Strange Magnetic Particle Pattern over the Cylindrical Surface of a Pin with a Through Hole

On the basis of the physical characteristic of the magnetic dipole chains and the geometrical feature of a pin with a circular through hole and a pin with a rectangular through hole, the shape of magnetic particle pattern over the cylindrical surface of the pin with a circular or a rectangular through hole was deduced, and it all coincided with the strange magnetic particle pattern obtained by the magnetic particle testing experiment.