measure dependency of these properties to magnetic fields. In this method, longitudinal and shear sound wave velocities in Permendur are measured in different magnetic fields. Using these data, dependency of Young modulus, shear modulus and Poisson ratio on magnetic bias field in Permendur are calculated. Measurements are repeated 30 times in order to study test uncertainty. Changing in Poisson ratio can be interpreted as a result of changing in volume of magnetostrictive materials in different magnetic field (Nagaoka-Honda effect). The amount of this effect in ferromagnetic material is small. Hence, change in Poisson ratio in this material is predicted to be remarkably slight. For instance, based on presented results in Permendur, maximum changing in Poisson ratio is less than 0.014.