Determination of mechanical-stress variations by electromagnetic method

Study of the magnetoelastic effect in ferromagnetic materials has shown that the arising stresses are comparable with natural mechanical stresses. The boundary problem of the transient electromagnetic field in the presence of conducting magnetic films is reduced to the problem of eigenvalues. The sensitivity of transient signals to the magnetic permeability of metallic casing strings is determined. Electromagnetic noncontact method for controlling a borehole state and estimating mechanical-stress variations in the near-borehole space is physically justified.