Bonded Magnet is one of the most important and useful permanent magnets industrially. It enables to achieve complex shapes and is superior in strength to other kinds of magnets. Above all, NdFeB anisotropic bonded magnet is used for motors of automobiles and magnetic hard disk drives and sensors utilized in a wide variety of products. It will be expected for motors of hybrid vehicles (HV) and electric vehicles (EV) to realize smaller size and higher rotational speed. However, we have to pay attention to 'magnetic fatigue' of the magnet itself. Motors will be applied high frequency field with a maximum frequency of 10 kHz and average amplitude of 40 kA/m (0.5 kOe) at high temperature in near future. It will also be applied a static field of approximately 240 kA/m (3 kOe). As a result, high frequency field and thermal stress might demagnetize NdFeB anisotropic bonded magnetization. It is called 'magnetic fatigue'. In this study, magnet behavior in high frequency field and high temperature was simulated using micromagnetics simulator. A simple grain model and basic magnetic characteristics were assumed, and behaviour of magnetic fatigue was simulated.
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