Explosive-driven shock wave demagnetization of Nd₂Fe1 ₄B hard ferromagnets

Magnetic materials subjected to shock wave compression will undergo shock wave demagnetization. To further investigate the demagnetization performance of Nd2Fe14B ferromagnets, an open magnetic circuit cylinder was used as the energy-carrying body. The discharge process and circuit characteristics during shock wave demagnetization were analyzed. A series of the shock wave demagnetization tests were performed using the shock wave from the detonation of high explosives acting along the axial direction of the cylindrical magnets. The induced electromotive force and current were measured. The results indicate that Nd₂Fe₁₄B ferromagnet begins to demagnetize at approximately 0.28 μs after the shock wave enters its body. The induced electromotive force and current in coils are caused by the destruction of the magnetism in the smallest units of magnetic domains rather than the mechanical damage of the magnet structure. The influence of the shock wave pressure on the effect of demagnetization was investigated by altering the pressure of the shock wave acting the magnets. The results show that Nd2Fe14B ferromagnets can be absolutely demagnetized and destroyed by a high shock wave pressure, and that demagnetization is insufficient under a low 13 GPa shock wave pressure. In order to reduce eddy current losses during the process of the shock wave demagnetization, a new design of a split magnet with insulation layers was proposed. This process is very effective and beneficial to improve the energy conversion during the shock wave demagnetization.