The stress-magnetic behavior of ferromagnetic material under cyclic load and geomagnetic field

Semisinusoidal loads with constant amplitude or increasing amplitude were applied on steel specimens separately in earth magnetic field. The testing results indicated that the variation degree of the magnetic signals was mostly determined by the amplitude of the applied loads. With the load amplitude increasing to plastic loading stage, zero-crossing of the H_{p} (y) distribution curve occurred and stayed at certain position where the curve has large gradient. The zero-crossing position was exactly the necking point and unchangeable after unloading, which suggested that the plastic failures and microdefects can be identified through testing the H_{p} (y) signals.