Hui Meng

• Senior Engineer at Foresee Group

Macroscopic demagnetization in sintered Nd-Fe-B magnets by Tb grain boundary diffusion (GBD) is investigated in comparison with non-GBD ones. Demagnetization curves, the coercivity distributions, Tb content, and magnetic fields of the magnets at various external fields (μ0Hext) are analyzed. As μ0Hext approaches coercivity of the GBD magnet, S-N po...

The Maxwell magnetic force equation F = B^2*A/(2μ0) [1-6] can be used for determining the magnetic force of magnetic components, where F is the force in newton (N), B is the flux density in tesla (T), A is the area of cross-section in square meter (m^2), and μ0 is the permeability of the vacuum (4π×10−7 H/m). The formula can be converted to an easy...

The attraction between unequally sized like magnetic poles is characterized herein. Finite element analysis (FEA) simulation has verified that attraction can occur between like poles. Between two unequally sized like poles with various dimensions and alignments, a turning point (TP) appears on the curves of force vs. distance between them, which is...

The magnetic force of magnetic components can be determined by using the Maxwell magnetic force equation F = B^2 A/(2μ0), with A is the cross-section area and B is the flux density. However, in many practical cases it is difficult to determine the B, and the accuracy is usually unsatisfactory. This paper reports a simple equation F = Br^2 (aA^2 +bA...

Force between magnet pairs and surface flux density are studied to understand the attraction between magnetic like poles and repulsion between unlike poles with different permeance coefficients (Pc) and B-H characteristics. The magnet with a higher Pc can locally demagnetize the one with a lower Pc. A large localized demagnetization (LD) field can...

This investigation reveals the mystery of the cases where magnetic like poles attract each other, and unlike poles repel one another. It is identified that for two unequally sized like poles, the pole with a higher Pc (permeance coefficient) causes a localized demagnetization (LD) to the pole with a lower Pc. If the LD is large enough, the polarity...

Even though Gauss’ law for magnetic flux density (B-field) indicates there is no free magnetic charge, we can still define the effective bound magnetic charges from the magnetization of magnetic material [1]. The positive magnetic charge is what we usually called the “north pole”, and correspondingly, the negative magnetic charge is what we usually...

The principles for the design of smart magnetic devices using permanent magnet are presented. For a small air gap, replacing the uniform magnetization with a finely tuned multipolar magnetic pattern can enhance the attractive force greatly and limit the flux leakage obviously. The optimal multipolar magnetic pattern is different for different air g...