Damping of ferromagnetic materials at direct stress levels below the fatigue limit

Results are given of the stress-dependent damping of ferromagnetic materials at direct stress levels up to the fatigue limit. The magnetomechanical damping may undergo a change on stressing termed `semi-permanent' because it can be restored by demagnetizing. There is a critical cyclic stress σ_c at which the maximum semi-permanent change of magnetomechanical damping is caused, but this is not the stress σ_S required to cause saturation of this damping. The stress σ_c is a direct measure of the maximum internal stress. The value of σ_S is very high and was not approached in these tests, except for annealed nickel.

At low stress, the magnetomechanical energy dissipation is proportional to σⁿ, where n varies from 3·27 up to 8·78 for the materials tested here. At high stress, n decreases, the stress at which the decrease commences being higher the greater the hardness.