FEM simulation of bullet sensor

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Title FEM simulation of bullet sensor
Summary Simulate a magnetic reluctance sensor that detects speeding bullet
Keywords electro magnetism, physics
TimeFrame spring
References https://magnetospeed.com

https://patents.google.com/patent/US9709593B1/en"https://magnetospeed.com https://patents.google.com/patent/US9709593B1/en" cannot be used as a page name in this wiki.

Prerequisites electromagnetics
Author Stefan Axelsson
Supervisor Stefan Axelsson, Struan Gray, Pererik Andreasson
Level Flexible
Status Open

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A new entry on the market of ballistic chronographs (i.e. devices that measure the muzzle velocity of bullets) is Magnetospeed. While other, previous, sensors typically measure light occlusion, this chronograph works on the principle of magnetic reluctance (the same type of sensor that measures the rotational speed of the wheels in your car for the ABS system). Here a bullet, of a conducting but non-magnetic material, is shot into a static magnetic field. This field induces a current in the bullet, that in turn induces a magnetic field that is picked up by a coil.

Muzzle velocity is important from a number of aspects, i.e. developing loads that shoot accurately, but also make sure that hunting ammunition fulfill legal energy requirements for particular types of hunting etc.

I have already built such a sensor bar, and they are commercially available, but the geometry, field strengths etc. are not sufficiently well understood from an engineering perspective. An analytical solution is probably complex, but a FEM (Finite Element Modeling) solution is probably within reach. We have the COMSOL software at the school, but there are also free and open multi-physics simulation software available such as ELMER (from CSC in Finland).

So this thesis would develop such a model based on real bullets, speeds etc. and calibrate/compare it with real field measurements (using a .223 and .308 caliber hunting rifle with moderator). Sponsorship and guidance from the hunting/gun shop just across the parking lot from the school has been secured in the form of an experienced former police officer with access to rifles and the local range. (Thus also ensuring the legality and safety of the project).