APPROACH TO THE ANHYSTERETIC SURFACE

In this paper, we have investigated experimentally the approach to the anhysteretic surface in M-H-sigma space. in particular, for a 0.5 wt% carbon steel specimen, we have applied 73 MPa tension and a bias fiel d H and determined the end flux density after superimposing an ac fiel d of amplitude gradually decreasing to zero. We find that the point on the anhysteretic curve for 73 MPa tension and field H is not approach ed unless the initial amplitude of ac field is sufficiently large to o vercome domain wall pinning, which restrains redistribution of the dom ains. A similar experiment in which stress is cycled was also done. St ress was cycled discretely between 0 and 140 MPa, with the discrete ch anges about 73 MPa eventually decreasing to zero in bias field H, It w as found that the loci of(B,H) end points did not approach the anhyste retic, suggesting that larger amplitude changes in stress and perhaps more continuous changes are needed to overcome domain wall pinning. (C ) 1996 American Institute of Physics.