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Magnetic Latches and Fixtures: A Unique Multiphysics Solution


Permanent Magnets have become essential components in many household goods ranging from coffee mugs with magnetic lids to consumer electronics like laptops with detachable keyboards or tablets with smart covers that can automatically lock or unlock the tablet. A teardown of a consumer tablet revealed more than ninety magnets – some of them used for the purpose of easily attaching accessories. In recent years, there is a tendency to replace mechanical screws with permanent magnets to attach electronic components. A simple magnetic coupled device has two or more permanent magnets or permanent magnet(s) and ferrite(s) that latch together in a snapping action. Improper placement of magnets or inadequate design of magnets and surrounding components can compromise the structural integrity of the product due to excessive force when the magnets snap together, and a magnetic latch is established. Permanent magnet dimensions, material properties, and air gap between the latching objects are key factors in determining the magnetic force. Therefore, it is desirable to simulate and understand not only the magnetic forces between the permanent magnets but also the impact, this force will have on the structure when the bodies latch together. Even though the problem statement seems straightforward, the complexity of interlinked magnetics and structural changes combined with flexible/rigid body topologies make it a challenging simulation. The two physics viz. electromagnetism (EM forces) and motion (multibody simulation) can be individually studied using a wide variety of techniques via industrial/inhouse analytical/FE based codes however, to couple them together is a difficult endeavor. To study the magnetic latches accurately, a coupled physics approach is necessary. Unlike Fluid-Solid interaction (FSI) which has been studied for several decades, and has been well implemented in various commercial codes, there has been barely any development in coupling the magnetic and multi-body solvers. There are a few commercial solutions available for coupling the magnetic solvers with structural solvers however those are primarily focused on the static structural simulations and fall short on modeling impact behavior which necessitates a multibody solver. Two novel workflows were developed to provide a comprehensive simulation-based workflow for magnetically attached products. One workflow computes the static force between permanent magnets in Ansys Maxwell (EM solver), then generates a response surface in Ansys Twin Builder to interact with a Functional Mockup Unit (FMU) component from Ansys Motion (MBD solver). The second workflow utilizes Ansys Twin Builder to enable a handshake analysis between Ansys Maxwell and the transient solver in Ansys Motion for capturing the movement of the magnets and computing the deformation as well as the structural impact on the bodies when the magnets snap together. Using these techniques, it is possible to simulate the impact between various magnetic, ferromagnetic, and non-magnetic bodies.

Document Details

AuthorSarkar. D
Date 26th October 2021


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