Magnetomechanical effects under applied stresses and unloaded conditions by a probe with indirect pickup coil

In this work, a yoke probe with pickup coil wound around the yoke is adopted to study the magnetic property dependences on both external stress and stress induced defects under the condition of loading, reloading and unloading in the tensile test. A carbon steel plate annealed at 1273 K is used. A family of B-H hysteresis minor loops are measured under a triangle wave of 0.05 Hz at the current range between 0.005 and 1.0 A after each demagnetization. Magnetic flux density is calculated by integrating the detection signal of pickup coil. In the elastic range when applied field amplitude H_a is 11.5 kA/m, coercive field H_c decreases proportionally with the increasing of the external stresses because of the domain being re-orientated to the stress direction to minimize magnetoelastic energy. In the plastic range, H_c increases linearly with the external stress, because the effect of the dislocation pinning is much larger than that of the external stress. In addition, H_c decreases proportionally and quickly with the reload elastic external stress from 0 to 90 MPa, while it si nearly constant from 90 MPa to 180 MPa. This is attributed to the fact that the texture structure induced from plastic deformation under 180 MPa facilitates the domain reorientation under lower elastic external stresses. Measuring results by the current probe with indirect pickup coil effectively reflect the changes of magnetic properties derived from external stresses and micro-defects.