In this blog, we'll walk through a complete workflow in Ansys Maxwell to simulate the magnetization of a specific permanent magnet, the N48SH, using only its manufacturer datasheet. We will then validate our results against Maxwell’s built-in material library to demonstrate the accuracy of this powerful technique.
1. The Physics of Magnetization & Our Simulation Model
Before diving into the simulation, let's briefly review the underlying physics. The behavior of a magnetic material is described by its B-H curve, or hysteresis loop. When we first magnetize a material, it follows an "Initial Magnetizing" path from (0,0) up to saturation. Once the external magnetizing field is removed, the magnet's flux density "recoils" to a point in the second quadrant, known as its operating point. This second quadrant, the demagnetization curve, is what defines the magnet's performance in an application.
Hysteresis loop of a typical NdFeB magnet, showing the initial magnetization curve and the second-quadrant demagnetization region.
A permanent magnet in open air will generate a "demagnetizing" field within itself, where the magnetic field (H) opposes the direction of magnetization. The intersection of this self-demagnetizing field and the material's B-H curve determines the magnet's operating point.
Example operating point for an N48 magnet on its demagnetization curve (left). Vector plot of the H-field showing the external field and the internal demagnetizing field of a permanent magnet (right).
To simulate this process, we've created a simple magnetizer model in Ansys Maxwell. It consists of two current-carrying coils and two steel cores that work together to generate and direct a strong, uniform magnetic field (H-field) in the space between them. We will place our unmagnetized N48SH material, a simple rectangular block, in this region to be magnetized.
Simulation showing the current density (J) in the coils and the resulting magnetic field (H) generated between them.
Vector plot showing the magnetic field (H) in and around the entire magnetizer assembly.
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