| | B vs. H (hysteresis) characteristics of steel in different directions relative to the applied stress are presented. By means of tests, a difference is found in directions between flux density B and the field strength H because stress makes steel anisotropic. This difference in direction (called the rotation of magnetisation) is the basis of a nondestructive method of estimating stress. A review of the measurement of residual stress in steel by this magnetic method covers: the anisotropy due to stress in mild steel, stress and rotation of magnetisation, the rotation rig, measurement of the stress pattern in a mild steel disc compressed across a diameter, tests on railway wheels with an automatic version of the rotation rig, a comparison of Barkhausen emission (BE) magnetoacoustic emission (MAE) and the rotation rig, uniaxial stress measurement, biaxial stress measurement, and measurement of principal stress directions. Graphs. 6 ref.-A.R. |
