Mode Shapes in Abaqus

sheila · Jan 20, 2002

Hi,
I analyzed a mainframe and engine of motorcycle using ABAQUS to get natural frequencies and modeshapes. The natural frequencies I got are quite similar to the experimental results. But why the mode shapes are look different?What are the reasons for that?

brad · Jan 21, 2002

Any number of reasons. As you have not explained what method you used to obtain the FEA frequencies, I will presume that you used an eigenvalue extraction.

The most likely reason for differences is that your experimental approach was not 'apples-to-apples' with a the eigenvalue extraction procedure.

Experimental frequency tests usually are hammer-test or forced-frequency tests. You may want to try and find the numerically-equivalent approach to what your experimental test actually is doing.

Lacking more details than you have provided, I can't be more specific than that.

Brad

sheila · Jan 22, 2002

To Brad,
Thank you for replying. Actually,we performed Modal Analysis using hammer and shaker.I then used Lanszos solver to get the FEA frequencies.

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