Category Archives: FEA

Eddy Currents Induced by Motion Through a Magnetic Field

In a previous post, we built a quick model for eddy currents in a plate stationary in a time-varying magnetic field. Here we examine the induced currents and damping force that result from motion of the plate relative to the magnetic field.

Eddy currents induced in a plate moving through a static magentic field. Simulation done using Ansoft Maxwell from ANSYS.
Eddy currents induced in a plate moving through a static magentic field. Simulation done using Ansoft Maxwell from ANSYS.

Continue reading Eddy Currents Induced by Motion Through a Magnetic Field

Eddy Currents Induced by a Time-Varying Magnetic Field

In electric machines, there are two common causes of eddy currents: (1) time-varying currents in coils, and (2) motion of conductors relative to sources of magnetic field. In this post, we show how to estimate the current density arising from a time-varying magnetic field passing through a plate.

Still of current density due to oscillating magnetic field. Results generated using Ansoft Maxwell from ANSYS.

Continue reading Eddy Currents Induced by a Time-Varying Magnetic Field

Tuned-Mass Damper on a Cantilever Beam

In this article, we compare the performance of a tuned-mass damper mounted at the end of a cantilever beam to the Lanchester damper which was shown in the previous article.  The classic single-degree-of-freedom (SDOF) tuned-mass damper is sketched in the figure below.  The design approach is to find the equivalent SDOF system for the cantilever beam’s mode of interest and then use the design formulas for an optimal SDOF TMD to determine the stiffness and damping of the absorber.

SDOF tuned-mass damper
SDOF tuned-mass damper

Continue reading Tuned-Mass Damper on a Cantilever Beam

Lanchester Damper on a Cantilever Beam

In this article, we show the robust and broadband performance  of a Lanchester damper applied to a cantilever beam and how it achieves good performance without tuning and good performance over a number of modes, not just the primary mode.

lanchester damper
Lanchester damper

Continue reading Lanchester Damper on a Cantilever Beam

Setting Views and Lighting in ANSYS CFD Post

This post shows how to set exact view orientation, zoom, pan, and lighting in CFD post. This is especially useful for making consistent figures for reports or presentations.

This picture below is a stream-ribbon visualization of a swirling flow, viewed using the built in “Isometric View (Z up).” The view is centered too low and the lighting angle is not favorable.

ribbon-iso
Continue reading Setting Views and Lighting in ANSYS CFD Post

Using a Snippet to Extract Ansys Workbench Results to a Text File with vmask and vget

Commonly, we need to save results from an Ansys Workbench study as a text file for post-processing in another program, such as Excel.  One can right-click on a desired result and use Export, but that can be tedious if there a lot of results to save.  With a snippet one inserts a Commands (APDL) object in the solution and writes APDL code to perform the desired  functions.

Continue reading Using a Snippet to Extract Ansys Workbench Results to a Text File with vmask and vget

Setting Mechanical Contact Stiffness and Thermal Contact Conductivity Values in Ansys Workbench using Command Snippets

For a bonded contact, which is the default for models opened in Ansys Workbench Mechanical, the contacts are modeled using elements TARGE170 and CONTA174. The thermal conductivity and stiffness of the contact elements are calculated by Ansys based on the properties of the two bodies. The controls only allow one to change the contact stiffness factor FKN which is a multiplier but not the actual stiffness of the joint (ie with SI units of N/m/m^2). However if one would like to set the value of the contact stiffness or thermal contact resistance, it can be done using Command snippets (also known as the Commands Object) for each contact. Continue reading Setting Mechanical Contact Stiffness and Thermal Contact Conductivity Values in Ansys Workbench using Command Snippets