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## matrix operations

13 REPLIES 13
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Message 1 of 14
466 Views, 13 Replies

## matrix operations

Can matrix operations be performed? Can matrices be exported?

13 REPLIES 13
Message 2 of 14

Have you looked at the Matrix3D object?

What do you mean "exported"?

Message 3 of 14
Thank you for that help, JesusFreke. I was not familiar with the Matrix3D. I will check it out.

Bob Coleman
Message 4 of 14

I checked out the Matrix3D and found that it is used to locate and orient objects. I was looking for information on whether there is a way to access matrices used in resonance frequency simulation. When performing an analysis of resonance frequencies the software uses stiffness and mass matrices. An eigenvalue-eigenvector analysis is performed using those matrices. The results of the analysis yields the eigenvectors (frequency mode shapes, i.e., part vibration deformation patterns associated with each resonance frequency) and eigenvalues. The resonance frequencies are presented as squared circular frequencies, w^2, where frequency, f, in Hz, f = (1/2*pi)w. So, I was really looking for a way to access the stiffness matrix, mass matrix, and mode shape matrix. If I could at least access the mode shape matrix, I could use that along with the frequency values (those are available) to back calculate the mass and stiffness matrices.

Message 5 of 14

I'm not familiar with that aspect of fusion 360, so I can't help you there.

Although some friendly advice in general: your initial question was... quite vague. When asking on a technical forum like this for help, you want to be sure to give enough info for someone to be able to help you. As it was, I had to (incorrectly) guess that you were talking about affine geometry transformations using a matrix.

Message 6 of 14
Thanks. Appreciate the help and sorry to have been unclear.

Bob
Message 7 of 14

Is that analysis part of Fusion 360, or are you running a separate set of software?

Message 8 of 14
I'm running the analysis in Fusion 360 using simulation frequencies. Fusion gives me the list of resonance frequencies and also lets me display animated displays of my modeled body mode shapes (vibration deformation patterns at each resonance frequency). However, I cannot find a way to display the displacement values of the body points that are used within the program to display the graphical screen display of the vibrating body. I thought maybe the values of those displacements for each mode shape would be stored in a matrix. Each column of the matrix would store displacement values for a given mode shape deflection pattern. I'm sure the program uses such a matrix internally, but I can't find a path to accessing it. If I could find the mode shape matrix, I would want to write a Python script to do other calculations with it.
Message 9 of 14

I don't know how the data is being stored but I do know that there isn't any API for the Fusion Simulation functionality so it's not possible through the API to get access to any of the simulation data.

---------------------------------------------------------------
Brian Ekins
Inventor and Fusion 360 API Expert
Website/Blog: https://EkinsSolutions.com
Message 10 of 14

I was going to say this. To my knowledge, there isn't currently a method of getting that data from Fusion. I really hope there is one in the near future.

Message 11 of 14
Thanks very much, Joshua. I will keep an eye out in the future. But, I am amazed at the functionality and capabilities of Fusion 360. It boggles my mind how so much capability can be provided at such a low cost. In the mean time I'm finding solutions to many vibration problems--and very fast. The mesh generation and simulation frequency processes are so impressive. To be able to solve for resonances and immediately animate the mode shapes with deformation dynamic color coding is so easy and quick. The capabilities of Fusion 360 are far more than one would expect.

Thanks again for a wonderful product.

Bob Coleman
Message 12 of 14
Thank you very much for that valuable information. I was not knowledgeable of these details.

Bob Coleman
Message 13 of 14

I am a Fusion fan as well.

Curious as to what you want to do with the data you are looking for once you have extracted it? I would eventually like to report that data back to my platform and do a number of things with it.

Message 14 of 14

The discussion could get very detailed. I can go into the subject with more if desired. There are a number of applications in structural dynamics that utilize the mass, stiffness, and mode shape matrices along with the resonance frequencies of a vibrating structure. The one I'm focused on at the moment is comparing mode shapes from a simulation model (Finite Element Model) to mode shapes obtained experimentally for a given structure.

When I worked at NASA JSC ('73 - '92) my colleague Walt West and I developed FEM, test and analytical methods that utilized these matrices along with resonance frequencies to compare the FEM mode shape and frequency results to the similar modal test results. We could locate the elements of the FEM that needed adjustment to match the test data. This was used to validate the FEM. We calculated the residual force and displayed the Orbiter component mesh with color coded elements representing the residual force on each element. A red spot covering a small group of elements identified the location that needed adjustment of element properties in order to match the test data.

The residual force is obtained by enforcing the test mode shape (set of displacements) for a selected frequency, then back-calculating the force vectors (for FEM and Test models) required to enforce that mode shape. The residual force is found by simply computing the difference between the two sets of force vector components. I can provide a little more detail on why that works if desired.

We also used the residual force for force vectors calculated for the experimental modal tests performed before launch and after two or three flights (comparing pre-test mode shapes to post-test mode shapes). In this case the red spot showed location of damage to internal structural components. This was needed because much of the internal structure covered by Orbiter tile was unavailable to visual inspection. At that time we were using the SDRC I-deas FEM-test system. That company has sold a couple of times and the software is now owned by Siemens. The product is overly expensive for this limited application, besides Autodesk 360 is too attractive to not pursue if we find potential (we would use the application for our customers internationally).

The problem is actually more involved than outlined here, because we may need to do Guyan reductions and coordinate transformations that further utilize the FEM stiffness matrix and mode shape matrices. But this is the overview. I can do more detail if needed.

Thanks for your interest and response.

Bob Coleman

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