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Showing posts from November, 2017

MAC with Ansys for Measurement Locations

Where should the accelerometers be placed? - Test Person Test People are tough to work with! I was one before so I would know. Have a bit of sympathy for them though as they could be frantically troubleshooting equipment in the middle of no-where or spend countless hours rolling-and-unrolling cables.

Goal of Measurement Points Selection
OK, we have a model with natural frequencies and mode shapes. If your company is well endowed, this is a simple question with pretest software like FEMtools or some other software that optimizes the MAC matrix. This would also help with correlation later. Generally speaking, the software will maximize the diagonal matrix while minimize the off diagonal matrix values. Loosely defined, this means the modes are relatively unique (mathematically speaking) for the chosen measurement locations.

Poor Man's Method for Picking Measurement Locations
Alternately, we can pick measurement locations by hand based on past experience and liberal use of engineering …

DesignXplorer Design Point Alternative Save

Solving for many cases with small variations using DesignXplorer is quite convenient. After setting up an initial model, a parameter could be defined in SpaceClaim or elsewhere. The solution for multiple design points are then generated as I sip on my beer (legally at home).

As shown in this YouTube Video, the output parameters are single values like natural frequency, displacements and other maximum or minimum of available solution results. Unfortunately if you are interested in more complicated items that aren't easily available through the user defined results or *GET commands, how do you capture that output parameter?

One way would be to retain all design point results for later post processing but that would be overkill especially since I'll have to go into everyone of them to extract out the information which is a pain.

Alternately, a post-processing APDL script could be written to extract out key information at each run. An example would be the mode shape of a beam. Wi…