Modal Mass v. Modal-A

[TrickyDick]

How can I derive Modal mass parameters from the Modal-A results I have available.
Thanks in advance.

 

[MikeyP]

Have a look at the following pdf documents (requires Acrobat reader).

http://www.sdrl.uc.edu/ucme662/ucme662.html

The modal scaling section is in chapter 7

http://www.sdrl.uc.edu/ucme662/v2_7.pdf

Michael

 

[GregLocock]

That's a great reference, and a sensible discussion of the essential arbitrariness of the definition.

In experimental modal analysis we often take the modal mass at the point of excitation - so we know that if we add 5% of the modal mass to that point we'd expect a -2.5% shift in frequency (or at least, on a good day, that it will drop a bit!). What seems absurd is that by this definition the modal mass varies if you change the excitation point or direction, but that is correct - adding mass at a nodal point will have little effect, whereas adding it at an antinode will have a great effect. Cheers

Greg Locock