Analysis of the magnetomechanical behavior of a ferromagnetic beam plate

Ferritic stainless steel, hereafter called HT-9, is a prospective candidate material for the first wall of a fusion power reactor because of its high resistance to irradiation swelling due to 14 MeV neutrons. The large increase of the transition temperature has been proven to be in a range of 50°C even for a neutron fluence of more than 50 dpa. However, since it is magnetized in a magnetic field, it experiences magnetic stress due to magnetization when it is used in the field. The magnetomechanical behavior is not simple because its relative permeability is very high (∼1000) and the B-H curve is nonlinear and followed by saturation of the magnetization. Beam-plates of HT-9 and mild steel were provided to carry out tests on the magnetomechanical behavior and compare it to the theoretical prediction. The theoretical prediction of the mechanical behavior was made for the configuration of the beam-plate based on non-linear numerical analysis of magnetization. The field distribution of the finite specimen is very different from that of an infinite specimen. It is also found that the deformation is proportional to the squared field for a very small applied field and increases monotonously to a peak. For a specimen with small inclination to the incident field, the deformation decreases very rapidly after the peak.