A PHENOMENOLOGICAL MODEL OF THE MAGNETOELASTIC CHANGES IN THE MAGNETIZATION OF FERROMAGNETIC MATERIALS WHEN THEIR LOADING HAS A TENSOR FORMIN WEAK MAGNETIC-FIELDS

A phenomenological model is proposed which enables the changes in the magnetization of ferromagnetic materials in the region beyond the Rayl eigh region when weak magnetic fields (H << H-c where H-c is the coerc ive force) and high cyclic elastic tensile or compressive stresses (si gma > <(sigma)over bar>(i), where <(sigma)over bar>(i) is the mean val ue of the internal stresses) act on them in the collinear case (the fi eld is parallel to the resultant unidirectional stress, alpha = 0), ta king into account both its regular and irreversible changes. This enab les the analogous problem to be solved in the case when the loading of the ferromagnetic materials has a tensor form (0 less than or equal t o alpha less than or equal to 90 degrees), when different fields and t ensile and compressive stresses of different value and sign act in two mutually perpendicular directions (along and perpendicular to the dir ection of the resultant stress). It is shown that cyclic tension and c ompression lead to considerable anisotropy of the effective magnetic susceptibility. It is a maximum when tensile loads act on the material , and compressive stresses are approximately three times less effectiv e when they act in the transverse direction. When a compression is app lied this anisotropy gradually increases as the amplitude increases, r eaches a maximum and, finally, decreases and may even change sign. The latter can occur if the effective tensile stresses in the transverse direction are commensurable with the values of the characteristic stre sses which define the amplitude dependences of the parameters of the m odel.